Re: Ugly flickering in some views

[Eric Wasylishen]

Hi Germán,

On 2012-01-23, at 11:15 PM, Germán Arias wrote:

> On 2012-01-23 21:16:01 -0600 Eric Wasylishen <address@hidden> wrote:
> 
>> Thanks for the info.. this is bad because it sounds like the NSCopyBits is 
>> causing flickering.
>> I have another debugging request:
>> -update gui/back again
>> -verify the flickering is back.
>> -open back/Source/cairo/CairoContext.m
>> and change this section:
>> //#    define _CAIRO_SURFACE_CLASSNAME XGCairoSurface
>> //#    include "cairo/XGCairoSurface.h"
>> //#    define _CAIRO_SURFACE_CLASSNAME XGCairoXImageSurface
>> //#    include "cairo/XGCairoXImageSurface.h"
>> #    define _CAIRO_SURFACE_CLASSNAME XGCairoModernSurface
>> #    include "cairo/XGCairoModernSurface.h"
>> to this:
>> //#    define _CAIRO_SURFACE_CLASSNAME XGCairoSurface
>> //#    include "cairo/XGCairoSurface.h"
>> #    define _CAIRO_SURFACE_CLASSNAME XGCairoXImageSurface
>> #    include "cairo/XGCairoXImageSurface.h"
>> //#    define _CAIRO_SURFACE_CLASSNAME XGCairoModernSurface
>> //#    include "cairo/XGCairoModernSurface.h"
>> -make and install back, and try fisicalab again.
> 
> This change solves the problem.
> 
>> I'm assuing you're using the cairo backend. I'm curious if changing from 
>> XGCairoModernSurface to XGCairoXImageSurface will fix the problem. Also it 
>> might be worth trying art or xlib, and see if you still get the same 
>> flickering.
> 
> Yes, I'm using cairo. And with xlib and art all works fine. The problem is 
> only with
> cairo. I don't understand this problem. But, for example, the fisicalab's 
> chalkboard
> works fine. Even when is basically the same. An NSView with a lot of buttons 
> that
> can display images. The only difference is that its content isn't copied from 
> another
> window. And why this problem occurs only when I move the scrollbar to down?
> 
> Thanks.

Ok, thanks for testing. I'm not sure what we should do; I asked Fred's opinion.

If we end up keeping copy-on-scroll on for the release you can put in this hack 
for the problematic scroll view:

[[aScrollView contentView] setCopiesOnScroll: NO];

Not ideal, but debugging flickering problems tends to be very difficult.

-Eric