Support 3+ panels in the OverlayPanelManager

chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelManager.java

Index: chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelManager.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelManager.java b/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelManager.java
index dec1711f5190a8d5c5ea9f20fcea12d682bfb10b..b00505e370e954971846f15191e6bcdb4037ad7e 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelManager.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/OverlayPanelManager.java
@@ -10,12 +10,14 @@ import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.browser.compositor.bottombar.OverlayPanel.StateChangeReason;
 import org.chromium.ui.resources.dynamics.DynamicResourceLoader;
 
+import java.util.Comparator;
 import java.util.HashSet;
+import java.util.PriorityQueue;
+import java.util.Queue;
 import java.util.Set;
 
 /**
  * Used to decide which panel should be showing on screen at any moment.
- * NOTE(mdjones): Currently only supports two panels.
  */
 public class OverlayPanelManager {
 
@@ -29,6 +31,9 @@ public class OverlayPanelManager {
         HIGH;
     }
 
+    /** The initial size of the priority queue for suppressed panels. */
+    private static final int INITIAL_QUEUE_CAPACITY = 3;
+
     /** A map of panels that this class is managing. */
     private final Set<OverlayPanel> mPanelSet;
 
@@ -38,9 +43,8 @@ public class OverlayPanelManager {
     /**
      * If a panel was being shown and another panel with higher priority was requested to show,
      * the lower priority one is stored here.
-     * TODO(mdjones): This should be a list in the case that there are more than two panels.
      */
-    private OverlayPanel mSuppressedPanel;
+    private Queue<OverlayPanel> mSuppressedPanels;
 
     /** When a panel is suppressed, this is the panel waiting for the close animation to finish. */
     private OverlayPanel mPendingPanel;
@@ -58,6 +62,15 @@ public class OverlayPanelManager {
      * Default constructor.
      */
     public OverlayPanelManager() {
+        mSuppressedPanels = new PriorityQueue<>(INITIAL_QUEUE_CAPACITY,
+                new Comparator<OverlayPanel>() {
+                    @Override
+                    public int compare(OverlayPanel p1, OverlayPanel p2) {
+                        // The head of the queue is the smallest element, so subtract p1's priority
+                        // from p2's priority.
+                        return p2.getPriority().ordinal() - p1.getPriority().ordinal();
+                    }
+                });
         mPanelSet = new HashSet<>();
     }
 
@@ -79,8 +92,8 @@ public class OverlayPanelManager {
 
         } else if (panel.getPriority().ordinal() > mActivePanel.getPriority().ordinal()) {
             // If a panel with higher priority than the active one requests to be shown, suppress
-            // the active panel and show the requesting one.
-            // NOTE(mdjones): closePanel will trigger notifyPanelClosed.
+            // the active panel and show the requesting one. closePanel will trigger
+            // notifyPanelClosed.
             mPendingPanel = panel;
             mPendingReason = reason;
             mActivePanel.closePanel(StateChangeReason.SUPPRESS, true);
@@ -88,7 +101,7 @@ public class OverlayPanelManager {
         } else if (panel.canBeSuppressed()) {
             // If a panel was showing and the requesting panel has a lower priority, suppress it
             // if possible.
-            mSuppressedPanel = panel;
+            if (!mSuppressedPanels.contains(panel)) mSuppressedPanels.add(panel);
         }
     }
 
@@ -107,7 +120,7 @@ public class OverlayPanelManager {
         if (reason == StateChangeReason.SUPPRESS) {
             if (mActivePanel == panel) {
                 if (mActivePanel.canBeSuppressed()) {
-                    mSuppressedPanel = mActivePanel;
+                    mSuppressedPanels.add(mActivePanel);
                 }
                 mActivePanel = mPendingPanel;
                 mActivePanel.peekPanel(mPendingReason);
@@ -118,12 +131,13 @@ public class OverlayPanelManager {
             // Normal close panel flow.
             if (panel == mActivePanel) {
                 mActivePanel = null;
-                if (mSuppressedPanel != null) {
-                    mActivePanel = mSuppressedPanel;
+                if (!mSuppressedPanels.isEmpty()) {
+                    mActivePanel = mSuppressedPanels.poll();
                     mActivePanel.peekPanel(StateChangeReason.UNSUPPRESS);
                 }
+            } else {
+                mSuppressedPanels.remove(panel);
             }
-            mSuppressedPanel = null;
         }
     }
 
@@ -137,6 +151,14 @@ public class OverlayPanelManager {
     }
 
     /**
+     * @return The size of the suppressed panel queue.
+     */
+    @VisibleForTesting
+    public int getSuppressedQueueSize() {
+        return mSuppressedPanels.size();
+    }
+
+    /**
      * Destroy all panels owned by this manager.
      */
     public void destroy() {
@@ -145,7 +167,7 @@ public class OverlayPanelManager {
         }
         mPanelSet.clear();
         mActivePanel = null;
-        mSuppressedPanel = null;
+        mSuppressedPanels.clear();
 
         // Clear references to held resources.
         mDynamicResourceLoader = null;