WM_CTLCOLOR,WM_ERASEBKGND,WM_PAINT联系-优快云博客

本文链接：https://blog.youkuaiyun.com/coolboylai2/article/details/7238712

本文探讨了Windows消息处理机制中WM_ERASEBKGND与WM_PAINT的关系，特别是如何在对话框中自定义背景绘制而不依赖于默认的WM_CTLCOLOR消息。通过示例代码展示了如何直接在WM_ERASEBKGND消息处理函数中实现背景色和图片的绘制。

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首先感谢Rupesh Shukla大神指点

Default implementation of WM_ERASEBKGND message handler erases invalidated areas and fills it with color of the brush window was register with.
After that, native drawing is done in WM_PAINT handler. If you return TRUE from WM_ERASEBKGND you tell system to not to erase background and that is why you do not have background impact on your dialog.

Thanks

相关提问点击打开链接

缺省地，WM_ERASEBKGND消息先擦除有效区域，然后然后用画刷填充有效区域，这时候通过WM_CTLCOLOR消息响应函数获取画刷，然后再处理WM_PAINT消息，如果你在WM_ERASEBKGND函数里面返回TRUE的话，就不会去调用默认的处理方法，也就不会发送WM_CTLCOLOR消息

一个没有确定和取消按钮的对话框，它发送消息是这样的

WM_ERASEBKGND-->WM_CTLCOLOR(此时是整个对话框需要确定window画刷，），然后在发送WM_PAINT消息，

如果在WM_ERASEBKGND响应消息返回TRUE，则不会去调用默认的消息处理方法，那么自然不会调用WM_CTLCOLOR消息的处理函数；顺序为

WM_ERASEBKGND--WM_PAINT，如此循环

至此在WM_ERASEBKGND处理函数里面贴出来的图已经显示出来了，但是背景色没有改变，既然不能用到默认的调用WM_CTLCOLOR消息的处理函数，那么我们就可以先画背景，然后在贴图，代码如下：

BOOL CControl5Dlg::OnEraseBkgnd(CDC* pDC)
{
	this->OnCtlColor(pDC,this,CTLCOLOR_DLG);
	BITMAP m_bitinfo;
	m_bitmap.GetBitmap(&m_bitinfo);
	CDC dcCompatible;
	dcCompatible.CreateCompatibleDC(pDC);
	dcCompatible.SelectObject(&m_bitmap);
	pDC->StretchBlt(0,0,m_bitinfo.bmWidth,m_bitinfo.bmHeight,&dcCompatible,0,0,m_bitinfo.bmWidth,m_bitinfo.bmHeight,SRCCOPY);
	return true;
	//return CDialog::OnEraseBkgnd(pDC);
}

HBRUSH CControl5Dlg::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
	HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);

	switch(nCtlColor)
	{
	case CTLCOLOR_DLG:
		return m_brush;
		break;
	}

	return hbr;
}

如此效果如下：