[cairo-bugs] [Bug 11612] pack as many glyphs as possible in each cairo_show_glyphs() call

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Mon Feb 4 14:27:32 PST 2008


--- Comment #16 from Adrian Johnson <ajohnson at redneon.com>  2008-02-04 14:27:29 PST ---
(In reply to comment #15)
> One of the problems with calling cairo_show_glyphs() with one glyph at a time
> is that when text knockout is true (the default) overlapping transparent glyphs
> in each text object will composite with each other. Poppler needs to call
> cairo_show_glyphs() with all glyphs in the text object to ensure that the
> glyphs do not composite with each other. If TK is false poppler needs to call
> cairo_show_glyphs() with one glyph at a time.

I should also add that PDF can change the font, font scale, and maybe other
graphics state (the PDF reference is not clear on this) inside a a text object.
As cairo only supports cairo_show_glyphs() with the same font, font scale, and
pattern, poppler should, when TK=true, draw all text in a group with
CAIRO_OPERATOR_SOURCE then paint the group onto the page. This would be slower
and result in image fallbacks when printing so poppler should only do this if
it is not possible to draw all the text in the text object with a single
cairo_show_glyphs() call.

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