[ scummvm-Patches-1183808 ] GUI: Less CPU-intensive credits scroll

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Patches item #1183808, was opened at 2005-04-15 16:57
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Torbjörn Andersson (eriktorbjorn)
Assigned to: Nobody/Anonymous (nobody)
Summary: GUI: Less CPU-intensive credits scroll

Initial Comment:
Currently the credits scroll in the ScummVM "About"
window is agonizingly slow. This is because each time
the text is updated it issues a full redraw, which will
redraw both of the active dialogs. Both of them will
call the blendRect() function to draw the transparent
background.

On my 450 MHz PIII each call to blendRect() takes
something like a tenth of a second, possibly a bit
longer. The overhead from drawing the remaining parts
of the dialogs is trivial by comparision.

This patch is an attempt to speed things up. The first
time the dialog is drawn, it makes a "snapshot" of the
blended background. Then, instead of issuing a full
redraw every time it redraws only the "About" dialog
itself, and this time it uses that snapshot as
background. (The snapshot will be regenerated if the
screen changes.)

It is, perhaps, a bit hackish, but I really don't see
any other way.


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