How make wxPanel transparent on Windows and Linux?

[doublemax]

In principle it should work this way, but i can't tell you where exactly it fails.

First try without the child panels and make sure that the parent window redraws correctly. Then add the panel, try commenting out parts of the paining process to see where it fails.

[gpu]

In principle it should work this way, but i can't tell you where exactly it fails.

First try without the child panels and make sure that the parent window redraws correctly. Then add the panel, try commenting out parts of the paining process to see where it fails.

the parent is ok...but when I use wxBufferedPaintDC in Child, the background is black, it seems that the bitmap draws on a blackground buffer.....

[doublemax]

the parent is ok...but when I use wxBufferedPaintDC in Child, the background is black, it seems that the bitmap draws on a blackground buffer.....

Yes, by default it's empty (=black). You shouldn't rely on any content there, the rendering code from the parent would usually draw a background bitmap there or clear it with the background color.

[gpu]

the parent is just set a background color, and draw some simple geometry,
the child panel have a semi-transparent bitmap...but the background is still black, is there any API should be called else?

[doublemax]

Maybe show a screenshot and/or more real code. Ideally a minimal compilable sample that shows the problem.

[gpu]

Code: Select all

Parent::paintEvent(wxPaintEvent&)
{
wxPaintDC(this);  //
Render(dc, GetRect());
}
Parent::Render(wxDC& dc, const wxRect&)
{
//dc.setPen();
//HERE, just draw some simple line for test now
//dc.SetPen(wxNullPen);
}
//////////////////////////////////////
Child::paintEvent(wxPaintEvent&)
{
wxBufferedPaintDC(this);  //
Render(dc, GetRect());
}
Child::Render(wxDC& dc, const wxRect&)
{
//..getParent
parent->Render(dc, GetRect());
dc.DrawBitmap;  //draw the child's semi-transparent background
}

the code is simply like this....sry, that PC can't link to Internet.
And i don't use the rect got from GetRect(), is there problem?

[doublemax]

Code: Select all

Parent::Render(wxDC& dc, const wxRect&)
{
//dc.setPen();
//HERE, just draw some simple line for test now
//dc.SetPen(wxNullPen);
}

The question is what exactly you're drawing here, i.e. do you clear the background before drawing any lines?

Code: Select all

Parent::Render(wxDC& dc, const wxRect&)
{
   dc.SetBrush( *wxWHITE_BRUSH);
   dc.SetPen( *wxWHITE_PEN);
   dc.DrawRectangle( rect );

   dc.SetPen( *wxBLACK_PEN );
   ...
   // more drawing here
}

And i don't use the rect got from GetRect(), is there problem?

This will definitely be a problem in the final code, because the background of the panel will contain the same drawing as the upper left corner of the parent.

[gpu]

This will definitely be a problem in the final code, because the background of the panel will contain the same drawing as the upper left corner of the parent.

But where should I use it ?

[doublemax]

Use wxDC::SetDeviceOrigin(...) so that you're drawing the correct portion of the parent background into the panel's background.

[gpu]

Parent::Render(wxDC& dc, const wxRect&)
{
//dc.setPen();
//HERE, just draw some simple line for test now
//dc.SetPen(wxNullPen);
}

The question is what exactly you're drawing here, i.e. do you clear the background before drawing any lines?

I don't clear the background...I just use dc.DrawLine draw some lines, that's all i did, the only API i call.

[gpu]

the problem is solved, it's the SetdeviceOrigin problem
and I used wxPaintDC for both the parent and child, cause if use wxBufferedDC for the Child , the Child's background is always black!
thanks!