Carl asked for this on irc, its going to be needed to get atsui, win32 font
backends to pass the tests due to differences in kerning and hinting. Patch follows.
Created attachment 8232 [details] [review]
Enables backends-specific reference images
I made what seemed like the simplest change, a compile-time check. It
introduces a new element to test case names in front of the target, eg:
would be a valid reference image for 'dummy'. Backend-specific reference images
are tested for first.
Random comments on the patch:
1) I prefer finding the font backend using cairo_font_type_t. For example using
cairo_get_font_face() + cairo_font_face_get_type(). Unfortunately this probably
doesn't work. It probably returns CAIRO_FONT_TYPE_TOY. We need
cairo_get_scaled_font() API first.
2) Please call font backends "font-backend", not "backend".
3) We probably should do something more clever now that the involved parameters
are increasing. Marking tests as having text is probably one thing we want to do.
Behdad's comments are all good.
In addition I'd definitely consider the "font backend" to be secondary to the
"surface backend", (rather erroneously named "target" in the current test code).
So I'd rather see "image-atsui" than "atsui-image".
But, yes, as Behdad hints, this whole thing is a mess and could use some
re-architecting before we add too many more bandaids.
Moved to the test-suite section of the TODO.