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58 lines
2.5 KiB
Diff
58 lines
2.5 KiB
Diff
diff --git a/gfx/cairo/cairo/src/cairo-quartz-surface.c b/gfx/cairo/cairo/src/cairo-quartz-surface.c
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--- a/gfx/cairo/cairo/src/cairo-quartz-surface.c
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+++ b/gfx/cairo/cairo/src/cairo-quartz-surface.c
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@@ -690,31 +690,51 @@ ComputeGradientValue (void *info, const
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}
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static const float gradient_output_value_ranges[8] = {
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0.f, 1.f, 0.f, 1.f, 0.f, 1.f, 0.f, 1.f
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};
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static const CGFunctionCallbacks gradient_callbacks = {
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0, ComputeGradientValue, (CGFunctionReleaseInfoCallback) cairo_pattern_destroy
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};
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+/* Quartz will clamp input values to the input range.
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+
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+ Our stops are all in the range 0.0 to 1.0. However, the color before the
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+ beginning of the gradient line is obtained by Quartz computing a negative
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+ position on the gradient line, clamping it to the input range we specified
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+ for our color function, and then calling our color function (actually it
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+ pre-samples the color function into an array, but that doesn't matter just
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+ here). Therefore if we set the lower bound to 0.0, a negative position
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+ on the gradient line will pass 0.0 to ComputeGradientValue, which will
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+ select the last color stop with position 0, although it should select
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+ the first color stop (this matters when there are multiple color stops with
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+ position 0).
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+
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+ Therefore we pass a small negative number as the lower bound of the input
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+ range, so this value gets passed into ComputeGradientValue, which will
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+ return the color of the first stop. The number should be small because
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+ as far as I can tell, Quartz pre-samples the entire input range of the color
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+ function into an array of fixed size, so if the input range is larger
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+ than needed, the resolution of the gradient will be unnecessarily low.
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+*/
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+static const float nonrepeating_gradient_input_value_range[2] = { -0.001f, 1.f };
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static CGFunctionRef
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CreateGradientFunction (const cairo_gradient_pattern_t *gpat)
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{
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cairo_pattern_t *pat;
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- float input_value_range[2] = { 0.f, 1.f };
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if (_cairo_pattern_create_copy (&pat, &gpat->base))
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/* quartz doesn't deal very well with malloc failing, so there's
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* not much point in us trying either */
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return NULL;
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return CGFunctionCreate (pat,
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1,
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- input_value_range,
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+ nonrepeating_gradient_input_value_range,
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4,
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gradient_output_value_ranges,
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&gradient_callbacks);
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}
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static void
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UpdateLinearParametersToIncludePoint(double *min_t, double *max_t, CGPoint *start,
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double dx, double dy,
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