Refine WindowManagerInternal#getDisplayImePolicy

..by using cache without holing WM lock to get the displayImePolicy
settings.

Bug: 197848765
Test: atest CtsInputMethodTestCases
Change-Id: Ib00124b33409bce716fc01af33521bcd35ab02ec

services/core/java/com/android/server/wm/DisplayContent.java

@@ -2001,6 +2001,7 @@ class DisplayContent extends RootDisplayArea implements WindowManagerPolicy.Disp
     }
 
     void configureDisplayPolicy() {
+        mRootWindowContainer.updateDisplayImePolicyCache();
         mDisplayPolicy.updateConfigurationAndScreenSizeDependentBehaviors();
         mDisplayRotation.configure(mBaseDisplayWidth, mBaseDisplayHeight);
     }
@@ -3939,6 +3940,9 @@ class DisplayContent extends RootDisplayArea implements WindowManagerPolicy.Disp
         }
     }
 
+    // IMPORTANT: When introducing new dependencies in this method, make sure that
+    // changes to those result in RootWindowContainer.updateDisplayImePolicyCache()
+    // being called.
     @DisplayImePolicy int getImePolicy() {
         if (!isTrusted()) {
             return DISPLAY_IME_POLICY_FALLBACK_DISPLAY;

services/core/java/com/android/server/wm/RootWindowContainer.java

@@ -165,6 +165,7 @@ import java.io.PrintWriter;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
 import java.util.Set;
@@ -2530,9 +2531,16 @@ class RootWindowContainer extends WindowContainer<DisplayContent>
             // Drop any cached DisplayInfos associated with this display id - the values are now
             // out of date given this display changed event.
             mWmService.mPossibleDisplayInfoMapper.removePossibleDisplayInfos(displayId);
+            updateDisplayImePolicyCache();
         }
     }
 
+    void updateDisplayImePolicyCache() {
+        ArrayMap<Integer, Integer> displayImePolicyMap = new ArrayMap<>();
+        forAllDisplays(dc -> displayImePolicyMap.put(dc.getDisplayId(), dc.getImePolicy()));
+        mWmService.mDisplayImePolicyCache = Collections.unmodifiableMap(displayImePolicyMap);
+    }
+
     /** Update lists of UIDs that are present on displays and have access to them. */
     void updateUIDsPresentOnDisplay() {
         mDisplayAccessUIDs.clear();

services/core/java/com/android/server/wm/WindowManagerService.java

@@ -591,6 +591,13 @@ public class WindowManagerService extends IWindowManager.Stub
      */
     final ArrayList<WindowState> mResizingWindows = new ArrayList<>();
 
+    /**
+     * Mapping of displayId to {@link DisplayImePolicy}.
+     * Note that this can be accessed without holding the lock.
+     */
+    volatile Map<Integer, Integer> mDisplayImePolicyCache = Collections.unmodifiableMap(
+            new ArrayMap<>());
+
     /**
      * Windows whose surface should be destroyed.
      */
@@ -6947,6 +6954,7 @@ public class WindowManagerService extends IWindowManager.Stub
     void setForceDesktopModeOnExternalDisplays(boolean forceDesktopModeOnExternalDisplays) {
         synchronized (mGlobalLock) {
             mForceDesktopModeOnExternalDisplays = forceDesktopModeOnExternalDisplays;
+            mRoot.updateDisplayImePolicyCache();
         }
     }
 
@@ -7378,16 +7386,14 @@ public class WindowManagerService extends IWindowManager.Stub
         if (!checkCallingPermission(INTERNAL_SYSTEM_WINDOW, "getDisplayImePolicy()")) {
             throw new SecurityException("Requires INTERNAL_SYSTEM_WINDOW permission");
         }
-        final DisplayContent dc = mRoot.getDisplayContent(displayId);
-        if (dc == null) {
+        final Map<Integer, Integer> displayImePolicyCache = mDisplayImePolicyCache;
+        if (!displayImePolicyCache.containsKey(displayId)) {
             ProtoLog.w(WM_ERROR,
                     "Attempted to get IME policy of a display that does not exist: %d",
                     displayId);
             return DISPLAY_IME_POLICY_FALLBACK_DISPLAY;
         }
-        synchronized (mGlobalLock) {
-            return dc.getImePolicy();
-        }
+        return displayImePolicyCache.get(displayId);
     }
 
     @Override
@@ -7877,9 +7883,7 @@ public class WindowManagerService extends IWindowManager.Stub
 
         @Override
         public @DisplayImePolicy int getDisplayImePolicy(int displayId) {
-            synchronized (mGlobalLock) {
-                return WindowManagerService.this.getDisplayImePolicy(displayId);
-            }
+            return WindowManagerService.this.getDisplayImePolicy(displayId);
         }
 
         @Override