Add an empty message to the notification center.

ui/message_center/cocoa/tray_view_controller.mm

 // Copyright (c) 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.
 
 #import "ui/message_center/cocoa/tray_view_controller.h"
 
 #include <cmath>
 
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "base/time/time.h"
@@ skipping 341 matching lines @@
   return NSHeight(screenFrame) - kTrayBottomMargin - kControlAreaHeight;
 }
 
 + (CGFloat)trayWidth {
   return message_center::kNotificationWidth +
          2 * message_center::kMarginBetweenItems;
 }
 
 // Testing API /////////////////////////////////////////////////////////////////
 
+- (NSBox*)divider {
+  return divider_.get();
+}
+
+- (NSTextField*)emptyDescription {
+  return emptyDescription_.get();
+}
+
 - (NSScrollView*)scrollView {
   return scrollView_.get();
 }
 
 - (HoverImageButton*)pauseButton {
   return pauseButton_.get();
 }
 
 - (HoverImageButton*)clearAllButton {
   return clearAllButton_.get();
@@ skipping 11 matching lines @@
     (message_center::TrayAnimationEndedCallback)callback {
   testingAnimationEndedCallback_.reset(Block_copy(callback));
 }
 
 // Private /////////////////////////////////////////////////////////////////////
 
 - (void)layoutControlArea {
   ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
   NSView* view = [self view];
 
+  auto configureLabel = ^(NSTextField* textField) {
+      [textField setAutoresizingMask:NSViewMinYMargin];
+      [textField setBezeled:NO];
+      [textField setBordered:NO];
+      [textField setDrawsBackground:NO];
+      [textField setEditable:NO];
+      [textField setSelectable:NO];
+  };
+
   // Create the "Notifications" label at the top of the tray.
   NSFont* font = [NSFont labelFontOfSize:message_center::kTitleFontSize];
   title_.reset([[NSTextField alloc] initWithFrame:NSZeroRect]);
-  [title_ setAutoresizingMask:NSViewMinYMargin];
-  [title_ setBezeled:NO];
-  [title_ setBordered:NO];
-  [title_ setDrawsBackground:NO];
-  [title_ setEditable:NO];
+  configureLabel(title_);
+
   [title_ setFont:font];
-  [title_ setSelectable:NO];
   [title_ setStringValue:
       l10n_util::GetNSString(IDS_MESSAGE_CENTER_FOOTER_TITLE)];
   [title_ setTextColor:gfx::SkColorToCalibratedNSColor(
       message_center::kRegularTextColor)];
   [title_ sizeToFit];
 
   NSRect titleFrame = [title_ frame];
   titleFrame.origin.x = message_center::kMarginBetweenItems;
   titleFrame.origin.y = kControlAreaHeight/2 - NSMidY(titleFrame);
   [title_ setFrame:titleFrame];
@@ skipping 25 matching lines @@
   [backButton_ setHidden:YES];
   [backButton_ setKeyEquivalent:@"\e"];
   [backButton_ setToolTip:l10n_util::GetNSString(
       IDS_MESSAGE_CENTER_SETTINGS_GO_BACK_BUTTON_TOOLTIP)];
   [[backButton_ cell]
       accessibilitySetOverrideValue:[backButton_ toolTip]
                        forAttribute:NSAccessibilityDescriptionAttribute];
   [[self view] addSubview:backButton_];
 
   // Create the divider line between the control area and the notifications.
-  base::scoped_nsobject<NSBox> divider(
+  divider_.reset(
       [[NSBox alloc] initWithFrame:NSMakeRect(0, 0, NSWidth([view frame]), 1)]);
-  [divider setAutoresizingMask:NSViewMinYMargin];
-  [divider setBorderType:NSNoBorder];
-  [divider setBoxType:NSBoxCustom];
-  [divider setContentViewMargins:NSZeroSize];
-  [divider setFillColor:gfx::SkColorToCalibratedNSColor(
+  [divider_ setAutoresizingMask:NSViewMinYMargin];
+  [divider_ setBorderType:NSNoBorder];
+  [divider_ setBoxType:NSBoxCustom];
+  [divider_ setContentViewMargins:NSZeroSize];
+  [divider_ setFillColor:gfx::SkColorToCalibratedNSColor(
       message_center::kFooterDelimiterColor)];
-  [divider setTitlePosition:NSNoTitle];
-  [view addSubview:divider];
+  [divider_ setTitlePosition:NSNoTitle];
+  [view addSubview:divider_];
+
 
   auto getButtonFrame = ^NSRect(CGFloat maxX, NSImage* image) {
       NSSize size = [image size];
       return NSMakeRect(
           maxX - size.width,
           kControlAreaHeight/2 - size.height/2,
           size.width,
           size.height);
   };
 
