From 324bff30d15b3be66144a681a5ffa813b7592143 Mon Sep 17 00:00:00 2001
From: Hermet Park <hermet@lottiefiles.com>
Date: Thu, 19 Dec 2024 14:30:31 +0900
Subject: [PATCH] sw_engine: allow the stroke clipper

clipping with a stroke is useful for various visual effects.
TVG can support this approach as it offers better efficiency
compared to alpha masking.

If a valid stroke is defined in the clipper shape,
the renderer prioritizes clipping with the stroke over
 the shape's fill.

issue: https://github.com/thorvg/thorvg/issues/3063
---
 src/renderer/sw_engine/tvgSwRenderer.cpp | 12 +++++-------
 src/renderer/sw_engine/tvgSwShape.cpp    |  4 ----
 2 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/src/renderer/sw_engine/tvgSwRenderer.cpp b/src/renderer/sw_engine/tvgSwRenderer.cpp
index 7680548f..73ec94a9 100644
--- a/src/renderer/sw_engine/tvgSwRenderer.cpp
+++ b/src/renderer/sw_engine/tvgSwRenderer.cpp
@@ -88,14 +88,14 @@ struct SwShapeTask : SwTask
         return strokeWidth < 2.0f || rshape->stroke->dashCnt > 0 || rshape->stroke->strokeFirst || rshape->strokeTrim() || rshape->stroke->color.a < 255;
     }
 
-    float validStrokeWidth()
+    float validStrokeWidth(bool clipper)
     {
         if (!rshape->stroke) return 0.0f;
 
         auto width = rshape->stroke->width;
         if (tvg::zero(width)) return 0.0f;
 
-        if (!rshape->stroke->fill && (MULTIPLY(rshape->stroke->color.a, opacity) == 0)) return 0.0f;
+        if (!clipper && (!rshape->stroke->fill && (MULTIPLY(rshape->stroke->color.a, opacity) == 0))) return 0.0f;
         if (tvg::zero(rshape->stroke->trim.begin - rshape->stroke->trim.end)) return 0.0f;
 
         return (width * sqrt(transform.e11 * transform.e11 + transform.e12 * transform.e12));
@@ -103,8 +103,9 @@ struct SwShapeTask : SwTask
 
     bool clip(SwRle* target) override
     {
+        if (shape.strokeRle) return rleClip(target, shape.strokeRle);
         if (shape.fastTrack) return rleClip(target, &bbox);
-        else if (shape.rle) return rleClip(target, shape.rle);
+        if (shape.rle) return rleClip(target, shape.rle);
         return false;
     }
 
@@ -116,7 +117,7 @@ struct SwShapeTask : SwTask
             return;
         }
 
-        auto strokeWidth = validStrokeWidth();
+        auto strokeWidth = validStrokeWidth(clipper);
         SwBBox renderRegion{};
         auto visibleFill = false;
 
@@ -154,14 +155,11 @@ struct SwShapeTask : SwTask
         if (flags & (RenderUpdateFlag::Path | RenderUpdateFlag::Stroke | RenderUpdateFlag::Transform)) {
             if (strokeWidth > 0.0f) {
                 shapeResetStroke(&shape, rshape, transform);
-
                 if (!shapeGenStrokeRle(&shape, rshape, transform, bbox, renderRegion, mpool, tid)) goto err;
                 if (auto fill = rshape->strokeFill()) {
                     auto ctable = (flags & RenderUpdateFlag::GradientStroke) ? true : false;
                     if (ctable) shapeResetStrokeFill(&shape);
                     if (!shapeGenStrokeFillColors(&shape, fill, transform, surface, opacity, ctable)) goto err;
-                } else {
-                    shapeDelStrokeFill(&shape);
                 }
             } else {
                 shapeDelStroke(&shape);
diff --git a/src/renderer/sw_engine/tvgSwShape.cpp b/src/renderer/sw_engine/tvgSwShape.cpp
index cae99856..ccb592e8 100644
--- a/src/renderer/sw_engine/tvgSwShape.cpp
+++ b/src/renderer/sw_engine/tvgSwShape.cpp
@@ -511,10 +511,6 @@ bool shapePrepared(const SwShape* shape)
 
 bool shapeGenRle(SwShape* shape, TVG_UNUSED const RenderShape* rshape, bool antiAlias)
 {
-    //FIXME: Should we draw it?
-    //Case: Stroke Line
-    //if (shape.outline->opened) return true;
-
     //Case A: Fast Track Rectangle Drawing
     if (shape->fastTrack) return true;