[Octave-bug-tracker] [bug #33118] text rotation fails for angles other than 90 deg

[Andreas Weber]

Follow-up Comment #4, bug #33118 (project octave):

I had now a deeper look on this. Please keep in mind that I am a beginner with
the octave source code and some asumptions might be false.

hg id = f212ff846296

Since the text is rendered into a bitmap with freetype, fltk does not rotate
the text. Rather in 
  opengl_renderer::text_to_pixels 
which calls
  text_renderer.text_to_pixels

int ft_render::rotation_to_mode (double rotation) const;
does only accept 0,90,180,270 deg, all values which does not mache are set to
0

The "rotation" is done in txt-eng-ft.cc, ft_render::render
with "pixels = pixels.permute (perm);"

I guess if instead the FreeType function FT_Set_Transform
is used, we can display arbitrary rotated text and can get rid of the
"permute". (see http://www.freetype.org/freetype2/docs/tutorial/step1.html)

Andy



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