test: add multi-view test

tests/conftest.py

@@ -217,6 +217,62 @@ def _build_ui(self):
                 )
 
 
+class MultiView(TrameApp):
+    """Two LocalViews sharing one WASM session (issues/76 and issues/77).
+
+    Regression check: with a shared session, an update targeting one view must
+    not blank the other. A blacked-out half exceeds the screenshot threshold.
+    """
+
+    HALF = "width:50vw; height:100vh; display:inline-block; vertical-align:top;"
+
+    def __init__(self, server=None):
+        super().__init__(server)
+        enable_testing(self.server, "local_rendering_ready")
+        self.render_window_1 = self._create_pipeline(
+            vtk.vtkConeSource(), (0.1, 0.2, 0.4)
+        )
+        self.render_window_2 = self._create_pipeline(
+            vtk.vtkSphereSource(), (0.4, 0.2, 0.1)
+        )
+        self._build_ui()
+
+    @staticmethod
+    def _create_pipeline(source, background):
+        renderer = vtk.vtkRenderer()
+        rw = vtk.vtkRenderWindow()
+        rw.AddRenderer(renderer)
+        rwi = vtk.vtkRenderWindowInteractor(render_window=rw)
+        rwi.interactor_style.SetCurrentStyleToTrackballCamera()
+
+        mapper = vtk.vtkPolyDataMapper(input_connection=source.output_port)
+        actor = vtk.vtkActor(mapper=mapper)
+
+        renderer.AddActor(actor)
+        renderer.background = background
+        renderer.ResetCamera()
+
+        return rw
+
+    def _build_ui(self):
+        # Each view bumps the counter once when it first finishes updating, so
+        # the test waits for it to reach 2 (both views rendered).
+        self.state.local_rendering_ready = 0
+        with DivLayout(self.server) as self.ui:
+            html.Div("{{ local_rendering_ready }}", classes="readyCount")
+            client.Style(
+                "body { margin: 0; } .readyCount { z-index: 10; position: absolute; left: 0; top: 0; }"
+            )
+            with html.Div(style=self.HALF):
+                vtklocal.LocalView(
+                    self.render_window_1, updated="local_rendering_ready++"
+                )
+            with html.Div(style=self.HALF):
+                vtklocal.LocalView(
+                    self.render_window_2, updated="local_rendering_ready++"
+                )
+
+
 @pytest.fixture
 def ref_dir() -> Path:
     return Path(__file__).parent / "refs"
@@ -244,6 +300,11 @@ def ConeApp():
     return Cone
 
 
+@pytest.fixture
+def MultiViewApp():
+    return MultiView
+
+
 @pytest.fixture
 def VolumeApp():
     return VolumeRendering

tests/test_multi_view.py

@@ -0,0 +1,54 @@
+import asyncio
+from pathlib import Path
+from trame_vtklocal.module.wasm import wasm_downloaded
+
+import pytest
+from playwright.async_api import async_playwright, expect
+
+BASELINES = [
+    Path(__file__).with_name("assets") / "multi_view" / name
+    for name in [
+        "00_startup",
+    ]
+]
+
+
+@pytest.mark.asyncio
+async def test_multi_view(MultiViewApp, utils):
+    """Two LocalViews sharing one WASM session must both render (issues/76, /77).
+
+    Catches the updateAsync-serialization regression (a second view's update
+    being swallowed leaves it black). It does NOT catch the Size-property leak
+    on Linux/OSMesa: there the vtkOSOpenGLRenderWindow -> vtkRenderWindow remap
+    makes even the old skip match, so that bug only reproduces on a platform
+    whose render window serializes under its own child class (e.g. macOS).
+    """
+    app = MultiViewApp("multi-view")
+    task = app.server.start(exec_mode="task", port=0)
+    await app.server.ready
+    await wasm_downloaded()
+    RESULT_BASE = Path(__file__).with_name("results") / "multi_view"
+    valid_image_comparisons = []
+
+    async with async_playwright() as p:
+        browser = await p.chromium.launch(headless=True)
+        page = await browser.new_page()
+        await page.set_viewport_size({"width": 600, "height": 300})
+
+        await page.goto(f"http://localhost:{app.server.port}/")
+        await asyncio.sleep(0.1)  # wait for page load
+        # Both views increment the counter once they have rendered.
+        await expect(page.locator(".readyCount")).to_have_text("2")
+        valid_image_comparisons.append(
+            await utils.compare_screenshot(
+                page, BASELINES[0], RESULT_BASE, threshold=0.1
+            )
+        )
+
+        assert all(valid_image_comparisons), "Some images don't match"
+
+        # Clean up resource
+        await browser.close()
+
+    await app.server.stop()
+    await task