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glamor: fix repeat-reflect case in linear gradient shader

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If _pt_distance is negative, it causes the final distance to be negative
in the repeat-reflect case.  Moving the scaling by _pt_distance earlier
avoids this problem, and simplifies some equations as a bonus.

Bugzilla: https://bugs.freedesktop.org/98508
Signed-off-by: Jeff Smith <whydoubt@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
(cherry picked from commit 3e377e238f)
This commit is contained in:
Jeff Smith 2018-01-26 06:25:19 -06:00 • committed by Adam Jackson
parent f6cd99ed79
commit 38e6fb7573
1 changed files with 4 additions and 7 deletions
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11
glamor/glamor_gradient.c
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@ -458,7 +458,6 @@ _glamor_create_linear_gradient_program(ScreenPtr screen, int stops_count,
"float get_stop_len()\n"\
"{\n"\
" vec3 tmp = vec3(source_texture.x, source_texture.y, 1.0);\n"\
" float len_percentage;\n"\
" float distance;\n"\
" float _p1_distance;\n"\
" float _pt_distance;\n"\
@ -484,19 +483,17 @@ _glamor_create_linear_gradient_program(ScreenPtr screen, int stops_count,
" _pt_distance = pt_distance * source_texture_trans.z;\n"\
" } \n"\
" \n"\
" distance = distance - _p1_distance; \n"\
" distance = (distance - _p1_distance) / _pt_distance;\n"\
" \n"\
" if(repeat_type == %d){\n" /* repeat normal*/\
" distance = mod(distance, _pt_distance);\n"\
" distance = fract(distance);\n"\
" }\n"\
" \n"\
" if(repeat_type == %d) {\n" /* repeat reflect*/\
" distance = abs(mod(distance + _pt_distance, 2.0 * _pt_distance) - _pt_distance);\n"\
" distance = abs(fract(distance * 0.5 + 0.5) * 2.0 - 1.0);\n"\
" }\n"\
" \n"\
" len_percentage = distance/(_pt_distance);\n"\
" \n"\
" return len_percentage;\n"\
" return distance;\n"\
"}\n"\
"\n"\
"void main()\n"\