Merge "Dither HDR content when compositing to an 8-bit target" into tm-dev

#include <gui/TraceUtils.h>

#include <sync/sync.h>

#include <ui/BlurRegion.h>

#include <ui/DataspaceUtils.h>

#include <ui/DebugUtils.h>

#include <ui/GraphicBuffer.h>

#include <utils/Trace.h>

                                                  .requiresLinearEffect = requiresLinearEffect,

                                                  .layerDimmingRatio = layerDimmingRatio}));

            // Turn on dithering when dimming beyond this threshold.

            // Turn on dithering when dimming beyond this (arbitrary) threshold...

            static constexpr float kDimmingThreshold = 0.2f;

            if (layerDimmingRatio <= kDimmingThreshold) {

            // ...or we're rendering an HDR layer down to an 8-bit target

            // Most HDR standards require at least 10-bits of color depth for source content, so we

            // can just extract the transfer function rather than dig into precise gralloc layout.

            // Furthermore, we can assume that the only 8-bit target we support is RGBA8888.

            const bool requiresDownsample = isHdrDataspace(layer.sourceDataspace) &&

                    buffer->getPixelFormat() == PIXEL_FORMAT_RGBA_8888;

            if (layerDimmingRatio <= kDimmingThreshold || requiresDownsample) {

                paint.setDither(true);

            }

            paint.setAlphaf(layer.alpha);