backends/drm: handle missing brightness values in the EDID better

Most importantly, fall back to an assumption of 1000 nits peak brightness when the
max brightness is missing, instead of the sdr brightness, which causes more immediately
visible issues.
Ideally the user should configure this value in the display settings, but it's too
late to still do that for Plasma 6.0.

BUG: 478860

src/backends/drm/drm_output.cpp

@@ -59,11 +59,10 @@ DrmOutput::DrmOutput(const std::shared_ptr<DrmConnector> &conn)
         capabilities |= Capability::RgbRange;
         initialState.rgbRange = DrmConnector::broadcastRgbToRgbRange(conn->broadcastRGB.enumValue());
     }
-    if (m_connector->hdrMetadata.isValid() && m_connector->edid() && m_connector->edid()->hdrMetadata() && m_connector->edid()->hdrMetadata()->supportsPQ) {
+    if (m_connector->hdrMetadata.isValid() && m_connector->edid()->supportsPQ()) {
         capabilities |= Capability::HighDynamicRange;
     }
-    if (m_connector->colorspace.isValid() && m_connector->colorspace.hasEnum(DrmConnector::Colorspace::BT2020_RGB)
-        && m_connector->edid() && m_connector->edid()->hdrMetadata() && m_connector->edid()->hdrMetadata()->supportsBT2020) {
+    if (m_connector->colorspace.isValid() && m_connector->colorspace.hasEnum(DrmConnector::Colorspace::BT2020_RGB) && m_connector->edid()->supportsBT2020()) {
         capabilities |= Capability::WideColorGamut;
     }
     if (conn->isInternal()) {
@@ -72,8 +71,6 @@ DrmOutput::DrmOutput(const std::shared_ptr<DrmConnector> &conn)
     }
 
     const Edid *edid = conn->edid();
-
-    const auto hdrData = edid->hdrMetadata();
     setInformation(Information{
         .name = conn->connectorName(),
         .manufacturer = edid->manufacturerString(),
@@ -88,9 +85,9 @@ DrmOutput::DrmOutput(const std::shared_ptr<DrmConnector> &conn)
         .internal = conn->isInternal(),
         .nonDesktop = conn->isNonDesktop(),
         .mstPath = conn->mstPath(),
-        .maxPeakBrightness = hdrData && hdrData->hasValidBrightnessValues ? hdrData->desiredContentMaxLuminance : 0,
-        .maxAverageBrightness = hdrData && hdrData->hasValidBrightnessValues ? hdrData->desiredMaxFrameAverageLuminance : 0,
-        .minBrightness = hdrData && hdrData->hasValidBrightnessValues ? hdrData->desiredContentMinLuminance : 0,
+        .maxPeakBrightness = edid->desiredMaxLuminance(),
+        .maxAverageBrightness = edid->desiredMaxFrameAverageLuminance(),
+        .minBrightness = edid->desiredMinLuminance(),
     });
 
     initialState.modes = getModes();

