Implements core logic for Pixel Canvas

ui/compositor/paint_context.cc

Index: ui/compositor/paint_context.cc
diff --git a/ui/compositor/paint_context.cc b/ui/compositor/paint_context.cc
index b2b4fac54b39a4c19adb6b398cd1d3674d3a5e58..16e90f400d79d70ffcf1d78baa79c64ff53bb683 100644
--- a/ui/compositor/paint_context.cc
+++ b/ui/compositor/paint_context.cc
@@ -4,16 +4,26 @@
 
 #include "ui/compositor/paint_context.h"
 
+#include "ui/compositor/compositor_switches.h"
 #include "ui/gfx/canvas.h"
+#include "ui/gfx/transform.h"
 
 namespace ui {
 
 PaintContext::PaintContext(cc::DisplayItemList* list,
                            float device_scale_factor,
-                           const gfx::Rect& invalidation)
+                           const gfx::Rect& invalidation,
+                           const gfx::Size& size)
     : list_(list),
       device_scale_factor_(device_scale_factor),
-      invalidation_(invalidation) {
+      paint_recording_scale_x_(IsPixelCanvas() ? device_scale_factor_ : 1.f),
+      paint_recording_scale_y_(paint_recording_scale_x_),
+      invalidation_(
+          gfx::ScaleToEnclosingRect(invalidation, paint_recording_scale_x_)),
+      paint_recording_bounds_(
+          gfx::ScaleToCornerScaledRect(gfx::Rect(size),
+                                       paint_recording_scale_x_)) {
+  ComputePaintRecordingScales(size);
 #if DCHECK_IS_ON()
   root_visited_ = nullptr;
   inside_paint_recorder_ = false;
@@ -21,11 +31,17 @@ PaintContext::PaintContext(cc::DisplayItemList* list,
 }
 
 PaintContext::PaintContext(const PaintContext& other,
-                           const gfx::Vector2d& offset)
+                           const gfx::Rect& bounds,
+                           const gfx::Rect& parent_bounds,
+                           ScaleType scale_type)
     : list_(other.list_),
       device_scale_factor_(other.device_scale_factor_),
       invalidation_(other.invalidation_),
-      offset_(other.offset_ + offset) {
+      paint_recording_bounds_(
+          other.GetSnappedRecordingBounds(parent_bounds, bounds)),
+      offset_(other.offset_ + paint_recording_bounds_.OffsetFromOrigin()),
+      scale_type_(scale_type) {
+  ComputePaintRecordingScales(bounds.size());
 #if DCHECK_IS_ON()
   root_visited_ = other.root_visited_;
   inside_paint_recorder_ = other.inside_paint_recorder_;
@@ -36,7 +52,10 @@ PaintContext::PaintContext(const PaintContext& other,
                            CloneWithoutInvalidation c)
     : list_(other.list_),
       device_scale_factor_(other.device_scale_factor_),
+      paint_recording_scale_x_(other.paint_recording_scale_x_),
+      paint_recording_scale_y_(other.paint_recording_scale_y_),
       invalidation_(),
+      paint_recording_bounds_(other.paint_recording_bounds_),
       offset_(other.offset_) {
 #if DCHECK_IS_ON()
   root_visited_ = other.root_visited_;
@@ -52,8 +71,74 @@ gfx::Rect PaintContext::ToLayerSpaceBounds(
   return gfx::Rect(size_in_context) + offset_;
 }
 
-gfx::Rect PaintContext::ToLayerSpaceRect(const gfx::Rect& rect) const {
-  return rect + offset_;
+void PaintContext::ComputePaintRecordingScales(const gfx::Size& size) {
+  if (!IsPixelCanvas()) {
+    paint_recording_scale_x_ = paint_recording_scale_y_ = 1.f;
+    return;
+  }
+
+  paint_recording_scale_x_ = paint_recording_scale_y_ = device_scale_factor_;
+  if (scale_type_ == ScaleType::SCALE_TO_SCALE_FACTOR)
+    return;
+
+  if (size.width() > 0) {
+    paint_recording_scale_x_ =
+        static_cast<float>(paint_recording_bounds_.width()) /
+        static_cast<float>(size.width());
+  }
+
+  if (size.height() > 0) {
+    paint_recording_scale_y_ =
+        static_cast<float>(paint_recording_bounds_.height()) /
+        static_cast<float>(size.height());
+  }
+}
+
+bool PaintContext::IsPixelCanvas() const {
+  return IsPixelCanvasRecordingEnabled();
+}
+
+gfx::Transform PaintContext::TransformToParentRecordingSpace() const {
+  gfx::Transform to_parent_pixel_space;
+  if (IsPixelCanvas()) {
+    // This is just an optimization to prevent the computation of effective
+    // scale factors which would return 1.f if the Pixel Canvas is disabled.
+    to_parent_pixel_space.Scale(SkFloatToScalar(paint_recording_scale_x_),
+                                SkFloatToScalar(paint_recording_scale_y_));
+  }
+  to_parent_pixel_space.Translate(paint_recording_bounds().OffsetFromOrigin());
+  return to_parent_pixel_space;
+}
+
+gfx::Rect PaintContext::GetSnappedRecordingBounds(
+    const gfx::Rect& parent_bounds,
+    const gfx::Rect& child_bounds) const {
+  if (!IsPixelCanvas())
+    return child_bounds;
+
+  const gfx::Vector2d& child_origin = child_bounds.OffsetFromOrigin();
+
+  int right = child_origin.x() + child_bounds.width();
+  int bottom = child_origin.y() + child_bounds.height();
+
+  int new_x = std::round(child_origin.x() * device_scale_factor_);
+  int new_y = std::round(child_origin.y() * device_scale_factor_);
+
+  int new_right;
+  int new_bottom;
+
+  if (right == parent_bounds.width()) {
+    new_right = paint_recording_bounds_.width();
+  } else {
+    new_right = std::round(right * device_scale_factor_);
+  }
+
+  if (bottom == parent_bounds.height()) {
+    new_bottom = paint_recording_bounds_.height();
+  } else {
+    new_bottom = std::round(bottom * device_scale_factor_);
+  }
+  return gfx::Rect(new_x, new_y, new_right - new_x, new_bottom - new_y);
 }
 
 }  // namespace ui