ScalarBars.add_scalar_bar: correct annotation text scaling setting, w…

…hen fixed font size is given (#1750)

* ScalarBars.add_scalar_bar: correct annotation text scaling setting, when fixed font size is given

Even if a label font size was given, size of `below_label` and `above_label` was scaled with the view port.
Line 423 must be `SetAnnotationTextScalingOff` (value 0) for no scaling,
see <https://vtk.org/doc/nightly/html/classvtkScalarBarActor.html#acfe97b358b89cd544df5e7826d59e4f7>

* Annotation text scaling on, when none font size is given

(addition to last commit)

When you give none label or title font size, you want a scaling annotation text, at it was already true for the labels and the title texts.

Comment for Image Regression Testing: This will slightly change the images of the tests:
- test_above_below_scalar_range_annotations
- test_user_annotations_scalar_bar_mesh

* add test for fix/add_scalar_bar-AnnotationTextScaling

I union the both upper tests and add fixed settings for title and label font sizes.

* Add image for new test

image_cache/fixed_font_size_annotation_text_scaling_off.png

Co-authored-by: Alex Kaszynski <akascap@gmail.com>

pyvista/plotting/scalar_bars.py

@@ -422,6 +422,8 @@ def add_scalar_bar(self, title='', mapper=None, n_labels=5, italic=False,
 
         if label_font_size is not None or title_font_size is not None:
             scalar_bar.UnconstrainedFontSizeOn()
+            scalar_bar.AnnotationTextScalingOff()
+        else:
             scalar_bar.AnnotationTextScalingOn()
 
         label_text = scalar_bar.GetLabelTextProperty()

tests/plotting/test_plotting.py

@@ -1595,6 +1595,18 @@ def test_user_annotations_scalar_bar_mesh(uniform):
     p.show(before_close_callback=verify_cache_image)
 
 
+def test_fixed_font_size_annotation_text_scaling_off():
+    p = pyvista.Plotter()
+    sargs = {
+        'title_font_size': 12,
+        'label_font_size': 10}
+    p.add_mesh(examples.load_uniform(), clim=[100, 500], cmap='viridis',
+               below_color='blue', above_color='red',
+               annotations={300.: 'yum'},
+               scalar_bar_args=sargs)
+    p.show(before_close_callback=verify_cache_image)
+
+
 def test_user_annotations_scalar_bar_volume(uniform):
     p = pyvista.Plotter()
     p.add_volume(uniform, scalars='Spatial Point Data', annotations={100.: 'yum'})