Re: Accuracy of motion events

On Fri, 2014-08-29 at 16:58 -0500, richard boaz wrote:
you can find a discussion and one possible solution of this in a previous

I think unfortunately the solution is not that easy...

I have a similar problem with my CAD tool
( -- for fast object movements
moving is not as smooth as it could be. First I thought that simple my
drawing speed is still too slow, but after some optimizations that is
not the problem any more. Indeed it is not a big problem for me, and I
was busy with other tasks, so I have not spent time investigating it.
But I found same reports of other people with similar or related

As the author of this question did not provided a minimal test, I just
hacked together this code below. Well it is Ruby, but I would be
surprised if result is much better for plain C. When I move the mouse
pointer fast from left to right, I get the output below, with large gaps
in x coordinate. So I guess that the rate of motion notify events is
indeed low. (I know that there is a POINTER_MOTION_HINT_MASK available,
to suppress too high rates, but that should not help...)
My feeling is, that the maximum event rate is hard coded in GDK library,
I think I read that years ago. Would be not really nice...
stefan AMD64X2 ~ $ ruby test.rb 
4 481
20 481
37 481
57 481
70 481
87 483
104 483
120 483
140 483
160 483
181 483
207 481
226 481

require 'gtk3'

window =
window.set_default_size(800, 800)

window.signal_connect("destroy") {Gtk.main_quit}


window.signal_connect("motion_notify-event") {|w, e|
  print e.x.round, " ", e.y.round, "\n"



On Fri, Aug 29, 2014 at 4:29 PM, ax487 <ax487 gmx de> wrote:

Hello all,

I am wondering about the rate at which pointer motion events are
generated. In my application I draw strokes on a canvas. I noticed that
if I move the pointer at a high velocity the strokes no longer appear as
smooth as for slower pointer motions. The time between motion events (>=
10ms) seems to be inadequate to capture the motion correctly. Is there
anyway to increase the time accuracy?

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