feat: support round cap for polar bars

src/component/axis/AngleAxisView.js

@@ -96,19 +96,24 @@ export default AxisView.extend({
     _axisLine: function (angleAxisModel, polar, ticksAngles, radiusExtent) {
         var lineStyleModel = angleAxisModel.getModel('axisLine.lineStyle');
 
-        var circle = new graphic.Circle({
-            shape: {
-                cx: polar.cx,
-                cy: polar.cy,
-                r: radiusExtent[getRadiusIdx(polar)]
-            },
-            style: lineStyleModel.getLineStyle(),
-            z2: 1,
-            silent: true
-        });
-        circle.style.fill = null;
-
-        this.group.add(circle);
+        for (var rx = 0; rx < radiusExtent.length; ++rx) {
+            // Draw a circle for radius like [0, 100], and two circles for [20, 100]
+            if (radiusExtent[rx] > 0) {
+                var circle = new graphic.Circle({
+                    shape: {
+                        cx: polar.cx,
+                        cy: polar.cy,
+                        r: radiusExtent[rx]
+                    },
+                    style: lineStyleModel.getLineStyle(),
+                    z2: 1,
+                    silent: true
+                });
+                circle.style.fill = null;
+
+                this.group.add(circle);
+            }
+        }
     },
 
     /**

src/coord/polar/polarCreator.js

@@ -47,10 +47,23 @@ function resizePolar(polar, polarModel, api) {
 
     var radiusAxis = polar.getRadiusAxis();
     var size = Math.min(width, height) / 2;
-    var radius = parsePercent(polarModel.get('radius'), size);
+
+    var radius = polarModel.get('radius');
+    if (radius == null) {
+        radius = [0, "100%"];
+    }
+    else if (typeof radius === 'number' || typeof radius === 'string') {
+        // r0 = 0
+        radius = [0, radius];
+    }
+    radius = [
+        parsePercent(radius[0], size),
+        parsePercent(radius[1], size)
+    ];
+
     radiusAxis.inverse
-        ? radiusAxis.setExtent(radius, 0)
-        : radiusAxis.setExtent(0, radius);
+        ? radiusAxis.setExtent(radius[1], radius[0])
+        : radiusAxis.setExtent(radius[0], radius[1]);
 }
 
 /**