windows 边框函数 画笔

windows 边框函数 

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	HDC hdc;
	PAINTSTRUCT ps;
	RECT rect;
	static int cxClient, cyClient;
	static	POINT apt[4];

	int i;

	switch (message)
	{
	case WM_SIZE:
		cxClient = LOWORD(lParam);
		cyClient = HIWORD(lParam);

		return 0;

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

		Rectangle(hdc, cxClient / 8, cyClient / 8, 7 * cxClient / 8, 7 * cyClient / 8);

		MoveToEx(hdc, 0, 0, NULL);//修改起始位置
		LineTo(hdc, cxClient, cyClient);
		MoveToEx(hdc, 0, cyClient, NULL);
		LineTo(hdc, cxClient, 0);

		Ellipse(hdc, cxClient / 8, cyClient / 8, 7 * cxClient / 8, 7 * cyClient / 8);

		RoundRect(hdc, cxClient / 4, cyClient / 4, 3 * cxClient / 4, 3 * cyClient / 4, cxClient / 4, cyClient / 4);



		
		/*Rectangle(hdc, 100, 100, 300, 200);
		Rectangle(hdc, 150, 50, 250, 200);

		Ellipse(hdc, 350, 100, 500, 200);
		Ellipse(hdc, 550, 100, 700, 250);

		RoundRect(hdc, 750, 100, 900, 250,30,40);

		Arc(hdc,100, 300, 500, 500, 300, 300, 50, 500);

		Chord(hdc, 100, 300, 500, 500, 300, 300, 50, 500);

		Pie(hdc, 100, 300, 500, 500, 300, 300, 50, 500);*/



	
		EndPaint(hwnd, &ps);
		return 0;

			return 0;
	case WM_DESTROY:

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

画笔 

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	HDC hdc;
	PAINTSTRUCT ps;
	RECT rect;
	HPEN hPen, hOldPen;

	switch (message)
	{

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

		GetClientRect(hwnd, &rect);
		//hPen = (HPEN)GetStockObject(BLACK_PEN);
		hPen = CreatePen(BS_SOLID, 100, RGB(255, 0, 0));
		hOldPen = (HPEN)SelectObject(hdc, hPen);
//把画笔选入工作区，返回被替换的旧画笔
		MoveToEx(hdc, rect.left, (rect.bottom - rect.top) / 2, NULL);
		LineTo(hdc, rect.right, (rect.bottom - rect.top) / 2);
		SelectObject(hdc, hOldPen);
//把旧画笔送回环境中


	
		EndPaint(hwnd, &ps);
		return 0;

			return 0;
	case WM_DESTROY:

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

在代码中 

//hPen = (HPEN)GetStockObject(BLACK_PEN);
        hPen = CreatePen(BS_SOLID, 100, RGB(255, 0, 0));
        hOldPen = (HPEN)SelectObject(hdc, hPen);

GetStockObject 和SelectObject 默认生成HGDIOBJ 类型的队形句柄，如果去掉会报错

错误“C2440: ‘=’: 无法从‘HGDIOBJ’转换为‘HPEN’”

通常发生在尝试将HGDIOBJ类型的值直接赋值给HPEN类型的变量时。HGDIOBJ是一个通用的GDI对象句柄类型，而HPEN是专门用于表示画笔对象的句柄类型。虽然HPEN本质上也是HGDIOBJ，但直接赋值会导致类型不匹配的编译错误。

解决方法

要解决这个问题，可以通过显式类型转换将HGDIOBJ转换为HPEN。以下是两种常见的解决方法：

方法一：使用强制类型转换

HGDIOBJ hGdiObj = SelectObject(hdc, hPen);
HPEN hPenSelected = (HPEN)hGdiObj;

通过强制类型转换，将HGDIOBJ转换为HPEN。

方法二：直接使用SelectObject的返回值

如果SelectObject的返回值是HGDIOBJ类型，但你知道它实际上是一个HPEN，可以直接将其强制转换为HPEN：

HPEN hPenSelected = (HPEN)SelectObject(hdc, hPen);

 背景色和混合模式

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
	HDC hdc;
	PAINTSTRUCT ps;
	RECT rect;
	static HPEN hPen, hOldPen;

	switch (message)
	{

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

		GetClientRect(hwnd, &rect);
		hPen = CreatePen(PS_DOT, 1, RGB(255,255,255));
		hOldPen = (HPEN)SelectObject(hdc, hPen);
		SetBkColor(hdc, RGB(0, 255, 0)); //用于填充 画笔 画刷的背景色
		SetBkMode(hdc, TRANSPARENT);
		SetROP2(hdc, R2_NOT);//混合模式
		MoveToEx(hdc, rect.left, (rect.bottom - rect.top) / 2, NULL);
		LineTo(hdc, rect.right, (rect.bottom - rect.top) / 2);
		SelectObject(hdc, hOldPen);

		EndPaint(hwnd, &ps);
		return 0;

			return 0;
	case WM_DESTROY:
		DeleteObject(hPen);
		PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hwnd, message, wParam, lParam);
}