Mac App Launcher is positioned on center of dock in certain cases.

chrome/browser/ui/app_list/app_list_positioner.cc

 // Copyright 2013 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 "chrome/browser/ui/app_list/app_list_positioner.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "ui/gfx/point.h"
@@ skipping 63 matching lines @@
     case SCREEN_EDGE_BOTTOM:
       anchor = gfx::Point(screen_rect.x(), work_area.bottom());
       break;
     default:
       NOTREACHED();
       anchor = gfx::Point();
   }
   return ClampAnchorPoint(anchor);
 }
 
+gfx::Point AppListPositioner::GetAnchorPointForShelfCenter(
+    ScreenEdge shelf_edge) const {
+  const gfx::Rect& screen_rect = display_.bounds();
+  const gfx::Rect& work_area = display_.work_area();
+  gfx::Point anchor;
+  switch (shelf_edge) {
+    case SCREEN_EDGE_LEFT:
+      anchor = gfx::Point(work_area.x(),
+                          screen_rect.y() + screen_rect.height() / 2);

[tapted, 2013/11/29 02:12:51]

Maybe s/screen_rect/work_area? My left dock looks centred between the bottom of
the menu bar and the bottom of the screen. Same for right.
Perhaps |screen_rect| is not needed at all.

[Matt Giuca, 2013/11/29 05:24:08]

Done.

+      break;
+    case SCREEN_EDGE_RIGHT:
+      anchor = gfx::Point(work_area.right(),
+                          screen_rect.y() + screen_rect.height() / 2);
+      break;
+    case SCREEN_EDGE_TOP:

[tapted, 2013/11/29 02:12:51]

Do we need this? I'm not sure if consistency outweighs the badness of adding
dead code [except for tests]

[Matt Giuca, 2013/11/29 05:24:08]

I think that would be a Bad Idea. This is a general function for all platforms
to use. Just because it's only currently used by Mac should not mean it should
be made to fail in cases that aren't used on Mac.

[tapted, 2013/11/29 06:05:59]

I see the rationale for adding the case statement where the code currently is,
here. But are there plans for using it on other platforms? Usually code that's
only used on a single platform go into files like app_list_positioner_mac.cc .

[Matt Giuca, 2013/12/02 05:02:03]

No, there aren't (although there are probably Linux environments where we'll
want this, like Xfce which centers the dock). But again, that's sort of besides
the point. The idea of centering the launcher on the shelf isn't Mac-specific,
even if it's only used by Mac. I see the role of these *_mac files as being for
code that can't be compiled on non-Mac platforms because either it uses
Mac-specific APIs, or simply doesn't make sense outside the Mac platform. This
is not one of those.

+      anchor = gfx::Point(screen_rect.x() + screen_rect.width() / 2,
+                          work_area.y());
+      break;
+    case SCREEN_EDGE_BOTTOM:
+      anchor = gfx::Point(screen_rect.x() + screen_rect.width() / 2,
+                          work_area.bottom());
+      break;
+    default:
+      NOTREACHED();
+      anchor = gfx::Point();
+  }
+  return ClampAnchorPoint(anchor);
+}
+
 gfx::Point AppListPositioner::GetAnchorPointForShelfCursor(
     ScreenEdge shelf_edge,
     const gfx::Point& cursor) const {
   const gfx::Rect& work_area = display_.work_area();
   gfx::Point anchor;
   switch (shelf_edge) {
     case SCREEN_EDGE_LEFT:
       anchor = gfx::Point(work_area.x(), cursor.y());
       break;
     case SCREEN_EDGE_RIGHT:
@@ skipping 69 matching lines @@
 
   // Anchor the center of the window in a region that prevents the window
   // showing outside of the work area.
   bounds_rect.Inset(window_size_.width() / 2 + min_distance_from_edge_,
                     window_size_.height() / 2 + min_distance_from_edge_);
 
   anchor.SetToMax(bounds_rect.origin());
   anchor.SetToMin(bounds_rect.bottom_right());
   return anchor;
 }