[DisplayList] Create DrawDashedLine for paragraph code (flutter#53411)

With this minor addition to the DlCanvas/DisplayList API the code in the paragraph builder no longer needs to worry about PathEffect objects and their varying support on the backends.

At this point all PathEffect code in the engine is obsolete and can be deleted, but I'll leave that for a follow-on PR.

The only PathEffect related thing I did delete was support for rendering primitives with a PathEffect in the DL Rendering tests, both because it is a vestigial attribute and also because it would interfere with the new DrawDashedLine rendering test (a PathEffect on top of a PathEffect...).

Author: flar

display_list/benchmarking/dl_complexity_gl.cc

@@ -100,6 +100,16 @@ void DisplayListGLComplexityCalculator::GLHelper::drawLine(const SkPoint& p0,
   AccumulateComplexity(complexity);
 }
 
+void DisplayListGLComplexityCalculator::GLHelper::drawDashedLine(
+    const DlPoint& p0,
+    const DlPoint& p1,
+    DlScalar on_length,
+    DlScalar off_length) {
+  // Dashing is slightly more complex than a regular drawLine, but this
+  // op is so rare it is not worth measuring the difference.
+  drawLine(ToSkPoint(p0), ToSkPoint(p1));
+}
+
 void DisplayListGLComplexityCalculator::GLHelper::drawRect(const SkRect& rect) {
   if (IsComplex()) {
     return;

display_list/benchmarking/dl_complexity_gl.h

@@ -40,6 +40,10 @@ class DisplayListGLComplexityCalculator
                    const DlImageFilter* backdrop) override;
 
     void drawLine(const SkPoint& p0, const SkPoint& p1) override;
+    void drawDashedLine(const DlPoint& p0,
+                        const DlPoint& p1,
+                        DlScalar on_length,
+                        DlScalar off_length) override;
     void drawRect(const SkRect& rect) override;
     void drawOval(const SkRect& bounds) override;
     void drawCircle(const SkPoint& center, SkScalar radius) override;

display_list/benchmarking/dl_complexity_metal.cc

@@ -111,6 +111,16 @@ void DisplayListMetalComplexityCalculator::MetalHelper::drawLine(
   AccumulateComplexity(complexity);
 }
 
+void DisplayListMetalComplexityCalculator::MetalHelper::drawDashedLine(
+    const DlPoint& p0,
+    const DlPoint& p1,
+    DlScalar on_length,
+    DlScalar off_length) {
+  // Dashing is slightly more complex than a regular drawLine, but this
+  // op is so rare it is not worth measuring the difference.
+  drawLine(ToSkPoint(p0), ToSkPoint(p1));
+}
+
 void DisplayListMetalComplexityCalculator::MetalHelper::drawRect(
     const SkRect& rect) {
   if (IsComplex()) {

display_list/benchmarking/dl_complexity_metal.h

@@ -40,6 +40,10 @@ class DisplayListMetalComplexityCalculator
                    const DlImageFilter* backdrop) override;
 
     void drawLine(const SkPoint& p0, const SkPoint& p1) override;
+    void drawDashedLine(const DlPoint& p0,
+                        const DlPoint& p1,
+                        DlScalar on_length,
+                        DlScalar off_length) override;
     void drawRect(const SkRect& rect) override;
     void drawOval(const SkRect& bounds) override;
     void drawCircle(const SkPoint& center, SkScalar radius) override;

display_list/display_list.h

@@ -111,6 +111,7 @@ namespace flutter {
   V(DrawColor)                      \
                                     \
   V(DrawLine)                       \
+  V(DrawDashedLine)                 \
   V(DrawRect)                       \
   V(DrawOval)                       \
   V(DrawCircle)                     \

display_list/dl_builder.cc

@@ -1099,6 +1099,29 @@ void DisplayListBuilder::DrawLine(const SkPoint& p0,
   SetAttributesFromPaint(paint, DisplayListOpFlags::kDrawLineFlags);
   drawLine(p0, p1);
 }
+void DisplayListBuilder::drawDashedLine(const DlPoint& p0,
+                                        const DlPoint& p1,
+                                        DlScalar on_length,
+                                        DlScalar off_length) {
+  SkRect bounds = SkRect::MakeLTRB(p0.x, p0.y, p1.x, p1.y).makeSorted();
+  DisplayListAttributeFlags flags =
+      (bounds.width() > 0.0f && bounds.height() > 0.0f) ? kDrawLineFlags
+                                                        : kDrawHVLineFlags;
+  OpResult result = PaintResult(current_, flags);
+  if (result != OpResult::kNoEffect && AccumulateOpBounds(bounds, flags)) {
+    Push<DrawDashedLineOp>(0, p0, p1, on_length, off_length);
+    CheckLayerOpacityCompatibility();
+    UpdateLayerResult(result);
+  }
+}
+void DisplayListBuilder::DrawDashedLine(const DlPoint& p0,
+                                        const DlPoint& p1,
+                                        DlScalar on_length,
+                                        DlScalar off_length,
+                                        const DlPaint& paint) {
+  SetAttributesFromPaint(paint, DisplayListOpFlags::kDrawLineFlags);
+  drawDashedLine(p0, p1, on_length, off_length);
+}
 void DisplayListBuilder::drawRect(const SkRect& rect) {
   DisplayListAttributeFlags flags = kDrawRectFlags;
   OpResult result = PaintResult(current_, flags);

