Question

How to draw a dotted line on a window using Win32 API in C

Answer 1

#include <windows.h>

LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {
    switch (uMsg) {
    case WM_PAINT: {
        PAINTSTRUCT ps;
        HDC hdc = BeginPaint(hwnd, &ps);

        // Create a dotted pen
        HPEN hPen = CreatePen(PS_DOT, 1, RGB(0, 0, 0)); // PS_DOT for dotted style
        HPEN hOldPen = (HPEN)SelectObject(hdc, hPen);

        // Draw a dotted line
        MoveToEx(hdc, 75, 75, NULL); // Starting point
        LineTo(hdc, 600, 75);        // Ending point

        // Restore the old pen and clean up
        SelectObject(hdc, hOldPen);
        DeleteObject(hPen);

        EndPaint(hwnd, &ps);
    } break;

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;

    default:
        return DefWindowProc(hwnd, uMsg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
    const wchar_t CLASS_NAME[] = L"SampleWindowClass";

    WNDCLASS wc;
    ZeroMemory(&wc, sizeof(WNDCLASS));  // Explicitly zero-initialize in C
    wc.lpfnWndProc = WindowProc;
    wc.hInstance = hInstance;
    wc.lpszClassName = CLASS_NAME;

    RegisterClass(&wc);

    HWND hwnd = CreateWindowEx(
        0,                              // Optional window styles
        CLASS_NAME,                     // Window class
        L"Dotted Line Example",
        WS_OVERLAPPEDWINDOW,            // Window style
        CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
        NULL, NULL, hInstance, NULL);

    if (hwnd == NULL) {
        return 0;
    }

    ShowWindow(hwnd, nCmdShow);

    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    return 0;
}




/*
run



*/

 

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