AccessibleObject Classe

Definição

public ref class AccessibleObject : MarshalByRefObject, Accessibility::IAccessible, System::Reflection::IReflect

public ref class AccessibleObject : System::Runtime::InteropServices::StandardOleMarshalObject, Accessibility::IAccessible, System::Reflection::IReflect

[System.Runtime.InteropServices.ComVisible(true)]
public class AccessibleObject : MarshalByRefObject, Accessibility.IAccessible, System.Reflection.IReflect

[System.Runtime.InteropServices.ComVisible(true)]
public class AccessibleObject : System.Runtime.InteropServices.StandardOleMarshalObject, Accessibility.IAccessible, System.Reflection.IReflect

[<System.Runtime.InteropServices.ComVisible(true)>]
type AccessibleObject = class
    inherit MarshalByRefObject
    interface IReflect
    interface IAccessible
    interface UnsafeNativeMethods.IEnumVariant
    interface UnsafeNativeMethods.IMarshal

[<System.Runtime.InteropServices.ComVisible(true)>]
type AccessibleObject = class
    inherit StandardOleMarshalObject
    interface IReflect
    interface IAccessible
    interface UnsafeNativeMethods.IEnumVariant
    interface UnsafeNativeMethods.IOleWindow

[<System.Runtime.InteropServices.ComVisible(true)>]
type AccessibleObject = class
    inherit StandardOleMarshalObject
    interface IReflect
    interface IAccessible

Public Class AccessibleObject
Inherits MarshalByRefObject
Implements IAccessible, IReflect

Public Class AccessibleObject
Inherits StandardOleMarshalObject
Implements IAccessible, IReflect

Herança

Object

MarshalByRefObject

AccessibleObject

Herança

Object

MarshalByRefObject

StandardOleMarshalObject

AccessibleObject

Derivado

System.Windows.Forms.ComboBox.ChildAccessibleObject

System.Windows.Forms.Control.ControlAccessibleObject

System.Windows.Forms.DataGridColumnStyle.DataGridColumnHeaderAccessibleObject

System.Windows.Forms.DataGridView.DataGridViewTopRowAccessibleObject

System.Windows.Forms.DataGridViewCell.DataGridViewCellAccessibleObject

Mais…

Atributos

ComVisibleAttribute

Implementações

IAccessible IReflect

Exemplos

O exemplo de código seguinte demonstra a criação de um controlo de gráfico consciente da acessibilidade, usando as AccessibleObject classes e Control.ControlAccessibleObject para expor informação acessível. O controlo traça duas curvas juntamente com uma legenda. A ChartControlAccessibleObject classe, que deriva de ControlAccessibleObject, é usada no CreateAccessibilityInstance método para fornecer informação acessível personalizada para o controlo do mapa. Como a legenda do mapa não é um controlo -based real Control , mas sim desenhada pelo controlo do mapa, não tem qualquer informação acessível incorporada. Por causa disso, a ChartControlAccessibleObject classe sobrepõe o GetChild método para devolver o CurveLegendAccessibleObject que representa informação acessível para cada parte da legenda. Quando uma aplicação acessível-consciente utiliza este controlo, este pode fornecer a informação necessária e acessível.

#using <Accessibility.dll>
#using <System.dll>
#using <System.Windows.Forms.dll>
#using <System.Drawing.dll>

using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;

// Declare a chart control that demonstrates accessibility in Windows Forms.
public ref class ChartControl: public System::Windows::Forms::UserControl
{
public:
   ref class ChartControlAccessibleObject;

   // forward declaration
   // Inner Class that represents a legend for a curve in the chart.
   ref class CurveLegend
   {

      // Inner class CurveLegendAccessibleObject represents accessible information
      // associated with the CurveLegend object.
   public:
      ref class CurveLegendAccessibleObject: public AccessibleObject
      {
      private:
         CurveLegend^ curveLegend;

      public:
         CurveLegendAccessibleObject( CurveLegend^ curveLegend )
            : AccessibleObject()
         {
            this->curveLegend = curveLegend;
         }


      private:

         property ChartControlAccessibleObject^ ChartControl 
         {

            // Private property that helps get the reference to the parent ChartControl.
            ChartControlAccessibleObject^ get()
            {
               return dynamic_cast<ChartControlAccessibleObject^>(Parent);
            }

         }

      internal:

         property int ID 
         {

            // Internal helper function that returns the ID for this CurveLegend.
            int get()
            {
               for ( int i = 0; i < ChartControl->GetChildCount(); i++ )
               {
                  if ( ChartControl->GetChild( i ) == this )
                  {
                     return i;
                  }

               }
               return  -1;
            }

         }

      public:

         property Rectangle Bounds 
         {

            // Gets the Bounds for the CurveLegend. This is used by accessibility programs.
            virtual Rectangle get() override
            {
               
               // The bounds is in screen coordinates.
               Point loc = curveLegend->Location;
               return Rectangle(curveLegend->chart->PointToScreen( loc ),curveLegend->Size);
            }

         }

         property String^ Name 
         {

            // Gets or sets the Name for the CurveLegend. This is used by accessibility programs.
            virtual String^ get() override
            {
               return curveLegend->Name;
            }

            virtual void set( String^ value ) override
            {
               curveLegend->Name = value;
            }

         }

         property AccessibleObject^ Parent 
         {

            // Gets the Curve Legend Parent's Accessible object.
            // This is used by accessibility programs.
            virtual AccessibleObject^ get() override
            {
               return curveLegend->chart->AccessibilityObject;
            }

         }

         property System::Windows::Forms::AccessibleRole Role 
         {

            // Gets the role for the CurveLegend. This is used by accessibility programs.
            virtual System::Windows::Forms::AccessibleRole get() override
            {
               return ::AccessibleRole::StaticText;
            }

         }

         property AccessibleStates State 
         {

            // Gets the state based on the selection for the CurveLegend.
            // This is used by accessibility programs.
            virtual AccessibleStates get() override
            {
               AccessibleStates state = AccessibleStates::Selectable;
               if ( curveLegend->Selected )
               {
                  state = static_cast<AccessibleStates>(state | AccessibleStates::Selected);
               }

               return state;
            }

         }

         // Navigates through siblings of this CurveLegend. This is used by accessibility programs.
         virtual AccessibleObject^ Navigate( AccessibleNavigation navdir ) override
         {
            
