Add better text anchors for default polar radial ticks.

matplotlib · dopplershift · Dec 1, 2017 · Nov 27, 2017 · Nov 27, 2017 · Nov 28, 2017
commit 4341f00e9fe96216959feabaf0f59ed17f9499ca
diff --git a/lib/matplotlib/projections/polar.py b/lib/matplotlib/projections/polar.py
@@ -505,17 +505,59 @@ def _get_text2(self):
        t.set_rotation_mode('anchor')
        return t

-    def _determine_anchor(self, angle, start):
-        if start:
-            if -90 <= angle <= 90:
-                return 'left', 'center'
+    def _determine_anchor(self, mode, angle, start):
+        # Note: angle is the (spine angle - 90) because it's used for the tick
+        # & text setup, so all numbers below are -90 from (normed) spine angle.
+        if mode == 'auto':
+            if start:
+                if -90 <= angle <= 90:
+                    return 'left', 'center'
+                else:
+                    return 'right', 'center'
            else:
-                return 'right', 'center'
+                if -90 <= angle <= 90:
+                    return 'right', 'center'
+                else:
+                    return 'left', 'center'
        else:
-            if -90 <= angle <= 90:
-                return 'right', 'center'
+            if start:
+                if angle < -68.5:
+                    return 'center', 'top'
+                elif angle < -23.5:
+                    return 'left', 'top'
+                elif angle < 22.5:
+                    return 'left', 'center'
+                elif angle < 67.5:
+                    return 'left', 'bottom'
+                elif angle < 112.5:
+                    return 'center', 'bottom'
+                elif angle < 157.5:
+                    return 'right', 'bottom'
+                elif angle < 202.5:
+                    return 'right', 'center'
+                elif angle < 247.5:
+                    return 'right', 'top'
+                else:
+                    return 'center', 'top'
            else:
-                return 'left', 'center'
+                if angle < -68.5:
+                    return 'center', 'bottom'
+                elif angle < -23.5:
+                    return 'right', 'bottom'
+                elif angle < 22.5:
+                    return 'right', 'center'
+                elif angle < 67.5:
+                    return 'right', 'top'
+                elif angle < 112.5:
+                    return 'center', 'top'
+                elif angle < 157.5:
+                    return 'left', 'top'
+                elif angle < 202.5:
+                    return 'left', 'center'
+                elif angle < 247.5:
+                    return 'left', 'bottom'
+                else:
+                    return 'center', 'bottom'

    def update_position(self, loc):
        super(RadialTick, self).update_position(loc)
@@ -559,7 +601,7 @@ def update_position(self, loc):
                ha = 'left'
                va = 'bottom'
            else:
-                ha, va = self._determine_anchor(angle, direction > 0)
+                ha, va = self._determine_anchor(mode, angle, direction > 0)
            self.label1.set_ha(ha)
            self.label1.set_va(va)
            self.label1.set_rotation(text_angle)
@@ -603,7 +645,7 @@ def update_position(self, loc):
        else:
            text_angle = user_angle
        if self.label2On:
-            ha, va = self._determine_anchor(angle, direction < 0)
+            ha, va = self._determine_anchor(mode, angle, direction < 0)
            self.label2.set_ha(ha)
            self.label2.set_va(va)
            self.label2.set_rotation(text_angle)