Add unconstrained_font_size to add_scalar_bar (#5317)

* Add `unconstrained_font_size` to `add_scalar_bar`

* Apply suggestions from code review

* Apply suggestions from code review

* Add versionadded

* Add test

* Apply suggestions from code review

pyvista/plotting/scalar_bars.py

@@ -182,6 +182,7 @@ def add_scalar_bar(
         fill=False,
         render=False,
         theme=None,
+        unconstrained_font_size=False,
     ):
         """Create scalar bar using the ranges as set by the last input mesh.
 
@@ -304,6 +305,14 @@ def add_scalar_bar(
             ``Plotter``, will use the plotter theme.  Setting to
             ``None`` will use the global theme.
 
+        unconstrained_font_size : bool, default: False
+            Whether the font size of title and labels is unconstrained.
+            When it is constrained, the size of the scalar bar will constrain the font size.
+            When it is not, the size of the font will always be respected.
+            Using custom labels will force this to be ``True``.
+
+            .. versionadded:: 0.44.0
+
         Returns
         -------
         vtk.vtkScalarBarActor
@@ -552,6 +561,9 @@ def add_scalar_bar(
         else:
             scalar_bar.SetDrawFrame(False)
 
+        if unconstrained_font_size:
+            scalar_bar.SetUnconstrainedFontSize(True)
+
         # finally, add to the actor and return the scalar bar
         self._plotter.add_actor(scalar_bar, reset_camera=False, pickable=False, render=render)
 

tests/plotting/test_plotting.py

@@ -765,6 +765,14 @@ def test_plot_invalid_add_scalar_bar():
         plotter.add_scalar_bar()
 
 
+def test_add_scalar_bar_with_unconstrained_font_size(sphere):
+    sphere['test_scalars'] = sphere.points[:, 2]
+    plotter = pv.Plotter()
+    plotter.add_mesh(sphere)
+    actor = plotter.add_scalar_bar(unconstrained_font_size=True)
+    assert actor.GetUnconstrainedFontSize()
+
+
 def test_plot_list():
     sphere_a = pv.Sphere(0.5)
     sphere_b = pv.Sphere(1.0)