Improve Delegate Width Sizing

Create a cpp helper class to calculate the correct delegate width given it's parent width.

This is designed to be more robust and hopefully easier to understand than the current mass of javascript calcs.

BUG: 470167

src/qml/Component/Timeline/StateDelegate.qml

@@ -14,11 +14,7 @@ QQC2.Control {
 
     readonly property bool sectionVisible: model.showSection
 
-    // extraWidth defines how the delegate can grow after the listView gets very wide
-    readonly property int extraWidth: parent ? (parent.width >= Kirigami.Units.gridUnit * 46 ? Math.min((parent.width - Kirigami.Units.gridUnit * 46), Kirigami.Units.gridUnit * 20) : 0) : 0
-    readonly property int delegateMaxWidth: parent ? (Config.compactLayout ? parent.width: Math.min(parent.width, Kirigami.Units.gridUnit * 40 + extraWidth)) : 0
-
-    width: delegateMaxWidth
+    width: stateDelegateSizeHelper.currentWidth
 
     state: Config.compactLayout ? "alignLeft" : "alignCenter"
     // Align left when in compact mode and center when using bubbles
@@ -170,4 +166,15 @@ QQC2.Control {
             excessAvatars: excessReadMarkers
         }
     }
+
+    DelegateSizeHelper {
+        id: stateDelegateSizeHelper
+        startBreakpoint: Kirigami.Units.gridUnit * 46
+        endBreakpoint: Kirigami.Units.gridUnit * 66
+        startPercentWidth: 100
+        endPercentWidth: Config.compactLayout ? 100 : 85
+        maxWidth: Config.compactLayout ? -1 : Kirigami.Units.gridUnit * 60
+
+        parentWidth: stateDelegate.parent ? stateDelegate.parent.width : 0
+    }
 }