BufferedGraphics Classe

Definizione

Fornisce un buffer grafico per il doppio buffer.Provides a graphics buffer for double buffering.

public ref class BufferedGraphics sealed : IDisposable
public sealed class BufferedGraphics : IDisposable
type BufferedGraphics = class
    interface IDisposable
Public NotInheritable Class BufferedGraphics
Implements IDisposable
Ereditarietà
BufferedGraphics
Implementazioni

Esempi

Nell'esempio di codice riportato di seguito BufferedGraphics viene illustrato l'utilizzo di un oggetto per creare elementi grafici utilizzando diversi tipi di implementazioni di buffering.The following code example demonstrates using a BufferedGraphics object to draw graphics using several types of buffering implementations. Quando si fa clic sul form viene avviato in modo alternativo e viene arrestato un timer che provoca gli aggiornamenti di tipo.Clicking the form alternately starts and stops a timer that causes draw updates. Gli aggiornamenti di estrazione consentono di osservare l'effetto del doppio buffer.The draw updates allow you to observe the effect of double buffering. Il clic con il pulsante destro del mouse sul modulo scorre le modalità di disegno seguenti:Right-clicking the form cycles through the following drawing modes:

In ogni modalità viene disegnato un testo che identifica la modalità corrente e descrive il comportamento che si verifica quando viene premuto ogni pulsante del mouse.In each mode, text is drawn that identifies the current mode and describes the behavior that occurs when each mouse button is pressed.

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

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

namespace BufferingExample
{
   public ref class BufferingExample: public Form
   {
   private:
      BufferedGraphicsContext^ context;
      BufferedGraphics^ grafx;
      Byte bufferingMode;
      array<String^>^bufferingModeStrings;
      System::Windows::Forms::Timer^ timer1;
      Byte count;

   public:
      BufferingExample()
         : Form()
      {
         array<String^>^tempStrings = {"Draw to Form without OptimizedDoubleBufferring control style","Draw to Form using OptimizedDoubleBuffering control style","Draw to HDC for form"};
         bufferingModeStrings = tempStrings;

         // Configure the Form for this example.
         this->Text = "User double buffering";
         this->MouseDown += gcnew MouseEventHandler( this, &BufferingExample::MouseDownHandler );
         this->Resize += gcnew EventHandler( this, &BufferingExample::OnResize );
         this->SetStyle( static_cast<ControlStyles>(ControlStyles::AllPaintingInWmPaint | ControlStyles::UserPaint), true );

         // Configure a timer to draw graphics updates.
         timer1 = gcnew System::Windows::Forms::Timer;
         timer1->Interval = 200;
         timer1->Tick += gcnew EventHandler( this, &BufferingExample::OnTimer );
         bufferingMode = 2;
         count = 0;

         // Retrieves the BufferedGraphicsContext for the 
         // current application domain.
         context = BufferedGraphicsManager::Current;

         // Sets the maximum size for the primary graphics buffer
         // of the buffered graphics context for the application
         // domain.  Any allocation requests for a buffer larger 
         // than this will create a temporary buffered graphics 
         // context to host the graphics buffer.
         context->MaximumBuffer = System::Drawing::Size( this->Width + 1, this->Height + 1 );

         // Allocates a graphics buffer the size of this form
         // using the pixel format of the Graphics created by 
         // the Form.CreateGraphics() method, which returns a 
         // Graphics object that matches the pixel format of the form.
         grafx = context->Allocate( this->CreateGraphics(), Rectangle(0,0,this->Width,this->Height) );

         // Draw the first frame to the buffer.
         DrawToBuffer( grafx->Graphics );
      }

   private:
      void MouseDownHandler( Object^ /*sender*/, MouseEventArgs^ e )
      {
         if ( e->Button == ::MouseButtons::Right )
         {
            // Cycle the buffering mode.
            if ( ++bufferingMode > 2 )
                        bufferingMode = 0;

            // If the previous buffering mode used 
            // the OptimizedDoubleBuffering ControlStyle,
            // disable the control style.
            if ( bufferingMode == 1 )
                        this->SetStyle( ControlStyles::OptimizedDoubleBuffer, true );

