Use 100ms delay before overview and add a flag for setting the delay.

BUG=310269
TEST=Alt tabbing should very quickly enter overview mode.

Review URL: https://codereview.chromium.org/37273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230656 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 79 insertions, 3 deletions

diff --git a/ash/ash_switches.cc b/ash/ash_switches.cc
index 118f787..5800bbc 100644
--- a/ash/ash_switches.cc
+++ b/ash/ash_switches.cc
@@ -153,6 +153,10 @@ const char kAshImmersiveHideTabIndicators[] =
 const char kAshOemWallpaperLarge[] = "ash-oem-wallpaper-large";
 const char kAshOemWallpaperSmall[] = "ash-oem-wallpaper-small";
 
+// Specifies the delay in milliseconds before beginning overview mode after
+// getting an alt tab keypress.
+const char kAshOverviewDelayOnAltTab[] = "ash-overview-delay-on-alt-tab";
+
 // Specifies the layout mode and offsets for the secondary display for
 // testing. The format is "<t|r|b|l>,<offset>" where t=TOP, r=RIGHT,
 // b=BOTTOM and L=LEFT. For example, 'r,-100' means the secondary display
diff --git a/ash/ash_switches.h b/ash/ash_switches.h
index 908c897..d502c82 100644
--- a/ash/ash_switches.h
+++ b/ash/ash_switches.h
@@ -62,6 +62,7 @@ ASH_EXPORT extern const char kAshHostWindowBounds[];
 ASH_EXPORT extern const char kAshImmersiveHideTabIndicators[];
 ASH_EXPORT extern const char kAshOemWallpaperLarge[];
 ASH_EXPORT extern const char kAshOemWallpaperSmall[];
+ASH_EXPORT extern const char kAshOverviewDelayOnAltTab[];
 ASH_EXPORT extern const char kAshSecondaryDisplayLayout[];
 ASH_EXPORT extern const char kAshTouchHud[];
 ASH_EXPORT extern const char kAshUseAlternateShelfLayout[];
diff --git a/ash/wm/overview/window_selector.cc b/ash/wm/overview/window_selector.cc
index 47d3c49..e23f5b3 100644
--- a/ash/wm/overview/window_selector.cc
+++ b/ash/wm/overview/window_selector.cc
@@ -6,6 +6,7 @@
 
 #include <algorithm>
 
+#include "ash/ash_switches.h"
 #include "ash/root_window_controller.h"
 #include "ash/shell.h"
 #include "ash/wm/mru_window_tracker.h"
@@ -15,7 +16,9 @@
 #include "ash/wm/overview/window_selector_window.h"
 #include "ash/wm/window_state.h"
 #include "base/auto_reset.h"
+#include "base/command_line.h"
 #include "base/metrics/histogram.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/timer/timer.h"
 #include "ui/aura/client/activation_client.h"
 #include "ui/aura/client/focus_client.h"
@@ -29,7 +32,29 @@ namespace ash {
 
 namespace {
 
-const int kOverviewDelayOnCycleMilliseconds = 500;
+// The time from when the user pressed alt+tab while still holding alt before
+// overview is engaged.
+const int kOverviewDelayOnCycleMilliseconds = 100;
+
+// The maximum amount of time allowed for the delay before overview on cycling.
+// If the specified time exceeds this the timer will not be started.
+const int kMaxOverviewDelayOnCycleMilliseconds = 10000;
+
+int GetOverviewDelayOnCycleMilliseconds() {
+  static int value = -1;
+  if (value == -1) {
+    value = kOverviewDelayOnCycleMilliseconds;
+    if (CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kAshOverviewDelayOnAltTab)) {
+      if (!base::StringToInt(CommandLine::ForCurrentProcess()->
+            GetSwitchValueASCII(switches::kAshOverviewDelayOnAltTab), &value)) {
+        LOG(ERROR) << "Expected int value for "
+                   << switches::kAshOverviewDelayOnAltTab;
+      }
+    }
+  }
+  return value;
+}
 
 // A comparator for locating a given target window.
 struct WindowSelectorItemComparator
@@ -209,8 +234,11 @@ WindowSelector::WindowSelector(const WindowList& windows,
                                WindowSelector::Mode mode,
                                WindowSelectorDelegate* delegate)
     : mode_(mode),
+      timer_enabled_(GetOverviewDelayOnCycleMilliseconds() <
+                         kMaxOverviewDelayOnCycleMilliseconds),
       start_overview_timer_(FROM_HERE,
-          base::TimeDelta::FromMilliseconds(kOverviewDelayOnCycleMilliseconds),
+          base::TimeDelta::FromMilliseconds(
+              GetOverviewDelayOnCycleMilliseconds()),
           this, &WindowSelector::StartOverview),
       delegate_(delegate),
       selected_window_(0),
@@ -259,7 +287,8 @@ WindowSelector::WindowSelector(const WindowList& windows,
 
