generate opacity warning for gpu renderer and versions blacklist

src/geovista/common.py

@@ -57,6 +57,7 @@
     "triangulated",
     "vtk_warnings_off",
     "vtk_warnings_on",
+    "warn_opacity",
     "wrap",
 ]
 
@@ -103,6 +104,11 @@
 #: LRU cache size, which is auto-disabled for testing
 LRU_CACHE_SIZE: int = 0 if "pytest" in sys.modules else 128
 
+#: Known GPU renderer and version combinations that don't support opacity.
+OPACITY_BLACKLIST = [
+    ("llvmpipe (LLVM 7.0, 256 bits)", "3.3 (Core Profile) Mesa 18.3.4"),
+]
+
 #: Default period for wrapped longitude half-open interval, in degrees.
 PERIOD: float = 360.0
 
@@ -881,6 +887,35 @@ def vtk_warnings_on() -> None:
     vtkLogger.SetStderrVerbosity(vtkLogger.VERBOSITY_INFO)
 
 
+def warn_opacity(plotter: pv.Plotter) -> None:
+    """Add text opacity support warning to plotter scene.
+
+    Convenience for adding a text warning to the render scene for known GPU
+    configurations that don't support opacity.
+
+    Parameters
+    ----------
+    plotter : pv.Plotter
+        The plotter rendering the scene.
+
+    Notes
+    -----
+    .. versionadded:: 0.4.0
+
+    """
+    info = pv.GPUInfo()
+    renderer_version = info.renderer, info.version
+
+    if renderer_version in OPACITY_BLACKLIST:
+        plotter.add_text(
+            "Requires Opacity Support",
+            position="lower_right",
+            font_size=7,
+            color="red",
+            shadow=True,
+        )
+
+
 def wrap(
     lons: ArrayLike,
     base: float | None = None,

src/geovista/examples/clouds.py

@@ -12,6 +12,7 @@
 from matplotlib.colors import LinearSegmentedColormap
 
 import geovista as gv
+from geovista.common import warn_opacity
 from geovista.pantry import cloud_amount
 import geovista.theme  # noqa: F401
 
@@ -91,6 +92,7 @@ def main() -> None:
         font_size=10,
         shadow=True,
     )
+    warn_opacity(plotter)
     plotter.camera.zoom(1.5)
     plotter.show()