feat(pie):add tangential-fixed rotation mode to keep labels tangential without flipping. close #21257

Author: 春秋半夏

src/chart/pie/PieSeries.ts

@@ -68,7 +68,7 @@ export interface PieStateOption<TCbParams = never> {
     labelLine?: PieLabelLineOption
 }
 interface PieLabelOption extends Omit<SeriesLabelOption, 'rotate' | 'position'> {
-    rotate?: number | boolean | 'radial' | 'tangential'
+    rotate?: number | boolean | 'radial' | 'tangential' | 'tangential-fixed'
     alignTo?: 'none' | 'labelLine' | 'edge'
     edgeDistance?: string | number
     /**

src/chart/pie/labelLayout.ts

@@ -484,15 +484,15 @@ export default function pieLabelLayout(
             const radialAngle = nx < 0 ? -midAngle + PI : -midAngle;
             labelRotate = radialAngle;
         }
-        else if (rotate === 'tangential'
+        else if (rotate === 'tangential' || rotate === 'tangential-fixed'
             && labelPosition !== 'outside' && labelPosition !== 'outer'
         ) {
             let rad = Math.atan2(nx, ny);
             if (rad < 0) {
                 rad = PI * 2 + rad;
             }
             const isDown = ny > 0;
-            if (isDown) {
+            if (isDown && rotate !== 'tangential-fixed') {
                 rad = PI + rad;
             }
             labelRotate = rad - PI;