Re: graphics!!

[Michael L Torrie <torriem chem byu edu>]

On Mon, 2006-05-08 at 22:27 +0300, Juhana Sadeharju wrote:
> > I think you may need to use a canvas. For example:
> > http://developer.gnome.org/doc/API/2.0/libgnomecanvas/index.html
> > http://www.dachaplin.dsl.pipex.com/goocanvas/
>
> Do they have a graph widget? Or are they more primitive?

No. GTK only provides primitives.  There have been several graph widgets
implemented using GTK.  

> I need such a widget in audio apps:
> (1) Envelopes drawn over the audio waveform widget.
> (2) Frequency response curves of multiple parametric filters
>     drawn in one canvas.
> (3) Control envelopes.

All of these things would need to be implemented using primitives.  GTK
is just a GUI toolkit, not a domain-specific toolbox.  Audacity (which
uses wxWidgets not GTK) implemented their own widgets for dealing with
waveform graphs and selections and things.

> Much of the stuff what can be seen in VST plugins, in Absynth
> (specially envelopes), Waves' plugins, etc. They look nice too
> unlike what I most see here.
>
> Does GTK canvases provide transparency? What programs uses the
> canvases? I might want see how they look like.

There is no GTK canvas officially yet.  There are several
implementations of canvases for GTK including gnome-canvas, foo-canvas,
etc.  They vary in purpose and function.

> With gtkglext/opengl all seems to be eventually simpler.
> Multiple "widgets" can be combined by using suitable transparency
> and depth coordinates. Decorations are done easily, e.g., by
> modeling objects in 3D. But then I cannot use the GTK widgets
> indistinctly. Interaction with the opengl objects comes a problem
> as well, making it tempting to use, e.g., OSG (openscenegraph.org).
> But that is a large software and written with C++, which could be
> a problem if I want code in C.
>
> How would GTK's Cairo integration help? If at all.

Using Cairo do do you drawing of wave forms, envelopes, etc is a good
idea if Cairo is fast enough to do what you need to.  Certainly it seems
to me that a waveform graph, envelopes, etc would be well-suited to a
vector-drawing API.

> Juhana