src/backends/drm/drm_pipeline.cpp

@@ -769,13 +769,11 @@ ColorDescription DrmPipeline::createColorDescription() const
 {
     if (m_pending.transferFunction == NamedTransferFunction::PerceptualQuantizer && m_connector->edid()) {
         const auto colorimetry = m_pending.BT2020 ? NamedColorimetry::BT2020 : NamedColorimetry::BT709;
-        if (const auto hdr = m_connector->edid()->hdrMetadata(); hdr && hdr->hasValidBrightnessValues) {
-            return ColorDescription(colorimetry, m_pending.transferFunction, m_pending.sdrBrightness, hdr->desiredContentMinLuminance, hdr->desiredMaxFrameAverageLuminance, hdr->desiredContentMaxLuminance, m_pending.sdrGamutWideness);
-        } else if (m_pending.peakBrightnessOverride && m_pending.averageBrightnessOverride) {
-            return ColorDescription(colorimetry, m_pending.transferFunction, m_pending.sdrBrightness, m_pending.minBrightnessOverride.value_or(0), *m_pending.averageBrightnessOverride, *m_pending.peakBrightnessOverride, m_pending.sdrGamutWideness);
-        } else {
-            return ColorDescription(colorimetry, m_pending.transferFunction, m_pending.sdrBrightness, 0, m_pending.sdrBrightness, m_pending.sdrBrightness, m_pending.sdrGamutWideness);
-        }
+        return ColorDescription(colorimetry, m_pending.transferFunction, m_pending.sdrBrightness,
+                                m_pending.minBrightnessOverride.value_or(m_connector->edid()->desiredMinLuminance()),
+                                m_pending.averageBrightnessOverride.value_or(m_connector->edid()->desiredMaxFrameAverageLuminance().value_or(m_pending.sdrBrightness)),
+                                m_pending.peakBrightnessOverride.value_or(m_connector->edid()->desiredMaxLuminance().value_or(1000)),
+                                m_pending.sdrGamutWideness);
     } else if (m_pending.iccProfile) {
         return ColorDescription(m_pending.iccProfile->colorimetry(), NamedTransferFunction::sRGB, 200, 0, 200, 200, 0);
     } else {
@@ -789,11 +787,7 @@ std::shared_ptr<DrmBlob> DrmPipeline::createHdrMetadata(NamedTransferFunction tr
         // for sRGB / gamma 2.2, don't send any metadata, to ensure the non-HDR experience stays the same
         return nullptr;
     }
-    if (!m_connector->edid() || !m_connector->edid()->hdrMetadata()) {
-        return nullptr;
-    }
-    const auto metadata = *m_connector->edid()->hdrMetadata();
-    if (!metadata.supportsPQ) {
+    if (!m_connector->edid()->supportsPQ()) {
         return nullptr;
     }
     const auto colorimetry = m_connector->edid()->colorimetry();
@@ -820,12 +814,12 @@ std::shared_ptr<DrmBlob> DrmPipeline::createHdrMetadata(NamedTransferFunction tr
             },
             .white_point = {to16Bit(colorimetry.white.x()), to16Bit(colorimetry.white.y())},
             // in nits
-            .max_display_mastering_luminance = uint16_t(std::round(metadata.desiredMaxFrameAverageLuminance)),
+            .max_display_mastering_luminance = uint16_t(std::round(m_connector->edid()->desiredMaxFrameAverageLuminance().value_or(0))),
             // in 0.0001 nits
-            .min_display_mastering_luminance = uint16_t(std::round(metadata.desiredContentMinLuminance * 10000)),
+            .min_display_mastering_luminance = uint16_t(std::round(m_connector->edid()->desiredMaxLuminance().value_or(0) * 10000)),
             // in nits
-            .max_cll = uint16_t(std::round(metadata.desiredMaxFrameAverageLuminance)),
-            .max_fall = uint16_t(std::round(metadata.desiredMaxFrameAverageLuminance)),
+            .max_cll = uint16_t(std::round(m_connector->edid()->desiredMaxFrameAverageLuminance().value_or(0))),
+            .max_fall = uint16_t(std::round(m_connector->edid()->desiredMaxFrameAverageLuminance().value_or(0))),
         },
     };
     return DrmBlob::create(gpu(), &data, sizeof(data));

src/core/output.cpp

@@ -624,14 +624,14 @@ const ColorDescription &Output::colorDescription() const
     return m_state.colorDescription;
 }
 
-double Output::maxPeakBrightness() const
+std::optional<double> Output::maxPeakBrightness() const
 {
-    return m_state.maxPeakBrightnessOverride.value_or(m_information.maxPeakBrightness);
+    return m_state.maxPeakBrightnessOverride ? m_state.maxPeakBrightnessOverride : m_information.maxPeakBrightness;
 }
 
-double Output::maxAverageBrightness() const
+std::optional<double> Output::maxAverageBrightness() const
 {
-    return m_state.maxAverageBrightnessOverride.value_or(m_information.maxAverageBrightness);
+    return m_state.maxAverageBrightnessOverride ? *m_state.maxAverageBrightnessOverride : m_information.maxAverageBrightness;
 }
 
 double Output::minBrightness() const

src/core/output.h

@@ -341,8 +341,8 @@ public:
 
     virtual bool updateCursorLayer();
 
-    double maxPeakBrightness() const;
-    double maxAverageBrightness() const;
+    std::optional<double> maxPeakBrightness() const;
+    std::optional<double> maxAverageBrightness() const;
     double minBrightness() const;
     std::optional<double> maxPeakBrightnessOverride() const;
     std::optional<double> maxAverageBrightnessOverride() const;
@@ -431,8 +431,8 @@ protected:
         bool placeholder = false;
         bool nonDesktop = false;
         QByteArray mstPath;
-        double maxPeakBrightness = 0;
-        double maxAverageBrightness = 0;
+        std::optional<double> maxPeakBrightness;
+        std::optional<double> maxAverageBrightness;
         double minBrightness = 0;
     };
 
@@ -456,9 +456,9 @@ protected:
         QString iccProfilePath;
         std::shared_ptr<IccProfile> iccProfile;
         ColorDescription colorDescription = ColorDescription::sRGB;
-        std::optional<float> maxPeakBrightnessOverride;
-        std::optional<float> maxAverageBrightnessOverride;
-        std::optional<float> minBrightnessOverride;
+        std::optional<double> maxPeakBrightnessOverride;
+        std::optional<double> maxAverageBrightnessOverride;
+        std::optional<double> minBrightnessOverride;
         double sdrGamutWideness = 0;
     };
 

