Re: Transparent binary bitmap outside a window

[Jonathon Jongsma <jonathon jongsma gmail com>]

The "Wheelbarrow" example may be helpful here:
http://www.gtkmm.org/docs/gtkmm-2.4/examples/window/wheelbarrow.cc

I couldn't find it in the current tutorial, but it seems to me it used
to in the tutorial (maybe it still is and I couldn't find it).  But
the example file still exists on the server.
jonathon

On 11/23/05, Paul Davis <paul linuxaudiosystems com> wrote:
> On Wed, 2005-11-23 at 01:37 -0500, Martin Bailey wrote:
> > Hi,
> >
> > Sorry for asking such a basic question; I'm simply unable to unable to
> > find my answer in the documentation and this is my first attempt at gtkmm.
> >
> > I'd like draw a Bitmap outside a Window. That is, I would like to draw
> > an irregular black shape (from a bitmap matrix) directly in the display,
> > over any other programs.
> > I don't want to draw inside a Window because I don't want my application
> > to receive any events; just draw over other applications, or in a way
> > hide some parts of them with a binary bitmap.
> > For example, with a 1024x768 resolution, I want a background PDF viewer
> > to remain visible while I can draw anything over it in the same 1024x768
> > region.
> >
> > So as I understand, I must create a Bitmap in the same way that I create
> > a Window, and then create a GC to draw inside my bitmap.
> > Is that right?
> > What C++ code do I need to get these elements created properly?
>
> it doesn't work this way.
>
> all drawing goes to a window. no exceptions.
>
> what you can do is to use Gtk::Window::shape_combine_mask() to change
> the shape of the window from rectangular to the outline of your bitmap.
> you will need to experiment with shape_combine_mask() - i have used it
> long ago, and its slightly more complex than it appears. google may even
> find some postings of my (and others') code.
>
> the other thing you might look at for insight is a program called
> gromit, which allows the user to scribble directly on the display,
> although AFAIK it also uses the shape_combine_mask() trick. i use gromit
> for presentations when i want to be able to draw over the top of (e.g)
> an openoffice slide show.
>
> --p
>
>
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