            // Uses the internal NavigateFromChild helper function that exists
            // on ChartControlAccessibleObject.
            return ChartControl->NavigateFromChild( this, navdir );
         }


         // Selects or unselects this CurveLegend. This is used by accessibility programs.
         virtual void Select( AccessibleSelection selection ) override
         {
            
            // Uses the internal SelectChild helper function that exists
            // on ChartControlAccessibleObject.
            ChartControl->SelectChild( this, selection );
         }

      };


   private:

      // class CurveLgendAccessibleObject
      String^ name;
      ChartControl^ chart;
      CurveLegendAccessibleObject^ accObj;
      bool selected;
      Point location;

   public:
      CurveLegend( ChartControl^ chart, String^ name )
      {
         this->chart = chart;
         this->name = name;
         selected = true;
      }


      property AccessibleObject^ AccessibilityObject 
      {

         // Gets the accessibility object for the curve legend.
         AccessibleObject^ get()
         {
            if ( accObj == nullptr )
            {
               accObj = gcnew CurveLegendAccessibleObject( this );
            }

            return accObj;
         }

      }

      property Rectangle Bounds 
      {

         // Gets the bounds for the curve legend.
         Rectangle get()
         {
            return Rectangle(Location,Size);
         }

      }

      property Point Location 
      {

         // Gets or sets the location for the curve legend.
         Point get()
         {
            return location;
         }

         void set( Point value )
         {
            location = value;
            chart->Invalidate();
            
            // Notifies the chart of the location change. This is used for
            // the accessibility information. AccessibleEvents::LocationChange
            // tells the chart the reason for the notification.
            chart->AccessibilityNotifyClients( AccessibleEvents::LocationChange, (dynamic_cast<CurveLegendAccessibleObject^>(AccessibilityObject))->ID );
         }

      }

      property String^ Name 
      {

         // Gets or sets the Name for the curve legend.
         String^ get()
         {
            return name;
         }

         void set( String^ value )
         {
            if ( name != value )
            {
               name = value;
               chart->Invalidate();
               
               // Notifies the chart of the name change. This is used for
               // the accessibility information. AccessibleEvents::NameChange
               // tells the chart the reason for the notification.
               chart->AccessibilityNotifyClients( AccessibleEvents::NameChange, (dynamic_cast<CurveLegendAccessibleObject^>(AccessibilityObject))->ID );
            }
         }

      }

      property bool Selected 
      {

         // Gets or sets the Selected state for the curve legend.
         bool get()
         {
            return selected;
         }

         void set( bool value )
         {
            if ( selected != value )
            {
               selected = value;
               chart->Invalidate();
               
               // Notifies the chart of the selection value change. This is used for
               // the accessibility information. The AccessibleEvents value depends upon
               // if the selection is true (AccessibleEvents::SelectionAdd) or
               // false (AccessibleEvents::SelectionRemove).
               chart->AccessibilityNotifyClients( selected ? AccessibleEvents::SelectionAdd : AccessibleEvents::SelectionRemove, (dynamic_cast<CurveLegendAccessibleObject^>(AccessibilityObject))->ID );
            }
         }

      }

      property System::Drawing::Size Size 
      {

         // Gets the Size for the curve legend.
         System::Drawing::Size get()
         {
            int legendHeight = chart->Font->Height + 4;
            Graphics^ g = chart->CreateGraphics();
            int legendWidth = (int)g->MeasureString( Name, chart->Font ).Width + 4;
            return System::Drawing::Size( legendWidth, legendHeight );
         }

      }

   };


private:

   // class CurveLegend
   CurveLegend^ legend1;
   CurveLegend^ legend2;

public:
   ChartControl()
   {
      
      // The ChartControl draws the chart in the OnPaint .
      SetStyle( ControlStyles::ResizeRedraw, true );
      SetStyle( ControlStyles::DoubleBuffer, true );
      SetStyle( ControlStyles::AllPaintingInWmPaint, true );
      this->BackColor = System::Drawing::Color::White;
      this->Name = "ChartControl";
      this->Click += gcnew System::EventHandler( this, &ChartControl::ChartControl_Click );
      this->QueryAccessibilityHelp += gcnew System::Windows::Forms::QueryAccessibilityHelpEventHandler( this, &ChartControl::ChartControl_QueryAccessibilityHelp );
      
      // The CurveLengend is not Control-based, it just
      // represents the parts of the legend.
      legend1 = gcnew CurveLegend( this,"A" );
      legend1->Location = Point(20,30);
      legend2 = gcnew CurveLegend( this,"B" );
      legend2->Location = Point(20,50);
   }



protected:
   // Overridden to return the custom AccessibleObject
   // for the entire chart.
   virtual AccessibleObject^ CreateAccessibilityInstance() override
   {
      return gcnew ChartControlAccessibleObject( this );
   }

   virtual void OnPaint( PaintEventArgs^ e ) override
   {
      
      // The ChartControl draws the chart in the OnPaint .
      System::Windows::Forms::UserControl::OnPaint( e );
      Rectangle bounds = this->ClientRectangle;
      int border = 5;
      
      // Draws the legends first.
      StringFormat^ format = gcnew StringFormat;
      format->Alignment = StringAlignment::Center;
      format->LineAlignment = StringAlignment::Center;
      if ( legend1 != nullptr )
      {
         if ( legend1->Selected )
         {
            e->Graphics->FillRectangle( gcnew SolidBrush( Color::Blue ), legend1->Bounds );
         }
         else
         {
            e->Graphics->DrawRectangle( Pens::Blue, legend1->Bounds );
         }

         e->Graphics->DrawString( legend1->Name, this->Font, Brushes::Black, legend1->Bounds, format );
      }

      if ( legend2 != nullptr )
      {
         if ( legend2->Selected )
         {
            e->Graphics->FillRectangle( gcnew SolidBrush( Color::Red ), legend2->Bounds );
         }
         else
         {
            e->Graphics->DrawRectangle( Pens::Red, legend2->Bounds );
         }

         e->Graphics->DrawString( legend2->Name, this->Font, Brushes::Black, legend2->Bounds, format );
      }

