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sw_engine: fix focal point clamping

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This approach should be introduced in d8ebd8b4f5.
Using FLOAT_EPSILON is not sufficient due to numerical precision,
since it's later inverted, and its very small value leads to
significant errors during inversion.
This commit is contained in:
Mira Grudzinska 2025-06-18 12:13:39 +02:00
parent 5d7c27eccb
commit 65844fa590
1 changed files with 5 additions and 4 deletions
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9
src/renderer/sw_engine/tvgSwFill.cpp
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@ -277,11 +277,12 @@ bool _prepareRadial(SwFill* fill, const RadialGradient* radial, const Matrix& tr
//This condition fulfills the SVG 1.1 std:
//the focal point, if outside the end circle, is moved to be on the end circle
//See: the SVG 2 std requirements: https://www.w3.org/TR/SVG2/pservers.html#RadialGradientNotes
if (fill->radial.a <= FLOAT_EPSILON) {
constexpr float precision = 0.01f;
if (fill->radial.a <= precision) {
auto dist = sqrtf(fill->radial.dx * fill->radial.dx + fill->radial.dy * fill->radial.dy);
constexpr const float precision = 0.99f; //retract focal point slightly from edge to avoid numerical errors
fill->radial.fx = cx + r * precision * (fx - cx) / dist;
fill->radial.fy = cy + r * precision * (fy - cy) / dist;
//retract focal point slightly from edge to avoid numerical errors:
fill->radial.fx = cx + r * (1.0f - precision) * (fx - cx) / dist;
fill->radial.fy = cy + r * (1.0f - precision) * (fy - cy) / dist;
fill->radial.dx = cx - fill->radial.fx;
fill->radial.dy = cy - fill->radial.fy;
// Prevent loss of precision on Apple Silicon when dr=dy and dx=0 due to FMA