【发布时间】：2018-12-22 01:33:50
【问题描述】：
所以我正在尝试制作 Gyazo（截图工具）的廉价副本
问题是光标坐标在闪烁，我该如何防止呢？我已经尝试过WM_ERASEBKGND，但没有任何帮助。
我的代码还有什么问题吗？有什么不好的做法/技术吗？
#include <Windows.h>
#include <string>
#include <gdiplus.h>
#pragma comment (lib, "Gdiplus.lib")
// Store the "screenshot" when first launching the program
HBITMAP hbm;
// This draws the cursor coordinates close to the cursor
void DrawCursorCoords(Gdiplus::Graphics &graphics, Gdiplus::Bitmap &bitmap, Gdiplus::Color c)
{
POINT cursorPos;
GetCursorPos(&cursorPos);
std::wstring x = std::to_wstring(cursorPos.x);
std::wstring y = std::to_wstring(cursorPos.y);
graphics.DrawString(x.c_str(), x.length(), &Gdiplus::Font(L"Consolas", 16), Gdiplus::PointF(cursorPos.x, cursorPos.y), &Gdiplus::SolidBrush(c));
graphics.DrawString(y.c_str(), y.length(), &Gdiplus::Font(L"Consolas", 16), Gdiplus::PointF(cursorPos.x, cursorPos.y + 16), &Gdiplus::SolidBrush(c));
}
// Paint our stuff
void Paint(HDC &hdc)
{
Gdiplus::Graphics * gfx = new Gdiplus::Graphics(hdc);
Gdiplus::Bitmap * bmap = new Gdiplus::Bitmap(hbm, (HPALETTE)0);
gfx->DrawImage(bmap, 0, 0, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN));
if (GetAsyncKeyState(VK_LBUTTON))
DrawCursorCoords(*gfx, *bmap, Gdiplus::Color::Red);
else
DrawCursorCoords(*gfx, *bmap, Gdiplus::Color::Green);
delete gfx;
delete bmap;
}
LRESULT APIENTRY WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
PAINTSTRUCT ps;
HDC hdc;
switch (message)
{
case WM_PAINT:
{
hdc = BeginPaint(hwnd, &ps);
Paint(hdc);
EndPaint(hwnd, &ps);
break;
}
case WM_TIMER:
{
InvalidateRect(hwnd, NULL, NULL);
break;
}
case WM_CLOSE:
{
DestroyWindow(hwnd);
break;
}
case WM_RBUTTONUP:
case WM_KEYDOWN:
case WM_DESTROY:
{
PostQuitMessage(0);
break;
}
case WM_ERASEBKGND: return TRUE;
default: return DefWindowProc(hwnd, message, wParam, lParam);
}
return 0L;
}
BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
{
char className[] = "_className";
HWND hwnd = NULL;
WNDCLASS wc;
wc.style = 0;
wc.lpfnWndProc = WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hIcon = NULL;
wc.hCursor = LoadCursor(NULL, IDC_CROSS);
wc.hbrBackground = (HBRUSH)(0);
wc.lpszMenuName = NULL;
wc.lpszClassName = className;
if (RegisterClass(&wc))
{
hwnd = CreateWindowEx(
WS_EX_TRANSPARENT | WS_EX_TOPMOST,
className, NULL,
WS_POPUP | WS_VISIBLE,
0, 0, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN),
NULL, NULL, hInstance, NULL);
}
if (!hwnd) return FALSE;
ShowWindow(hwnd, SW_SHOW);
UpdateWindow(hwnd);
SetTimer(hwnd, 1, 1, NULL);
return TRUE;
}
int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
// Take a screenshot and store it to 'hbm'
HWND hwndDesktop = GetDesktopWindow();
HDC hdcDesktop = GetDC(hwndDesktop);
HDC hdcCapture = CreateCompatibleDC(hdcDesktop);
hbm = CreateCompatibleBitmap(hdcDesktop, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN));
SelectObject(hdcCapture, hbm);
BitBlt(hdcCapture, 0, 0, GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN),
hdcDesktop, 0, 0, SRCCOPY | CAPTUREBLT);
// Start GDI+
Gdiplus::GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
MSG msg;
InitInstance(hInstance, nCmdShow);
while (GetMessage(&msg, NULL, 0, 0) > 0)
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
Gdiplus::GdiplusShutdown(gdiplusToken);
DeleteObject(hbm);
ReleaseDC(hwndDesktop, hdcDesktop);
DeleteDC(hdcDesktop);
DeleteDC(hdcCapture);
return msg.wParam;
}
【问题讨论】：
-
是 DrawImage() 调用导致闪烁。它覆盖先前绘制的文本，然后 DrawCursorCoords() 将其放回原处。需要双缓冲来消除它，谷歌“c++ gdi+双缓冲”以获得良好的命中率。
-
@JesperJuhl：那么...您建议使用哪种 C++ 工具来实现与平台无关的 GUI？如果你不能说出一个，是什么让选择正确的工具成为你标记“不好的做法”？
-
@IInspectable 我的首选是 Qt、SFML 和 SDL。很可能是Qt。希望这算作“命名”。
-
@JesperJuhl：因此，您建议不要为仅针对 Windows 的工具编写特定于 Windows 的代码，而是建议添加另一个依赖项，现在使其特定于 Windows 的和库特定的？最近是否将过度工程传播到最佳实践？此外，Qt 是一个玩具，它永远无法生成与本机 Windows 桌面 GUI 相媲美的 GUI。它的实现在核心上被破坏了，无法修复。您可以通过使用其键盘界面轻松识别 Qt 应用程序，然后等待它中断。它会，不可避免地。总是。无一例外。
-
我的 $.02 - Qt 对我来说太重了，除非你真的非常需要它。
标签： c++ winapi gdi+ flicker double-buffering