Merge "Limit HLG to 4.926x SDR" into main

Author: Treehugger Robot

libs/ui/include_types/ui/HdrRenderTypeUtils.h

@@ -61,4 +61,24 @@ inline HdrRenderType getHdrRenderType(ui::Dataspace dataspace,
     return HdrRenderType::SDR;
 }
 
-} // namespace android
+/**
+ * Returns the maximum headroom allowed for this content under "idealized"
+ * display conditions (low surround luminance, high-enough display brightness).
+ *
+ * TODO: take into account hdr metadata, but square it with the fact that some
+ * HLG content has CTA.861-3 metadata
+ */
+inline float getIdealizedMaxHeadroom(ui::Dataspace dataspace) {
+    const auto transfer = dataspace & HAL_DATASPACE_TRANSFER_MASK;
+
+    switch (transfer) {
+        case HAL_DATASPACE_TRANSFER_ST2084:
+            return 10000.0f / 203.0f;
+        case HAL_DATASPACE_TRANSFER_HLG:
+            return 1000.0f / 203.0f;
+        default:
+            return 1.0f;
+    }
+}
+
+} // namespace android

services/surfaceflinger/CompositionEngine/src/OutputLayer.cpp

@@ -26,6 +26,7 @@
 #include <ui/FloatRect.h>
 #include <ui/HdrRenderTypeUtils.h>
 #include <cstdint>
+#include <limits>
 #include "system/graphics-base-v1.0.h"
 
 #include <com_android_graphics_libgui_flags.h>
@@ -398,11 +399,22 @@ void OutputLayer::updateCompositionState(
     // For hdr content, treat the white point as the display brightness - HDR content should not be
     // boosted or dimmed.
     // If the layer explicitly requests to disable dimming, then don't dim either.
-    if (hdrRenderType == HdrRenderType::GENERIC_HDR ||
-        getOutput().getState().displayBrightnessNits == getOutput().getState().sdrWhitePointNits ||
-        getOutput().getState().displayBrightnessNits == 0.f || !layerFEState->dimmingEnabled) {
+    if (getOutput().getState().displayBrightnessNits == getOutput().getState().sdrWhitePointNits ||
+        getOutput().getState().displayBrightnessNits <= 0.f || !layerFEState->dimmingEnabled) {
         state.dimmingRatio = 1.f;
         state.whitePointNits = getOutput().getState().displayBrightnessNits;
+    } else if (hdrRenderType == HdrRenderType::GENERIC_HDR) {
+        float deviceHeadroom = getOutput().getState().displayBrightnessNits /
+                getOutput().getState().sdrWhitePointNits;
+        float idealizedMaxHeadroom = deviceHeadroom;
+
+        if (FlagManager::getInstance().begone_bright_hlg()) {
+            idealizedMaxHeadroom =
+                    std::min(idealizedMaxHeadroom, getIdealizedMaxHeadroom(state.dataspace));
+        }
+
+        state.dimmingRatio = std::min(idealizedMaxHeadroom / deviceHeadroom, 1.0f);
+        state.whitePointNits = getOutput().getState().displayBrightnessNits * state.dimmingRatio;
     } else {
         float layerBrightnessNits = getOutput().getState().sdrWhitePointNits;
         // RANGE_EXTENDED can "self-promote" to HDR, but is still rendered for a particular

services/surfaceflinger/SurfaceFlinger.cpp

@@ -3201,7 +3201,15 @@ void SurfaceFlinger::onCompositionPresented(PhysicalDisplayId pacesetterId,
                                             snapshot.desiredHdrSdrRatio < 1.f
                                             ? std::numeric_limits<float>::infinity()
                                             : snapshot.desiredHdrSdrRatio;
-                                    info.mergeDesiredRatio(desiredHdrSdrRatio);
+
+                                    float desiredRatio = desiredHdrSdrRatio;
+                                    if (FlagManager::getInstance().begone_bright_hlg() &&
+                                        desiredHdrSdrRatio ==
+                                                std::numeric_limits<float>::infinity()) {
+                                        desiredRatio = getIdealizedMaxHeadroom(snapshot.dataspace);
+                                    }
+
+                                    info.mergeDesiredRatio(desiredRatio);
                                     info.numberOfHdrLayers++;
                                     const auto displayFrame = outputLayer->getState().displayFrame;
                                     const int32_t area =

services/surfaceflinger/common/FlagManager.cpp

@@ -160,6 +160,7 @@ void FlagManager::dump(std::string& result) const {
     DUMP_READ_ONLY_FLAG(connected_display_hdr);
     DUMP_READ_ONLY_FLAG(deprecate_frame_tracker);
     DUMP_READ_ONLY_FLAG(skip_invisible_windows_in_input);
+    DUMP_READ_ONLY_FLAG(begone_bright_hlg);
 
 #undef DUMP_READ_ONLY_FLAG
 #undef DUMP_SERVER_FLAG
@@ -268,6 +269,7 @@ FLAG_MANAGER_READ_ONLY_FLAG(display_config_error_hal, "");
 FLAG_MANAGER_READ_ONLY_FLAG(connected_display_hdr, "");
 FLAG_MANAGER_READ_ONLY_FLAG(deprecate_frame_tracker, "");
 FLAG_MANAGER_READ_ONLY_FLAG(skip_invisible_windows_in_input, "");
+FLAG_MANAGER_READ_ONLY_FLAG(begone_bright_hlg, "debug.sf.begone_bright_hlg");
 
 /// Trunk stable server flags ///
 FLAG_MANAGER_SERVER_FLAG(refresh_rate_overlay_on_external_display, "")

services/surfaceflinger/common/include/common/FlagManager.h

@@ -98,6 +98,7 @@ class FlagManager {
     bool connected_display_hdr() const;
     bool deprecate_frame_tracker() const;
     bool skip_invisible_windows_in_input() const;
+    bool begone_bright_hlg() const;
 
 protected:
     // overridden for unit tests

services/surfaceflinger/surfaceflinger_flags_new.aconfig

@@ -34,6 +34,14 @@ flag {
   is_fixed_read_only: true
 } # arr_surfacecontrol_setframerate_api
 
+flag {
+  name: "begone_bright_hlg"
+  namespace: "core_graphics"
+  description: "Caps HLG brightness relative to SDR"
+  bug: "362510107"
+  is_fixed_read_only: true
+} # begone_bright_hlg
+
 flag {
   name: "ce_fence_promise"
   namespace: "window_surfaces"