display_list/dl_builder.h

@@ -156,6 +156,12 @@ class DisplayListBuilder final : public virtual DlCanvas,
                 const SkPoint& p1,
                 const DlPaint& paint) override;
   // |DlCanvas|
+  void DrawDashedLine(const DlPoint& p0,
+                      const DlPoint& p1,
+                      DlScalar on_length,
+                      DlScalar off_length,
+                      const DlPaint& paint) override;
+  // |DlCanvas|
   void DrawRect(const SkRect& rect, const DlPaint& paint) override;
   // |DlCanvas|
   void DrawOval(const SkRect& bounds, const DlPaint& paint) override;
@@ -419,6 +425,11 @@ class DisplayListBuilder final : public virtual DlCanvas,
   // |DlOpReceiver|
   void drawLine(const SkPoint& p0, const SkPoint& p1) override;
   // |DlOpReceiver|
+  void drawDashedLine(const DlPoint& p0,
+                      const DlPoint& p1,
+                      DlScalar on_length,
+                      DlScalar off_length) override;
+  // |DlOpReceiver|
   void drawRect(const SkRect& rect) override;
   // |DlOpReceiver|
   void drawOval(const SkRect& bounds) override;

display_list/dl_canvas.h

@@ -8,6 +8,7 @@
 #include "flutter/display_list/dl_blend_mode.h"
 #include "flutter/display_list/dl_paint.h"
 #include "flutter/display_list/dl_vertices.h"
+#include "flutter/display_list/geometry/dl_geometry_types.h"
 #include "flutter/display_list/image/dl_image.h"
 
 #include "third_party/skia/include/core/SkM44.h"
@@ -132,6 +133,11 @@ class DlCanvas {
   virtual void DrawLine(const SkPoint& p0,
                         const SkPoint& p1,
                         const DlPaint& paint) = 0;
+  virtual void DrawDashedLine(const DlPoint& p0,
+                              const DlPoint& p1,
+                              DlScalar on_length,
+                              DlScalar off_length,
+                              const DlPaint& paint) = 0;
   virtual void DrawRect(const SkRect& rect, const DlPaint& paint) = 0;
   virtual void DrawOval(const SkRect& bounds, const DlPaint& paint) = 0;
   virtual void DrawCircle(const SkPoint& center,

display_list/dl_op_receiver.h

@@ -343,6 +343,10 @@ class DlOpReceiver {
   virtual void drawColor(DlColor color, DlBlendMode mode) = 0;
   virtual void drawPaint() = 0;
   virtual void drawLine(const SkPoint& p0, const SkPoint& p1) = 0;
+  virtual void drawDashedLine(const DlPoint& p0,
+                              const DlPoint& p1,
+                              DlScalar on_length,
+                              DlScalar off_length) = 0;
   virtual void drawRect(const SkRect& rect) = 0;
   virtual void drawOval(const SkRect& bounds) = 0;
   virtual void drawCircle(const SkPoint& center, SkScalar radius) = 0;

display_list/dl_op_records.h

@@ -736,6 +736,28 @@ DEFINE_DRAW_2ARG_OP(Circle, SkPoint, center, SkScalar, radius)
 DEFINE_DRAW_2ARG_OP(DRRect, SkRRect, outer, SkRRect, inner)
 #undef DEFINE_DRAW_2ARG_OP
 
+// 4 byte header + 24 byte payload packs into 32 bytes (4 bytes unused)
+struct DrawDashedLineOp final : DrawOpBase {
+  static constexpr auto kType = DisplayListOpType::kDrawDashedLine;
+
+  DrawDashedLineOp(const DlPoint& p0,
+                   const DlPoint& p1,
+                   DlScalar on_length,
+                   DlScalar off_length)
+      : p0(p0), p1(p1), on_length(on_length), off_length(off_length) {}
+
+  const DlPoint p0;
+  const DlPoint p1;
+  const SkScalar on_length;
+  const SkScalar off_length;
+
+  void dispatch(DispatchContext& ctx) const {
+    if (op_needed(ctx)) {
+      ctx.receiver.drawDashedLine(p0, p1, on_length, off_length);
+    }
+  }
+};
+
 // 4 byte header + 28 byte payload packs efficiently into 32 bytes
 struct DrawArcOp final : DrawOpBase {
   static constexpr auto kType = DisplayListOpType::kDrawArc;