Follow-up Comment #5, bug #21003 (project mypaint):
Here's a sample of the improved smoothness at a faked (linearly interpolated)
400 Hz. Column on the left is master (without this patch); column on the right
is the experimental branch I've been working on.
I've measured my raw input processing speeds with my equipment and (without
background dabs to render) got ~50 or ~60 events per second with a Synaptics
touchpad, and (to my surprise) ~200 (still!) with my Wacom Intuos 5. That's
with the queueing branch.
Input event call average time since last event, in seconds
Measured with Debian GTK+ 3.8.2, brush "deevad/2b_pencil"
Branch Work? Synaptics Wacom
------------------ ----- --------- --------
master@cf723b7 n 0.0121 0.0050
master@cf723b7 Y 0.0121 0.0050
master@3973dae n 0.0121 0.0051
master@3973dae Y 0.0218 0.0217
gtk3-stroke-queue n 0.0121 0.0050
gtk3-stroke-queue Y 0.0192 0.0196
- "Work" means dabs (i.e. button pressed or pen nib down)
- Times are settled averages after ~5s of fast input to allow
queues to fill up with work, tiles to be allocated etc.
So I guess that means I'm not yet affected by the upstream regression with
Debian's GTK+ 3.8.2. 3.9 may deliver *every* event arriving at 50Hz or 60Hz,
lamentably, so let's prepare for that as best we can.
Any visible angularity in the "wacom pen + no queues" scribble must have been
due to rendering work *alone* slowing things down under GTK3. The upstream
changes introduced in the linked bug do not explain the observed angularity
for a device which would be processed at 200Hz *without* background work to
do.
(I assume nothing's changed in the MyPaint rendering engine, so I'm stumped as
to why GTK3 would be generally slower than GTK2 for processing input events,
but it is and we have to deal with it. Scheduling changes? A refusal to
re-schedule slow input handlers at a fast rate? I don't know.)
(file #18694)
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