configstore/1.0/ISurfaceFlingerConfigs.hal

/*
 * Copyright (C) 2017 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 android.hardware.configstore@1.0;

interface ISurfaceFlingerConfigs {
    /*
     * The following two methods define (respectively):
     *
     * - The phase offset between hardware vsync and when apps are woken up by the
     *   Choreographer callback
     * - The phase offset between hardware vsync and when SurfaceFlinger wakes up
     *   to consume input
     *
     * Their values may be tuned to trade off between display pipeline latency (both
     * overall latency and the lengths of the app --> SF and SF --> display phases)
     * and frame delivery jitter (which typically manifests as "jank" or "jerkiness"
     * while interacting with the device). The default values must produce a
     * relatively low amount of jitter at the expense of roughly two frames of
     * app --> display latency, and unless significant testing is performed to avoid
     * increased display jitter (both manual investigation using systrace [1] and
     * automated testing using dumpsys gfxinfo [2] are recommended), they should not
     * be modified.
     *
     * [1] https://developer.android.com/studio/profile/systrace.html
     * [2] https://developer.android.com/training/testing/performance.html
     */
    vsyncEventPhaseOffsetNs() generates (OptionalInt64 value);
    vsyncSfEventPhaseOffsetNs() generates (OptionalInt64 value);

    useTripleFramebuffer() generates (OptionalBool value);
};