Re: How did Gnome/KDE do it?

[Tristan Van Berkom <tristan van berkom gmail com>]

On Tue, 30 Nov 2004 15:48:50 -0800 (PST), G B
<gbpublicemailaddress yahoo com> wrote:
> Tristan,
> Thanks for that.
> Do you mean that X composite extensions aren't
> available for QT, or for QT and also for gtk?  So in
> gtk, if you move the label, does it know to only
> redraw (clear) the area where the label was
> previously, and then redraw it in the new position, or
> do you, as I suppose, have to take care of what
> regions you want redrawn?  Is the same true of QT?  

If you play with a GtkLabel, the gtklabel.c code will ensure
that the widget was drawn correctly, If you write a custom
widget or use, say; a GtkDrawingArea in conjunction with
a PangoLayout, you'd have a finer grain of control to make
text "scroll" but you'd have to take care of invalidating regions
to be redrawn and drawing to the screen in expose events.
(I have no idea about QT)

> If
> neither toolkits do this, then maybe this function can
> be better done in OpenGL, since you can access the
> framebuffer directly and erase only the old position
> of only the text, which I read that you can't do
> (can't access frame buffer directly) in, at least, QT.
>  However, I've been advised not to use OpenGL in this
> way on the EFNET channel.  Perhaps I misread the
> advise given there.  What are your thoughts on all
> this?

Using OpenGL will probably be faster / more optimized / nicer
depending how you do it (i.e. Render your text once and then just
do fast copies or compositing), but it implies a bunch of portability
issues (also I guess, depending on the approach).
I think that mixing rendering techniques in an application also opens
up a can of worms, but thats nothing that cant be taken care of; or
might already be taken care of by the technologies that are used;
gtk/gtkglext for example.

Thats not really an answer but, its all I've got ;-)

Cheers,
                                                 -Tristan