Make resizing a window by snapping it left or right take into account the window's minimum width

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/screen_ash.h"
 #include "ash/wm/property_util.h"
 #include "ash/wm/window_resizer.h"
 #include "ash/wm/window_util.h"
 #include "ui/aura/window.h"
+#include "ui/aura/window_delegate.h"
 #include "ui/gfx/screen.h"
 
 namespace ash {
 namespace internal {
 
 namespace {
 
-// A list of ideal window width in pixel which will be used to populate the
+// A list of ideal window widths in DIP which will be used to populate the
 // |usable_width_| list.
 const int kIdealWidth[] = { 1280, 1024, 768, 640 };
 
 // Windows are initially snapped to the size in |usable_width_| at index 0.
 // The index into |usable_width_| 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 = 25;
 const int kPixelsBeforeAdjust = 100;
 
-// When the smallest resolution does not fit on the screen, we take this
-// fraction of the available space.
-const int kMinimumScreenPercent = 90;
+// The maximum fraction of the screen width that a snapped window is allowed
+// to take up.
+const int kMaximumScreenPercent = 90;
 
-// Create the list of possible width for the current screen configuration:
+// The width that a window should be snapped to if resizing is disabled in the
+// SnapSizer for devices with small screen resolutions.
+const int kDefaultWidthSmallScreen = 1024;
+
+// Returns the minimum width that |window| can be snapped to. The returned width
+// may not be in the width list generated by BuildIdealWidthList().
+int GetMinWidth(aura::Window* window) {
+  return window->delegate() ? window->delegate()->GetMinimumSize().width() : 0;
+}
+
+// Returns the maximum width that |window| can be snapped to. The returned width
+// may not be in the width list generated by BuildIdealWidthList().
+// The aura::WindowDelegate's max size is ignored because
+// ash::wm::CanSnapWindow() returns false when a max size is specified.
+int GetMaxWidth(aura::Window* window) {
+  gfx::Rect work_area(ScreenAsh::GetDisplayWorkAreaBoundsInParent(window));
+  return std::max(work_area.width() * kMaximumScreenPercent / 100,
+                  GetMinWidth(window));
+}
+
+// Returns the width that |window| should be snapped to if resizing is disabled
+// in the SnapSizer.
+int GetDefaultWidth(aura::Window* window) {
+  gfx::Rect work_area(ScreenAsh::GetDisplayWorkAreaBoundsInParent(window));
+  int width = std::max(kDefaultWidthSmallScreen, work_area.width() / 2);
+
+  width = std::min(width, GetMaxWidth(window));
+  return std::max(width, GetMinWidth(window));
+}
+
+// Create the list of possible widths for the current screen configuration:
 // Fill the |usable_width_| list with items from |kIdealWidth| which fit on
 // the screen and supplement it with the 'half of screen' size. Furthermore,
-// add an entry for 90% of the screen size if it is smaller then the biggest
+// add an entry for 90% of the screen size if it is smaller than the biggest
 // value in the |kIdealWidth| list (to get a step between the values).
 std::vector<int> BuildIdealWidthList(aura::Window* window) {
+  int minimum_width = GetMinWidth(window);
+  int maximum_width = GetMaxWidth(window);
+
+  gfx::Rect work_area(ScreenAsh::GetDisplayWorkAreaBoundsInParent(window));
+  int half_width = work_area.width() / 2;
+  if (half_width < minimum_width || half_width > maximum_width)
+    half_width = 0;
+
   std::vector<int> ideal_width_list;
-  gfx::Rect work_area(ScreenAsh::GetDisplayWorkAreaBoundsInParent(window));
-  int half_size = work_area.width() / 2;
-  int maximum_width = (kMinimumScreenPercent * work_area.width()) / 100;
   for (size_t i = 0; i < arraysize(kIdealWidth); i++) {
-    if (maximum_width >= kIdealWidth[i]) {
+    if (kIdealWidth[i] >= minimum_width && kIdealWidth[i] <= maximum_width) {
       if (i && !ideal_width_list.size() && maximum_width != kIdealWidth[i])
         ideal_width_list.push_back(maximum_width);
-      if (half_size > kIdealWidth[i])
-        ideal_width_list.push_back(half_size);
-      if (half_size >= kIdealWidth[i])
-        half_size = 0;
+      if (half_width > kIdealWidth[i])
+        ideal_width_list.push_back(half_width);
+      if (half_width >= kIdealWidth[i])
+        half_width = 0;
       ideal_width_list.push_back(kIdealWidth[i]);
     }
   }
-  if (half_size)
-    ideal_width_list.push_back(half_size);
+  if (half_width)
+    ideal_width_list.push_back(half_width);
+  if (ideal_width_list.empty()) {
+    if (minimum_width > 0)
+      ideal_width_list.push_back(minimum_width);
+    else
+      ideal_width_list.push_back(maximum_width);
+  }
 
   return ideal_width_list;
 }
 
 }  // namespace
 
 SnapSizer::SnapSizer(aura::Window* window,
                      const gfx::Point& start,
                      Edge edge,
                      InputType input_type)
@@ skipping 71 matching lines @@
   int current = 0;
   if (!resize_disabled_) {
     for (current = usable_width_.size() - 1; current >= 0; current--) {
       gfx::Rect target = GetTargetBoundsForSize(current);
       if (target == bounds) {
         ++current;
         break;
       }
     }
   }
   return GetTargetBoundsForSize(current % usable_width_.size());

[James Cook, 2013/09/09 23:03:01]

Also, if the loop above terminates, does this do:

current ==-1 => 18446744073709551615
% 5 == 0

Then cast to a size_t?  This appears to work, but only because -1 happens to be
represented by a number evenly divisible by 5?

 }
 
 void SnapSizer::SelectDefaultSizeAndDisableResize() {
   resize_disabled_ = true;
   size_index_ = 0;
   target_bounds_ = GetTargetBounds();
 }
 
 gfx::Rect SnapSizer::GetTargetBoundsForSize(size_t size_index) const {
   gfx::Rect work_area(ScreenAsh::GetDisplayWorkAreaBoundsInParent(window_));
   int y = work_area.y();
-  // We don't align to the bottom of the grid as the launcher may not
-  // necessarily align to the grid (happens when auto-hidden).
   int max_y = work_area.bottom();
   int width = 0;
   if (resize_disabled_) {
-    // Make sure that we keep the size of the window smaller then a certain
-    // fraction of the screen space.
-    int minimum_size = (kMinimumScreenPercent * work_area.width()) / 100;
-    width = std::max(std::min(minimum_size, 1024), work_area.width() / 2);
+    width = GetDefaultWidth(window_);
   } else {
     DCHECK(size_index < usable_width_.size());
     width = usable_width_[size_index];
   }
 
   if (edge_ == LEFT_EDGE) {
     int x = work_area.x();
     int mid_x = x + width;
     return gfx::Rect(x, y, mid_x - x, max_y - y);
   }
@@ skipping 33 matching lines @@
   return GetTargetBoundsForSize(size_index_);
 }
 
 bool SnapSizer::AlongEdge(int x) const {
   gfx::Rect area(ScreenAsh::GetDisplayBoundsInParent(window_));
   return (x <= area.x()) || (x >= area.right() - 1);
 }
 
 }  // namespace internal
 }  // namespace ash