            // If the current buffering mode uses
            // the OptimizedDoubleBuffering ControlStyle,
            // enabke the control style.
            if ( bufferingMode == 2 )
                        this->SetStyle( ControlStyles::OptimizedDoubleBuffer, false );

            // Cause the background to be cleared and redraw.
            count = 6;
            DrawToBuffer( grafx->Graphics );
            this->Refresh();
         }
         else
         {
            
            // Toggle whether the redraw timer is active.
            if ( timer1->Enabled )
                        timer1->Stop();
            else
                        timer1->Start();
         }
      }

   private:
      void OnTimer( Object^ /*sender*/, EventArgs^ /*e*/ )
      {
         // Draw randomly positioned ellipses to the buffer.
         DrawToBuffer( grafx->Graphics );

         // If in bufferingMode 2, draw to the form's HDC.
         if ( bufferingMode == 2 )

         // Render the graphics buffer to the form's HDC.
         grafx->Render( Graphics::FromHwnd( this->Handle ) );
         // If in bufferingMode 0 or 1, draw in the paint method.
         else

         // If in bufferingMode 0 or 1, draw in the paint method.
         this->Refresh();
      }

      void OnResize( Object^ /*sender*/, EventArgs^ /*e*/ )
      {
         // Re-create the graphics buffer for a new window size.
         context->MaximumBuffer = System::Drawing::Size( this->Width + 1, this->Height + 1 );
         if ( grafx != nullptr )
         {
            delete grafx;
            grafx = nullptr;
         }

         grafx = context->Allocate( this->CreateGraphics(), Rectangle(0,0,this->Width,this->Height) );

         // Cause the background to be cleared and redraw.
         count = 6;
         DrawToBuffer( grafx->Graphics );
         this->Refresh();
      }

      void DrawToBuffer( Graphics^ g )
      {
         // Clear the graphics buffer every five updates.
         if ( ++count > 5 )
         {
            count = 0;
            grafx->Graphics->FillRectangle( Brushes::Black, 0, 0, this->Width, this->Height );
         }

         // Draw randomly positioned and colored ellipses.
         Random^ rnd = gcnew Random;
         for ( int i = 0; i < 20; i++ )
         {
            int px = rnd->Next( 20, this->Width - 40 );
            int py = rnd->Next( 20, this->Height - 40 );
            g->DrawEllipse( gcnew Pen( Color::FromArgb( rnd->Next( 0, 255 ), rnd->Next( 0, 255 ), rnd->Next( 0, 255 ) ), 1.0f ), px, py, px + rnd->Next( 0, this->Width - px - 20 ), py + rnd->Next( 0, this->Height - py - 20 ) );
         }

         // Draw information strings.
         g->DrawString( String::Format( "Buffering Mode: {0}", bufferingModeStrings[ bufferingMode ] ), gcnew System::Drawing::Font( "Arial",8 ), Brushes::White, 10, 10 );
         g->DrawString( "Right-click to cycle buffering mode", gcnew System::Drawing::Font( "Arial",8 ), Brushes::White, 10, 22 );
         g->DrawString( "Left-click to toggle timed display refresh", gcnew System::Drawing::Font( "Arial",8 ), Brushes::White, 10, 34 );
      }

   protected:
      virtual void OnPaint( PaintEventArgs^ e ) override
      {
         grafx->Render( e->Graphics );
      }
   };
}

[STAThread]
int main()
{
   Application::Run( gcnew BufferingExample::BufferingExample );
}
using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;

namespace BufferingExample 
{
    public class BufferingExample : Form
    {
        private BufferedGraphicsContext context;
        private BufferedGraphics grafx;

    private byte bufferingMode;
    private string[] bufferingModeStrings = 
        { "Draw to Form without OptimizedDoubleBufferring control style",
          "Draw to Form using OptimizedDoubleBuffering control style",
          "Draw to HDC for form" };

    private System.Windows.Forms.Timer timer1;
    private byte count;

        public BufferingExample() : base()
        {
            // Configure the Form for this example.
            this.Text = "User double buffering";
            this.MouseDown += new MouseEventHandler(this.MouseDownHandler);
            this.Resize += new EventHandler(this.OnResize);
            this.SetStyle( ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint, true );

