CircleMeter: values text marks and helper functions

qml/CircleMeter.qml

@@ -11,13 +11,33 @@ Item {
 	property double min: -1
 	/// maximum level
 	property double max: 1
+	/// numbers to write on the scale
+	property variant marks: [-1, -0.5, 0, 0.5, 1, -0.2, 0.2, -0.8, 0.8]
 	/// theme object
 	property QtObject theme
 
+	/// positions helper functions
+	function angle(level) {
+		return (level - min) / (max - min) * Math.PI - Math.PI / 2
+	}
+	function getx(angle, k) {
+		return width * 0.5 + width * 0.5 * k * Math.sin(angle)
+	}
+	function gety(angle, k) {
+		// k: [0,1]
+		return height - height * k * Math.cos(angle)
+	}
+
 	/// Ellipse
 	Canvas {
 		id: ellipse
 		anchors.fill: parent
+
+		property double mark_k_min: 0.90
+		property double mark_k_max: 0.95
+		property double mark_k_text: 0.85
+		property int font_size: 16
+
 		onPaint: {
 			var ctx = getContext('2d');
 			ctx.strokeStyle = theme.primaryColor
@@ -28,6 +48,18 @@ Item {
 			//ctx.closePath()
 			ctx.stroke()
 			console.log("ellipse done")
+			ctx.font = font_size + "px sans-serif"
+			ctx.textAlign = "center"
+
+			for (var i = 0; i < marks.length; i++) {
+				var a = angle(marks[i])
+				ctx.beginPath()
+				ctx.moveTo(getx(a, mark_k_min), gety(a, mark_k_min))
+				ctx.lineTo(getx(a, mark_k_max), gety(a, mark_k_max))
+				ctx.stroke()
+				ctx.fillText(marks[i], getx(a, mark_k_text), gety(a, mark_k_text))
+				ctx.strokeText()
+			}
 		}
 	}
 
@@ -36,16 +68,16 @@ Item {
 		id: arrow
 		anchors.fill: parent
 		property double k: 0.99
-		property double offset_base: 0.95
-		property double angle: (level - min) / (max - min) * Math.PI - Math.PI / 2
+		property double k_base: 0.1
+		property double angle: parent.angle(level)
 
 		onPaint: {
 			var ctx = getContext('2d');
 			ctx.strokeStyle = theme.primaryColor
 			ctx.lineWidth = 1
 			ctx.beginPath()
-			ctx.moveTo(width / 2, (height - 1) * offset_base)
-			ctx.lineTo(width * 0.5 + width * 0.5 * k * Math.sin(angle), height * k * (1 - Math.cos(angle) + 1 - k))
+			ctx.moveTo(getx(angle, k_base), gety(angle, k_base))
+			ctx.lineTo(getx(angle, k), gety(angle, k))
 			ctx.stroke()
 
 			console.log("angle: " + angle)