System properties in SurfaceFlinger

The ConfigStore HAL remains in AOSP to support legacy vendor partitions. On devices running Android 10+, surfaceflinger reads system properties first; if no system property is defined for a config item in SurfaceFlingerProperties.sysprop, surfaceflinger falls back to the ConfigStore HAL.

Build flags and system properties

Each build flag in ConfigStore has a matching system property, as shown in the following table. For details on these properties, refer to frameworks/native/services/surfaceflinger/sysprop/SurfaceFlingerProperties.sysprop.

Build flags	System properties
`TARGET_FORCE_HWC_FOR_VIRTUAL_DISPLAYS`	`ro.surface_flinger.force_hwc_copy_for_virtual_displays`
`TARGET_HAS_HDR_DISPLAY`	`ro.surface_flinger.has_HDR_display`
`TARGET_HAS_WIDE_COLOR_DISPLAY`	`ro.surface_flinger.has_wide_color_display`
`NUM_FRAMEBUFFER_SURFACE_BUFFERS`	`ro.surface_flinger.max_frame_buffer_acquired_buffers`
`MAX_VIRTUAL_DISPLAY_DIMENSION`	`ro.surface_flinger.max_virtual_display_dimension`
`PRIMARY_DISPLAY_ORIENTATION`	`ro.surface_flinger.primary_display_orientation`
`PRESENT_TIME_OFFSET_FROM_VSYNC_NS`	`ro.surface_flinger.present_time_offset_from_vsync_ns`
`TARGET_RUNNING_WITHOUT_SYNC_FRAMEWORK`	`ro.surface_flinger.running_without_sync_framework`
`SF_START_GRAPHICS_ALLOCATOR_SERVICE`	`ro.surface_flinger.start_graphics_allocator_service`
`TARGET_USE_CONTEXT_PRIORITY`	`ro.surface_flinger.use_context_priority`
`USE_VR_FLINGER`	`ro.surface_flinger.use_vr_flinger`
`VSYNC_EVENT_PHASE_OFFSET_NS`	`ro.surface_flinger.vsync_event_phase_offset_ns`
`SF_VSYNC_EVENT_PHASE_OFFSET_NS`	`ro.surface_flinger.vsync_sf_event_phase_offset_ns`

Using SurfaceFlingerProperties

The following examples show how to use the SurfaceFlingerProperties library and the Surface Flinger property ro.surface_flinger.vsync_event_phase_offset_ns.

To query for the value of the property in reference, use the property's api_name as the function name.

Include SurfaceFlingerProperties in your build file, as follows:

cc_binary {
    name: "cc_client",
    srcs: ["baz.cpp"],
    shared_libs: ["SurfaceFlingerProperties"],
}
java_library {
    name: "JavaClient",
    srcs: ["foo/bar.java"],
    libs: ["SurfaceFlingerProperties"],
}

The following Java code snippet uses the ro.surface_flinger.vsync_event_phase_offset_ns system property:

import android.sysprop.SurfaceFlingerProperties;
...

static void foo() {
    ...
    boolean temp = SurfaceFlingerProperties.vsync_event_phase_offset_ns().orElse(true);
    ...
}
...

The following C++ code snippet uses the ro.surface_flinger.vsync_event_phase_offset_ns system property:

#include <SurfaceFlingerProperties.sysprop.h>
using namespace android::sysprop;

...

void bar() {
    ...
    bool temp = SurfaceFlingerProperties::vsync_event_phase_offset_ns(true);
    ...
}
...