BufferedGraphics 類別

定義

提供雙重緩衝 (Double Buffering) 的圖形緩衝區。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
繼承
BufferedGraphics
實作

範例

下列程式碼範例示範如何使用BufferedGraphics物件來繪製使用數種緩衝處理的類型的圖形。The following code example demonstrates using a BufferedGraphics object to draw graphics using several types of buffering implementations. 按一下表單就會啟動, 並停止導致繪製更新的計時器。Clicking the form alternately starts and stops a timer that causes draw updates. 繪製更新可讓您觀察雙重緩衝的效果。The draw updates allow you to observe the effect of double buffering. 以滑鼠右鍵按一下表單會迴圈流覽下列繪製模式:Right-clicking the form cycles through the following drawing modes:

在每個模式中, 會繪製文字來識別目前的模式, 並描述按下每個滑鼠按鍵時所發生的行為。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

備註

BufferedGraphics類別可讓您針對圖形執行自訂雙重緩衝。The BufferedGraphics class allows you to implement custom double buffering for your graphics. 它提供圖形緩衝區的包裝函式, 以及您可以用來寫入緩衝區並將其內容轉譯為輸出裝置的方法。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.

使用雙重緩衝的圖形可以減少或消除因重新繪製顯示介面而造成的閃爍。Graphics that use double buffering can reduce or eliminate flicker that is caused by redrawing a display surface. 當您使用雙重緩衝時, 會先在記憶體中將更新的圖形繪製到緩衝區, 然後再將此緩衝區的內容快速寫入部分或所有顯示的表面。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. 這項相對簡短的顯示圖形覆寫通常會減少或消除當圖形更新時有時會發生的閃爍。This relatively brief overwrite of the displayed graphics typically reduces or eliminates the flicker that sometimes occurs when graphics are updated.

注意

使用雙重緩衝最簡單的方式, 就是OptimizedDoubleBuffer SetStyle使用方法, 在控制項上設定控制項樣式旗標。The simplest way to use double buffering is to set the OptimizedDoubleBuffer control style flag on a control using the SetStyle method. 設定控制項OptimizedDoubleBuffer的旗標會透過預設圖形緩衝區重新導向控制項的所有繪製, 而不需要任何額外的程式碼。Setting the OptimizedDoubleBuffer flag for a control redirects all painting for the control through a default graphics buffer, without requiring any additional code. 預設會將此旗true標設為。This flag is set to true by default.

類別沒有公用BufferedGraphicsContext的函式, 而且必須使用其Allocate方法, 針對應用程式域建立。 BufferedGraphicsThe BufferedGraphics class has no public constructor and must be created by the BufferedGraphicsContext for an application domain using its Allocate method. 您可以從靜態BufferedGraphicsContext BufferedGraphicsManager.Current屬性取得目前應用程式域的。You can retrieve the BufferedGraphicsContext for the current application domain from the static BufferedGraphicsManager.Current property.

Graphics屬性可以用來繪製至圖形緩衝區。The Graphics property can be used for drawing to the graphics buffer. 這個屬性會提供Graphics物件的存取權, 該物件繪製到為此BufferedGraphics物件配置的圖形緩衝區。This property provides access to the Graphics object that draws to the graphics buffer allocated for this BufferedGraphics object.

沒有Render引數的方法會將圖形緩衝區的內容繪製至配置緩衝區時所指定的介面。The Render method with no arguments draws the contents of the graphics buffer to the surface specified when the buffer was allocated. 方法的其他多載可讓您Graphics指定物件或IntPtr物件, 指向要繪製圖形緩衝區內容的裝置內容。 RenderOther 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.

如需繪製雙重緩衝圖形的詳細資訊, 請參閱雙重緩衝圖形For more information about drawing double-buffered graphics, see Double Buffered Graphics.

屬性

Graphics

取得 Graphics 物件,該物件輸出至圖形緩衝區。Gets a Graphics object that outputs to the graphics buffer.

方法

Dispose()

釋放由 BufferedGraphics 物件使用的所有資源。Releases all resources used by the BufferedGraphics object.

Equals(Object)

判斷指定的物件是否等於目前的物件。Determines whether the specified object is equal to the current object.

(繼承來源 Object)
Finalize()

允許物件在記憶體回收進行回收之前,嘗試釋放資源並執行其他清除作業。Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.

GetHashCode()

做為預設雜湊函式。Serves as the default hash function.

(繼承來源 Object)
GetType()

取得目前執行個體的 TypeGets the Type of the current instance.

(繼承來源 Object)
MemberwiseClone()

建立目前 Object 的淺層複本 (Shallow Copy)。Creates a shallow copy of the current Object.

(繼承來源 Object)
Render()

將圖形緩衝區的內容寫入預設裝置。Writes the contents of the graphics buffer to the default device.

Render(Graphics)

將圖形緩衝區的內容寫入指定的 Graphics 物件。Writes the contents of the graphics buffer to the specified Graphics object.

Render(IntPtr)

將圖形緩衝區的內容寫入與指定 IntPtr 控制代碼關聯的裝置內容。Writes the contents of the graphics buffer to the device context associated with the specified IntPtr handle.

ToString()

傳回代表目前物件的字串。Returns a string that represents the current object.

(繼承來源 Object)

適用於

執行緒安全性

BufferedGraphics 類別不具備執行緒安全。The BufferedGraphics class is not thread safe. 從不同的執行緒存取圖形緩衝區時, 請務必使用執行緒存取控制機制來避免衝突。When accessing a graphics buffer from separate threads, it is important to use a thread-access control mechanism to prevent conflicts.

另請參閱