在win32中绘制鼠标光标 [英] draw mouse cursor in win32

问题描述

GDI的新手.

我正在尝试模拟Win32窗体中的鼠标光标.在每一个WM_MOUSEMOVE上

I'm trying to simulate a mouse cursor in Win32 forms. On every WM_MOUSEMOVE I have

hCursor = LoadCursor(NULL, IDC_ARROW);
////Get device context
hDeviceContext = GetDC(hwnd);
hDCMem = CreateCompatibleDC(hDeviceContext);
hBitmap = CreateCompatibleBitmap(hDCMem, 50, 50);
hbmOld = SelectObject(hDCMem, hBitmap);
DrawIcon(hDCMem, x, y, hCursor);
SelectObject(hDCMem, hbmOld);

但是我看不到有什么画.但是，如果我直接绘制到DC:

But I don't see anything being drawn. However if I drew directly on the to DC:

    DrawIcon(hDeviceContext , x, y, hCursor);

我确实看到了光标，但是当我移动光标时它并没有擦除图像，留下了长长的尾巴.

I do see the cursor but it does not erase the image as I move the cursor, leaving a long tail behind.

推荐答案

不要用 WM_MOUSEMOVE 绘制，这就是 WM_PAINT 的用途.基本上，您需要处理三则消息:

Don't paint in WM_MOUSEMOVE, that's what WM_PAINT is for. Basically, you need to handle three messages:

    case WM_CREATE:
        hCursor = LoadCursor(NULL, IDC_ARROW);
        cWidth  = GetSystemMetrics(SM_CXCURSOR); // saving the cursor dimensions
        cHeight = GetSystemMetrics(SM_CYCURSOR);
    break;

    case WM_MOUSEMOVE:
        rcOld = rcNew;
        rcNew.left   = GET_X_LPARAM(lParam);     // saving the mouse coordinates
        rcNew.top    = GET_Y_LPARAM(lParam);
        rcNew.right  = rcNew.left + cWidth;
        rcNew.bottom = rcNew.top + cHeight;
        InvalidateRect(hwnd, &rcOld, TRUE);      // asking to redraw the rectangles
        InvalidateRect(hwnd, &rcNew, TRUE);
        UpdateWindow(hwnd);
    break;

    case WM_PAINT:
        hDC = BeginPaint(hwnd, &ps);
        DrawIcon(hDC, rcNew.left, rcNew.top, hCursor);
        EndPaint(hwnd, &ps);
    break;

注意:我不确定模拟鼠标光标"是什么意思，但是可能会有更好的方法来做您可能想要的事情.请检查功能 SetCursor() 和 SetWindowLongPtr()与GCL_HCURSOR .

Note: I'm not sure what do you mean by "simulating a mouse cursor", but there could be a better way of doing what you probably want. Please check functions SetCursor() and SetWindowLongPtr() with GCL_HCURSOR.

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