[Devel] Possibly a bug

[Ulf Ochsenfahrt]

Hi,

I do have a problem with the FreeType library.

I have RedHat 7.2 and have tested both 2.0.3 and 2.0.9.

My problem is the following:
I am writing an import unit for FreePascal (1.0.4) under Linux and I get
very interesting problems. The import unit itself works - in a way. I have
already rendered single characters - no problem. But then I tried rendering
several (say two) letters and it crashes every time. I stripped the program down
to:

FT_Init_FreeType(alibrary);
FT_New_Face(alibrary, 'test1.ttf', 0, face);
FT_Set_Pixel_Sizes(face, 8, 16);
// No problem so far.
FT_Load_Char(face, 65, 0);
FT_Load_Char(face, 65, 0);

// Now crash!
FT_Render_Glyph(face^.glyph, 0);
...

When FT_Load_Char is called only once, no problem, the character is rendered
and I can display it - looks really good, yeah ! -, but when it is called
twice, it crashes in FT_Render_Glyph.

I then looked into the data structures after the two calls of FT_Load_Char.
The first time everything is alright, the second time face->glyph.metrics is
almost completely trash, horiAdvance and vertAdvance are still correct, but
the other values are completely wrong.

metrics.width: 151001472
metrics.height: 285217024
metrics.horiBearingX: -64
metrics.horiBearingY: 285217024
metrics.horiAdvance: 448              <- correct
metrics.vertBearingX: -75500736
metrics.vertBearingY: -285216256
metrics.vertAdvance: 1152            <- correct

I thought that it might be a problem with the calling convention. So - I
wrote the same program in C and it works. I compared the assembler code of both
programs. It was actually different. (C always pushes at least 16 bytes on
the stack before calling a function. FP only pushes as many bytes as the amount
of parameters dictates.) FreePascal is able to compile assembler code, so I
wrote the program in FreePascal in Assembler -> Crash.

I thought it could be a problem with the memory management, but between the
two calls to FT_Load_Char there is NO memory access - at least not from the
point of FreePascal.

I thought it could be a problem with the font file. So I tried two other
font files -> same problem.

I tried the same program without modifications under Windows using
FreePascal for Win32 and freetype.dll -> works perfectly.

Could it be that the library needs some library-initialization function
called that is automatically called by C but not be FP? But why does that only
make a difference for the second call? Possibly the memory management of C must
be initialized?

Can anyone help?

-- Ulf.

P.S.: The attachment is the FP import unit.

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freetype.pas
Description: Binary data