Make touch-resizing windows to screen edge possible

ash/wm/window_resizer.cc

Index: ash/wm/window_resizer.cc
diff --git a/ash/wm/window_resizer.cc b/ash/wm/window_resizer.cc
index 3773d0735099072ee932d1ffc915df274181a16b..f7a3395fceda90f7c5233cc3af9b587b43bda6df 100644
--- a/ash/wm/window_resizer.cc
+++ b/ash/wm/window_resizer.cc
@@ -4,6 +4,8 @@
 
 #include "ash/wm/window_resizer.h"
 
+#include <cmath>
+
 #include "ash/screen_ash.h"
 #include "ash/shell.h"
 #include "ash/wm/property_util.h"
@@ -107,7 +109,8 @@ WindowResizer::Details::Details()
       bounds_change(0),
       position_change_direction(0),
       size_change_direction(0),
-      is_resizable(false) {
+      is_resizable(false),
+      is_touch(false) {
 }
 
 WindowResizer::Details::Details(aura::Window* window,
@@ -124,7 +127,13 @@ WindowResizer::Details::Details(aura::Window* window,
           GetPositionChangeDirectionForWindowComponent(window_component)),
       size_change_direction(
           GetSizeChangeDirectionForWindowComponent(window_component)),
-      is_resizable(bounds_change != kBoundsChangeDirection_None) {
+      is_resizable(bounds_change != kBoundsChangeDirection_None),
+      is_touch(false) {
+  // Set |is_touch| if |current_event| is not NULL. |current_event| may be NULL
+  // in unit tests that don't use synthetically generated events and test window
+  // resizers directly.
+  if (window->GetRootWindow()->current_event())
+    is_touch = window->GetRootWindow()->current_event()->IsGestureEvent();
   if (wm::IsWindowNormal(window) &&
       GetRestoreBoundsInScreen(window) &&
       window_component == HTCAPTION)
@@ -181,6 +190,9 @@ gfx::Rect WindowResizer::CalculateBoundsForDrag(
   int delta_x = location.x() - details.initial_location_in_parent.x();
   int delta_y = location.y() - details.initial_location_in_parent.y();
 
+  // Adjust values of |delta_x| and |delta_y| for touch resizes.
+  AdjustDeltaForTouch(details, &delta_x, &delta_y);
+
   // The minimize size constraint may limit how much we change the window
   // position.  For example, dragging the left edge to the right should stop
   // repositioning the window when the minimize size is reached.
@@ -265,6 +277,49 @@ gfx::Rect WindowResizer::CalculateBoundsForDrag(
 }
 
 // static
+void WindowResizer::AdjustDeltaForTouch(const Details& details,
+                                        int* delta_x,
+                                        int* delta_y) {
+  if (!details.is_touch || !(details.bounds_change & kBoundsChange_Resizes))
+    return;
+
+  if (details.size_change_direction & kBoundsChangeDirection_Horizontal) {
+    if (IsRightEdge(details.window_component) && *delta_x > 0) {
+      int display_width = Shell::GetScreen()->GetDisplayNearestWindow(
+          details.window).bounds().width();
+      int right = details.initial_bounds_in_parent.right();
+      float window_distance = display_width - right;
+      float touch_distance = display_width -
+          details.initial_location_in_parent.x();
+      *delta_x = static_cast<int>(
+          ceil(*delta_x * window_distance / touch_distance));
+    } else if (!IsRightEdge(details.window_component) && *delta_x < 0) {
+      float window_distance = details.initial_bounds_in_parent.x();
+      float touch_distance = details.initial_location_in_parent.x();
+      *delta_x = static_cast<int>(
+          floor(*delta_x * window_distance / touch_distance));
+    }
+  }
+  if (details.size_change_direction & kBoundsChangeDirection_Vertical) {
+    if (IsBottomEdge(details.window_component) && *delta_y > 0) {
+      int display_height = Shell::GetScreen()->GetDisplayNearestWindow(
+          details.window).bounds().height();
+      int bottom = details.initial_bounds_in_parent.bottom();
+      float window_distance = display_height - bottom;
+      float touch_distance = display_height -
+          details.initial_location_in_parent.y();
+      *delta_y = static_cast<int>(
+          ceil(*delta_y * window_distance / touch_distance));
+    } else if (!IsBottomEdge(details.window_component) && *delta_y < 0) {
+      float window_distance = details.initial_bounds_in_parent.y();
+      float touch_distance = details.initial_location_in_parent.y();
+      *delta_y = static_cast<int>(
+          floor(*delta_y * window_distance / touch_distance));
+    }
+  }
+}
+
+// static
 bool WindowResizer::IsBottomEdge(int window_component) {
   return window_component == HTBOTTOMLEFT ||
       window_component == HTBOTTOM ||