Re: Ugly flickering in some views

[Germán Arias]

On 2012-01-24 16:55:21 -0600 Fred Kiefer <address@hidden> wrote:

> On 24.01.2012 20:04, Eric Wasylishen wrote:
>> 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.
> 
> German's problem was before you applied r34614, how did that change affect 
> this problem? But that patch seems to have its own problems.
> 
> My main problem is when resizing a whole window, this flickers horribly, but 
> I am not sure whether GNUstep is causing this or my driver for the graphic 
> card. But it happens only with GNUstep windows.
> 
> 
> What are our options here?
> 
> - Find a proper solution within the next few days.
> 
> - Disable copy-on-scroll in all scroll views.
> 
> - Revert to the old cairo surface.
> 
> - Ignore the problem as it only happens for some views.
> 
> None of that (apart from the first one, which isn't that realistic) sounds 
> too attractive. Disabling copy-on-scroll will make scroll views horribly slow 
> and affect everybody, even people not using cairo. I think I hate the option 
> to revert the standard cairo surface the least. This should send us back to 
> the way GNUstep was about a year ago, but we can revert this step if we find 
> a proper fix for the open issues.
> 
> Fred
> 

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