I decided to engage in some blingineering today, and put together a self contained demo of how to make a semi-transparent window (ie with an alpha channel) using GTK+. For this, you will need GTK+ 2.8 or higher, Cairo, a modern X server and a running compositing manager. Any very recent Linux distro should meet the bill, I’m using SUSE 10.1.
And here is the heavily commented source code (python version).
This stuff should be documented in the GTK+ manual proper I guess, but hopefully Google will see this and it’ll go into the global pool of knowledge along with everything else. There are still a couple of problems:
- It’s not clear to me how to detect if a compositor is running or not. I guess there should be (maybe is) a simple X property on the root window you can check to see if one is running. Until we fix that it’s hard to use this technique in production software because people not running a compositing manager will see a black background instead of a transparent one.
- There should be a more convenient API in GTK+ for this, gtk_window_set_translucent() or something. Maybe we need a SexyWindow class, Christian?
March 26, 2006 at 3:27 pm |
The “how to detect if a compositing manager is running” was discussed on xdg a while ago. See this thread:
http://lists.freedesktop.org/archives/xdg/2005-September/007355.html
AFAIK, nothing was agreed on though
March 26, 2006 at 5:43 pm |
Hi Mike!
You’ll maybe also like to take a look at some code I wrote a couple of weeks ago not only offering decoration-less and transparent windows, but also input-shape support. Take a look at it here: http://macslow.thepimp.net/?p=26
There’s the code: http://macslow.thepimp.net/projects/input_shape_test.c
And also a screencast of it in action: http://macslow.thepimp.net/clips/shape-input-example.avi
Btw, that circular redish thing looks familiar
Best regards…
MacSlow
March 26, 2006 at 7:08 pm |
Metacity’s compositor takes ownership of the CM_Sn selections (where n is 0 to the number of screens).
You can just watch that to see when when a compositing manager becomes available or unavailable.
March 26, 2006 at 8:08 pm |
Your code appears to have a small bug.
If you switch from a alpha-supporting display to a non-alpha-supporting display then the supports_alpha boolean never gets set back to FALSE.
March 27, 2006 at 6:30 am |
MacSlow, I put links to our demos on the Cairo page, and linked to your work in a new blog entry. Great stuff there, you should definitely be on planet gnome!
March 27, 2006 at 10:36 am |
Thanks, Mike! Well, being on p.g.o would sure be something
Best regards…
MacSlow
March 27, 2006 at 12:57 pm |
Yeah, I hope that stuff goes directly into gtk! I have also written that kind of code for gnome-launch-box (http://developer.imendio.com/wiki/GNOME_Launch) a while ago. And also a gdk_screen_has_compositor () or something would be ueber-useful.
March 27, 2006 at 7:56 pm |
See also http://neugeirig.org/software/ghosd/ . (Or Google for “ghosd” if your blog strips out links…)
March 27, 2006 at 7:57 pm |
See also http://neugierig.org/software/ghosd/ . (Or Google for “ghosd” if your blog strips out links…)
Sorry for the double-post. Typo.
September 10, 2006 at 10:09 pm |
Hi , great job , i was exactly looking HOW TO use alpha channels , so , if isnt too much to ask , dont you have the same code in perl? I am actually using perl-Gtk
Thanks lot man!
February 15, 2007 at 5:46 pm |
Hi,
Do you plan to implement a nice gtk engine base on your cairo trick in order to have translucent windows background ? Couple with beryl and emerald, this might allow us to mimic Vista Aero Glass. I don’t mean a want a gratis Vista Aero Glass, the point is the technical challenge. It’s up to us to use it nicely. (ex. beryl use heavily effect to provide consistency and accessibility to the desktop).
Keep up the good work !
Étienne.
April 23, 2008 at 2:31 pm |
I was trying this code to add transparency to a widget. In this code i have added a drawing area as a child of Window and drawn the shape in drawing area. But the drawing area was having black background. Could anyone tell me how to make that drawing area transparent.
December 19, 2008 at 4:10 pm |
Hi,
I’ve manage to translate your code to Ruby/GTK, and it works well too!
I was looking for a way to create a custom tooltip to be displayed next to a StatusIcon (in the system tray) and this code give me many highlights on it. Thank you very much.
The code can be checked here (I’ve kept the comments in it, hope you don’t mind):
http://pastie.org/343287
Vicente
February 23, 2009 at 5:56 pm |
… and here’s a Perl version
http://pastie.org/397570
Su-Shee
May 17, 2009 at 7:47 am |
[...] windows with alpha channels and Cairo http://mikehearn.wordpress.com/2006/03/26/gtk-windows-with-alpha-channels/ [EXAMPLE] [...]