Re: GTK/GDK equivalent to UpdateWindow() ?

[John Emmas <johne53 tiscali co uk>]

On 4 Jul 2010, at 17:51, jcupitt gmail com wrote:

> What are you trying to achieve? Perhaps there's some other way to get
> the effect you need.

Actually John, it's the same problem that I had in my other thread (where I was trying to draw a "now line" 
onto a scrolling canvas).  Here's what I wrote at the time:-

> I'd like the viewport to have a vertical "now line" (similar to the play head on a tape recorder).  At the 
> moment, this is drawn onto the canvas.  Therefore every 1/30th second, it needs to be erased, then the 
> viewport needs to be adjusted, then the "now line" needs to be redrawn.  This produces a very flickery now 
> line.

Upon closer inspection, the now line isn't really flickery; it's actually "wobbling" slightly, from side to 
side.  I suspect that the erase stage is being queued and not really taking place at the right time (i.e. the 
now line hasn't yet been erased by the time the scrolling movement takes place).  So before trying your 
suggestion of utilising a pixmap (which might be quite difficult to achieve, due to the window needing scroll 
bars and stuff) I thought I might try to 'force' a redraw, immediately after the erase stage (just so that I 
can be certain it's actually being done, and not simply being queued).  gdk_window_process_updates() does 
look as though it should work (assuming it does still do something).  In fact, it looks as if it was designed 
precisely with this kind of scenario in mind.  I'll give it a try and see what happens.