Re: (severe) performance issues

[Ivan Baldo <ibaldo adinet com uy>]

 Hello.

El 29/03/07 12:26, Paul Davis escribi� this is a sort of known "bug". setting the text of a label causes a
> 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
> their contents.
>
> 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.
>   
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.

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 :).

Goodbye.

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