      
      // Charts out the actual curves that represent data in the Chart.
      bounds.Inflate(  -border,  -border );
      array<Point>^ temp1 = {Point(bounds.Left,bounds.Bottom),Point(bounds.Left + bounds.Width / 3,bounds.Top + bounds.Height / 5),Point(bounds.Right - bounds.Width / 3,(bounds.Top + bounds.Bottom) / 2),Point(bounds.Right,bounds.Top)};
      array<Point>^curve1 = temp1;
      array<Point>^ temp2 = {Point(bounds.Left,bounds.Bottom - bounds.Height / 3),Point(bounds.Left + bounds.Width / 3,bounds.Top + bounds.Height / 5),Point(bounds.Right - bounds.Width / 3,(bounds.Top + bounds.Bottom) / 2),Point(bounds.Right,bounds.Top + bounds.Height / 2)};
      array<Point>^curve2 = temp2;
      
      // Draws the actual curve only if it is selected.
      if ( legend1->Selected )
            e->Graphics->DrawCurve( Pens::Blue, curve1 );

      if ( legend2->Selected )
            e->Graphics->DrawCurve( Pens::Red, curve2 );

      e->Graphics->DrawRectangle( Pens::Blue, bounds );
   }

   // Handles the QueryAccessibilityHelp event.
   void ChartControl_QueryAccessibilityHelp( Object^ /*sender*/, System::Windows::Forms::QueryAccessibilityHelpEventArgs^ e )
   {
      e->HelpString = "Displays chart data";
   }

   // Handles the Click event for the chart.
   // Toggles the selection of whatever legend was clicked on
   void ChartControl_Click( Object^ /*sender*/, System::EventArgs^ /*e*/ )
   {
      Point pt = this->PointToClient( Control::MousePosition );
      if ( legend1->Bounds.Contains( pt ) )
      {
         legend1->Selected =  !legend1->Selected;
      }
      else
      if ( legend2->Bounds.Contains( pt ) )
      {
         legend2->Selected =  !legend2->Selected;
      }
   }


public:

   property array<CurveLegend^>^ Legends 
   {

      // Gets an array of CurveLengends used in the Chart.
      array<CurveLegend^>^ get()
      {
         array<CurveLegend^>^temp3 = {legend1,legend2};
         return temp3;
      }

   }

   // Inner class ChartControlAccessibleObject represents accessible information associated with the ChartControl.
   // The ChartControlAccessibleObject is returned in the ChartControl::CreateAccessibilityInstance .
   ref class ChartControlAccessibleObject: public ControlAccessibleObject
   {
   private:
      ChartControl^ chartControl;

   public:
      ChartControlAccessibleObject( ChartControl^ ctrl )
         : ControlAccessibleObject( ctrl )
      {
         chartControl = ctrl;
      }


      property System::Windows::Forms::AccessibleRole Role 
      {

         // Gets the role for the Chart. This is used by accessibility programs.
         virtual System::Windows::Forms::AccessibleRole get() override
         {
            return ::AccessibleRole::Chart;
         }

      }

      property AccessibleStates State 
      {

         // Gets the state for the Chart. This is used by accessibility programs.
         virtual AccessibleStates get() override
         {
            return AccessibleStates::ReadOnly;
         }

      }

      // The CurveLegend objects are "child" controls in terms of accessibility so
      // return the number of ChartLengend objects.
      virtual int GetChildCount() override
      {
         return chartControl->Legends->Length;
      }


      // Gets the Accessibility object of the child CurveLegend idetified by index.
      virtual AccessibleObject^ GetChild( int index ) override
      {
         if ( index >= 0 && index < chartControl->Legends->Length )
         {
            return chartControl->Legends[ index ]->AccessibilityObject;
         }

         return nullptr;
      }


   internal:

      // Helper function that is used by the CurveLegend's accessibility object
      // to navigate between sibiling controls. Specifically, this function is used in
      // the CurveLegend::CurveLegendAccessibleObject.Navigate function.
      AccessibleObject^ NavigateFromChild( CurveLegend::CurveLegendAccessibleObject^ child, AccessibleNavigation navdir )
      {
         switch ( navdir )
         {
            case AccessibleNavigation::Down:
            case AccessibleNavigation::Next:
               return GetChild( child->ID + 1 );

            case AccessibleNavigation::Up:
            case AccessibleNavigation::Previous:
               return GetChild( child->ID - 1 );
         }
         return nullptr;
      }


      // Helper function that is used by the CurveLegend's accessibility object
      // to select a specific CurveLegend control. Specifically, this function is used
      // in the CurveLegend::CurveLegendAccessibleObject.Select function.
      void SelectChild( CurveLegend::CurveLegendAccessibleObject^ child, AccessibleSelection selection )
      {
         int childID = child->ID;
         
         // Determine which selection action should occur, based on the
         // AccessibleSelection value.
         if ( (selection & AccessibleSelection::TakeSelection) != (AccessibleSelection)0 )
         {
            for ( int i = 0; i < chartControl->Legends->Length; i++ )
            {
               if ( i == childID )
               {
                  chartControl->Legends[ i ]->Selected = true;
               }
               else
               {
                  chartControl->Legends[ i ]->Selected = false;
               }

            }
            
            // AccessibleSelection->AddSelection means that the CurveLegend will be selected.
            if ( (selection & AccessibleSelection::AddSelection) != (AccessibleSelection)0 )
            {
               chartControl->Legends[ childID ]->Selected = true;
            }
            
            // AccessibleSelection->AddSelection means that the CurveLegend will be unselected.
            if ( (selection & AccessibleSelection::RemoveSelection) != (AccessibleSelection)0 )
            {
               chartControl->Legends[ childID ]->Selected = false;
            }
         }
      }

   };

   // class ChartControlAccessibleObject
};


// class ChartControl
public ref class Form1: public System::Windows::Forms::Form
{
private:

   // Test out the Chart Control.
   ChartControl^ chart1;

public:
   Form1()
   {
      
      // Create a chart control and add it to the form.
      this->chart1 = gcnew ChartControl;
      this->ClientSize = System::Drawing::Size( 920, 566 );
      this->chart1->Location = System::Drawing::Point( 47, 16 );
      this->chart1->Size = System::Drawing::Size( 600, 400 );
      this->Controls->Add( this->chart1 );
   }

};


// class Form1

[STAThread]
int main()
{
   Application::Run( gcnew Form1 );
}

using System;
using System.Drawing;
using System.Windows.Forms;

namespace ChartControl
{
    public class Form1 : System.Windows.Forms.Form
    {
        // Test out the Chart Control.
        private ChartControl chart1;

