common: order(bool strokeFirst) api introduced

The new api is introduced to handle the rendering
order of a stroke and a fill. By default fill is
rendered as the first one, stroke as the second
one. This order can be reversed by calling
order(true).

@Issue: https://github.com/thorvg/thorvg/issues/1340

inc/thorvg.h

@@ -977,6 +977,18 @@ public:
      */
     Result fill(FillRule r) noexcept;
 
+
+    /**
+     * @brief Sets the rendering order of the stroke and the fill.
+     *
+     * @param[in] strokeFirst If @c true the stroke is rendered before the fill, otherwise the stroke is rendered as the second one (the default option).
+     *
+     * @return Result::Success when succeed, Result::FailedAllocation otherwise.
+     * @BETA_API
+     */
+    Result order(bool strokeFirst) noexcept;
+
+
     /**
      * @brief Gets the commands data of the path.
      *

src/lib/sw_engine/tvgSwRenderer.cpp

@@ -96,7 +96,7 @@ struct SwShapeTask : SwTask
     }
 
     void run(unsigned tid) override
-    {    
+    {
         if (opacity == 0 && !clipper) return;  //Invisible
 
         uint8_t strokeAlpha = 0;
@@ -136,7 +136,7 @@ struct SwShapeTask : SwTask
                    shape outline below stroke could be full covered by stroke drawing.
                    Thus it turns off antialising in that condition.
                    Also, it shouldn't be dash style. */
-                auto antiAlias = (strokeAlpha == 255 && rshape->strokeWidth() > 2 && rshape->strokeDash(nullptr) == 0) ? false : true;
+                auto antiAlias = strokeAlpha < 255 || rshape->strokeWidth() <= 2 || rshape->strokeDash(nullptr) > 0 || (rshape->stroke && rshape->stroke->strokeFirst);
 
                 if (!shapeGenRle(&shape, rshape, antiAlias)) goto err;
             }
@@ -322,6 +322,31 @@ static void _termEngine()
 }
 
 
+static void _renderFill(SwShapeTask* task, SwSurface* surface, uint32_t opacity)
+{
+    uint8_t r, g, b, a;
+    if (auto fill = task->rshape->fill) {
+        rasterGradientShape(surface, &task->shape, fill->identifier());
+    } else {
+        task->rshape->fillColor(&r, &g, &b, &a);
+        a = static_cast<uint8_t>((opacity * (uint32_t) a) / 255);
+        if (a > 0) rasterShape(surface, &task->shape, r, g, b, a);
+    }
+}
+
+static void _renderStroke(SwShapeTask* task, SwSurface* surface, uint32_t opacity)
+{
+    uint8_t r, g, b, a;
+    if (auto strokeFill = task->rshape->strokeFill()) {
+        rasterGradientStroke(surface, &task->shape, strokeFill->identifier());
+    } else {
+        if (task->rshape->strokeColor(&r, &g, &b, &a)) {
+            a = static_cast<uint8_t>((opacity * (uint32_t) a) / 255);
+            if (a > 0) rasterStroke(surface, &task->shape, r, g, b, a);
+        }
+    }
+}
+
 /************************************************************************/
 /* External Class Implementation                                        */
 /************************************************************************/
@@ -482,23 +507,12 @@ bool SwRenderer::renderShape(RenderData data)
     }
 
     //Main raster stage
-    uint8_t r, g, b, a;
+    if (task->rshape->stroke && task->rshape->stroke->strokeFirst) {
-
+        _renderStroke(task, surface, opacity);
-    if (auto fill = task->rshape->fill) {
+        _renderFill(task, surface, opacity);
-        rasterGradientShape(surface, &task->shape, fill->identifier());
     } else {
-        task->rshape->fillColor(&r, &g, &b, &a);
+        _renderFill(task, surface, opacity);
-        a = static_cast<uint8_t>((opacity * (uint32_t) a) / 255);
+        _renderStroke(task, surface, opacity);
-        if (a > 0) rasterShape(surface, &task->shape, r, g, b, a);
-    }
-
-    if (auto strokeFill = task->rshape->strokeFill()) {
-        rasterGradientStroke(surface, &task->shape, strokeFill->identifier());
-    } else {
-        if (task->rshape->strokeColor(&r, &g, &b, &a)) {
-            a = static_cast<uint8_t>((opacity * (uint32_t) a) / 255);
-            if (a > 0) rasterStroke(surface, &task->shape, r, g, b, a);
-        }
     }
 
     if (task->cmpStroking) endComposite(cmp);

src/lib/tvgRender.h

@@ -94,6 +94,7 @@ struct RenderStroke
     uint32_t dashCnt = 0;
     StrokeCap cap = StrokeCap::Square;
     StrokeJoin join = StrokeJoin::Bevel;
+    bool strokeFirst = false;
 
     ~RenderStroke()
     {

src/lib/tvgShape.cpp

@@ -288,6 +288,14 @@ const Fill* Shape::fill() const noexcept
 }
 
 
+Result Shape::order(bool strokeFirst) noexcept
+{
+    if (!pImpl->strokeFirst(strokeFirst)) return Result::FailedAllocation;
+
+    return Result::Success;
+}
+
+
 Result Shape::stroke(float width) noexcept
 {
     if (!pImpl->strokeWidth(width)) return Result::FailedAllocation;
@@ -390,4 +398,4 @@ Result Shape::fill(FillRule r) noexcept
 FillRule Shape::fillRule() const noexcept
 {
     return pImpl->rs.rule;
-}
+}

src/lib/tvgShapeImpl.h

@@ -262,6 +262,15 @@ struct Shape::Impl
         return true;
     }
 
+    bool strokeFirst(bool strokeFirst)
+    {
+        if (!rs.stroke) rs.stroke = new RenderStroke();
+        rs.stroke->strokeFirst = strokeFirst;
+        flag |= RenderUpdateFlag::Stroke;
+
+        return true;
+    }
+
     Paint* duplicate()
     {
         auto ret = Shape::gen();
@@ -295,6 +304,7 @@ struct Shape::Impl
             dup->rs.stroke->dashCnt = rs.stroke->dashCnt;
             dup->rs.stroke->cap = rs.stroke->cap;
             dup->rs.stroke->join = rs.stroke->join;
+            dup->rs.stroke->strokeFirst = rs.stroke->strokeFirst;
             memcpy(dup->rs.stroke->color, rs.stroke->color, sizeof(rs.stroke->color));
 
             if (rs.stroke->dashCnt > 0) {