Re: Emacs flickers periodically

[Dmitry Gutov <dgutov@yandex.ru>]

On 6/17/17 9:35 PM, Eli Zaretskii wrote:

> Flickering is not caused by display synchronization.  It is caused by
> constant redrawing of large portions of display with the same content.

Not necessarily large ones. And vice versa, large portions of display 
can be redrawn often and the user might be fine with it if only 
consistent states are shown. The result might be called "animation".

>>> AFAIK, Emacs never redraws display in inconsistent state (barring
>>> bugs, of course).
>>
>> But that's the effect that the double-buffering patch brings: limiting
>> redrawing to consistent states only.
>>
>> So maybe those were bugs (like 12363 and 16621), but they went unfixed
>> until Daniel's patch.
> 
> That's not what double-buffering does.  What it does, AFAIU, is let
> Emacs redraw however many times it wants, and then bitblt the result
> only once to the glass.

Those are implementation details. In effect, the redraw happens once.

But *when* does it happen? If the choice of this moment was not good 
enough, bugs 12363 and 16621 would continue occurring.