            // Configure a timer to draw graphics updates.
        timer1 = new System.Windows.Forms.Timer();
        timer1.Interval = 200;
        timer1.Tick += new EventHandler(this.OnTimer);

        bufferingMode = 2;
        count = 0;

            // Retrieves the BufferedGraphicsContext for the 
            // current application domain.
            context = BufferedGraphicsManager.Current;

            // Sets the maximum size for the primary graphics buffer
            // of the buffered graphics context for the application
            // domain.  Any allocation requests for a buffer larger 
            // than this will create a temporary buffered graphics 
            // context to host the graphics buffer.
            context.MaximumBuffer = new Size(this.Width+1, this.Height+1);

            // Allocates a graphics buffer the size of this form
            // using the pixel format of the Graphics created by 
            // the Form.CreateGraphics() method, which returns a 
            // Graphics object that matches the pixel format of the form.
            grafx = context.Allocate(this.CreateGraphics(), 
                 new Rectangle( 0, 0, this.Width, this.Height ));

        // Draw the first frame to the buffer.
        DrawToBuffer(grafx.Graphics);
        }

    private void MouseDownHandler(object sender, MouseEventArgs e)
        {
        if( e.Button == MouseButtons.Right )
        {
                 // Cycle the buffering mode.
             if( ++bufferingMode > 2 )
                     bufferingMode = 0;

                 // If the previous buffering mode used 
                 // the OptimizedDoubleBuffering ControlStyle,
                 // disable the control style.
                 if( bufferingMode == 1 )
                     this.SetStyle( ControlStyles.OptimizedDoubleBuffer, true );

                 // If the current buffering mode uses
                 // the OptimizedDoubleBuffering ControlStyle,
                 // enabke the control style.
                 if( bufferingMode == 2 )
                     this.SetStyle( ControlStyles.OptimizedDoubleBuffer, false );

                 // Cause the background to be cleared and redraw.
                 count = 6;
                 DrawToBuffer(grafx.Graphics);                 
         this.Refresh();
        }
        else
        {
                // Toggle whether the redraw timer is active.
        if( timer1.Enabled )
            timer1.Stop();
        else
            timer1.Start(); 
        }
        }

    private void OnTimer(object sender, EventArgs e)
    {
            // Draw randomly positioned ellipses to the buffer.
        DrawToBuffer(grafx.Graphics);

            // If in bufferingMode 2, draw to the form's HDC.
        if( bufferingMode == 2 )            
                    // Render the graphics buffer to the form's HDC.
            grafx.Render(Graphics.FromHwnd(this.Handle));            
            // If in bufferingMode 0 or 1, draw in the paint method.
        else
            this.Refresh();
    }

        private void OnResize(object sender, EventArgs e)
        {
           // Re-create the graphics buffer for a new window size.
           context.MaximumBuffer = new Size(this.Width+1, this.Height+1);
           if( grafx != null )
           {
           grafx.Dispose();
               grafx = null;               
           }
           grafx = context.Allocate(this.CreateGraphics(), 
               new Rectangle( 0, 0, this.Width, this.Height ));
           
           // Cause the background to be cleared and redraw.
           count = 6;
           DrawToBuffer(grafx.Graphics);                 
       this.Refresh();
        }	

    private void DrawToBuffer(Graphics g)
    {
            // Clear the graphics buffer every five updates.
        if( ++count > 5 )
            {
                count = 0;                
                grafx.Graphics.FillRectangle(Brushes.Black, 0, 0, this.Width, this.Height);
            }

            // Draw randomly positioned and colored ellipses.
        Random rnd = new Random();
        for( int i=0; i<20; i++ )
        {
        int px = rnd.Next(20,this.Width-40);
        int py = rnd.Next(20,this.Height-40);
        g.DrawEllipse(new Pen(Color.FromArgb(rnd.Next(0, 255), rnd.Next(0,255), rnd.Next(0,255)), 1), 
            px, py, px+rnd.Next(0, this.Width-px-20), py+rnd.Next(0, this.Height-py-20)); 	    			
        }

