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List:       gtk-app-devel
Subject:    Re: I can't understand the difference output of only a line differ
From:       Binary Chen <binary.chen () gmail ! com>
Date:       2007-12-06 12:29:17
Message-ID: 1196944157.12516.32.camel () binch-laptop
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On Thu, 2007-12-06 at 11:53 +0000, Emmanuele Bassi wrote:
> On Thu, 2007-12-06 at 19:40 +0800, Binary Chen wrote:
> >  
> > > gdk_draw_image() forces a flush. but that is not the problem: you should
> > > never use a while() loop inside a GTK+ application, because you are
> > > effectively blocking the real main loop from spinning. remember: GTK+ is
> > > not threaded.
> > 
> > Yes, I know GTK+ is not threaded, there is only one thread running, so
> > this make things more complecated, whats loop am I prohibit running?
> 
> the main loop that processes and delivers the events and handles the
> redraws, and that is invoked by gtk_main(). you should read the GTK+
> documentation, at this point.
> 
> > Again I'd like to say in both testing the gtk_main() is not running at
> > all, so whats the difference? Can you point out the exact source of such
> > headache problem?
> 
> the exact source is, in this case, a PEBKAC; the documentation available
> on how GTK+ works (at this level, at least) is quite abundant; the GTK+
> tutorial should shed some more light.
> 
> > > 
> > > use a timeout or an idle source to repaint your window with the
> > > GdkImage.
> > > 
> > This is just a testing program, not production code, I just want to find
> > out whats happening.
> 
> what's happening is that you are blocking the main loop from ever
> running, so any result you see is an undefined behaviour.
> 
> for the third time: use a timeout/idle source instead of the while()
> loop to hook into the GTK+ main loop.
You don't know my situation. I am writing a media player which need to
copy the decoded bitmap into screen.
I am using gdk_draw_image to draw a GdkImage to the drawing area.
g_timeout_add is too slow because it need to update the screen  > 20
times/sec.
So I need to use a FAST blit to screen, which is only possible using
busy while... but only if the delay is very small using usleep(1), the
result is - no things on screen.
Image a situation that a thread is doing decoding and put the result in
somewhere memory, another thread drawing to GTK+ widget.

Bin

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