add volume and brightness control

config/Config.qml

@@ -65,6 +65,27 @@ Singleton {
     // ".desktop" is accepted.
     readonly property var quickLaunch: ["firefox", "org.kde.dolphin"]
 
+    // ---- Volume and brightness -------------------------------------------
+
+    // Set false to drop the volume slider. The button also hides itself where
+    // pipewire has no default sink.
+    readonly property bool showVolume: true
+
+    // Set false to drop the brightness slider. It also hides itself on machines
+    // with no controllable backlight, or without brightnessctl to drive it, so
+    // leaving this on costs a desktop nothing.
+    readonly property bool showBrightness: true
+
+    // One wheel notch, one arrow key, one `ipc call volume up`.
+    readonly property real volumeStep: 0.05
+    readonly property real brightnessStep: 0.05
+
+    // Floor on the backlight, as a fraction of its maximum. A screen at zero
+    // looks broken, and on most laptops the only way back is a hardware key.
+    readonly property real minBrightness: 0.01
+
+    readonly property int controlsMenuWidth: 280
+
     // ---- Wifi ------------------------------------------------------------
 
     // Set false to drop the wifi button. It also hides itself where there is no

config/Theme.qml

@@ -12,6 +12,11 @@ Singleton {
     readonly property int iconSize: 22
     readonly property int borderWidth: 1
 
+    // Slider groove and knob. The knob is deliberately larger than the groove
+    // is thick: the sliders get dragged with a finger as well as a pointer.
+    readonly property int sliderTrack: 6
+    readonly property int sliderKnob: 16
+
     // Palette
     readonly property color background: "#14161b"
     readonly property color surface: "#1c1f26"