Document the text_placeholders fixture

QuLogic · timhoffm · web-flow · commit d46840e8cb98 · 2025-04-08T22:52:17.000-04:00
Co-authored-by: Tim Hoffmann &lt;2836374+timhoffm@users.noreply.github.com&gt;
diff --git a/lib/matplotlib/testing/conftest.py b/lib/matplotlib/testing/conftest.py
@@ -129,6 +129,14 @@ def test_imshow_xarray(xr):
 
 @pytest.fixture
 def _text_placeholders(monkeypatch):
+    """
+    Replace texts with placeholder rectangles.
+    
+    The rectangle size only depends on the font size and the number of
+    characters. It is thus insensitive to font properties and rendering
+    details. This should be used for tests that depend on text geometries
+    but not the actual text rendering, e.g. layout tests.
+    """
     from matplotlib.patches import Rectangle
 
     def patched_get_text_metrics_with_cache(renderer, text, fontprop, ismath, dpi):
