调整椭圆大小

2011-05-25 126 views 0 likes

我不明白为什么这不起作用。在消息WM_LBUTTONDOWN上，存储指针的坐标。然后在WM_MOUSEMOVE上，如果左边的按钮是关闭的，我希望它用原始点和鼠标现在的新点绘制一个椭圆。但是当我调试时没有任何反应。这里是我的WindowProc调整椭圆大小

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) 
{ 
PAINTSTRUCT ps; 
HDC hdc; 


switch (uMsg) 
{ 

    case WM_DESTROY: 
    { 
    DestroyWindow(hwnd); 
    PostQuitMessage(0); 
    break; 

    } 
    case WM_PAINT: 
    { 
     hdc = BeginPaint(hwnd, &ps); 
     EndPaint(hwnd, &ps); 
     break; 
    } 
    case WM_LBUTTONDOWN: 
    { 
     pnt.x = GET_X_LPARAM(lParam); 
     pnt.y = GET_Y_LPARAM(lParam); 
     break; 
    } 
    case WM_MOUSEMOVE: 
    { 
     if(wParam == MK_LBUTTON) 
     { 
      hdc = BeginPaint(hwnd, &ps); 
      Ellipse(hdc, pnt.x, pnt.y, GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam)); // nothing happens 
      EndPaint(hwnd, &ps); 
     } 
     break; 
    } 
    return 0; 
} 
    return DefWindowProc(hwnd, uMsg, wParam, lParam); 
}

来源

2011-05-25 Geore Shg

回答

try代码是这样的：

static POINT begin, end; 
static BOOL drawing = false; 

// ... 


case WM_PAINT: 
    hdc = BeginPaint(hWnd, &ps); 
    if (drawing) 
     Ellipse(hdc, begin.x, begin.y, end.x, end.y); 
    EndPaint(hWnd, &ps); 
    break; 

case WM_LBUTTONDOWN: 
    begin.x = GET_X_LPARAM(lParam); 
    begin.y = GET_Y_LPARAM(lParam); 
    SetCapture(hWnd); 
    drawing = true; 
    break; 

case WM_LBUTTONUP: 
    ReleaseCapture(); 
    drawing = false; 
    break; 

case WM_MOUSEMOVE: 
    end.x = GET_X_LPARAM(lParam); 
    end.y = GET_Y_LPARAM(lParam); 
    { 
     RECT invalid = {begin.x, begin.y, end.x, end.y}; 
     InvalidateRect(hWnd, &invalid, true); 
    } 
    break;

来源

2011-05-25 04:53:59

你还没有使窗口的任何区域无效，所以BeginPaint是不会做任何事情。您应该将该点存储在WM_MOUSEMOVE（与pnt类似的结构中），并在当时调用InvalidateRect()。然后，在WM_PAINT中进行绘画。有关更多信息，请参阅此link。

来源

2011-05-25 03:55:55 dlev

调整椭圆大小

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