Implements core logic for Pixel Canvas

ui/views/paint_info.h

Index: ui/views/paint_info.h
diff --git a/ui/views/paint_info.h b/ui/views/paint_info.h
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+++ b/ui/views/paint_info.h
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+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_VIEWS_PAINT_INFO_H_
+#define UI_VIEWS_PAINT_INFO_H_
+
+#include "ui/compositor/paint_context.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/views/views_export.h"
+
+namespace views {
+
+class VIEWS_EXPORT PaintInfo {
+ public:
+  enum class ScaleType {
+    // Scales the context by the default dsf. Use this if you dont want any form
+    // of distortion during scaling.
+    kScaleToScaleFactor = 0,
+
+    // Scales the context based on the effective dsf. This may lead to minor
+    // distortion during scaling due to edge snapping.
+    kScaleToFit
+  };
+
+  PaintInfo(const ui::PaintContext& context, const gfx::Size& size);
+  PaintInfo(const PaintInfo& other,
+            const gfx::Rect& bounds,
+            const gfx::Rect& parent_bounds,
+            ScaleType scale_type);
+  PaintInfo(const PaintInfo& other);
+  ~PaintInfo();
+
+  const ui::PaintContext& context() const {
+    return root_context_ ? *root_context_ : context_;
+  }
+
+  gfx::Vector2d offset_from_root() const {
+    return paint_recording_bounds_.OffsetFromOrigin();
+  }
+
+  bool IsPixelCanvas() const;
+
+  gfx::Vector2d offset_from_parent() const { return offset_from_parent_; }
+
+  gfx::PointF paint_recording_scale() const {
+    return gfx::PointF(paint_recording_scale_x_, paint_recording_scale_y_);
+  }
+
+  const gfx::Size& paint_recording_size() const {
+    return paint_recording_bounds_.size();
+  }
+
+  const gfx::Rect& paint_recording_bounds() const {
+    return paint_recording_bounds_;
+  }
+
+ private:
+  // The scale at which the paint commands are recorded at. Due to the decimal
+  // rounding and snapping to edges during scaling operations, the effective
+  // paint recording scale may end up being slightly different between the x and
+  // y axis.
+  float paint_recording_scale_x_;
+  float paint_recording_scale_y_;
+
+  // Paint Recording bounds for this view. The offset is relative to the root
+  // paint context.
+  const gfx::Rect paint_recording_bounds_;
+
+  // Offset relative to the parent paint context.
+  gfx::Vector2d offset_from_parent_;
+
+  // Compositor PaintContext associated with the view this object belongs to.
+  ui::PaintContext context_;
+  const ui::PaintContext* root_context_;
+
+  // Given the DIP |size|, this function updates the paint recording scales.
+  void ComputePaintRecordingScales(const gfx::Size& size, ScaleType scale_type);
+
+  // Scales the |child_bounds| to its recording bounds based on the
+  // |context.device_scale_factor()|. The recording bounds are snapped to the
+  // |parent_bound|'s right and/or bottom edge if required.
+  // If pixel canvas is disabled, this function returns |child_bounds| as is.
+  gfx::Rect GetSnappedRecordingBounds(const gfx::Rect& parent_bounds,
+                                      const gfx::Rect& child_bounds) const;
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_PAINT_INFO_H_