Update overall brightness slider if all monitors match

AdaptiveBrightness/main_window.cpp

@@ -331,6 +331,7 @@ bool MainWindow::setMonitorBrightness(float brightness)
     }
 
     bool errorOccurred = false;
+    bool allMonitorsSameBrightness = true;
 
     for(size_t i = 0; i < m_monitors.size(); ++i) {
         if(!std::isnan(brightness) && !m_monitors[i].manualOverride) {
@@ -339,14 +340,20 @@ bool MainWindow::setMonitorBrightness(float brightness)
 
         m_monitors[i].brightness = std::clamp(m_monitors[i].brightness, m_monitors[i].minBrightness, m_monitors[i].maxBrightness);
 
+        if(i > 0 && m_monitors[i - 1].brightness != m_monitors[i].brightness) {
+            allMonitorsSameBrightness = false;
+        }
+
         if(!m_monitors[i].driver.setBrightness(m_monitors[i].brightness)) {
             errorOccurred = true;
         }
-        else {
-            if(m_ui.monitorDropdown->currentIndex() == i) {
+        else if(m_ui.monitorDropdown->currentIndex() == i) {
             updateCurrentMonitorGUI(i);
         }
     }
+
+    if(allMonitorsSameBrightness) {
+        m_ui.monitorOverallBrightnessSlider->setValue(utils::map(m_monitors.front().brightness, 0.f, 1.f, 0, 100));
     }
 
     return !errorOccurred;