问题
This question was generated by a response to another question: Common Controls on a Transparent Window?.
Apparently, there is a way to only paint the background without a control painting itself again This would solve the problem of having common control buttons on a transparent background.
So my question is, how do I paint only the background around a common control after the common control has painted itself?
回答1:
About how to redraw visible borders.
The rounded rectangle drawn by RoundRect is used as representative
The FrameRgn function draws a border around the specified region by using the specified brush.
Simple code demonstration：
HRGN hRegion = ::CreateRoundRectRgn (0, 0, ClientWidth, ClientHeight,12,12);
Canvas->Brush->Style = bsSolid;
Canvas->Brush->Color = RGB(96, 96, 96);
::FrameRgn(Canvas->Handle, hRegion, Canvas->Brush->Handle, 2, 2);
::DeleteObject(hRegion); // Don't leak a GDI object
Link you need: Redraw Border
来源：https://stackoverflow.com/questions/56694648/how-do-i-force-a-repaint-of-only-the-background-so-a-control-doesnt-repaint-ove