window.c

#include <windows.h>
#include "rect.h"

#define EXIT_IF(cond) if (cond) ExitProcess(1)

#define SCREEN_WIDTH 780
#define SCREEN_HEIGHT 480
#define RECT_WIDTH 10
#define RECT_HEIGHT 10

#define WHITE 0xFFFFFF

GL_RECT dot;

// Callback for arrow keys
void onArrowKeyPress(WPARAM vkCode)
{
    switch (vkCode)
    {
        case VK_LEFT:  moveRect(&dot, -RECT_WIDTH / 2,                0, SCREEN_WIDTH, SCREEN_HEIGHT); break;
        case VK_RIGHT: moveRect(&dot,  RECT_WIDTH / 2,                0, SCREEN_WIDTH, SCREEN_HEIGHT); break;
        case VK_DOWN:  moveRect(&dot,               0, -RECT_HEIGHT / 2, SCREEN_WIDTH, SCREEN_HEIGHT); break;
        case VK_UP:    moveRect(&dot,               0,  RECT_HEIGHT / 2, SCREEN_WIDTH, SCREEN_HEIGHT); break;
    }
}

// Set up the pixel format for the window
void setupPixelFormat(HDC hdc)
{
    PIXELFORMATDESCRIPTOR pfd = {sizeof(PIXELFORMATDESCRIPTOR), 1,
                                        PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL,
                                        PFD_TYPE_RGBA,                            // RGBA or palettes?
                                        32,                                       // Colour depth
                                        0, 0, 0, 0, 0, 0, 0, 0,                   // Bitplanes in RGBA colour buffer
                                        0, 0, 0, 0, 0,                            // Bitplanes in accumulation buffer
                                        24,                                       // z-axis buffer depth
                                        8,                                        // Stencil buffer depth
                                        0, 0, 0, 0, 0, 0};
    int pixel_format = ChoosePixelFormat(hdc, &pfd);
    SetPixelFormat(hdc, pixel_format, &pfd);
    DescribePixelFormat(hdc, pixel_format, sizeof(PIXELFORMATDESCRIPTOR), &pfd);
}

// Callback for the message loop
LRESULT CALLBACK WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    static HDC hdc;
    static HGLRC hglrc;
    static PAINTSTRUCT ps;

    switch (msg)
    {
        case WM_PAINT:
        {
            drawRect(dot.x_L, dot.y_T, dot.x_R, dot.y_B, SCREEN_WIDTH, SCREEN_HEIGHT, WHITE);

            // These 2 functions are necessary to clear WM_PAINT messages from the queue
            BeginPaint(hwnd, &ps);
            EndPaint(hwnd, &ps);
            break;
        }
        case WM_KEYDOWN:
        {
            if (BETWEEN(wParam, VK_LEFT, VK_DOWN))  // If an arrow key's pressed
            {
                onArrowKeyPress(wParam);
                PostMessage(hwnd, WM_PAINT, 0, 0);  // Re-paint the window
            }
            break;
        }
        case WM_SIZE:
        {
            glViewport(0, 0, LOWORD(lParam), HIWORD(lParam));
            PostMessage(hwnd, WM_PAINT, 0, 0);  // Re-paint the window
            break;
        }
        case WM_DESTROY:
        {
            wglMakeCurrent(hdc, NULL);  // De-select the OpenGL context
            wglDeleteContext(hglrc);    // Delete the context
            PostQuitMessage(0);
            break;
        }
        case WM_CLOSE:
        {
            DestroyWindow(hwnd);
            break;
        }
        case WM_CREATE:
        {                         
            hdc = GetDC(hwnd);              // Get the device context for the window
            setupPixelFormat(hdc);          // Set up the pixel format for the device context

            hglrc = wglCreateContext(hdc);  // Create an OpenGL context
            wglMakeCurrent(hdc, hglrc);     // Make the context current

            setRect(&dot, (SCREEN_WIDTH - RECT_WIDTH) / 2, (SCREEN_HEIGHT - RECT_HEIGHT) / 2, (SCREEN_WIDTH + RECT_WIDTH) / 2, (SCREEN_HEIGHT + RECT_HEIGHT) / 2);
            break;
        }
        default:
            return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

// Entry point (analogous to 'int main()')
int WINAPI WinMainCRTStartup()
{
    // Get the handle of the current process
    HMODULE hInstance = GetModuleHandleA(NULL);

    // Initialize the window class
    WNDCLASSEXA windowClass = {sizeof(WNDCLASSEX),
                               CS_OWNDC | CS_HREDRAW | CS_VREDRAW,
                               WindowProc,
                               0, 0,
                               hInstance,
                               NULL,                                // Handle to class icon
                               LoadCursorA(NULL, IDC_ARROW),        // Handle to class cursor
                               NULL,                                // Handle to background brush
                               NULL,
                               "a",
                               NULL};                               // Handle to small icon

    // Register the window class
    EXIT_IF(!RegisterClassExA(&windowClass));

    // Create the window
    HWND window = CreateWindowExA(0,                             // Extended styles
                                  "a",                           // Window class name
                                  "Moving dot",                  // Window title
                                  WS_OVERLAPPEDWINDOW,           // Window style
                                  CW_USEDEFAULT, CW_USEDEFAULT,  // Position
                                  SCREEN_WIDTH, SCREEN_HEIGHT,   // Size
                                  NULL, NULL, hInstance, NULL);
    EXIT_IF(!window);

    // Show the window
    ShowWindow(window, SW_SHOW);
    UpdateWindow(window);

    // Run the message loop
    MSG msg = {0};
    BOOL ret;
    while ((ret = GetMessage(&msg, NULL, 0, 0)) != 0)
    {
        if (ret == -1)  // Error!
            break;
        TranslateMessage(&msg);
        DispatchMessage(&msg); 
    }

    // Stop the program (analogous to 'return 0')
    ExitProcess(0);
}