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[PATCH] Faster text rendering by optimizing font glyph lookup


From: Colin D Bennett
Subject: [PATCH] Faster text rendering by optimizing font glyph lookup
Date: Sun, 8 Feb 2009 13:49:53 -0800

This patch greatly—*tremendously*, even, if higher-numbered Unicode
characters are used—speeds up retrieving a glyph for a particular
Unicode character.  This makes text rendering in general much faster.

My text benchmark shows the new text rendering speed is somewhere from
2.6x to 31x of the previous speed.  Basically, PFF2 font files are now
required to have the character index ordered in ascending order of code
point.

Fonts created by 'grub-mkfont' already satisfy this requirement.  Fonts
created by my old Java 'fonttool' do not, and cannot be used any longer.

The font loader verifies that fonts fulfill the character ordering
requirement, refusing to load invalid fonts, but the primary change is
in the 'find_glyph()' function, which now uses a binary search rather
than a linear search to find the glyph.

Regards,
Colin

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