LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam){ HDC hdc; PAINTSTRUCT ps; RECT rect; static int cxClient, cyClient; static POINT pt[POINT_MAX]; static int iCount; int x, y;
switch (message) { case WM_LBUTTONDOWN: iCount = 0; InvalidateRect(hwnd, NULL, TRUE); break; case WM_MOUSEMOVE: //当处理完一个WM_MOUSEMOVE消息后，才会到系统消息队列中去取出下一个，所以，并不是鼠标一直移动就会一直产生WM_MOUSEMOVE消息在消息队列中，其中还可以产生其他消息 if (wParam&MK_LBUTTON && iCount<POINT_MAX) { pt[iCount].x = GET_X_LPARAM(lParam); //相比于LOWORD(lParam)更加可靠，在多屏显示时LOWORD(lParam)易出错 pt[iCount++].y = GET_Y_LPARAM(lParam);
hdc = GetDC(hwnd); SetPixelV(hdc, GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam), 0); ReleaseDC(hwnd, hdc); } break; case WM_LBUTTONUP: InvalidateRect(hwnd, NULL, FALSE);//不擦除背景，产生WM_PAINT消息 break; case WM_SIZE: cxClient = LOWORD(lParam); cyClient = HIWORD(lParam); break; case WM_PAINT: hdc = BeginPaint(hwnd, &ps); GetClientRect(hwnd, &rect);
SetCursor(LoadCursor(NULL, IDC_WAIT)); //Windows为鼠标光标保存了一个「显示计数」若是安装了鼠标，就会初始为0，否则为-1 //showcursor(true)会增加显示计数，当其非0 时会显示鼠标光标 //ShowCursor(TRUE);//1 for (x = 0; x < iCount;x++) { for (y = x+1; y < iCount;y++) { MoveToEx(hdc, pt[x].x, pt[x].y, NULL); LineTo(hdc, pt[y].x, pt[y].y); } } //减少显示计数 //ShowCursor(FALSE);//0 //使两个成对出现，才不会影响其他地方对鼠标的操作
SetCursor(LoadCursor(NULL, IDC_ARROW)); //切换两个备用指针 //设置后鼠标就会显示出样式,不需要showCursor(true) //（在不移动鼠标情况下不会改变，当鼠标移动时会回复为原来光标图，是因为当产生WM_MOUSEOVE时，系统会自动将鼠标改为原来的（注册时设置的光标）
EndPaint(hwnd, &ps); break; case WM_DESTROY: PostQuitMessage(0); return 0; }
return DefWindowProc(hwnd, message, wParam, lParam);}
转载于:https://www.cnblogs.com/ssyfj/p/8525308.html
