Implement getting monitor brightness

AdaptiveBrightness/monitor.hpp

@@ -38,6 +38,12 @@ class Monitor {
 
     bool hasBrightnessCapability() const;
 
+    template<typename InType, typename OutType>
+    auto map(InType value, InType inMin, InType inMax, OutType outMin, OutType outMax)
+    {
+        return (value - inMin) * (outMax - outMin) / (inMax - inMin) + outMin;
+    }
+
     const HMONITOR m_hMonitor;
     const PhysicalMonitor m_physicalMonitor;
 };

AdaptiveBrightness/monitor_win.cpp

@@ -2,6 +2,8 @@
 
 #ifdef _MSC_VER
 
+    #include <algorithm>
+
     #include <cmath>
 
     #include <QtDebug>
@@ -37,7 +39,25 @@ bool Monitor::setBrightness(float percentage)
 
 float Monitor::getBrightness()
 {
-    return NAN;
+    qDebug(ltr("Getting brightness of monitor '%1' with handle '0x%2' and physical handle '0x%3'")
+               .arg(m_physicalMonitor.name)
+               .arg(reinterpret_cast<qulonglong>(m_hMonitor), 0, 16)
+               .arg(reinterpret_cast<qulonglong>(m_physicalMonitor.handle), 0, 16));
+
+    DWORD minBrightness = 0;
+    DWORD brightness = 0;
+    DWORD maxBrightness = 0;
+
+    if(!GetMonitorBrightness(m_physicalMonitor.handle, &minBrightness, &brightness, &maxBrightness)) {
+        qCritical(ltr("Failed to get brightness of monitor '%1' with handle '0x%2' and physical handle '0x%3', error: %4")
+                      .arg(m_physicalMonitor.name)
+                      .arg(reinterpret_cast<qulonglong>(m_hMonitor), 0, 16)
+                      .arg(reinterpret_cast<qulonglong>(m_physicalMonitor.handle), 0, 16)
+                      .arg(getLastErrorString()));
+        return NAN;
+    }
+
+    return std::clamp(map(brightness, minBrightness, maxBrightness, 0.f, 1.f), 0.f, 1.f);
 }
 
 Monitor::operator bool() const