[plasma/powerdevil] daemon/controllers: daemon/controllers: remove supportsDimmingMultiplier

Git commit 5a4b07f139376f2add4ddf9a325f98e9657b4519 by Xaver Hugl.
Committed on 18/08/2026 at 12:38.
Pushed by zamundaaa into branch 'master'.

daemon/controllers: remove supportsDimmingMultiplier

Only KWin brightness control is supported, which always supports
dimming. This simplifies some code.

M  +0    -5    daemon/controllers/displaybrightness.cpp
M  +0    -9    daemon/controllers/displaybrightness.h
M  +0    -5    daemon/controllers/kwinbrightness.cpp
M  +0    -1    daemon/controllers/kwinbrightness.h
M  +4    -57   daemon/controllers/screenbrightnesscontroller.cpp
M  +0    -7    daemon/controllers/screenbrightnesscontroller.h

https://invent.kde.org/plasma/powerdevil/-/commit/5a4b07f139376f2add4ddf9a325f98e9657b4519

diff --git a/daemon/controllers/displaybrightness.cpp b/daemon/controllers/displaybrightness.cpp
index cde735635..d7b4c4670 100644
--- a/daemon/controllers/displaybrightness.cpp
+++ b/daemon/controllers/displaybrightness.cpp
@@ -31,11 +31,6 @@ bool DisplayBrightness::usesDdcCi() const
     return false;
 }
 
-bool DisplayBrightness::supportsDimmingMultiplier() const
-{
-    return false;
-}
-
 void DisplayBrightness::setDimmingMultiplier(double)
 {
 }
diff --git a/daemon/controllers/displaybrightness.h b/daemon/controllers/displaybrightness.h
index 4471cf067..c29a259b5 100644
--- a/daemon/controllers/displaybrightness.h
+++ b/daemon/controllers/displaybrightness.h
@@ -68,19 +68,10 @@ public:
      */
     virtual bool usesDdcCi() const;
 
-    /**
-     * Returns false by default. Override to return true if the display device can set a dimming
-     * multiplier independently of the brightness() itself. If this is supported,
-     * setDimmingMultiplier() must be overridden as well.
-     */
-    virtual bool supportsDimmingMultiplier() const;
-
     /**
      * Set a dimming multiplier between 0.0 and 1.0 to scale down display brightness temporarily,
      * without affecting the value returned by brightness(). It is not assumed that this value will
      * persist across disconnection or reboot scenarios.
-     *
-     * Must be implemented if supportsDimmingMultiplier() returns true, otherwise never called.
      */
     virtual void setDimmingMultiplier(double multiplier);
 
diff --git a/daemon/controllers/kwinbrightness.cpp b/daemon/controllers/kwinbrightness.cpp
index 44d8382c2..b63fd8de4 100644
--- a/daemon/controllers/kwinbrightness.cpp
+++ b/daemon/controllers/kwinbrightness.cpp
@@ -206,11 +206,6 @@ void KWinDisplayBrightness::setConfigOperationDone()
     }
 }
 
-bool KWinDisplayBrightness::supportsDimmingMultiplier() const
-{
-    return true;
-}
-
 void KWinDisplayBrightness::setDimmingMultiplier(double multiplier)
 {
     if (m_desiredDimming == multiplier) {
diff --git a/daemon/controllers/kwinbrightness.h b/daemon/controllers/kwinbrightness.h
index 96c4cff09..521cb21f3 100644
--- a/daemon/controllers/kwinbrightness.h
+++ b/daemon/controllers/kwinbrightness.h
@@ -28,7 +28,6 @@ public:
     void setBrightness(int brightness) override;
     bool isInternal() const override;
     std::optional<QByteArray> edidData() const override;
-    bool supportsDimmingMultiplier() const override;
     void setDimmingMultiplier(double multiplier) override;
 
     void applyPendingBrightness();
diff --git a/daemon/controllers/screenbrightnesscontroller.cpp b/daemon/controllers/screenbrightnesscontroller.cpp
index 64bd8ef8e..966d9cf15 100644
--- a/daemon/controllers/screenbrightnesscontroller.cpp
+++ b/daemon/controllers/screenbrightnesscontroller.cpp
@@ -161,13 +161,10 @@ void ScreenBrightnessController::onDetectorDisplaysChanged()
 
     QStringList addedDisplayIds;
     QStringList brightnessChangedDisplayIds;
-    auto newRememberedDisplayState = m_rememberedDisplayState;
 