        [STAThread]
        static void Main() 
        {
            Application.Run(new Form1());
        }

        public Form1() {
            // Create a chart control and add it to the form.
            this.chart1 = new ChartControl();
            this.ClientSize = new System.Drawing.Size(920, 566);

            this.chart1.Location = new System.Drawing.Point(47, 16);
            this.chart1.Size = new System.Drawing.Size(600, 400);

            this.Controls.Add(this.chart1);
        }
    }

    // Declare a chart control that demonstrates accessibility in Windows Forms.
    public class ChartControl : System.Windows.Forms.UserControl
    {
        private CurveLegend legend1;
        private CurveLegend legend2; 

        public ChartControl()
        {
            // The ChartControl draws the chart in the OnPaint override.
            SetStyle(ControlStyles.ResizeRedraw, true);
            SetStyle(ControlStyles.DoubleBuffer, true);
            SetStyle(ControlStyles.AllPaintingInWmPaint, true);

            this.BackColor = System.Drawing.Color.White;
            this.Name = "ChartControl";

            this.Click += new System.EventHandler(this.ChartControl_Click);
            this.QueryAccessibilityHelp += 
                new System.Windows.Forms.QueryAccessibilityHelpEventHandler(
                                        this.ChartControl_QueryAccessibilityHelp);

            // The CurveLengend is not Control-based, it just
            // represents the parts of the legend.
            legend1 = new CurveLegend(this, "A");
            legend1.Location = new Point(20, 30);
            legend2 = new CurveLegend(this, "B");        
            legend2.Location = new Point(20, 50);
        }

        // Overridden to return the custom AccessibleObject 
        // for the entire chart.
        protected override AccessibleObject CreateAccessibilityInstance() 
        {            
            return new ChartControlAccessibleObject(this);
        }

        protected override void OnPaint(PaintEventArgs e) 
        {
            // The ChartControl draws the chart in the OnPaint override.
            base.OnPaint(e);

            Rectangle bounds = this.ClientRectangle;
            int border = 5;

            // Draws the legends first.
            StringFormat format = new StringFormat();
            format.Alignment = StringAlignment.Center;
            format.LineAlignment = StringAlignment.Center;
            
            if (legend1 != null) {
                if (legend1.Selected) {
                    e.Graphics.FillRectangle(new SolidBrush(Color.Blue), legend1.Bounds);
                } else {
                    e.Graphics.DrawRectangle(Pens.Blue, legend1.Bounds);
                }

                e.Graphics.DrawString(legend1.Name, this.Font, Brushes.Black, legend1.Bounds, format);                
            }
            if (legend2 != null) {
                if (legend2.Selected) {
                    e.Graphics.FillRectangle(new SolidBrush(Color.Red), legend2.Bounds);
                } else {
                    e.Graphics.DrawRectangle(Pens.Red, legend2.Bounds);
                }
                e.Graphics.DrawString(legend2.Name, this.Font, Brushes.Black, legend2.Bounds, format);
            }            

            // Charts out the actual curves that represent data in the Chart.
            bounds.Inflate(-border, -border);
            Point[] curve1 = new Point[] {new Point(bounds.Left, bounds.Bottom),
                            new Point(bounds.Left + bounds.Width / 3, bounds.Top + bounds.Height / 5),
                            new Point(bounds.Right - bounds.Width / 3, (bounds.Top + bounds.Bottom) / 2),
                            new Point(bounds.Right, bounds.Top)};

            Point[] curve2 = new Point[] {new Point(bounds.Left, bounds.Bottom - bounds.Height / 3),
                            new Point(bounds.Left + bounds.Width / 3, bounds.Top + bounds.Height / 5),
                            new Point(bounds.Right - bounds.Width / 3, (bounds.Top + bounds.Bottom) / 2),
                            new Point(bounds.Right, bounds.Top + bounds.Height / 2)};

            // Draws the actual curve only if it is selected.
            if (legend1.Selected) e.Graphics.DrawCurve(Pens.Blue, curve1);
            if (legend2.Selected) e.Graphics.DrawCurve(Pens.Red, curve2);

            e.Graphics.DrawRectangle(Pens.Blue, bounds);            
        }

        // Handles the QueryAccessibilityHelp event.
        private void ChartControl_QueryAccessibilityHelp(object sender, 
                                    System.Windows.Forms.QueryAccessibilityHelpEventArgs e)
        {            
            e.HelpString = "Displays chart data";
        }          

        // Handles the Click event for the chart. 
        // Toggles the selection of whatever legend was clicked on
        private void ChartControl_Click(object sender, System.EventArgs e)
        {
            Point pt = this.PointToClient(Control.MousePosition);
            if (legend1.Bounds.Contains(pt)) {
                legend1.Selected = !legend1.Selected;
            } else if (legend2.Bounds.Contains(pt)) {
                legend2.Selected = !legend2.Selected;
            }
        }

        // Gets an array of CurveLengends used in the Chart.
        public CurveLegend[] Legends
        {   
            get {                
                return new CurveLegend[] { legend1, legend2 };
            }            
        }                

        // Inner class ChartControlAccessibleObject represents accessible information associated with the ChartControl.
        // The ChartControlAccessibleObject is returned in the ChartControl.CreateAccessibilityInstance override.
        public class ChartControlAccessibleObject : ControlAccessibleObject
        {
            ChartControl chartControl;

            public ChartControlAccessibleObject(ChartControl ctrl) : base(ctrl) 
            {
                chartControl = ctrl;
            }

            // Gets the role for the Chart. This is used by accessibility programs.
            public override AccessibleRole Role
            {  
                get {
                    return AccessibleRole.Chart;
                }
            }

            // Gets the state for the Chart. This is used by accessibility programs.
            public override AccessibleStates State
            {  
                get {                    
                    return AccessibleStates.ReadOnly;
                }
            }

            // The CurveLegend objects are "child" controls in terms of accessibility so 
            // return the number of ChartLengend objects.
            public override int GetChildCount()
            {  
                return chartControl.Legends.Length;
            }

            // Gets the Accessibility object of the child CurveLegend idetified by index.
            public override AccessibleObject GetChild(int index)
            {  
                if (index >= 0 && index < chartControl.Legends.Length) {
                    return chartControl.Legends[index].AccessibilityObject;
                }                
                return null;
            }

