On Wed, 2004-04-07 at 09:10, Xiong Huan wrote: > Hi, > > I am considering leverage DirectFB's RGBA support and exposing it on > GDK/GTK level. I noticed gdk-directfb uses standard GdkColor definition and > thus hides the underlying alpha-blending support. So I appended a new filed > "guchar alpha" in GdkColor structure, and in gdk_directfb_setup_for_drawing() > I assigned this value to "alpha" varialbe rather than used the original > hardcoded one(0xFF). I think this is a simple way to pass alpha value from > user to directfb and, at the same time, make as little change as possible. > > Then I modified gtk_style_real_realize() in gtkstyle.c trying to test my > change. I hardcoded style->black.alpha to be 120, which is later passed to > gc_values.foreground. Then I run a simple gtk button application, thinking > its foregound color will be semi-transparent. However, there is no change at > all. > > I added some debug information in gdk_directfb_draw_lines() function and > notieced the alpha value(120 in my case) was really passed in it. But why it > has no effect at all? > > Am I missing somthing here? Can anyone throw some light on it?
I believe this was just discussed a few weeks ago on the list, so you may want to check the archives. My understanding is that gdk-DirectFB only supports transparency at the "window" level. Now there is often confusion about what is a window, since the meaning differs from platform to platform and framework to framework. To make a long story short: you are not assigning the transparency at a high-enough hierarchy level. I'm just rehashing my understanding of what was discussed. I'm not a GTK/DirectFB expert. -- Thanks, Bill Hayden -- Info: To unsubscribe send a mail to [EMAIL PROTECTED] with "unsubscribe directfb-users" as subject.
