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

ash/wm/workspace/snap_sizer.cc

Index: ash/wm/workspace/snap_sizer.cc
diff --git a/ash/wm/workspace/snap_sizer.cc b/ash/wm/workspace/snap_sizer.cc
index 11b59470fcd87d5be27e934cc992feac57b7c90a..6403740ceb372b71bfaf411d89f0e0d9a697a62d 100644
--- a/ash/wm/workspace/snap_sizer.cc
+++ b/ash/wm/workspace/snap_sizer.cc
@@ -11,6 +11,7 @@
 #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 {
@@ -18,7 +19,7 @@ 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 };
 
@@ -33,33 +34,74 @@ 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) {
-  std::vector<int> ideal_width_list;
+  int minimum_width = GetMinWidth(window);
+  int maximum_width = GetMaxWidth(window);
+
   gfx::Rect work_area(ScreenAsh::GetDisplayWorkAreaBoundsInParent(window));
-  int half_size = work_area.width() / 2;
-  int maximum_width = (kMinimumScreenPercent * work_area.width()) / 100;
+  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;
   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;
 }
@@ -163,15 +205,10 @@ void SnapSizer::SelectDefaultSizeAndDisableResize() {
 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];