The highlighter doesn't work under Windows about ardesia HOT 14 CLOSED

The problem is that the gdk_screen_get_rgba_colormap doesn't work correctly 
under Windows and then Ardesia is working without an alpha channell.
We must investigate furthermore if exist a way to work with RGBA color with 
Cairo on windows.
In the current implementation on windows in order to have a transparent window 
I use
a layered window using the black as the "transparent color" but the colormap is 
rgb.

Ypu can read an explanation about 
this problem on http://cairographics.org/samples/dotnet-gdi-rendering/
and a sort of solution also

The example on http://cairographics.org/samples/dotnet-gdi-rendering/
is written in C# and works using an other image surface. This is out of our 
scope because we want have a surface connected to the gtkwindow (or the HDC 
associated)

I have attempt to create a surface with cairo_win32_surface_create_with_ddb
in this way:

cairo_win32_surface_create_with_ddb(hdc, CAIRO_FORMAT_ARGB32, 
gdk_screen_width(), gdk_screen_height());

But I have a not paintable white window as result. It doesn't work  

The goal is have a cairo surface and cairo context attached to the GdkWindow as 
done 
with this code (copied by annotation_window_callback.c):

--------------------------------------------------------------------------------
-----
/* The hdc has depth 32 and the technology is DT_RASDISPLAY */
      HDC hdc = GetDC(GDK_WINDOW_HWND(data->annotation_window->window));
      /* 
       * @TODO Use an HDC that support the ARGB32 format to support the alpha channel and the highlighter
       * In the documentation is written that the now the resulting surface is in RGB24 format
       * 
       */
      cairo_surface_t* surface = cairo_win32_surface_create(hdc);

      data->annotation_cairo_context = cairo_create(surface);

--------------------------------------------------------------------------------
---

but using ARGB32

If will achieve the goal to have a paintable surface with alpha could be 
possible deny the layered window usage to have the transparent window.

Can Help use UpdateLayeredWindow with a blend function?

I have tried to use the UpdateLayeredWindow with a blend function but I have 
the same misbehaviour

http://comments.gmane.org/gmane.comp.lib.cairo/21593

Seems that the not RGBA colormap is a gdi limit that will be fixed by the GTK3

The Gtk 3 is out; the bug could be fixed porting the code from the gtk 2 to the 
gtk 3

Ardesia on subversion repository has been ported on gtk3.
Are there some volunters that want to try to build Ardesia on WIndows and 
update the issue status.

Ardesia is ported on GTK3 that this issue has become invalid.