            // Helper function that is used by the CurveLegend's accessibility object
            // to navigate between sibiling controls. Specifically, this function is used in
            // the CurveLegend.CurveLegendAccessibleObject.Navigate function.
            internal AccessibleObject NavigateFromChild(CurveLegend.CurveLegendAccessibleObject child, 
                                                        AccessibleNavigation navdir) 
            {  
                switch(navdir) {
                    case AccessibleNavigation.Down:
                    case AccessibleNavigation.Next:
                        return GetChild(child.ID + 1);
                        
                    case AccessibleNavigation.Up:
                    case AccessibleNavigation.Previous:
                        return GetChild(child.ID - 1);                        
                }
                return null;
            }

            // Helper function that is used by the CurveLegend's accessibility object
            // to select a specific CurveLegend control. Specifically, this function is used
            // in the CurveLegend.CurveLegendAccessibleObject.Select function.
            internal void SelectChild(CurveLegend.CurveLegendAccessibleObject child, AccessibleSelection selection) 
            {   
                int childID = child.ID;

                // Determine which selection action should occur, based on the
                // AccessibleSelection value.
                if ((selection & AccessibleSelection.TakeSelection) != 0) {
                    for(int i = 0; i < chartControl.Legends.Length; i++) {
                        if (i == childID) {
                            chartControl.Legends[i].Selected = true;                        
                        } else {
                            chartControl.Legends[i].Selected = false;
                        }
                    }

                    // AccessibleSelection.AddSelection means that the CurveLegend will be selected.
                    if ((selection & AccessibleSelection.AddSelection) != 0) {
                        chartControl.Legends[childID].Selected = true;                        
                    }

                    // AccessibleSelection.AddSelection means that the CurveLegend will be unselected.
                    if ((selection & AccessibleSelection.RemoveSelection) != 0) {
                        chartControl.Legends[childID].Selected = false;                        
                    }
                }            
            }
        }

        // Inner Class that represents a legend for a curve in the chart.
        public class CurveLegend 
        {
            private string name;
            private ChartControl chart;
            private CurveLegendAccessibleObject accObj;
            private bool selected = true;
            private Point location;

            public CurveLegend(ChartControl chart, string name) 
            {
                this.chart = chart;
                this.name = name;
            }

            // Gets the accessibility object for the curve legend.
            public AccessibleObject AccessibilityObject
            {
                get
                {
                    accObj ??= new CurveLegendAccessibleObject(this);
                    return accObj;
                }
            }
            
            // Gets the bounds for the curve legend.
            public Rectangle Bounds
            {   
                get
                {
                    return new Rectangle(Location, Size);
                }
            }

            // Gets or sets the location for the curve legend.
            public Point Location
            {   
                get {
                    return location;
                }
                set {
                    location = value;
                    chart.Invalidate();

                    // Notifies the chart of the location change. This is used for
                    // the accessibility information. AccessibleEvents.LocationChange
                    // tells the chart the reason for the notification.

                    chart.AccessibilityNotifyClients(AccessibleEvents.LocationChange, 
                        ((CurveLegendAccessibleObject)AccessibilityObject).ID);
                }
            }            
        
            // Gets or sets the Name for the curve legend.
            public string Name
            {   
                get {
                    return name;
                }
                set {
                    if (name != value) 
                    {
                        name = value;
                        chart.Invalidate();

                        // Notifies the chart of the name change. This is used for
                        // the accessibility information. AccessibleEvents.NameChange
                        // tells the chart the reason for the notification.

                        chart.AccessibilityNotifyClients(AccessibleEvents.NameChange, 
                            ((CurveLegendAccessibleObject)AccessibilityObject).ID);
                    }
                }
            }

            // Gets or sets the Selected state for the curve legend.
            public bool Selected
            {   
                get {
                    return selected;
                }
                set {
                    if (selected != value) 
                    {
                        selected = value;
                        chart.Invalidate();

                        // Notifies the chart of the selection value change. This is used for
                        // the accessibility information. The AccessibleEvents value depends upon
                        // if the selection is true (AccessibleEvents.SelectionAdd) or 
                        // false (AccessibleEvents.SelectionRemove).
                        chart.AccessibilityNotifyClients(
                            selected ? AccessibleEvents.SelectionAdd : AccessibleEvents.SelectionRemove, 
                            ((CurveLegendAccessibleObject)AccessibilityObject).ID);
                    }
                }
            }

            // Gets the Size for the curve legend.
            public Size Size
            {   
                get {                    
                    int legendHeight = chart.Font.Height + 4;
                    Graphics g = chart.CreateGraphics();
                    int legendWidth = (int)g.MeasureString(Name, chart.Font).Width + 4;            

                    return new Size(legendWidth, legendHeight);
                }
            }
    
            // Inner class CurveLegendAccessibleObject represents accessible information 
            // associated with the CurveLegend object.
            public class CurveLegendAccessibleObject : AccessibleObject
            {
                private CurveLegend curveLegend;

                public CurveLegendAccessibleObject(CurveLegend curveLegend) : base() 
                {
                    this.curveLegend = curveLegend;                    
                }                

                // Private property that helps get the reference to the parent ChartControl.
                private ChartControlAccessibleObject ChartControl
                {   
                    get {
                        return Parent as ChartControlAccessibleObject;
                    }
                }

                // Internal helper function that returns the ID for this CurveLegend.
                internal int ID
                {
                    get {
                        for(int i = 0; i < ChartControl.GetChildCount(); i++) {
                            if (ChartControl.GetChild(i) == this) {
                                return i;
                            }
                        }
                        return -1;
                    }
                }

                // Gets the Bounds for the CurveLegend. This is used by accessibility programs.
                public override Rectangle Bounds
                {
                    get {                        
                        // The bounds is in screen coordinates.
                        Point loc = curveLegend.Location;
                        return new Rectangle(curveLegend.chart.PointToScreen(loc), curveLegend.Size);
                    }
                }

                // Gets or sets the Name for the CurveLegend. This is used by accessibility programs.
                public override string Name
                {
                    get {
                        return curveLegend.Name;
                    }
                    set {
                        curveLegend.Name = value;                        
                    }
                }

                // Gets the Curve Legend Parent's Accessible object.
                // This is used by accessibility programs.
                public override AccessibleObject Parent
                {
                    get {
                        return curveLegend.chart.AccessibilityObject;
                    }
                }

                // Gets the role for the CurveLegend. This is used by accessibility programs.
                public override AccessibleRole Role 
                {
                    get {
                        return AccessibleRole.StaticText;
                    }
                }

