Re: evaluating GTK+ for embedded system design

[Tristan Van Berkom <tvb gnome org>]

peter greve bst-international com wrote:
> Hello,
>
> I am actually planning the GUI for an embedded system driven by a PowerPC.
> So GTK++ is one of the options I can go with. I like the GIMP tool, so GTK
> should be a good choise.
> But I have no feeling concerning resources, CPU load and library size
> needed to run a GTK app in the "embedded world".
> Maybe someone can give me some rough ideas or experiences.
>
> Is GTK a tool for desktop computers only or does is also fit into the
> embedded world?

GTK+ is taylored for the desktop, but that has given me little or
no trouble fitting it in to an embedded environment.

For example... if you're developing full-out colorfull GUIs on
a fixed resolution you might want to work with GtkFixed instead of
variable size placement containers.

I've found this particularly usefull where the graphist will taylor make
the graphic for every single button & background by hand (i.e. the
graphist doesnt want to hear about scaled graphics nonsence... he wants
his button to fit with his background at position x,y).

> What is the size of all libraries needed to run GTK ?

I'm not sure... are you using straight-up libc or uClibc or
somthing else ?

> Do I really need the whole GIMP to run GTK as I red somewhere? (that sounds
> very large)

Umm, no ? ... to run GTK+ you only need GTK+

> Do I need a lot of CPU power to run a GTK GUI ?
> Is there a spezialied version for the "embedded world"? What is about "GTK+
> on DirectFB" ?

I dont know if there's a stable version of DirectFB that works with
modern versions of GTK+, if so I'd like to try it out ;-)

> Does GTK needs the X-Window system? Can I go with Tiny-X?

Yes for now, and yes (GTK+ with X backend needs an xlib implementation).

although I believe people are working on another backend implementation
for OS X (since you are targeting a Mac right ?).

> We have to handle a lot of large images on the GUI (1280x1024, 24bit). Is
> there a bottleneck in GTK or X11 to handle these data so I should avoid
> these tools?

When you are working with X, you have to keep the round-trips in mind...
and the difference between server and client memory, for example if you
want to animate some frames... loading them as GdkPixmaps first will
be a performance gain.

> Is there a "visualizing" tool to help to design the GUI and the underlying
> dialogs?

There is glade, we find it very powerfull since it allows us to
update the look'n'feel of our device simply by updating the graphics
files, the glade xml GUI layout and the gtkrc "theme" file (no code).

> Is there a way to adapt a special graphics processor (coming with an
> appropriate API) to an GTK application ?

I dont see that in the scope of a GUI toolkit, this belongs in the
backend (i.e. the drm kernel modules, the dri etc).

> Do I need to write something like a driver for that graphics processor to
> connect to the GTK app? (I red something about GDK)
> How can I support special features of that graphics processor like alpha
> blending and text anti aliasing? Are these features already supported by
> GTK ?

AFAIK HW acceleration is not used for alphablending using your
typical client-side rendering routines (GdkPixbuf), you'll probably
want to throw in a little GtkGLExt OpenGL sugar on top for that.
(also take a look at what the Xgl people are doing).

(/me is completely clueless when it comes to font rendering in
Cairo too).

Cheers,
                              -Tristan