More robust. eg. loading wqy-microhei.ttc

[neoedmund]

No description provided.

[nothings]

Does this fix a bug?

[nothings]

Oh, I see from the title the implication is it does. Can you be specific about what character at what size fails?

[neoedmund]

1. The font file "wqy-microhei.ttc" is from
   https://packages.ubuntu.com/xenial/all/fonts-wqy-microhei/filelist , it contains thousands of Unicode CJK characters and the font should be widely used.

2. I tested with imgui which uses stb_truetype.h , it seems try to load all characters to generate a large texture for rendering in opengl.

3. I don't know how this code(stb_truetype.h) works, and what is it about. But after change the code, It seems worked good. (the font size is 16.0f)
   The values(z->ey, scan_y_top) be skipped are:

-13.187839 , -11.000000
-11.855061 , -11.000000
-11.228655 , -11.000000
-11.088713 , -11.000000
-12.321533 , -11.000000
-12.321533 , -11.000000
-12.321533 , -11.000000
-12.321533 , -11.000000
-11.002083 , -11.000000
-11.002083 , -11.000000
-12.001666 , -12.000000
-12.208246 , -12.000000
-12.468139 , -11.000000
-12.394835 , -11.000000
-11.588505 , -11.000000
-11.588505 , -11.000000
-16.912952 , -12.000000
-16.912952 , -12.000000
-14.733861 , -12.000000
-14.733861 , -12.000000
-13.134527 , -12.000000
-13.134527 , -12.000000
-12.048313 , -12.000000
-12.194919 , -12.000000
-12.408163 , -12.000000
-12.041650 , -12.000000
-11.301957 , -11.000000

4. hope this helps.

[nothings]

This seems like it's hiding an actual bug, since it implies some edges are discarded without ever being processed. I'll need to look at the actual cases that are failing (I can figure out for myself from the above info, I think).