src/utils/edid.cpp

@@ -166,10 +166,9 @@ Edid::Edid(const void *data, uint32_t size)
         }
         if (hdr_static_metadata) {
             m_hdrMetadata = HDRMetadata{
-                .hasValidBrightnessValues = hdr_static_metadata->desired_content_min_luminance > 0 && hdr_static_metadata->desired_content_max_luminance > 0 && hdr_static_metadata->desired_content_max_frame_avg_luminance,
                 .desiredContentMinLuminance = hdr_static_metadata->desired_content_min_luminance,
-                .desiredContentMaxLuminance = hdr_static_metadata->desired_content_max_luminance,
-                .desiredMaxFrameAverageLuminance = hdr_static_metadata->desired_content_max_frame_avg_luminance,
+                .desiredContentMaxLuminance = hdr_static_metadata->desired_content_max_luminance > 0 ? std::make_optional(hdr_static_metadata->desired_content_max_luminance) : std::nullopt,
+                .desiredMaxFrameAverageLuminance = hdr_static_metadata->desired_content_max_frame_avg_luminance > 0 ? std::make_optional(hdr_static_metadata->desired_content_max_frame_avg_luminance) : std::nullopt,
                 .supportsPQ = hdr_static_metadata->eotfs->pq,
                 .supportsBT2020 = colorimetry && colorimetry->bt2020_rgb,
             };
@@ -252,9 +251,29 @@ Colorimetry Edid::colorimetry() const
     return m_colorimetry;
 }
 
-std::optional<Edid::HDRMetadata> Edid::hdrMetadata() const
+double Edid::desiredMinLuminance() const
 {
-    return m_hdrMetadata;
+    return m_hdrMetadata ? m_hdrMetadata->desiredContentMinLuminance : 0;
+}
+
+std::optional<double> Edid::desiredMaxFrameAverageLuminance() const
+{
+    return m_hdrMetadata ? m_hdrMetadata->desiredMaxFrameAverageLuminance : std::nullopt;
+}
+
+std::optional<double> Edid::desiredMaxLuminance() const
+{
+    return m_hdrMetadata ? m_hdrMetadata->desiredContentMaxLuminance : std::nullopt;
+}
+
+bool Edid::supportsPQ() const
+{
+    return m_hdrMetadata && m_hdrMetadata->supportsPQ;
+}
+
+bool Edid::supportsBT2020() const
+{
+    return m_hdrMetadata && m_hdrMetadata->supportsBT2020;
 }
 
 QByteArray Edid::identifier() const

src/utils/edid.h

@@ -81,16 +81,11 @@ public:
 
     Colorimetry colorimetry() const;
 
-    struct HDRMetadata
-    {
-        bool hasValidBrightnessValues;
-        float desiredContentMinLuminance;
-        float desiredContentMaxLuminance;
-        float desiredMaxFrameAverageLuminance;
-        bool supportsPQ;
-        bool supportsBT2020;
-    };
-    std::optional<HDRMetadata> hdrMetadata() const;
+    double desiredMinLuminance() const;
+    std::optional<double> desiredMaxFrameAverageLuminance() const;
+    std::optional<double> desiredMaxLuminance() const;
+    bool supportsPQ() const;
+    bool supportsBT2020() const;
 
     /**
      * @returns a string that is intended to identify the monitor uniquely.
@@ -106,6 +101,14 @@ private:
     QByteArray m_serialNumber;
     QString m_hash;
     Colorimetry m_colorimetry;
+    struct HDRMetadata
+    {
+        double desiredContentMinLuminance;
+        std::optional<double> desiredContentMaxLuminance;
+        std::optional<double> desiredMaxFrameAverageLuminance;
+        bool supportsPQ;
+        bool supportsBT2020;
+    };
     std::optional<HDRMetadata> m_hdrMetadata;
 
     QByteArray m_identifier;

src/wayland/outputdevice_v2.cpp

@@ -133,8 +133,8 @@ public:
     bool m_wideColorGamut = false;
     auto_rotate_policy m_autoRotation = auto_rotate_policy::auto_rotate_policy_in_tablet_mode;
     QString m_iccProfilePath;
-    double m_maxPeakBrightness = 0;
-    double m_maxAverageBrightness = 0;
+    std::optional<double> m_maxPeakBrightness;
+    std::optional<double> m_maxAverageBrightness;
     double m_minBrightness = 0;
     double m_sdrGamutWideness = 0;
     std::optional<double> m_maxPeakBrightnessOverride;
@@ -445,7 +445,7 @@ void OutputDeviceV2InterfacePrivate::sendIccProfilePath(Resource *resource)
 void OutputDeviceV2InterfacePrivate::sendBrightnessMetadata(Resource *resource)
 {
     if (resource->version() >= KDE_OUTPUT_DEVICE_V2_BRIGHTNESS_METADATA_SINCE_VERSION) {
-        send_brightness_metadata(resource->handle, std::round(m_maxPeakBrightness), std::round(m_maxAverageBrightness), std::round(m_minBrightness * 10'000));
+        send_brightness_metadata(resource->handle, std::round(m_maxPeakBrightness.value_or(0)), std::round(m_maxAverageBrightness.value_or(0)), std::round(m_minBrightness * 10'000));
     }
 }