向 WM_PAINT 发送消息 [英] Sending message to WM_PAINT

问题描述

我正在尝试编写一个程序，用箭头键控制盒子的移动.我的代码有问题.是否可以通过 SendMessage 向 WM_PAINT 发送消息以在按 LEFT 键时绘制新矩形?以下是我的代码

I am trying to make a program for controlling the movement of a box with arrow key.I have a problem in my code.Is it possible to send a message through SendMessage to WM_PAINT to draw a new rectangle on pressing LEFT key? Following is my code

case WM_KEYDOWN:
    switch(wParam)
    {
       case VK_LEFT:                              //LEFT MOVEMENT


    SendMessage(hwnd,WM_PAINT,VK_LEFT,0);
        break;



       case VK_ESCAPE: 
           //FOR ENDING THE GAME WITH ESCAPE KEY
           SendMessage(hwnd,WM_DESTROY,VK_ESCAPE,0);
        break;
    }


case WM_PAINT:
    hdc=BeginPaint(hwnd,&ps);


      Rectangle(hdc,x,600,x1,700);
    if(wParam==VK_LEFT)
    { Rectangle(hdc,x-50,600,x1-50,700);

    }
    EndPaint(hwnd,&ps);
    return 0;
case WM_DESTROY:

    PostQuitMessage(0);
    return 0;
}
return DefWindowProc(hwnd,message,wParam,lParam);
}
where 

         x1=550;
          x=500

当按下左键时，控件会转到 WM_PAINT

When left key is pressed then does the control goes to WM_PAINT

因为当我写

if(wParam==VK_LEFT)
        { Rectangle(hdc,x-50,600,x1-50,700);

        }

什么都没有发生，但是当我写的时候

nothing happens but when I write

if(wParam==VK_ESCAPE)
    PostQuitMessage(0);
    return 0;

窗口退出并带有转义键它不是最终代码.我只是想了解为什么 VK_LEFT 不执行?

The window exits with escape key Its not the final code .I am just trying to understand that why VK_LEFT doesn't executes?

推荐答案

你从不发送 WM_PAINT.系统负责这样做.相反，您调用 InvalidateRect 指定您希望重新绘制的矩形.系统会将该矩形标记为无效，并在下一个绘制周期发生时，重新绘制该矩形.

You never send WM_PAINT. The system is in charge of doing that. Instead, you call InvalidateRect specifying the rectangle that you wish to be re-painted. The system will mark that rectangle as invalid, and when the next paint cycle occurs, that rectangle will be re-painted.

如果您想使更复杂的区域无效，则使用 InvalidateRgn.

If you want to invalidate more complicated regions there is InvalidateRgn.

如果您只是希望整个窗口无效，请将 NULL 传递给 InvalidateRect 的 lpRect 参数.

If you just wish for the entire window to be invalidated, pass NULL to the lpRect parameter of InvalidateRect.

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