{,Range}Slider: accept callable valfmt arguments

doronbehar · doronbehar · commit 41ba77fb78de · 2025-07-27T12:52:29.000+03:00
diff --git a/lib/matplotlib/widgets.py b/lib/matplotlib/widgets.py
@@ -547,7 +547,10 @@ def _update(self, event):
     def _format(self, val):
         """Pretty-print *val*."""
         if self.valfmt is not None:
-            return self.valfmt % val
+            if callable(self.valfmt):
+                return self.valfmt(val)
+            else:
+                return self.valfmt % val
         else:
             _, s, _ = self._fmt.format_ticks([self.valmin, val, self.valmax])
             # fmt.get_offset is actually the multiplicative factor, if any.
@@ -890,7 +893,10 @@ def _update(self, event):
     def _format(self, val):
         """Pretty-print *val*."""
         if self.valfmt is not None:
-            return f"({self.valfmt % val[0]}, {self.valfmt % val[1]})"
+            if callable(self.valfmt):
+                self.valfmt(val)
+            else:
+                return f"({self.valfmt % val[0]}, {self.valfmt % val[1]})"
         else:
             _, s1, s2, _ = self._fmt.format_ticks(
                 [self.valmin, *val, self.valmax]
diff --git a/lib/matplotlib/widgets.pyi b/lib/matplotlib/widgets.pyi
@@ -64,7 +64,7 @@ class SliderBase(AxesWidget):
     valmax: float
     valstep: float | ArrayLike | None
     drag_active: bool
-    valfmt: str
+    valfmt: str | Callable[[float], str]
     def __init__(
         self,
         ax: Axes,
@@ -73,7 +73,7 @@ class SliderBase(AxesWidget):
         closedmax: bool,
         valmin: float,
         valmax: float,
-        valfmt: str,
+        valfmt: str | Callable[[float], str],
         dragging: Slider | None,
         valstep: float | ArrayLike | None,
     ) -> None: ...
@@ -130,7 +130,7 @@ class RangeSlider(SliderBase):
         valmax: float,
         *,
         valinit: tuple[float, float] | None = ...,
-        valfmt: str | None = ...,
+        valfmt: str | None | Callable[[Sequence[float]], str] = ...,
         closedmin: bool = ...,
         closedmax: bool = ...,
         dragging: bool = ...,
