Re: [Emacs-diffs] master 5c9304e: Disable some display optimizations when frames need redisplay

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> Fundamentally, the only redisplay flags needed are the window ones.
>> The frame and buffer's redisplay flags could be dispensed with, at the
>> cost of making [bf]set_redisplay more expensive since they'd have to
>> loop through all the windows of that frame/buffer.
> Yes, I agree.  But is that justified?

I did not make any measurements, I only went with my intuition.

> At least for the frame's flag, a test for each window of the frame's
> window tree has the same cost as setting the window-specific flag in
> fset_redisplay.

Right.  Tho we loop through all the frame's windows in the redisplay
anyway (IOW, I reused pre-existing loops).

> However, the test is made only once per redisplay cycle, whereas the
> setting could be done several times, depending on what Lisp is being
> run.  Right?

I think for fset_frame either way would work about as well: it should be
relatively rarely used anyway.  OTOH for bset_redisplay, I expect that the
cost of finding all the buffer's windows would be clearly too costly.


        Stefan