C言語／C++/Mandelbrot - Sample is best!

開発環境	Microsoft Visual Studio Community 2019 / Visual C++
実行環境	Microsoft Windows 10 Home (64bit)
プロジェクト テンプレート	Windows デスクトップ ウィザード
プロジェクト名	Mandelbrot
アプリケーションの種類	デスクトップ アプリケーション (.exe)
追加のオプション	空のプロジェクト

Mandelbrot.cpp

#include <Windows.h>
 
#define APP_NAME L"Mandelbrot"
#define WND_SIZE 512
 
LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
void OnCreate(HWND hWnd);
void OnDestroy();
void OnPaint(HWND hWnd);
 
HDC hMemDC = NULL;
HBITMAP hBmp = NULL;
HBITMAP hBmpOld = NULL;
 
int WINAPI wWinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE, _In_ LPWSTR, _In_ int nCmdShow)
{
	// ウィンドウクラスの登録
	WNDCLASSEX wc = { sizeof WNDCLASSEX };
	wc.style = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc = WndProc;
	wc.hInstance = hInstance;
	wc.hCursor = LoadCursor(NULL, IDC_ARROW);
	wc.hbrBackground = HBRUSH(COLOR_WINDOW + 1);
	wc.lpszClassName = APP_NAME;
	if (RegisterClassEx(&wc) == 0) {
		return 0;
	}
 
	// ウィンドウの作成
	HWND hWnd = CreateWindow(
		APP_NAME, APP_NAME,
		WS_OVERLAPPEDWINDOW & ~WS_MAXIMIZEBOX & ~WS_THICKFRAME,
		CW_USEDEFAULT, 0,
		CW_USEDEFAULT, 0,
		NULL, NULL, hInstance, NULL);
	if (hWnd == NULL) {
		return 0;
	}
	ShowWindow(hWnd, nCmdShow);
	UpdateWindow(hWnd);
 
	// メッセージループ
	MSG msg;
	while (GetMessage(&msg, NULL, 0, 0)) {
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	return msg.wParam;
}
 
LRESULT CALLBACK WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	switch (uMsg) {
	case WM_PAINT:
		OnPaint(hWnd);
		break;
 
	case WM_CREATE:
		OnCreate(hWnd);
		break;
 
	case WM_DESTROY:
		OnDestroy();
		PostQuitMessage(0);
		break;
 
	default:
		return DefWindowProc(hWnd, uMsg, wParam, lParam);
	}
	return 0;
}
 
void OnCreate(HWND hWnd)
{
	RECT rcw, rcc;
	GetWindowRect(hWnd, &rcw);
	GetClientRect(hWnd, &rcc);
	int cx = WND_SIZE + (rcw.right - rcw.left) - rcc.right;
	int cy = WND_SIZE + (rcw.bottom - rcw.top) - rcc.bottom;
	SetWindowPos(hWnd, NULL, 0, 0, cx, cy, SWP_NOZORDER | SWP_NOMOVE);
 
	BITMAPINFOHEADER bmih = { sizeof BITMAPINFOHEADER };
	bmih.biWidth = WND_SIZE;
	bmih.biHeight = WND_SIZE;
	bmih.biPlanes = 1;
	bmih.biBitCount = 32;
	bmih.biCompression = BI_RGB;
	LPDWORD pixel;
	hBmp = CreateDIBSection(NULL, (BITMAPINFO*)& bmih, DIB_RGB_COLORS, (LPVOID*)& pixel, NULL, 0);
	if (!hBmp) return;
 
	HDC hdc = GetDC(hWnd);
	hMemDC = CreateCompatibleDC(hdc);
//	hBmp = CreateCompatibleBitmap(hdc, WND_SIZE, WND_SIZE);
	hBmpOld = (HBITMAP)SelectObject(hMemDC, hBmp);
 
	for (int y = 0; y < WND_SIZE; y++) {
		double b = ((double)y / WND_SIZE - .5) * 4;
		for (int x = 0; x < WND_SIZE; x++) {
			double a = ((double)x / WND_SIZE - .5) * 4;
			double u = a, v = b, uu, vv;
			for (int i = 1; i < 256; i++) {
				uu = u * u;
				vv = v * v;
				if (uu + vv > 4) {
					int c = i & 0xff;
					*pixel = (c << 8) | c;
//					SetPixel(hMemDC, x, y, RGB(0, i, i));
					break;
				}
				v = 2 * u * v + b;
				u = uu - vv + a;
			}
			pixel++;
		}
	}
 
	ReleaseDC(hWnd, hdc);
}
 
void OnDestroy()
{
	SelectObject(hMemDC, hBmpOld);
	DeleteObject(hBmp);
	DeleteDC(hMemDC);
}
 
void OnPaint(HWND hWnd)
{
	PAINTSTRUCT ps;
	HDC hdc = BeginPaint(hWnd, &ps);
	BitBlt(hdc, 0, 0, WND_SIZE, WND_SIZE, hMemDC, 0, 0, SRCCOPY);
	EndPaint(hWnd, &ps);
}