[Win32]增强型元文件

上一个程序使用的元文件的PlayMetaFile不能指定显示位置，增强的元文件解决了这一麻烦。
这个程序也有一定的问题，两条线的起点和重点可能跟矩形的顶点不在一个位置。

1.1.main.c

#include <windows.h>

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

TCHAR szAppName[] = TEXT("EMF1");

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
	HWND     hwnd;
	MSG      msg;
	WNDCLASS wndclass;

	wndclass.style = CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc = WndProc;
	wndclass.cbClsExtra = 0;
	wndclass.cbWndExtra = 0;
	wndclass.hInstance = hInstance;
	wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wndclass.lpszMenuName = NULL;
	wndclass.lpszClassName = szAppName;

	if (!RegisterClass(&wndclass))
	{
		MessageBox(NULL, TEXT("This program requires Windows NT!"),
			szAppName, MB_ICONERROR);
		return 0;
	}

	hwnd = CreateWindow(szAppName, TEXT("Enhanced Metafile Demo #1"),
		WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN,
		CW_USEDEFAULT, CW_USEDEFAULT,
		CW_USEDEFAULT, CW_USEDEFAULT,
		NULL, NULL, hInstance, NULL);

	ShowWindow(hwnd, iCmdShow);
	UpdateWindow(hwnd);

	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	static HENHMETAFILE hemf;
	HDC hdc, hdcEMF;
	PAINTSTRUCT ps;
	RECT rect;

	switch (message)
	{
	case WM_CREATE:
		// 创建内存增强元文件，最简单的方式
		hdcEMF = CreateEnhMetaFile(NULL, NULL, NULL, NULL);

		Rectangle(hdcEMF, 100, 100, 200, 200);

		MoveToEx(hdcEMF, 100, 100, NULL);
		LineTo(hdcEMF, 200, 200);

		MoveToEx(hdcEMF, 200, 100, NULL);
		LineTo(hdcEMF, 100, 200);

		// 关闭元文件，获得句柄
		hemf = CloseEnhMetaFile(hdcEMF);
		return 0;

	case WM_PAINT:
		hdc = BeginPaint(hwnd, &ps);

		GetClientRect(hwnd, &rect);

		rect.left = rect.right / 4;
		rect.right = 3 * rect.right / 4;
		rect.top = rect.bottom / 4;
		rect.bottom = 3 * rect.bottom / 4;

		// 显示
		PlayEnhMetaFile(hdc, hemf, &rect);

		EndPaint(hwnd, &ps);
		return 0;

	case WM_DESTROY:
		// 删除
		DeleteEnhMetaFile(hemf);

		PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hwnd, message, wParam, lParam);
}

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