fontselect: eagerly compute is_postscript in get_font_info

This lets us get rid of the font format check in ass_coretext,
which is not available on Mac OS X 10.5 and prerelease 10.6.
This fixes https://github.com/libass/libass/issues/595,
which is about 10.6 prerelease build 10A190, the last Mac OS X
build available for PowerPC CPUs. A separate commit will expand
on this and make us compatible with 10.5 on all CPUs.

This partly reverts commit d0566318ee5035ca3a4d2d65d46a80a4e3d8244c,
where eager is_postscript was replaced by lazy check_postscript because
back then ass_directwrite eagerly loaded all of the system's fonts
and reading is_postscript from each font slowed it down significantly.
But eventually (in particular but not only because even without this
it was still slow for huge font collections) ass_directwrite learnt
to load fonts lazily, so there's a decent chance that this lazy
check_postscript (as well as the lazy get_font_index) isn't necessary
at all any more and can be removed in the future.

1 files changed, 7 insertions, 1 deletions

diff --git a/libass/ass_fontselect.h b/libass/ass_fontselect.h
index 07fad7b..43366bb 100644
--- a/libass/ass_fontselect.h
+++ b/libass/ass_fontselect.h
@@ -158,7 +158,7 @@ typedef char   *(*GetFallbackFunc)(void *priv,
 
 typedef struct font_provider_funcs {
     GetDataFunc         get_data;               /* optional/mandatory */
-    CheckPostscriptFunc check_postscript;       /* mandatory */
+    CheckPostscriptFunc check_postscript;       /* optional */
     CheckGlyphFunc      check_glyph;            /* mandatory */
     DestroyFontFunc     destroy_font;           /* optional */
     DestroyProviderFunc destroy_provider;       /* optional */
@@ -211,6 +211,12 @@ struct ass_font_provider_meta_data {
                         // See FONT_WEIGHT_*
     int width;          // Font weight in percent, normally 100
                         // See FONT_WIDTH_*
+
+    /**
+     * Whether the font contains PostScript outlines.
+     * Unused if the font provider has a check_postscript function.
+     */
+    bool is_postscript;
 };
 
 struct ass_font_stream {