Restore the density when it has been overridden

When the density is overridden, the new density remains the same during
the resolution changes, which causes improper DPI on the screen. The
patch recalculates the suitable overridden density when the resolution
is changed and applies the new settings when the new resolution takes
place.

Bug: 233698163
Test: Switch resolution with customized density
Change-Id: I0914de61da0ab3b78380b355f47dbd3052079492

src/com/android/settings/display/ScreenResolutionFragment.java

@@ -19,6 +19,7 @@ package com.android.settings.display;
 import static com.android.settings.display.ScreenResolutionController.FHD_WIDTH;
 import static com.android.settings.display.ScreenResolutionController.QHD_WIDTH;
 
+import android.annotation.Nullable;
 import android.app.settings.SettingsEnums;
 import android.content.Context;
 import android.content.res.Resources;
@@ -34,6 +35,7 @@ import androidx.preference.PreferenceScreen;
 import com.android.settings.R;
 import com.android.settings.search.BaseSearchIndexProvider;
 import com.android.settings.widget.RadioButtonPickerFragment;
+import com.android.settingslib.display.DisplayDensityUtils;
 import com.android.settingslib.search.SearchIndexable;
 import com.android.settingslib.widget.CandidateInfo;
 import com.android.settingslib.widget.FooterPreference;
@@ -48,7 +50,6 @@ import java.util.Set;
 /** Preference fragment used for switch screen resolution */
 @SearchIndexable
 public class ScreenResolutionFragment extends RadioButtonPickerFragment {
-
     private static final String TAG = "ScreenResolution";
 
     private Resources mResources;
@@ -60,6 +61,7 @@ public class ScreenResolutionFragment extends RadioButtonPickerFragment {
     private String[] mScreenResolutionSummaries;
 
     private IllustrationPreference mImagePreference;
+    private DensityRestorer mDensityRestorer;
 
     @Override
     public void onAttach(Context context) {
@@ -74,6 +76,7 @@ public class ScreenResolutionFragment extends RadioButtonPickerFragment {
                 mResources.getStringArray(R.array.config_screen_resolution_summaries_strings);
         mResolutions = getAllSupportedResolution();
         mImagePreference = new IllustrationPreference(context);
+        mDensityRestorer = new DensityRestorer(context);
     }
 
     @Override
@@ -151,16 +154,21 @@ public class ScreenResolutionFragment extends RadioButtonPickerFragment {
 
     /** Using display manager to set the display mode. */
     @VisibleForTesting
-    public void setDisplayMode(int width) {
+    public void setDisplayMode(final int width) {
+        if (width == getDisplayMode().getPhysicalWidth()) {
+            return;
+        }
+
+        mDensityRestorer.startObserve();
         mDefaultDisplay.setUserPreferredDisplayMode(getPreferMode(width));
     }
 
     /** Get the key corresponding to the resolution. */
     @VisibleForTesting
     String getKeyForResolution(int width) {
-        return width == FHD_WIDTH ? mScreenResolutionOptions[FHD_INDEX]
+        return width == FHD_WIDTH
-                : width == QHD_WIDTH ? mScreenResolutionOptions[QHD_INDEX]
+                ? mScreenResolutionOptions[FHD_INDEX]
-                : null;
+                : width == QHD_WIDTH ? mScreenResolutionOptions[QHD_INDEX] : null;
     }
 
     @Override
@@ -171,7 +179,7 @@ public class ScreenResolutionFragment extends RadioButtonPickerFragment {
     }
 
     @Override
-    protected boolean setDefaultKey(String key) {
+    protected boolean setDefaultKey(final String key) {
         if (mScreenResolutionOptions[FHD_INDEX].equals(key)) {
             setDisplayMode(FHD_WIDTH);
 
@@ -236,10 +244,6 @@ public class ScreenResolutionFragment extends RadioButtonPickerFragment {
 
     public static final BaseSearchIndexProvider SEARCH_INDEX_DATA_PROVIDER =
             new BaseSearchIndexProvider(R.xml.screen_resolution_settings) {
-
-                boolean mIsFHDSupport = false;
-                boolean mIsQHDSupport = false;
-
                 @Override
                 protected boolean isPageSearchEnabled(Context context) {
                     ScreenResolutionController mController =
@@ -247,4 +251,76 @@ public class ScreenResolutionFragment extends RadioButtonPickerFragment {
                     return mController.checkSupportedResolutions();
                 }
             };
+
+    private static final class DensityRestorer implements DisplayManager.DisplayListener {
+        private final @Nullable Context mContext;
+        private int mDefaultDensity;
+        private int mCurrentIndex;
+
+        DensityRestorer(Context context) {
+            mContext = context;
+        }
+
+        public void startObserve() {
+            if (mContext == null) {
+                return;
+            }
+
+            final DisplayDensityUtils density = new DisplayDensityUtils(mContext);
+            final int currentIndex = density.getCurrentIndex();
+            final int defaultDensity = density.getDefaultDensity();
+
+            if (density.getValues()[mCurrentIndex] == density.getDefaultDensity()) {
+                return;
+            }
+
+            mDefaultDensity = defaultDensity;
+            mCurrentIndex = currentIndex;
+            final DisplayManager dm = mContext.getSystemService(DisplayManager.class);
+            dm.registerDisplayListener(this, null);
+        }
+
+        public void stopObserve() {
+            if (mContext == null) {
+                return;
+            }
+
+            final DisplayManager dm = mContext.getSystemService(DisplayManager.class);
+            dm.unregisterDisplayListener(this);
+        }
+
+        @Override
+        public void onDisplayAdded(int displayId) {}
+
+        @Override
+        public void onDisplayRemoved(int displayId) {}
+
+        @Override
+        public void onDisplayChanged(int displayId) {
+            if (displayId != Display.DEFAULT_DISPLAY) {
+                return;
+            }
+
+            restoreDensity();
+        }
+
+        private void restoreDensity() {
+            if (mContext == null) {
+                return;
+            }
+
+            final DisplayDensityUtils density = new DisplayDensityUtils(mContext);
+            if (density.getDefaultDensity() == mDefaultDensity) {
+                return;
+            }
+
+            if (density.getValues()[mCurrentIndex] != density.getDefaultDensity()) {
+                DisplayDensityUtils.setForcedDisplayDensity(
+                        Display.DEFAULT_DISPLAY, density.getValues()[mCurrentIndex]);
+            }
+
+            mDefaultDensity = density.getDefaultDensity();
+            stopObserve();
+        }
+    }
 }