Blur developer setting

New dev-option for enabling and disabling blurs, on devices that support
it.

Bug: 149792636
Test: manual
Test: atest EnableBlursPreferenceControllerTest
Change-Id: I26b4739a7b811c461557316a9247f6a9c397048a

src/com/android/settings/development/EnableBlursPreferenceController.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.development;
+
+import android.content.Context;
+import android.os.SystemProperties;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.preference.Preference;
+import androidx.preference.SwitchPreference;
+
+import com.android.settings.core.PreferenceControllerMixin;
+import com.android.settingslib.development.DeveloperOptionsPreferenceController;
+import com.android.settingslib.development.SystemPropPoker;
+
+/**
+ * Controller that toggles window blurs on SurfaceFlinger on devices that support it.
+ */
+public final class EnableBlursPreferenceController extends DeveloperOptionsPreferenceController
+        implements Preference.OnPreferenceChangeListener, PreferenceControllerMixin {
+
+    @VisibleForTesting
+    static final String DISABLE_BLURS_SYSPROP = "persist.sys.sf.disable_blurs";
+    private static final String ENABLE_BLURS_ON_WINDOWS = "enable_blurs_on_windows";
+    private final boolean mBlurSupported;
+
+    public EnableBlursPreferenceController(Context context) {
+        this(context, SystemProperties
+                .getBoolean("ro.surface_flinger.supports_background_blur", false));
+    }
+
+    @VisibleForTesting
+    public EnableBlursPreferenceController(Context context, boolean blurSupported) {
+        super(context);
+        mBlurSupported = blurSupported;
+    }
+
+    @Override
+    public String getPreferenceKey() {
+        return ENABLE_BLURS_ON_WINDOWS;
+    }
+
+    @Override
+    public boolean onPreferenceChange(Preference preference, Object newValue) {
+        final boolean isDisabled = !(Boolean) newValue;
+        SystemProperties.set(DISABLE_BLURS_SYSPROP, isDisabled ? "1" : "0");
+        SystemPropPoker.getInstance().poke();
+        return true;
+    }
+
+    @Override
+    public boolean isAvailable() {
+        return mBlurSupported;
+    }
+
+    @Override
+    public void updateState(Preference preference) {
+        boolean isEnabled = !SystemProperties.getBoolean(
+                DISABLE_BLURS_SYSPROP, false /* default */);
+        ((SwitchPreference) mPreference).setChecked(isEnabled);
+    }
+
+    @Override
+    protected void onDeveloperOptionsSwitchDisabled() {
+        super.onDeveloperOptionsSwitchDisabled();
+        SystemProperties.set(DISABLE_BLURS_SYSPROP, null);
+        updateState(null);
+    }
+}