問題描述
繪製鼠標光標 (Draw mouse cursor)
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);
But I don't see anything being drawn. However if I drew directly on the DC:
DrawIcon(hDeviceContext, x, y, hCursor);
I do see the cursor but it does not erase the image as I move the cursor, leaving a long tail behind.
參考解法
方法 1:
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;
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.
方法 2:
For what it's worth:
Another approach that might be worth looking at is to use a WS_EX_TOPMOST|WS_EX_LAYERED window that you move around as needed, and let Windows handle the drawing/transparency for you. This has the advantage that it won't interfere at all with the drawing main window, and will work even if the main window has child controls or similar.
It will also allow your 'mouse pointer' to 'hang over the edge' of your window - eg. when when mouse is positioned to point at the extreme bottom-right pixel, the tail and arrow of a regular mouse pointer will be over the frame and other windows behind it, and you can't do this just by drawing your own window's client area.
--
Having said that, I'm not sure that 'faking' the mouse position is the proper thing to do here, though it may well get you up and running. Another approach is to let the mouse behave as normal, but for apps that require the higher resolution, have another API that exposes the more exact values. Along with the usual mouse/keyboard messages and APIs, windows also has various techniques and APIs (eg Raw Input) for getting input information, defining additional input devices, and I think also associating additional information with messages, and one of those techniques might be more appropriate here. It might be worthwhile to re-ask your question, but focus on the higher-level on, not the cursor drawing.
(by dave、skink、BrendanMcK)