winapi – Page 20 – Tarik Billa

How can I take a screenshot in a windows application?

March 28, 2023 by Tarik

HDC hScreenDC = GetDC(nullptr); // CreateDC(“DISPLAY”,nullptr,nullptr,nullptr); HDC hMemoryDC = CreateCompatibleDC(hScreenDC); int width = GetDeviceCaps(hScreenDC,HORZRES); int height = GetDeviceCaps(hScreenDC,VERTRES); HBITMAP hBitmap = CreateCompatibleBitmap(hScreenDC,width,height); HBITMAP hOldBitmap = static_cast<HBITMAP>(SelectObject(hMemoryDC,hBitmap)); BitBlt(hMemoryDC,0,0,width,height,hScreenDC,0,0,SRCCOPY); hBitmap = static_cast<HBITMAP>(SelectObject(hMemoryDC,hOldBitmap)); DeleteDC(hMemoryDC); DeleteDC(hScreenDC);

How do I call ::CreateProcess in c++ to launch a Windows executable?

March 28, 2023 by Tarik

Something like this: STARTUPINFO info={sizeof(info)}; PROCESS_INFORMATION processInfo; if (CreateProcess(path, cmd, NULL, NULL, TRUE, 0, NULL, NULL, &info, &processInfo)) { WaitForSingleObject(processInfo.hProcess, INFINITE); CloseHandle(processInfo.hProcess); CloseHandle(processInfo.hThread); }

How do I properly map a `MagImageScalingCallback` using JNA?

March 24, 2023 by Tarik

The callback is proper – there is no flaw in your code, besides you are using deprecated functions. Consider using this: try { Rectangle screenRect = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize()); BufferedImage capture = new Robot().createScreenCapture(screenRect); ImageIO.write(capture, “JPEG”, new File(“printed1.jpg”)); } catch (Exception e) { e.printStackTrace(); }

How to use Win32 API with Python?

March 24, 2023 by Tarik

PyWin32 is the way to go – but how to use it? One approach is to begin with a concrete problem you’re having and attempting to solve it. PyWin32 provides bindings for the Win32 API functions for which there are many, and you really have to pick a specific goal first. In my Python 2.5 … Read more

Get current cursor position

March 22, 2023 by Tarik

You get the cursor position by calling GetCursorPos. POINT p; if (GetCursorPos(&p)) { //cursor position now in p.x and p.y } This returns the cursor position relative to screen coordinates. Call ScreenToClient to map to window coordinates. if (ScreenToClient(hwnd, &p)) { //p.x and p.y are now relative to hwnd’s client area } You hide and … Read more

What does “WINAPI” in main function mean?

March 21, 2023 by Tarik

WINAPI is a macro that evaluates to __stdcall, a Microsoft-specific keyword that specifies a calling convention where the callee cleans the stack. The function’s caller and callee need to agree on a calling convention to avoid corrupting the stack.

How do I get a list of available serial ports in Win32?

March 20, 2023 by Tarik

The EnumSerialPorts v1.20 suggested by Nick D uses nine different methods to list the serial ports! We’re certainly not short on choice, though the results seem to vary. To save others the trouble, I’ll list them here and indicate their success in finding the com0com ports on my PC (XP Pro SP2): CreateFile(“COM” + 1->255) … Read more

How to get installed Windows SDK version?

March 12, 2023 by Tarik

On English locale at least: dir “%ProgramFiles%\Microsoft SDKs\Windows” should work. It is quite likely that there will be multiple versions installed, which is the right one for an one build can only be specified by that project.

How to make thread sleep less than a millisecond on Windows

March 11, 2023 by Tarik

This indicates a mis-understanding of sleep functions. The parameter you pass is a minimum time for sleeping. There’s no guarantee that the thread will wake up after exactly the time specified. In fact, threads don’t “wake up” at all, but are rather chosen for execution by the OS scheduler. The scheduler might choose to wait … Read more

How to convert char* to wchar_t*?

March 10, 2023 by Tarik

In your example, wc is a local variable which will be deallocated when the function call ends. This puts you into undefined behavior territory. The simple fix is this: const wchar_t *GetWC(const char *c) { const size_t cSize = strlen(c)+1; wchar_t* wc = new wchar_t[cSize]; mbstowcs (wc, c, cSize); return wc; } Note that the … Read more