Centralizes snap sizing and implements spec'd behavior. Three resize

ash/wm/workspace/snap_sizer.cc

+// Copyright (c) 2012 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/wm/workspace/snap_sizer.h"
+
+#include <cmath>
+
+#include "ash/wm/window_resizer.h"
+#include "ui/aura/window.h"
+#include "ui/gfx/screen.h"
+
+namespace ash {
+namespace internal {
+
+namespace {
+
+// Percent of the screen (width) to give the window.
+const float kPercents[] = { .5f, 2.0f / 3.0f, .8f };
+
+// Windows are initially snapped to the percent at index 0. The index into
+// |kPercents| is changed if any of the following happen:
+// . The user stops moving the mouse for |kDelayBeforeIncreaseMS| and then moves
+//   the mouse again.
+// . The mouse moves |kPixelsBeforeAdjust| horizontal pixels.
+// . The mouse is against the edge of the screen and the mouse is moved
+//   |kMovesBeforeAdjust| times.
+const int kDelayBeforeIncreaseMS = 500;
+const int kMovesBeforeAdjust = 50;
+const int kPixelsBeforeAdjust = 200;
+
+}  // namespace
+
+SnapSizer::SnapSizer(aura::Window* window,
+                     const gfx::Point& start,
+                     Edge edge,
+                     int grid_size)
+    : window_(window),
+      edge_(edge),
+      grid_size_(grid_size),
+      time_last_update_(base::TimeTicks::Now()),
+      percent_index_(0),
+      num_moves_since_adjust_(0),
+      last_adjust_x_(start.x()),
+      last_update_x_(start.x()) {
+  target_bounds_ = GetTargetBounds();
+}
+
+void SnapSizer::Update(const gfx::Point& location) {
+  // See description above for details on this behavior.
+  num_moves_since_adjust_++;
+  if ((base::TimeTicks::Now() - time_last_update_).InMilliseconds() >
+      kDelayBeforeIncreaseMS) {
+    ChangeBounds(location.x(),
+                 CalculateIncrement(location.x(), last_update_x_));
+  } else {
+    bool along_edge = AlongEdge(location.x());
+    if (std::abs(location.x() - last_adjust_x_) >= kPixelsBeforeAdjust ||
+        (along_edge && num_moves_since_adjust_ >= kMovesBeforeAdjust)) {
+      ChangeBounds(location.x(),
+                   CalculateIncrement(location.x(), last_adjust_x_));
+    }
+  }
+  last_update_x_ = location.x();
+  time_last_update_ = base::TimeTicks::Now();
+}
+
+int SnapSizer::CalculateIncrement(int x, int reference_x) const {
+  if (AlongEdge(x))
+    return 1;
+  if (x == reference_x)
+    return 0;
+  if (edge_ == LEFT_EDGE) {
+    if (x < reference_x)
+      return 1;
+    return -1;
+  }
+  // edge_ == RIGHT_EDGE.
+  if (x > reference_x)
+    return 1;
+  return -1;
+}
+
+void SnapSizer::ChangeBounds(int x, int delta) {
+  int index = std::min(static_cast<int>(arraysize(kPercents)) - 1,
+                       std::max(percent_index_ + delta, 0));
+  if (index != percent_index_) {
+    percent_index_ = index;
+    target_bounds_ = GetTargetBounds();
+  }
+  num_moves_since_adjust_ = 0;
+  last_adjust_x_ = x;
+}
+
+gfx::Rect SnapSizer::GetTargetBounds() const {
+  gfx::Rect work_area(gfx::Screen::GetMonitorWorkAreaNearestWindow(window_));
+  int y = WindowResizer::AlignToGridRoundUp(work_area.y(), grid_size_);
+  int max_y =
+      WindowResizer::AlignToGridRoundDown(work_area.bottom(), grid_size_);
+  int width = static_cast<float>(work_area.width()) * kPercents[percent_index_];
+  if (edge_ == LEFT_EDGE) {
+    int x = WindowResizer::AlignToGridRoundUp(work_area.x(), grid_size_);
+    int mid_x = WindowResizer::AlignToGridRoundUp(
+        work_area.x() + width, grid_size_);
+    return gfx::Rect(x, y, mid_x - x, max_y - y);
+  }
+  int max_x =
+      WindowResizer::AlignToGridRoundDown(work_area.right(), grid_size_);
+  int x = WindowResizer::AlignToGridRoundUp(max_x - width, grid_size_);
+  return gfx::Rect(x , y, max_x - x, max_y - y);
+}
+
+bool SnapSizer::AlongEdge(int x) const {
+  // TODO: need to support multi-monitor.
+  gfx::Rect area(gfx::Screen::GetMonitorAreaNearestWindow(window_));
+  return (x <= area.x()) || (x >= area.right() - 1);
+}
+
+}  // namespace internal
+}  // namespace ash