Add the stroke align interface to the ShapeLayer to set the position …

…of the stroke.

include/tgfx/layers/ShapeLayer.h

@@ -24,6 +24,24 @@
 #include "tgfx/layers/ShapeStyle.h"
 
 namespace tgfx {
+/**
+ * The alignment of the stroke concerning the boundaries of the shape.
+ */
+enum class StrokeAlign {
+  /**
+  * Draw a stroke centered along the shape boundary.
+  */
+  Center,
+  /**
+  * Draw a stroke inside the shape boundary.
+  */
+  Inside,
+  /**
+  * Draw a stroke outside the shape boundary.
+  */
+  Outside
+};
+
 /**
  * ShapeLayer represents a layer that draws a shape.
  */
@@ -207,6 +225,18 @@ class ShapeLayer : public Layer {
    */
   void setStrokeEnd(float end);
 
+  /**
+ * Returns the stroke alignment applied to the shape’s path when stroked. The default stroke alignment is Center.
+ */
+  StrokeAlign strokeAlign() const {
+    return _strokeAlign;
+  }
+
+  /**
+ * Sets the stroke alignment applied to the shape’s path when stroked.
+ */
+  void setStrokeAlign(StrokeAlign align);
+
   ~ShapeLayer() override;
 
  protected:
@@ -223,5 +253,6 @@ class ShapeLayer : public Layer {
   float _lineDashPhase = 0.0f;
   float _strokeStart = 0.0f;
   float _strokeEnd = 1.0f;
+  StrokeAlign _strokeAlign = StrokeAlign::Center;
 };
 }  // namespace tgfx

src/layers/ShapeLayer.cpp

@@ -153,6 +153,14 @@ void ShapeLayer::setStrokeEnd(float end) {
   invalidateContent();
 }
 
+void ShapeLayer::setStrokeAlign(StrokeAlign align) {
+  if (_strokeAlign == align) {
+    return;
+  }
+  _strokeAlign = align;
+  invalidateContent();
+}
+
 ShapeLayer::~ShapeLayer() {
   detachProperty(_strokeStyle.get());
   detachProperty(_fillStyle.get());
@@ -182,7 +190,18 @@ std::unique_ptr<LayerContent> ShapeLayer::onUpdateContent() {
           PathEffect::MakeDash(dashes.data(), static_cast<int>(dashes.size()), _lineDashPhase);
       strokeShape = Shape::ApplyEffect(std::move(strokeShape), std::move(pathEffect));
     }
-    strokeShape = Shape::ApplyStroke(std::move(strokeShape), &stroke);
+    if (_strokeAlign != StrokeAlign::Center) {
+      auto terminalStroke = stroke;
+      terminalStroke.width *= 2;
+      strokeShape = Shape::ApplyStroke(std::move(strokeShape), &terminalStroke);
+      if (_strokeAlign == StrokeAlign::Inside) {
+        strokeShape = Shape::Merge(std::move(strokeShape), _shape, PathOp::Intersect);
+      } else {
+        strokeShape = Shape::Merge(std::move(strokeShape), _shape, PathOp::Difference);
+      }
+    } else {
+      strokeShape = Shape::ApplyStroke(std::move(strokeShape), &stroke);
+    }
     auto content =
         std::make_unique<ShapeContent>(std::move(strokeShape), _strokeStyle->getShader());
     contents.push_back(std::move(content));

test/baseline/version.json

@@ -83,7 +83,7 @@
         "Layer_hitTestPointNested": "0ee494a",
         "ModeColorFilter": "43cd416",
         "PassThoughAndNormal": "43cd416",
-        "draw_shape": "d069eb4",
+        "draw_shape": "738fc92",
         "draw_solid": "b4a1231",
         "draw_text": "612c09e",
         "dropShadow": "43cd416",

test/src/LayerTest.cpp

@@ -441,35 +441,45 @@ TGFX_TEST(LayerTest, shapeLayer) {
   auto device = DevicePool::Make();
   ASSERT_TRUE(device != nullptr);
   auto context = device->lockContext();
-  auto surface = Surface::Make(context, 200, 100);
+  auto surface = Surface::Make(context, 200, 300);
   auto displayList = std::make_unique<DisplayList>();
   auto layer = Layer::Make();
   displayList->root()->addChild(layer);
-  auto shaperLayer = ShapeLayer::Make();
-  auto rect = Rect::MakeXYWH(10, 10, 150, 80);
-  Path path = {};
-  path.addRect(rect);
-  shaperLayer->setPath(path);
-  auto filleStyle = Gradient::MakeLinear({10, 10}, {150, 80});
-  filleStyle->setColors({{0.f, 0.f, 1.f, 1.f}, {0.f, 1.f, 0.f, 1.f}});
-  shaperLayer->setFillStyle(filleStyle);
-  // stroke style
-  shaperLayer->setLineWidth(10.0f);
-  shaperLayer->setLineCap(LineCap::Butt);
-  shaperLayer->setLineJoin(LineJoin::Miter);
-  shaperLayer->setMiterLimit(2.0f);
-  auto strokeStyle = SolidColor::Make(Color::Red());
-  shaperLayer->setStrokeStyle(strokeStyle);
-  std::vector<float> dashPattern = {10.0f, 10.0f};
-  shaperLayer->setLineDashPattern(dashPattern);
-  shaperLayer->setLineDashPhase(0.0f);
-
-  layer->addChild(shaperLayer);
-  auto shapeLayerRect = shaperLayer->getBounds();
-  auto bounds = Rect::MakeXYWH(5, 5, 160, 90);
-
-  EXPECT_EQ(shapeLayerRect, bounds);
-
+  for (int i = 0; i < 3; i++) {
+    auto shaperLayer = ShapeLayer::Make();
+    auto rect = Rect::MakeXYWH(10, 10 + 100 * i, 140, 80);
+    Path path = {};
+    path.addRect(rect);
+    shaperLayer->setPath(path);
+    auto filleStyle = Gradient::MakeLinear({rect.left, rect.top}, {rect.right, rect.bottom});
+    filleStyle->setColors({{0.f, 0.f, 1.f, 1.f}, {0.f, 1.f, 0.f, 1.f}});
+    shaperLayer->setFillStyle(filleStyle);
+    // stroke style
+    shaperLayer->setLineWidth(10.0f);
+    shaperLayer->setLineCap(LineCap::Butt);
+    shaperLayer->setLineJoin(LineJoin::Miter);
+    auto strokeStyle = SolidColor::Make(Color::Red());
+    shaperLayer->setStrokeStyle(strokeStyle);
+    std::vector<float> dashPattern = {10.0f, 10.0f};
+    shaperLayer->setLineDashPattern(dashPattern);
+    shaperLayer->setLineDashPhase(5.0f);
+    shaperLayer->setStrokeAlign(static_cast<StrokeAlign>(i));
+    layer->addChild(shaperLayer);
+    auto shapeLayerRect = shaperLayer->getBounds();
+    switch (i) {
+      case 0:
+        EXPECT_EQ(shapeLayerRect, Rect::MakeLTRB(5, 5, 155, 95));
+        break;
+      case 1:
+        EXPECT_EQ(shapeLayerRect, Rect::MakeLTRB(0, 100, 160, 200));
+        break;
+      case 2:
+        EXPECT_EQ(shapeLayerRect, Rect::MakeLTRB(0, 200, 160, 300));
+        break;
+      default:
+        break;
+    }
+  }
   displayList->render(surface.get());
   context->submit();
   EXPECT_TRUE(Baseline::Compare(surface, "LayerTest/draw_shape"));