@@ skipping 49 matching lines @@
   [pauseButton_ setHoverImage: rb.GetNativeImageNamed(
       IDR_NOTIFICATION_DO_NOT_DISTURB_HOVER).ToNSImage()];
   [pauseButton_ setToolTip:
       l10n_util::GetNSString(IDS_MESSAGE_CENTER_QUIET_MODE_BUTTON_TOOLTIP)];
   [[pauseButton_ cell]
       accessibilitySetOverrideValue:[pauseButton_ toolTip]
                        forAttribute:NSAccessibilityDescriptionAttribute];
   [pauseButton_ setAction:@selector(toggleQuietMode:)];
   configureButton(pauseButton_);
   [view addSubview:pauseButton_];
+
+  // Create the description field for the empty message center.  Initially it is
+  // invisible.
+  emptyDescription_.reset([[NSTextField alloc] initWithFrame:NSZeroRect]);
+  configureLabel(emptyDescription_);
+
+  NSFont* smallFont =
+      [NSFont labelFontOfSize:message_center::kEmptyCenterFontSize];
+  [emptyDescription_ setFont:smallFont];
+  [emptyDescription_ setStringValue:
+      l10n_util::GetNSString(IDS_MESSAGE_CENTER_NO_MESSAGES)];
+  [emptyDescription_ setTextColor:gfx::SkColorToCalibratedNSColor(
+      message_center::kDimTextColor)];
+  [emptyDescription_ sizeToFit];
+  [emptyDescription_ setHidden:YES];
+
+  [view addSubview:emptyDescription_];
 }
 
 - (void)updateTrayViewAndWindow {
-  CGFloat scrollContentHeight = 0;
+  CGFloat scrollContentHeight = message_center::kMinScrollViewHeight;
   if ([notifications_ count]) {
+    [emptyDescription_ setHidden:YES];
+    [scrollView_ setHidden:NO];
+    [divider_ setHidden:NO];
     scrollContentHeight = NSMaxY([[[notifications_ lastObject] view] frame]) +
         message_center::kMarginBetweenItems;;
+  } else {
+    [emptyDescription_ setHidden:NO];
+    [scrollView_ setHidden:YES];
+    [divider_ setHidden:YES];
+
+    NSRect centeredFrame = [emptyDescription_ frame];
+    NSPoint centeredOrigin = NSMakePoint(
+      floor((NSWidth([[self view] frame]) - NSWidth(centeredFrame))/2 + 0.5),
+      floor((scrollContentHeight - NSHeight(centeredFrame))/2 + 0.5));
+
+    centeredFrame.origin = centeredOrigin;
+    [emptyDescription_ setFrame:centeredFrame];
   }
 
   // Resize the scroll view's content.
   NSRect scrollViewFrame = [scrollView_ frame];
   NSRect documentFrame = [[scrollView_ documentView] frame];
   documentFrame.size.width = NSWidth(scrollViewFrame);
   documentFrame.size.height = scrollContentHeight;
   [[scrollView_ documentView] setFrame:documentFrame];
 
   // Resize the container view.
@@ skipping 215 matching lines @@
     [pauseButton_ setDefaultImage: rb.GetNativeImageNamed(
         IDR_NOTIFICATION_DO_NOT_DISTURB_PRESSED).ToNSImage()];
   } else {
     [pauseButton_ setTrackingEnabled:YES];
     [pauseButton_ setDefaultImage:
         rb.GetNativeImageNamed(IDR_NOTIFICATION_DO_NOT_DISTURB).ToNSImage()];
   }
 }
 
 @end