                // Gets the state based on the selection for the CurveLegend. 
                // This is used by accessibility programs.
                public override AccessibleStates State 
                {
                    get {
                        AccessibleStates state = AccessibleStates.Selectable;
                        if (curveLegend.Selected) 
                        {
                            state |= AccessibleStates.Selected;
                        }
                        return state;
                    }
                }

                // Navigates through siblings of this CurveLegend. This is used by accessibility programs.
                public override AccessibleObject Navigate(AccessibleNavigation navdir) 
                {
                    // Uses the internal NavigateFromChild helper function that exists
                    // on ChartControlAccessibleObject.
                    return ChartControl.NavigateFromChild(this, navdir);
                }

                // Selects or unselects this CurveLegend. This is used by accessibility programs.
                public override void Select(AccessibleSelection selection) 
                {
                    // Uses the internal SelectChild helper function that exists
                    // on ChartControlAccessibleObject.
                    ChartControl.SelectChild(this, selection);
                }
            }
        }
    }
}

Option Explicit

Imports System.Drawing
Imports System.Windows.Forms

Namespace ChartControlNameSpace
    
    Public Class Form1 
        Inherits System.Windows.Forms.Form

        ' Test out the Chart Control.
        Private chart1 As ChartControl

        <System.STAThread()> _
        Public Shared Sub Main()
            System.Windows.Forms.Application.Run(New Form1())
        End Sub

        Public Sub New() 
            ' Create a chart control and add it to the form.
            Me.chart1 = New ChartControl()
            Me.ClientSize = New System.Drawing.Size(920, 566)

            Me.chart1.Location = New System.Drawing.Point(47, 16)
            Me.chart1.Size = New System.Drawing.Size(600, 400)

            Me.Controls.Add(Me.chart1)
        End Sub
    End Class

    ' Declares a chart control that demonstrates Accessibility in Windows Forms.
    Public Class ChartControl
        Inherits System.Windows.Forms.UserControl

        Private legend1 As CurveLegend
        Private legend2 As CurveLegend
        
        Public Sub New()
            ' The ChartControl draws the chart in the OnPaint override.
            SetStyle(ControlStyles.ResizeRedraw, True)
            SetStyle(ControlStyles.DoubleBuffer, True)
            SetStyle(ControlStyles.AllPaintingInWmPaint, True)
            
            Me.BackColor = System.Drawing.Color.White
            Me.Name = "ChartControl"

            ' The CurveLengend is not Control-based, it just
            ' represent the parts of the legend.
            legend1 = New CurveLegend(Me, "A")
            legend1.Location = New Point(20, 30)
            legend2 = New CurveLegend(Me, "B")
            legend2.Location = New Point(20, 50)
        End Sub
              
        ' Overridden to return the custom AccessibleObject 
        ' for the entire chart.
        Protected Overrides Function CreateAccessibilityInstance() As AccessibleObject
            Return New ChartControlAccessibleObject(Me)
        End Function 

        Protected Overrides Sub OnPaint(e As PaintEventArgs)
            ' The ChartControl draws the chart in the OnPaint override.
            MyBase.OnPaint(e)
            
            Dim bounds As Rectangle = Me.ClientRectangle
            Dim border As Integer = 5
            
            ' Draw the legends first.
            Dim format As New StringFormat()
            format.Alignment = StringAlignment.Center
            format.LineAlignment = StringAlignment.Center
            
            If (legend1 IsNot Nothing) Then
                If legend1.Selected Then
                    e.Graphics.FillRectangle(New SolidBrush(Color.Blue), legend1.Bounds)
                Else
                    e.Graphics.DrawRectangle(Pens.Blue, legend1.Bounds)
                End If
                e.Graphics.DrawString(legend1.Name, Me.Font, Brushes.Black, RectangleF.op_Implicit(legend1.Bounds), format)
            End If
            If (legend2 IsNot Nothing) Then
                If legend2.Selected Then
                    e.Graphics.FillRectangle(New SolidBrush(Color.Red), legend2.Bounds)
                Else
                    e.Graphics.DrawRectangle(Pens.Red, legend2.Bounds)
                End If
                e.Graphics.DrawString(legend2.Name, Me.Font, Brushes.Black, RectangleF.op_Implicit(legend2.Bounds), format)
            End If
            
            ' Chart out the actual curves that represent data in the Chart.
            bounds.Inflate(-border, -border)
            Dim curve1() As Point = {New Point(bounds.Left, bounds.Bottom), _
                                     New Point(bounds.Left + bounds.Width / 3, bounds.Top + bounds.Height / 5), _
                                     New Point(bounds.Right - bounds.Width / 3,(bounds.Top + bounds.Bottom) / 2), _
                                     New Point(bounds.Right, bounds.Top)}

            Dim curve2() As Point = {New Point(bounds.Left, bounds.Bottom - bounds.Height / 3), _
                                     New Point(bounds.Left + bounds.Width / 3, bounds.Top + bounds.Height / 5), _
                                     New Point(bounds.Right - bounds.Width / 3,(bounds.Top + bounds.Bottom) / 2), _
                                     New Point(bounds.Right, bounds.Top + bounds.Height / 2)}
            
            ' Draw the actual curve only if it is selected.
            If legend1.Selected Then
                e.Graphics.DrawCurve(Pens.Blue, curve1)
            End If
            If legend2.Selected Then
                e.Graphics.DrawCurve(Pens.Red, curve2)
            End If 
            e.Graphics.DrawRectangle(Pens.Blue, bounds)
        End Sub
        
        ' Handle the QueryAccessibilityHelp event.
        Private Sub ChartControl_QueryAccessibilityHelp(sender As Object, _
                           e As System.Windows.Forms.QueryAccessibilityHelpEventArgs) Handles MyBase.QueryAccessibilityHelp
            e.HelpString = "Displays chart data"
        End Sub 

        ' Handle the Click event for the chart. 
        ' Toggle the selection of whatever legend was clicked.     
        Private Sub ChartControl_Click(sender As Object, e As System.EventArgs) Handles MyBase.Click

            Dim pt As Point = Me.PointToClient(Control.MousePosition)
            If legend1.Bounds.Contains(pt) Then
                legend1.Selected = Not legend1.Selected
            Else
                If legend2.Bounds.Contains(pt) Then
                    legend2.Selected = Not legend2.Selected
                End If
            End If
        End Sub