            // Draw information strings.
        g.DrawString("Buffering Mode: "+bufferingModeStrings[bufferingMode], new Font("Arial", 8), Brushes.White, 10, 10);
            g.DrawString("Right-click to cycle buffering mode", new Font("Arial", 8), Brushes.White, 10, 22);
            g.DrawString("Left-click to toggle timed display refresh", new Font("Arial", 8), Brushes.White, 10, 34);
    }

    protected override void OnPaint(PaintEventArgs e)
        {            
        grafx.Render(e.Graphics);
    }

        [STAThread]
        public static void Main(string[] args)
        {
        Application.Run(new BufferingExample());
        }
    }
}
Imports System.ComponentModel
Imports System.Drawing
Imports System.Windows.Forms

Public Class BufferingExample
    Inherits Form
    Private context As BufferedGraphicsContext
    Private grafx As BufferedGraphics
    
    Private bufferingMode As Byte
    Private bufferingModeStrings As String() = _
        {"Draw to Form without OptimizedDoubleBufferring control style", _
         "Draw to Form using OptimizedDoubleBuffering control style", _
         "Draw to HDC for form"}
    
    Private timer1 As System.Windows.Forms.Timer
    Private count As Byte    
    
    Public Sub New()
        ' Configure the Form for this example.
        Me.Text = "User double buffering"
        AddHandler Me.MouseDown, AddressOf Me.MouseDownHandler
        AddHandler Me.Resize, AddressOf Me.ResizeHandler
        Me.SetStyle(ControlStyles.AllPaintingInWmPaint Or ControlStyles.UserPaint, True)
        
        ' Configure a timer to draw graphics updates.
        timer1 = New System.Windows.Forms.Timer()
        timer1.Interval = 200
        AddHandler timer1.Tick, AddressOf Me.OnTimer
        
        bufferingMode = 2
        count = 0
        
        ' Retrieves the BufferedGraphicsContext for the 
        ' current application domain.
        context = BufferedGraphicsManager.Current
        
        ' Sets the maximum size for the primary graphics buffer
        ' of the buffered graphics context for the application
        ' domain.  Any allocation requests for a buffer larger 
        ' than this will create a temporary buffered graphics 
        ' context to host the graphics buffer.
        context.MaximumBuffer = New Size(Me.Width + 1, Me.Height + 1)
        
        ' Allocates a graphics buffer the size of this form
        ' using the pixel format of the Graphics created by 
        ' the Form.CreateGraphics() method, which returns a 
        ' Graphics object that matches the pixel format of the form.
        grafx = context.Allocate(Me.CreateGraphics(), _
            New Rectangle(0, 0, Me.Width, Me.Height))
        
        ' Draw the first frame to the buffer.
        DrawToBuffer(grafx.Graphics)
    End Sub    
    
    Private Sub MouseDownHandler(sender As Object, e As MouseEventArgs)
        If e.Button = MouseButtons.Right Then
            ' Cycle the buffering mode.
            bufferingMode = bufferingMode+1
            If bufferingMode > 2 Then
                bufferingMode = 0
            End If 
            ' If the previous buffering mode used 
            ' the OptimizedDoubleBuffering ControlStyle,
            ' disable the control style.
            If bufferingMode = 1 Then
                Me.SetStyle(ControlStyles.OptimizedDoubleBuffer, True)
            End If 
            ' If the current buffering mode uses
            ' the OptimizedDoubleBuffering ControlStyle,
            ' enabke the control style.
            If bufferingMode = 2 Then
                Me.SetStyle(ControlStyles.OptimizedDoubleBuffer, False)
            End If 
            ' Cause the background to be cleared and redraw.
            count = 6
            DrawToBuffer(grafx.Graphics)
            Me.Refresh()
        Else
            ' Toggle whether the redraw timer is active.
            If timer1.Enabled Then
                timer1.Stop()
            Else
                timer1.Start()
            End If
        End If
    End Sub
     
    Private Sub OnTimer(sender As Object, e As EventArgs)
        ' Draw randomly positioned ellipses to the buffer.
        DrawToBuffer(grafx.Graphics)
        
