how-to do Crossplatform transparent windows in c++?

Question

Hello, I'm woundering how to make a window transparent, not cutout holes or the same transparency overall.

Well, just say I wanna slap a PNG-picture of a rose or something and have it blend nicely with stuff in behind and allow stuff behind to redraw and have their changes shine throught the transparent parts of the picture/window.

I could ( or would like to ) use something like wxWidgets or OpenGL. But rather not QT or GTK.

Thanx in advance.

Answer 1

See wxTopLevelWindow::SetTransparent.

If the platform supports it will set the window to be translucent.

So I guess wxWidgets can do it.

Answer 2

If you are willing to do something other than C++, there may be other cross platform options like JavaFx and Adobe AIR.

Answer 3

I found out that it's actually pretty simple to throw up a transparent picture on the screen using wxW:

wxScreenDC dc;

wxBitmap bmp(wxT("test.png"), wxBITMAP_TYPE_PNG);
dc.DrawBitmap(bmp, 250, 100, true);

Now I has to find out how to handle updates and such, it has to be ( maybe partially redrawn ) when something beneath updates.

As it is right now it just redraws itself ontop of itself, making it become fully opacue in a while.

There was another version of wxScreenDC::DrawBitmap that took a window as an argument, maybe it's that one solves this?

Answer 4

How about using shaped frames?

wxBitmap m_bmp = wxBitmap(_T("redroseonwhite.png"), wxBITMAP_TYPE_PNG);
SetSize(wxSize(m_bmp.GetWidth(), m_bmp.GetHeight()));
wxRegion region(m_bmp, *wxWHITE);
bool m_hasShape = SetShape(region);

Look *wxWidgets-2.9.0\samples\shaped* for the full example.