[Ardour-Dev] SuperRapidScreenUpdates are neither rapid, nor super.

Paul Davis paul at linuxaudiosystems.com
Tue Mar 10 06:26:46 PDT 2009

On Tue, Mar 10, 2009 at 8:09 AM, John Emmas <johne53 at tiscali.co.uk> wrote:

> ----- Original Message -----
> From: "Paul Davis"
>> that said, nick mainsbridge did come up a way (a rather obvious way, in
>> retrospect) for us to use the canvas and make this work. but it involved
>> ceasing all use of the canvas's own scrolling/zoom mechanism, and setting
>> up redraws in our own code.
>>  It's entirely possible that I've misunderstood this (or maybe I'm looking
> in
> the wrong place) but that doesn't tie in with what I can see (at least, not
> in Ardour 2).  Scrolling the canvas in 'moving timeline' mode appears to be
> accomplished by programmatically 'repositioning' its horizontal scrollbar
> and letting gtk do the work.

nope. we have the move the scrollbar, but that would conventionally been
done so that the GtkAdjustment connected to the scrollbar was changed. And
then, when the adjustment changed, the canvas gets notified and repositions
itself. at this point in time, the canvas no longer pays any attenton to the

editor_canvas.cc contains Editor::scroll_canvas_horizontally() - you will
find that we change the scrollbar (for appearance sake) and then "manually"
move each part of the canvas as needed.

Unless Nick's changes were done a long time
> ago (or after version 2.7.1) that seems to have been the mechanism for a
> very long time (at least dating back to Ardour 2.4)..
> I'd love to be proved wrong but from what I've observed, around 90 percent
> of Ardour's work is being done in a single thread - and the more work that
> gets added to that thread, the slower it gets.

the GUI thread is not using very much CPU, and we'd have to add a lot more
to it before it would be overloaded.

 But at this point in time - and expecially, given the evidence that
> the problem has crept up slowly and progressively

there's no evidence of this john. you might be the only person on the planet
who is using the stationary playhead mode, certainly with any recent
versions of ardour. the problem could easily have started with a single

> - I'd be surprised if it's
> anything more complicated than an overworked thread.

an overworked thread implies that a CPU monitor (and i cannot believe that
you have been unable to find this on your system) would show the CPU maxxed
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