        ' If in bufferingMode 2, draw to the form's HDC.
        If bufferingMode = 2 Then
            ' Render the graphics buffer to the form's HDC.
            grafx.Render(Graphics.FromHwnd(Me.Handle))
        ' If in bufferingMode 0 or 1, draw in the paint method.
        Else
            Me.Refresh()
        End If
    End Sub
     
    Private Sub ResizeHandler(sender As Object, e As EventArgs)
        ' Re-create the graphics buffer for a new window size.
        context.MaximumBuffer = New Size(Me.Width + 1, Me.Height + 1)
        If (grafx IsNot Nothing) Then
            grafx.Dispose()
            grafx = Nothing
        End If
        grafx = context.Allocate(Me.CreateGraphics(), New Rectangle(0, 0, Me.Width, Me.Height))
        
        ' Cause the background to be cleared and redraw.
        count = 6
        DrawToBuffer(grafx.Graphics)
        Me.Refresh()
    End Sub    
    
    Private Sub DrawToBuffer(g As Graphics)
        ' Clear the graphics buffer every five updates.
        count = count+1
        If count > 5 Then
            count = 0
            grafx.Graphics.FillRectangle(Brushes.Black, 0, 0, Me.Width, Me.Height)
        End If
        
        ' Draw randomly positioned and colored ellipses.
        Dim rnd As New Random()
        Dim i As Integer
        For i = 0 To 21
            Dim px As Integer = rnd.Next(20, Me.Width - 40)
            Dim py As Integer = rnd.Next(20, Me.Height - 40)
            g.DrawEllipse(New Pen(Color.FromArgb(rnd.Next(0, 255), rnd.Next(0, 255), _
                rnd.Next(0, 255)), 1), px, py, px + rnd.Next(0, Me.Width - px - 20), _
                py + rnd.Next(0, Me.Height - py - 20))
        Next i
        
        ' Draw information strings.
        g.DrawString("Buffering Mode: " + bufferingModeStrings(bufferingMode), _
            New Font("Arial", 8), Brushes.White, 10, 10)
        g.DrawString("Right-click to cycle buffering mode", New Font("Arial", 8), _
            Brushes.White, 10, 22)
        g.DrawString("Left-click to toggle timed display refresh", _
            New Font("Arial", 8), Brushes.White, 10, 34)
    End Sub    
    
    Protected Overrides Sub OnPaint(e As PaintEventArgs)
        grafx.Render(e.Graphics)
    End Sub   
    
    <STAThread()>  _
    Public Shared Sub Main(args() As String)
        Application.Run(New BufferingExample())
    End Sub

End Class

Commenti

La BufferedGraphics classe consente di implementare il doppio buffering personalizzato per la grafica.The BufferedGraphics class allows you to implement custom double buffering for your graphics. Fornisce un wrapper per un buffer grafico, insieme ai metodi che è possibile usare per scrivere nel buffer ed eseguire il rendering del relativo contenuto in un dispositivo di output.It provides a wrapper for a graphics buffer, along with methods that you can use to write to the buffer and render its contents to an output device.

I grafici che utilizzano il doppio buffer possono ridurre o eliminare lo sfarfallio causato dalla ridisegno di una superficie di visualizzazione.Graphics that use double buffering can reduce or eliminate flicker that is caused by redrawing a display surface. Quando si usa il doppio buffer, i grafici aggiornati vengono prima disegnati in un buffer in memoria e il contenuto di questo buffer viene quindi scritto rapidamente in parte o in tutta la superficie visualizzata.When you use double buffering, updated graphics are first drawn to a buffer in memory, and the contents of this buffer are then quickly written to some or all of the displayed surface. Questa breve sovrascrittura della grafica visualizzata in genere riduce o Elimina lo sfarfallio che talvolta si verifica quando viene aggiornata la grafica.This relatively brief overwrite of the displayed graphics typically reduces or eliminates the flicker that sometimes occurs when graphics are updated.