        ' Get an array of the CurveLengends used in the Chart.
        Public ReadOnly Property Legends() As CurveLegend()
            Get
                Return New CurveLegend() {legend1, legend2}
            End Get
        End Property
        
        Protected Sub ExposeAccessibilityNotifyClients(ByVal accEvent As AccessibleEvents, ByVal childID As Integer)
            AccessibilityNotifyClients(accEvent, childID) 
        End Sub

        ' Inner Class ChartControlAccessibleObject represents accessible information 
        ' associated with the ChartControl.
        ' The ChartControlAccessibleObject is returned in the         ' ChartControl.CreateAccessibilityInstance override.
        Public Class ChartControlAccessibleObject
            Inherits Control.ControlAccessibleObject

            Private chartControl As ChartControl
            
            Public Sub New(ctrl As ChartControl)
                MyBase.New(ctrl)
                chartControl = ctrl
            End Sub
            
            ' Get the role for the Chart. This is used by accessibility programs.            
            Public Overrides ReadOnly Property Role() As AccessibleRole
                Get
                    Return System.Windows.Forms.AccessibleRole.Chart
                End Get
            End Property
            
            ' Get the state for the Chart. This is used by accessibility programs.            
            Public Overrides ReadOnly Property State() As AccessibleStates
                Get
                    Return AccessibleStates.ReadOnly
                End Get
            End Property                        
            
            ' The CurveLegend objects are "child" controls in terms of accessibility so 
            ' return the number of ChartLengend objects.            
            Public Overrides Function GetChildCount() As Integer
                Return chartControl.Legends.Length
            End Function 
            
            ' Get the Accessibility object of the child CurveLegend idetified by index.
            Public Overrides Function GetChild(index As Integer) As AccessibleObject
                If index >= 0 And index < chartControl.Legends.Length Then
                    Return chartControl.Legends(index).AccessibilityObject
                End If
                Return Nothing
            End Function 
            
            ' Helper function that is used by the CurveLegend's accessibility object
            ' to navigate between sibiling controls. Specifically, this function is used in
            ' the CurveLegend.CurveLegendAccessibleObject.Navigate function.
            Friend Function NavigateFromChild(child As CurveLegend.CurveLegendAccessibleObject, _
                                            navdir As AccessibleNavigation) As AccessibleObject
                Select Case navdir
                    Case AccessibleNavigation.Down, AccessibleNavigation.Next
                            Return GetChild(child.ID + 1)
                    
                    Case AccessibleNavigation.Up, AccessibleNavigation.Previous
                            Return GetChild(child.ID - 1)
                End Select
                Return Nothing
            End Function            

            ' Helper function that is used by the CurveLegend's accessibility object
            ' to select a specific CurveLegend control. Specifically, this function is used 
            ' in the CurveLegend.CurveLegendAccessibleObject.Select function.            
            Friend Sub SelectChild(child As CurveLegend.CurveLegendAccessibleObject, selection As AccessibleSelection)
                Dim childID As Integer = child.ID
                
                ' Determine which selection action should occur, based on the
                ' AccessibleSelection value.
                If (selection And AccessibleSelection.TakeSelection) <> 0 Then
                    Dim i As Integer
                    For i = 0 To chartControl.Legends.Length - 1
                        If i = childID Then
                            chartControl.Legends(i).Selected = True
                        Else
                            chartControl.Legends(i).Selected = False
                        End If
                    Next i
                    
                    ' AccessibleSelection.AddSelection means that the CurveLegend will be selected.
                    If (selection And AccessibleSelection.AddSelection) <> 0 Then
                        chartControl.Legends(childID).Selected = True
                    End If

                    ' AccessibleSelection.AddSelection means that the CurveLegend will be unselected.                    
                    If (selection And AccessibleSelection.RemoveSelection) <> 0 Then
                        chartControl.Legends(childID).Selected = False
                    End If
                End If
            End Sub
        End Class

        ' Inner Class that represents a legend for a curve in the chart.
        Public Class CurveLegend
            Private m_name As String
            Private chart As ChartControl
            Private accObj As CurveLegendAccessibleObject
            Private m_selected As Boolean = True
            Private m_location As Point
            
            Public Sub New(chart As ChartControl, name As String)
                Me.chart = chart
                Me.m_name = name
            End Sub

            ' Gets the accessibility object for the curve legend.            
            Public ReadOnly Property AccessibilityObject() As AccessibleObject
                Get
                    If accObj Is Nothing Then
                        accObj = New CurveLegendAccessibleObject(Me)
                    End If
                    Return accObj
                End Get
            End Property
            
            ' Gets the bounds for the curve legend.            
            Public ReadOnly Property Bounds() As Rectangle
                Get
                    Return New Rectangle(Location, Size)
                End Get
            End Property

            ' Gets or sets the location for the curve legend.            
            Public Property Location() As Point
                Get
                    Return m_location
                End Get
                Set
                    m_location = value
                    chart.Invalidate()

                    ' Notifies the chart of the location change. This is used for
                    ' the accessibility information. AccessibleEvents.LocationChange
                    ' tells the chart the reason for the notification.
                    chart.ExposeAccessibilityNotifyClients(AccessibleEvents.LocationChange, _
                            CType(AccessibilityObject, CurveLegendAccessibleObject).ID)
                End Set
            End Property
            
            ' Gets or sets the Name for the curve legend.            
            Public Property Name() As String
                Get
                    Return m_name
                End Get
                Set
                    If m_name <> value Then
                        m_name = value
                        chart.Invalidate()

                        ' Notifies the chart of the name change. This is used for
                        ' the accessibility information. AccessibleEvents.NameChange
                        ' tells the chart the reason for the notification. 
                        chart.ExposeAccessibilityNotifyClients(AccessibleEvents.NameChange, _
                                CType(AccessibilityObject, CurveLegendAccessibleObject).ID)
                    End If
                End Set
            End Property
            
            ' Gets or sets the Selected state for the curve legend.            
            Public Property Selected() As Boolean
                Get
                    Return m_selected
                End Get
                Set
                    If m_selected <> value Then
                        m_selected = value
                        chart.Invalidate()

