From c112bb5c56cc2cac07893dcf58dfa8b008afe317 Mon Sep 17 00:00:00 2001
From: Xaver Hugl <xaver.hugl@gmail.com>
Date: Wed, 14 Jun 2023 12:59:29 +0200
Subject: [PATCH] backends/drm: fix color management with sRGB output

We need to target the linear EOTF for rendering, even if the output EOTF
is sRGB
---
 src/backends/drm/drm_egl_layer_surface.cpp | 7 ++++---
 src/backends/drm/drm_egl_layer_surface.h   | 1 +
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/backends/drm/drm_egl_layer_surface.cpp b/src/backends/drm/drm_egl_layer_surface.cpp
index e6e23d02b7..4a9f09ba0b 100644
--- a/src/backends/drm/drm_egl_layer_surface.cpp
+++ b/src/backends/drm/drm_egl_layer_surface.cpp
@@ -89,12 +89,13 @@ std::optional<OutputLayerBeginFrameInfo> EglGbmLayerSurface::startRendering(cons
     }
     m_surface.currentBuffer = buffer;
 
-    if (m_surface.targetColorDescription != colorDescription || m_surface.channelFactors != channelFactors) {
+    if (m_surface.targetColorDescription != colorDescription || m_surface.channelFactors != channelFactors || m_surface.colormanagementEnabled != enableColormanagement) {
         m_surface.gbmSwapchain->resetDamage();
         repaint = infiniteRegion();
+        m_surface.colormanagementEnabled = enableColormanagement;
         m_surface.targetColorDescription = colorDescription;
         m_surface.channelFactors = channelFactors;
-        if (colorDescription != ColorDescription::sRGB) {
+        if (enableColormanagement) {
             m_surface.intermediaryColorDescription = ColorDescription(colorDescription.colorimetry(), NamedTransferFunction::linear,
                                                                       colorDescription.sdrBrightness(), colorDescription.minHdrBrightness(),
                                                                       colorDescription.maxHdrBrightness(), colorDescription.maxHdrHighlightBrightness());
@@ -126,7 +127,7 @@ std::optional<OutputLayerBeginFrameInfo> EglGbmLayerSurface::startRendering(cons
 
 bool EglGbmLayerSurface::endRendering(const QRegion &damagedRegion)
 {
-    if (m_surface.shadowTexture) {
+    if (m_surface.colormanagementEnabled) {
         const auto &[texture, fbo] = m_surface.textureCache[m_surface.currentBuffer->bo()];
         GLFramebuffer::pushFramebuffer(fbo.get());
         ShaderBinder binder(ShaderTrait::MapTexture | ShaderTrait::TransformColorspace);
diff --git a/src/backends/drm/drm_egl_layer_surface.h b/src/backends/drm/drm_egl_layer_surface.h
index ef09b76256..97ddd267b8 100644
--- a/src/backends/drm/drm_egl_layer_surface.h
+++ b/src/backends/drm/drm_egl_layer_surface.h
@@ -69,6 +69,7 @@ private:
     };
     struct Surface
     {
+        bool colormanagementEnabled = false;
         std::shared_ptr<GLTexture> shadowTexture;
         std::shared_ptr<GLFramebuffer> shadowBuffer;
         ColorDescription targetColorDescription = ColorDescription::sRGB;