Nota

Il modo più semplice per usare il doppio buffer consiste nell'impostare il OptimizedDoubleBuffer flag di stile del controllo su un controllo SetStyle usando il metodo.The simplest way to use double buffering is to set the OptimizedDoubleBuffer control style flag on a control using the SetStyle method. Impostando OptimizedDoubleBuffer il flag per un controllo, viene reindirizzato tutto il disegno per il controllo tramite un buffer grafico predefinito, senza richiedere codice aggiuntivo.Setting the OptimizedDoubleBuffer flag for a control redirects all painting for the control through a default graphics buffer, without requiring any additional code. Questo flag è impostato su true per impostazione predefinita.This flag is set to true by default.

La BufferedGraphics classe non ha un costruttore pubblico e deve essere creata BufferedGraphicsContext da per un dominio dell'applicazione usando Allocate il relativo metodo.The BufferedGraphics class has no public constructor and must be created by the BufferedGraphicsContext for an application domain using its Allocate method. È possibile recuperare l' BufferedGraphicsContext oggetto per il dominio dell'applicazione corrente dalla BufferedGraphicsManager.Current proprietà statica.You can retrieve the BufferedGraphicsContext for the current application domain from the static BufferedGraphicsManager.Current property.

La Graphics proprietà può essere utilizzata per il disegno nel buffer grafico.The Graphics property can be used for drawing to the graphics buffer. Questa proprietà consente di accedere all' Graphics oggetto che disegna sul buffer grafico allocato per questo BufferedGraphics oggetto.This property provides access to the Graphics object that draws to the graphics buffer allocated for this BufferedGraphics object.

Il Render metodo senza argomenti consente di disegnare il contenuto del buffer grafico sulla superficie specificata al momento dell'allocazione del buffer.The Render method with no arguments draws the contents of the graphics buffer to the surface specified when the buffer was allocated. Altri overload del Render metodo consentono di specificare un Graphics oggetto o un IntPtr oggetto che punta a un contesto di dispositivo in cui creare il contenuto del buffer grafico.Other overloads of the Render method allow you to specify a Graphics object or an IntPtr object that points to a device context to which to draw the contents of the graphics buffer.

Per ulteriori informazioni sulla creazione di immagini con doppio buffer, vedere la pagina relativa alla grafica con doppio buffer.For more information about drawing double-buffered graphics, see Double Buffered Graphics.

Proprietà

Graphics

Ottiene un oggetto Graphics con output nel buffer grafico.Gets a Graphics object that outputs to the graphics buffer.

Metodi

Dispose()

Rilascia tutte le risorse usate dall'oggetto BufferedGraphics.Releases all resources used by the BufferedGraphics object.

Equals(Object)

Determina se l'oggetto specificato è uguale all'oggetto corrente.Determines whether the specified object is equal to the current object.

(Ereditato da Object)
Finalize()

Consente a un oggetto di effettuare un tentativo di liberare risorse ed eseguire altre operazioni di pulizia prima che venga recuperato da Garbage Collection.Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.

GetHashCode()

Funge da funzione hash predefinita.Serves as the default hash function.

(Ereditato da Object)
GetType()

Ottiene l'oggetto Type dell'istanza corrente.Gets the Type of the current instance.

(Ereditato da Object)
MemberwiseClone()

Crea una copia superficiale dell'oggetto Object corrente.Creates a shallow copy of the current Object.

(Ereditato da Object)
Render()

Scrive il contenuto del buffer grafico nella periferica predefinita.Writes the contents of the graphics buffer to the default device.

Render(Graphics)

Scrive il contenuto del buffer grafico nell'oggetto specificato Graphics.Writes the contents of the graphics buffer to the specified Graphics object.

Render(IntPtr)

Scrive il contenuto del buffer grafico nel contesto di periferica associato all'handle IntPtr specificato.Writes the contents of the graphics buffer to the device context associated with the specified IntPtr handle.

ToString()

Restituisce una stringa che rappresenta l'oggetto corrente.Returns a string that represents the current object.

(Ereditato da Object)

Si applica a

Thread safety

La classe BufferedGraphics non è thread-safe.The BufferedGraphics class is not thread safe. Quando si accede a un buffer grafico da thread distinti, è importante usare un meccanismo di controllo dell'accesso ai thread per evitare conflitti.When accessing a graphics buffer from separate threads, it is important to use a thread-access control mechanism to prevent conflicts.

Vedi anche