程式語言 - MinGW - C/C++ - Painting - Draw Line

參考資訊：
http://www.winprog.org/tutorial/
http://winapi.freetechsecrets.com/win32/
https://github.com/gammasoft71/Examples_Win32
http://masm32.com/board/index.php?topic=3584.0
https://learn.microsoft.com/en-us/windows/win32/winmsg/window-styles

線的起始點位置是位於(x=0, y=0)，使用者可以呼叫MoveToEx()設定新的起始點，而使用LineTo()就可以畫出一條直線，新的起始點則是線的結束位置

main.c

#include <windows.h>

HWND hWin = NULL;
WNDPROC defWndProc = NULL;

LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    HDC hdc = NULL;
    HPEN r_pen = NULL;
    HPEN g_pen = NULL;
    HPEN b_pen = NULL;
    PAINTSTRUCT ps = {0};

    switch (uMsg) {
    case WM_CLOSE:
        DestroyWindow(hWnd);
        return 0;
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    case WM_PAINT:
        hdc = BeginPaint(hWnd, &ps);
        r_pen = CreatePen(PS_SOLID, 3, RGB(0xff, 0x00, 0x00));
        g_pen = CreatePen(PS_SOLID, 3, RGB(0x00, 0xff, 0x00));
        b_pen = CreatePen(PS_SOLID, 3, RGB(0x00, 0x00, 0xff));

        SelectObject(hdc, r_pen);
        MoveToEx(hdc, 10, 100, NULL);
        LineTo(hdc, 250, 100);

        SelectObject(hdc, g_pen);
        MoveToEx(hdc, 10, 150, NULL);
        LineTo(hdc, 250, 150);

        SelectObject(hdc, b_pen);
        MoveToEx(hdc, 10, 200, NULL);
        LineTo(hdc, 250, 200);

        EndPaint(hWnd, &ps);
        DeleteObject(r_pen);
        DeleteObject(g_pen);
        DeleteObject(b_pen);
        break;
    }
    return CallWindowProc(defWndProc, hWnd, uMsg, wParam, lParam);
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    hWin = CreateWindow(WC_DIALOG, "main", 
        WS_OVERLAPPEDWINDOW | WS_VISIBLE, 0, 0, 300, 300, NULL, NULL, NULL, NULL);
    defWndProc = (WNDPROC)SetWindowLongPtr(hWin, GWLP_WNDPROC, (long int)WndProc);

    MSG msg = {0};
    while (GetMessage(&msg, NULL, 0, 0)) {
        DispatchMessage(&msg);
    }
    ExitProcess(0);
    return 0;
}

Line 23~37：產生三支Pen並且畫出三條直線，需要注意的是，同一時間只能選擇一支Pen

編譯、執行

$ i686-w64-mingw32-gcc -mwindows main.c -o main.exe
$ wine ./main.exe