   if (mode == WindowSelector::CYCLE) {
     event_handler_.reset(new WindowSelectorEventFilter(this));
-    start_overview_timer_.Reset();
+    if (timer_enabled_)
+      start_overview_timer_.Reset();
   } else {
     StartOverview();
   }
@@ -307,6 +336,8 @@ void WindowSelector::Step(WindowSelector::Direction direction) {
     showing_window_.reset(new ScopedShowWindow);
     showing_window_->Show(windows_[selected_window_]->SelectionWindow());
     start_overview_timer_.Reset();
+    if (timer_enabled_)
+      start_overview_timer_.Reset();
   }
 }
 
diff --git a/ash/wm/overview/window_selector.h b/ash/wm/overview/window_selector.h
index 2f178b6..4fc29d1 100644
--- a/ash/wm/overview/window_selector.h
+++ b/ash/wm/overview/window_selector.h
@@ -117,6 +117,7 @@ class ASH_EXPORT WindowSelector
   // of the stacking order and made visible).
   scoped_ptr<ScopedShowWindow> showing_window_;
 
+  bool timer_enabled_;
   base::DelayTimer<WindowSelector> start_overview_timer_;
   scoped_ptr<WindowOverview> window_overview_;
 
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index 95a04e3..03e5202 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -6028,6 +6028,24 @@ Keep your key file in a safe place. You will need it to create new versions of y
       <message name="IDS_FLAGS_DISABLE_OVERVIEW_MODE_DESCRIPTION" desc="Description for the flag to disable window overview mode.">
         Disable overview mode, activated by pushing the switch window button.
       </message>
+      <message name="IDS_FLAGS_OVERVIEW_DELAY_NAME" desc="Title for the delay before engaging overview on alt+tab.">
+        Delay before engaging overview when cycling.
+      </message>
+      <message name="IDS_FLAGS_OVERVIEW_DELAY_DESCRIPTION" desc="Description for what the delay before engaging overview means.">
+        The time from the last alt+tab press before engaging overview mode when cycling through windows.
+      </message>
+      <message name="IDS_FLAGS_OVERVIEW_DELAY_INSTANT" desc="The choice to have overview engage immediately on alt+tab.">
+        Instant
+      </message>
+      <message name="IDS_FLAGS_OVERVIEW_DELAY_SHORT" desc="The choice to have overview engage almost immediately on alt+tab.">
+        Very short
+      </message>
+      <message name="IDS_FLAGS_OVERVIEW_DELAY_LONG" desc="The choice to have overview engage after a fairly long delay.">
+        Long
+      </message>
+      <message name="IDS_FLAGS_OVERVIEW_DELAY_NEVER" desc="The choice to have overview not engage on alt+tab.">
+        Never
+      </message>
       <message name="IDS_FLAGS_SCROLL_END_EFFECT_NAME" desc="Title for the flag for scroll end effect from vertical overscroll.">
         Scroll end effect
       </message>
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 89fc692..c79dff3 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -261,6 +261,20 @@ const Experiment::Choice kDefaultTileWidthChoices[] = {
     switches::kDefaultTileWidth, "1024"}
 };
 
+#if defined(USE_ASH)
+const Experiment::Choice kAshOverviewDelayChoices[] = {
+  { IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT, "", "" },
+  { IDS_FLAGS_OVERVIEW_DELAY_INSTANT,
+    ash::switches::kAshOverviewDelayOnAltTab, "0" },
+  { IDS_FLAGS_OVERVIEW_DELAY_SHORT,
+    ash::switches::kAshOverviewDelayOnAltTab, "100" },
+  { IDS_FLAGS_OVERVIEW_DELAY_LONG,
+    ash::switches::kAshOverviewDelayOnAltTab, "500" },
+  { IDS_FLAGS_OVERVIEW_DELAY_NEVER,
+    ash::switches::kAshOverviewDelayOnAltTab, "10000" },
+};
+#endif
+
 const Experiment::Choice kDefaultTileHeightChoices[] = {
   { IDS_GENERIC_EXPERIMENT_CHOICE_DEFAULT, "", "" },
   { IDS_FLAGS_DEFAULT_TILE_HEIGHT_SHORT,
@@ -1064,6 +1078,13 @@ const Experiment kExperiments[] = {
     SINGLE_VALUE_TYPE(ash::switches::kAshDisableOverviewMode)
   },
   {
+    "overview-delay-on-alt-tab",
+    IDS_FLAGS_OVERVIEW_DELAY_NAME,
+    IDS_FLAGS_OVERVIEW_DELAY_DESCRIPTION,
+    kOsCrOS,
+    MULTI_VALUE_TYPE(kAshOverviewDelayChoices)
+  },
+  {
     "show-touch-hud",
     IDS_FLAGS_SHOW_TOUCH_HUD_NAME,
     IDS_FLAGS_SHOW_TOUCH_HUD_DESCRIPTION,