Palette tool laser prototype.

ash/common/system/chromeos/palette/tools/laser_pointer_view.cc

+// Copyright 2016 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.
+
+#include "ash/common/system/chromeos/palette/tools/laser_pointer_view.h"
+
+#include <memory>
+
+#include "ash/common/shell_window_ids.h"
+#include "ash/common/wm_root_window_controller.h"
+#include "ash/common/wm_shell.h"
+#include "ash/common/wm_window.h"
+#include "third_party/skia/include/core/SkColor.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "ui/gfx/canvas.h"
+
+namespace ash {
+namespace {
+
+const double kPointInitialRadius = 5;
+const double kPointFinalRadius = 0.25;
+const int kPointInitialOpacity = 200;
+const int kPointFinalOpacity = 0;
+const SkColor kPointColor = SkColorSetRGB(255, 0, 0);
+
+float DistanceBetweenPoints(const gfx::Point& point1,
+                            const gfx::Point& point2) {
+  return (point1 - point2).Length();
+}
+
+double LinearInterpolate(double initial_value,
+                         double final_value,
+                         double progress) {
+  return initial_value + (final_value - initial_value) * progress;
+}
+
+}  // namespace
+
+////////////////////////////////////////////////////////////////////////////////
+
+// LaserPointerView
+LaserPointerView::LaserPointerView(base::TimeDelta life_duration)
+    : laser_points_(life_duration) {
+  widget_.reset(new views::Widget);
+  views::Widget::InitParams params;
+  params.type = views::Widget::InitParams::TYPE_WINDOW_FRAMELESS;
+  params.name = "LaserOverlay";
+  params.accept_events = false;
+  params.activatable = views::Widget::InitParams::ACTIVATABLE_NO;
+  params.ownership = views::Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
+  params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
+  WmShell::Get()
+      ->GetRootWindowForNewWindows()
+      ->GetRootWindowController()
+      ->ConfigureWidgetInitParamsForContainer(
+          widget_.get(), kShellWindowId_OverlayContainer, &params);
+  widget_->Init(params);
+  widget_->Show();
+  widget_->SetContentsView(this);
+  set_owned_by_client();
+}
+
+LaserPointerView::~LaserPointerView() {}
+
+void LaserPointerView::Stop() {
+  laser_points_.Clear();
+  SchedulePaint();
+}
+
+void LaserPointerView::AddNewPoint(const gfx::Point& new_point) {
+  laser_points_.AddPoint(new_point);
+  // Expand the bounding box so that it includes the radius of the points on the
+  // edges.
+  gfx::Rect bounding_box;
+  bounding_box = laser_points_.GetBoundingBox();
+  bounding_box.SetRect(bounding_box.x() - kPointInitialRadius,
+                       bounding_box.y() - kPointInitialRadius,
+                       bounding_box.width() + (kPointInitialRadius * 2),
+                       bounding_box.height() + (kPointInitialRadius * 2));

[oshima, 2016/08/24 23:01:04]

Offset(-kPointInInitialRadius, -kPointInInitialRadius);

[sammiequon, 2016/08/25 17:59:05]

Done.

+  widget_->SetBounds(bounding_box);
+  SchedulePaint();
+}
+
+void LaserPointerView::OnPaint(gfx::Canvas* canvas) {
+  if (laser_points_.IsEmpty())
+    return;
+
+  canvas->Save();

[oshima, 2016/08/24 23:01:04]

Do you need this? (it doesn't looks like but) if you need it, then you need to
call Restore at the end.

[sammiequon, 2016/08/25 17:59:05]

Done.

+  SkPaint paint;
+  paint.setStyle(SkPaint::kStroke_Style);
+  paint.setAntiAlias(true);
+  paint.setStrokeJoin(SkPaint::kBevel_Join);
+
+  base::Time oldest = laser_points_.GetOldest().creation_time;
+  base::Time newest = laser_points_.GetNewest().creation_time;
+  gfx::Point previous_point = laser_points_.GetOldest().location;
+  gfx::Point current_point;
+  gfx::Rect widget_bounds = widget_->GetWindowBoundsInScreen();
+  int point_count = 0;

[oshima, 2016/08/24 23:01:04]

fyi: you can get the count by (itr - begin()) + 1.

[sammiequon, 2016/08/25 17:59:05]

I don't think this works with std::deque because the elements are not contiguous
in memory.

+  int num_points_ = laser_points_.GetNumberOfPoints();
+  for (auto it = laser_points_.PointsStart(); it != laser_points_.PointsEnd();
+       it++, point_count++) {
+    // relative_time is a value between [0,1] where 0 means the point is about
+    // to be removed and 1 means that the point was just added.
+    double relative_time = 1.0;
+    if (oldest != newest) {
+      relative_time = 1.0 - ((it->creation_time - oldest).InMillisecondsF() /
+                             (newest - oldest).InMillisecondsF());
+    }
+
+    // Set the radius and opacity based on the distance.
+    double radius = LinearInterpolate(kPointInitialRadius, kPointFinalRadius,
+                                      relative_time);
+
+    gfx::Vector2d center = it->location - widget_bounds.origin();
+    current_point = gfx::Point(center.x(), center.y());
+
+    // If we draw laser_points_ that are within a stroke width of each other,
+    // the result will be very jagged.
+    float distance_threshold = float{radius * 2};
+    if (DistanceBetweenPoints(previous_point, current_point) <=
+            distance_threshold &&
+        point_count != num_points_ - 1) {
+      continue;
+    }
+
+    int opacity =
+        int{LinearInterpolate(double{kPointInitialOpacity},
+                              double{kPointFinalOpacity}, relative_time)};

[oshima, 2016/08/24 23:01:04]

do you have a pointer to the doc that says this (using uniform initializer as a
way to cast) is allowed?

[sammiequon, 2016/08/25 17:59:05]

https://google.github.io/styleguide/cppguide.html#Casting - first line

[oshima, 2016/08/25 19:35:35]

ok thanks.

+    paint.setColor(SkColorSetA(kPointColor, opacity));
+    paint.setStrokeWidth(radius * 2);
+    canvas->DrawLine(previous_point, current_point, paint);
+    previous_point = current_point;
+  }
+  paint.setColor(SkColorSetA(kPointColor, kPointInitialOpacity));
+  paint.setStyle(SkPaint::kFill_Style);
+  canvas->DrawCircle(current_point, kPointInitialRadius, paint);
+}
+}  // namespace ash