                        ' Notifies the chart of the selection value change. This is used for
                        ' the accessibility information. The AccessibleEvents value varies
                        ' on whether the selection is true (AccessibleEvents.SelectionAdd) or 
                        ' false (AccessibleEvents.SelectionRemove). 
                        If m_selected Then
                            chart.ExposeAccessibilityNotifyClients(AccessibleEvents.SelectionAdd, _
                                    CType(AccessibilityObject, CurveLegendAccessibleObject).ID) 
                        Else
                            chart.ExposeAccessibilityNotifyClients(AccessibleEvents.SelectionRemove, _
                                    CType(AccessibilityObject, CurveLegendAccessibleObject).ID) 
                        End If
                    End If
                End Set
            End Property
            
            ' Gets the Size for the curve legend.            
            Public ReadOnly Property Size() As Size
                Get
                    Dim legendHeight As Integer = chart.Font.Height + 4
                    Dim g As Graphics = chart.CreateGraphics()
                    Dim legendWidth As Integer = CInt(g.MeasureString(Name, chart.Font).Width) + 4
                    
                    Return New Size(legendWidth, legendHeight)
                End Get
            End Property
            
            
            ' Inner class CurveLegendAccessibleObject represents accessible information 
            ' associated with the CurveLegend object.
            Public Class CurveLegendAccessibleObject
                Inherits AccessibleObject

                Private curveLegend As CurveLegend
                
                Public Sub New(curveLegend As CurveLegend)
                    Me.curveLegend = curveLegend
                End Sub
                
                ' Private property that helps get the reference to the parent ChartControl.                
                Private ReadOnly Property ChartControl() As ChartControlAccessibleObject
                    Get
                        Return CType(Parent, ChartControlAccessibleObject)
                    End Get
                End Property

                ' Friend helper function that returns the ID for this CurveLegend.                
                Friend ReadOnly Property ID() As Integer
                    Get
                        Dim i As Integer
                        For i = 0 To (ChartControl.GetChildCount()) - 1
                            If ChartControl.GetChild(i) Is Me Then
                                Return i
                            End If
                        Next i
                        Return - 1
                    End Get
                End Property
                
                ' Gets the Bounds for the CurveLegend. This is used by accessibility programs.
                Public Overrides ReadOnly Property Bounds() As Rectangle
                    Get
                        ' The bounds is in screen coordinates.
                        Dim loc As Point = curveLegend.Location
                        Return New Rectangle(curveLegend.chart.PointToScreen(loc), curveLegend.Size)
                    End Get
                End Property

                ' Gets or sets the Name for the CurveLegend. This is used by accessibility programs.                
                Public Overrides Property Name() As String
                    Get
                        Return curveLegend.Name
                    End Get
                    Set
                        curveLegend.Name = value
                    End Set
                End Property
                
                ' Gets the Curve Legend Parent's Accessible object.
                ' This is used by accessibility programs.                
                Public Overrides ReadOnly Property Parent() As AccessibleObject
                    Get
                        Return curveLegend.chart.AccessibilityObject
                    End Get
                End Property
                
                ' Gets the role for the CurveLegend. This is used by accessibility programs.                
                Public Overrides ReadOnly Property Role() As AccessibleRole
                    Get
                        Return System.Windows.Forms.AccessibleRole.StaticText
                    End Get
                End Property

                ' Gets the state based on the selection for the CurveLegend. 
                ' This is used by accessibility programs.                
                Public Overrides ReadOnly Property State() As AccessibleStates
                    Get
                        Dim stateTemp As AccessibleStates = AccessibleStates.Selectable
                        If curveLegend.Selected Then
                            stateTemp = stateTemp Or AccessibleStates.Selected
                        End If
                        Return stateTemp
                    End Get
                End Property
                
                ' Navigates through siblings of this CurveLegend. This is used by accessibility programs.                
                Public Overrides Function Navigate(navdir As AccessibleNavigation) As AccessibleObject
                    ' Use the Friend NavigateFromChild helper function that exists
                    ' on ChartControlAccessibleObject.
                    Return ChartControl.NavigateFromChild(Me, navdir)
                End Function
                
                ' Selects or unselects this CurveLegend. This is used by accessibility programs.
                Public Overrides Sub [Select](selection As AccessibleSelection)

                    ' Use the internal SelectChild helper function that exists
                    ' on ChartControlAccessibleObject.
                    ChartControl.SelectChild(Me, selection)
                End Sub

            End Class

        End Class

    End Class

End Namespace 'ChartControlNameSpace

Observações

As aplicações de acessibilidade podem ajustar as funcionalidades da aplicação para melhorar a usabilidade para utilizadores com deficiência.

Para utilizadores com deficiência visual, pode ajustar funcionalidades de software e sistema operativo para satisfazer as suas necessidades. Por exemplo, pode ampliar texto e imagens e renderizá-los com contraste. Além disso, pode acomodar o daltonismo com o uso adequado das cores. Para utilizadores com deficiência visual grave, os computadores são acessíveis com auxílios de revisão de ecrã que traduzem texto para fala no ecrã ou para um ecrã Braille dinâmico e atualizável.

Para utilizadores com deficiência auditiva, pode desenhar programas que utilizem pistas visuais, como uma barra de ferramentas intermitente; Ou pode mostrar mensagens faladas como texto. Por exemplo, quando ativada, a funcionalidade SoundSentry, uma opção de acessibilidade no Painel de Controlo, fornece um aviso visual sempre que o sistema emite um som de alarme.

Para utilizadores com deficiências de movimento, pode desenhar controlos que refinam ou eliminam o uso de teclado e rato, melhorando assim a acessibilidade ao computador. O Painel de Controlo oferece assistência. Por exemplo, uma alternativa é usar o teclado numérico em vez do rato para a navegação. Outra opção, chamada StickyKeys, permite que utilizadores que não conseguem manter pressionadas duas ou mais teclas ao mesmo tempo (como CTRL+P) obtenham o mesmo resultado ao digitar uma tecla de cada vez.

Para utilizadores com deficiências cognitivas e linguísticas, pode conceber programas de software que melhor se adaptem às suas necessidades. Por exemplo, usar sequenciação visível ou com sinais, exibições simples, menos palavras e um nível de leitura direcionado para os padrões do ensino básico pode beneficiar estes utilizadores.

Para utilizadores com distúrbios convulsivos, pode conceber programas de software para eliminar padrões provocadores de convulsões.

Para mais informações sobre acessibilidade, incluindo informações sobre aplicações de acessibilidade, consulte Windows Funcionalidades de acessibilidade.

Notas para Herdeiros

Quando herdas desta classe, podes sobrepor todos os membros.