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POGDIplus flickering
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copied!<p>I'm trying to draw with GDIplus on an transparent window and experiencing a lot of flickering. I've read plenty of threads that suggest implementing double-buffering or rendering to offscreen surface would help, which I've done but to no avail.</p> <p>Any idea what I've done wrong and how to fix it? Thanks.</p> <pre><code>#include <Windows.h> #include <stdio.h> #include <time.h> #include <GdiPlus.h> #pragma comment(lib, "GdiPlus.lib") HWND hWnd = NULL; WNDCLASSEX wcex; HDC hdc = NULL; PAINTSTRUCT ps; HGDIOBJ hfDefault; MSG msg; COLORREF transKey = RGB(37,14,103); ULONG_PTR m_gdiplusToken; char window_title[9] = "testings"; char window_class[9] = "testings"; int window_width = GetSystemMetrics(SM_CXSCREEN); int window_height = GetSystemMetrics(SM_CYSCREEN); DWORD MainThread(LPVOID lpArgs) { while(1) { RECT rc = {0,0,window_width,window_height}; InvalidateRect(hWnd, &rc, false); UpdateWindow(hWnd); Sleep(50); } } LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) { if(msg == WM_CREATE) { hfDefault = (HFONT)GetStockObject(DEFAULT_GUI_FONT); Gdiplus::GdiplusStartupInput gdiplusStartupInput; Gdiplus::GdiplusStartup(&m_gdiplusToken, &gdiplusStartupInput, NULL); SetLayeredWindowAttributes(hWnd, transKey, 128, LWA_COLORKEY); } else if(msg == WM_PAINT) { hdc = BeginPaint(hWnd, &ps); Gdiplus::Graphics g(hdc); g.Clear(Gdiplus::Color(37,14,103)); Gdiplus::Bitmap* curBitmap = new Gdiplus::Bitmap(window_width, window_height); Gdiplus::Graphics* g1 = g.FromImage(curBitmap); static int x=1,y=1; // x += 3; y += 2; Gdiplus::Pen pen(Gdiplus::Color(255, 255, 0, 255)); g1->DrawLine(&pen, x, y, window_width/2, window_height/2); g.DrawImage(curBitmap, 0, 0); EndPaint(hWnd, &ps); } else if(msg == WM_CLOSE) { DestroyWindow(hWnd); } else if(msg == WM_DESTROY) { PostQuitMessage(0); } else { return DefWindowProc(hWnd, msg, wParam, lParam); } return 0; } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) { HBRUSH hbrBackground = CreateSolidBrush(transKey); wcex.cbSize = sizeof(WNDCLASSEX); wcex.style = CS_HREDRAW | CS_VREDRAW; wcex.lpfnWndProc = WndProc; wcex.cbClsExtra = 0; wcex.cbWndExtra = 0; wcex.hInstance = hInstance; wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_APPLICATION)); wcex.hCursor = LoadCursor(NULL, IDC_ARROW); wcex.hbrBackground = hbrBackground; wcex.lpszMenuName = NULL; wcex.lpszClassName = window_class; wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_APPLICATION)); if(!RegisterClassEx(&wcex)) return 1; hWnd = CreateWindowEx( WS_EX_LAYERED | WS_EX_TRANSPARENT | WS_EX_TOPMOST, window_class, window_title, WS_POPUP, 0, 0, window_width, window_height, NULL, NULL, hInstance, NULL ); if(!hWnd) return 1; ShowWindow(hWnd, nCmdShow); UpdateWindow(hWnd); CreateThread(NULL, NULL, (LPTHREAD_START_ROUTINE)MainThread, NULL, NULL, NULL); while(GetMessage(&msg, NULL, 0, 0) > 0) { TranslateMessage(&msg); DispatchMessage(&msg); } Gdiplus::GdiplusShutdown(m_gdiplusToken); return msg.wParam; } </code></pre>

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