Re: (severe) performance issues
- From: Ivan Baldo <ibaldo adinet com uy>
- To: gtk-list gnome org
- Subject: Re: (severe) performance issues
- Date: Thu, 29 Mar 2007 16:22:24 -0300
El 29/03/07 12:26, Paul Davis escribi� this is a sort of known "bug". setting the text of a label causes a
I don't know if this applies to the original person with the problem,
but there is a simple optimization for when an application repeatedly
sets the same text to the label.
In gtk_label_set_text and gtk_label_set_label a simple strcmp of the str
argument against the label or text fields of the label structure can
avoid all re-computations and mallocs and frees when the text specified
is the same as the previously one.
recompute of the label's size, which can propagate up the containing
widget tree. add Pango into the mix, and that resetting is very costly.
the same is not true of text entries, because they never resize based on
evolution, sodipodi (the precursor to inkscape) and a few other projects
have implimented their own labels that do not do this, for precisely the
reason you are now discovering.
In my case, I write applications in a very dumb way, I expect that GTK
detects such silly things and avoid computations when it can.
For example in a current application that I am working I set values for
a group of spinbuttons when only one changes, so I set all the values to
the previously set ones and only change one.
Doing it in a smarter way means I need to put more time on it, slowing
the true advancement of the application. Luckily it seems that
gtk_spinbutton_set_value checks that the value has really changed and
avoid expensive operations if it doesn't.
I expect the same behavior in all GTK facilities, helping the user when
it is reasonable and easy to do.
In gtk_label_size_request there is code to get the desired width and
height of the label, that could be called on the set_text and set_label
functions to see if they differ to the current allocated ones by a
threshold, and only then call gtk_widget_queue_resize_no_redraw
(expensive?) and always do a redraw (since the text is different so
something has changed).
I am not an expert on GTK so I am really shy to try to implement this,
benchmark it, test it, etc. since I don't understand it fully...
Also because of that, maybe this email is totally wrong, I may be
misunderstanding everything :).
Ivan Baldo - ibaldo adinet com uy - http://ibaldo.codigolibre.net/
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