     for (auto &[displayId, info] : newDisplayById) {
         const auto it = m_displaysById.find(displayId);
-        const auto rememberedIt = m_rememberedDisplayState.find(info.match);
         const bool added = it == m_displaysById.end();
-        const bool readded = added && rememberedIt != m_rememberedDisplayState.end();
         const bool replaced = !added && info.display != it->second.display;
         const bool valueChanged = replaced
             && (it->second.brightnessLogic.info().value != info.display->brightness()
@@ -185,36 +182,9 @@ void ScreenBrightnessController::onDetectorDisplaysChanged()
         if (added) {
             addedDisplayIds.push_back(displayId);
         }
-        if (readded) {
-            const RememberedDisplayState &rds = rememberedIt->second;
-            info.brightnessLogic.setValueRange(rds.minBrightness, info.display->maxBrightness());
-
-            if (info.display->supportsDimmingMultiplier()) {
-                info.dimmingRatio = dimmingRatioForDisplay(displayId);
-                info.display->setDimmingMultiplier(info.dimmingRatio);
-            } else if (rds.latestActiveDimmingRatio.has_value()
-                       && info.display->brightness() == brightnessMultiplied(rds.brightness, *rds.latestActiveDimmingRatio, rds.minBrightness)) {
-                qCDebug(POWERDEVIL) << "Re-recognized display" << displayId << "at brightness" << rds.brightness << "* dimming ratio"
-                                    << *rds.latestActiveDimmingRatio;
-
-                info.brightnessLogic.setValue(rds.brightness);
-                info.dimmingRatio = dimmingRatioForDisplay(displayId);
-
-                if (info.dimmingRatio != *rds.latestActiveDimmingRatio) {
-                    qCDebug(POWERDEVIL) << "=> reset brightness for" << displayId << "to current dimming ratio" << info.dimmingRatio;
-                    const PowerDevil::BrightnessLogic::BrightnessInfo bi = info.brightnessLogic.info();
-                    const int dimmedValue = brightnessMultiplied(bi.value, info.dimmingRatio, bi.valueMin);
-                    info.display->setBrightness(dimmedValue);
-                }
-            }
-            // delay removing the display state from m_rememberedDisplayState, in case several
-            // simultaneously added displays both use the same EDID (some EDIDs lack serial numbers)
-            newRememberedDisplayState.erase(info.match);
-        }
     }
 
     m_displaysById = std::move(newDisplayById);
-    m_rememberedDisplayState = std::move(newRememberedDisplayState);
     m_externalBrightnessController->setDisplays(newForExternalControl);
 
     for (const QString &removed : removedDisplayIds) {
@@ -335,15 +305,11 @@ void ScreenBrightnessController::setBrightness(const QString &displayId,
         auto &[id, info] = *it;
         const PowerDevil::BrightnessLogic::BrightnessInfo bi = info.brightnessLogic.info();
         const int boundedValue = std::clamp(value, bi.valueMin, bi.valueMax);
-        const int dimmedValue = info.display->supportsDimmingMultiplier() ? boundedValue : brightnessMultiplied(boundedValue, info.dimmingRatio, bi.valueMin);
 
-        qCDebug(POWERDEVIL) << "Set screen brightness of" << displayId << "to" << dimmedValue << "/" << bi.valueMax;
+        qCDebug(POWERDEVIL) << "Set screen brightness of" << displayId << "to" << boundedValue << "/" << bi.valueMax;
         if (value != boundedValue) {
             qCDebug(POWERDEVIL) << "- clamped from" << value;
         }
-        if (boundedValue != dimmedValue) {
-            qCDebug(POWERDEVIL) << "- dimmed as" << boundedValue << "*" << info.dimmingRatio;
-        }
 
         // notify only when the internally tracked brightness value is actually different
         if (bi.value != boundedValue) {
@@ -357,9 +323,8 @@ void ScreenBrightnessController::setBrightness(const QString &displayId,
             }
         }
 
-        // but always call setBrightness() on the display, both for changes to the
-        // brightness multiplier and in case we're unaware of an external change
-        info.display->setBrightness(dimmedValue);
+        // but always call setBrightness() on the display, in case we're unaware of an external change
+        info.display->setBrightness(boundedValue);
     } else {
         qCWarning(POWERDEVIL) << "Set screen brightness failed: no display with id" << displayId;
     }
@@ -463,25 +428,7 @@ void ScreenBrightnessController::setDimmingRatio(const QString &dimmingId, doubl
     qCDebug(POWERDEVIL) << "Set screen brightness dimming ratio with ID" << dimmingId << "to" << boundedRatio;
 
     for (auto &[id, info] : m_displaysById) {
-        const double newRatio = dimmingRatioForDisplay(id);
-        if (info.display->supportsDimmingMultiplier()) {
-            info.display->setDimmingMultiplier(newRatio);
-        } else {
-            if (info.dimmingRatio == newRatio) {
-                continue;
-            }
-            info.dimmingRatio = newRatio;
-            // set brightness to the currently stored value, but with the new multiplier
-            setBrightness(id, info.brightnessLogic.info().value, u"(internal)"_s, u"dimming"_s);
-
-            if (newRatio != 1.0 && info.match.isValid()) {
-                m_rememberedDisplayState[info.match] = RememberedDisplayState{
-                    .brightness = info.brightnessLogic.info().value,
-                    .minBrightness = info.brightnessLogic.info().valueMin,
-                    .latestActiveDimmingRatio = info.dimmingRatio,
-                };
-            }
-        }
+        info.display->setDimmingMultiplier(dimmingRatioForDisplay(id));
     }
 }
 
diff --git a/daemon/controllers/screenbrightnesscontroller.h b/daemon/controllers/screenbrightnesscontroller.h
index 3bd9aef88..5b26f0e14 100644
--- a/daemon/controllers/screenbrightnesscontroller.h
+++ b/daemon/controllers/screenbrightnesscontroller.h
@@ -220,13 +220,6 @@ private:
     int m_finishedDetectingCount = 0;
     std::unique_ptr<ExternalBrightnessController> m_externalBrightnessController;
 
-    struct RememberedDisplayState {
-        int brightness;
-        int minBrightness = 0;
-        std::optional<double> latestActiveDimmingRatio;
-    };
-    std::map<DisplayMatch, RememberedDisplayState> m_rememberedDisplayState;
-
     struct DimmingLimit {
         double ratio = 1.0;
     };