Add test that screengrabs examples

.github/workflows/build.yml

@@ -60,6 +60,11 @@ jobs:
           .\activate_venv.ps1
           pre-commit run --all-files --show-diff-on-failure
 
+      - name: Run tests
+        run: |
+          .\activate_venv.ps1
+          pytest
+
       - name: Build docs
         run: |
           .\activate_venv.ps1

.vscode/c_cpp_properties.json

@@ -0,0 +1,8 @@
+{
+    "configurations": [
+        {
+            "configurationProvider": "ms-vscode.cmake-tools"
+        }
+    ],
+    "version": 4
+}

examples/Scatter.qml

@@ -10,18 +10,25 @@ import QuickGraphLib.PreFabs as QGLPreFabs
 QGLPreFabs.XYAxes {
     id: xyaxes
 
+    property var butterflyCurve: QuickGraphLib.Helpers.linspace(0, Math.PI * 24, 10000).map(butterflyPoint)
+
+    function butterflyPoint(t: real): point {
+        let middle = Math.exp(Math.cos(t)) - 2 * Math.cos(4 * t) - Math.pow(Math.sin(t / 12), 5) + Math.sin(t * 1000);
+        return Qt.point(Math.sin(t) * middle, Math.cos(t) * middle);
+    }
+
     title: "10,000 points"
-    viewRect: Qt.rect(-2, -2, 4, 4)
+    viewRect: Qt.rect(-4.5, -4, 9, 9)
 
     Repeater {
-        model: QuickGraphLib.Helpers.range(0, 10000).map(_ => [Math.sqrt(Math.random()) * 4 - 2, Math.sqrt(Math.random()) * 4 - 2])
+        model: xyaxes.butterflyCurve
 
         QGLGraphItems.Marker {
-            required property var modelData
+            required property point modelData
 
             color: "#22ff0000"
             dataTransform: xyaxes.dataTransform
-            position: Qt.point(modelData[0], modelData[1])
+            position: modelData
             width: 10
         }
     }

tests/test_exports.py

@@ -0,0 +1,87 @@
+# SPDX-FileCopyrightText: Copyright (c) 2024 Refeyn Ltd and other QuickGraphLib contributors
+# SPDX-License-Identifier: MIT
+
+import pathlib
+
+import numpy as np
+import pytest
+from PySide6 import QtCore, QtGui, QtQml
+
+import QuickGraphLib
+from examples import conway
+
+EXAMPLE_PATHS = [
+    path
+    for path in (pathlib.Path(__file__).parent.parent / "examples").glob("*.qml")
+    if path.name != "ExampleGallery.qml"
+]
+REFERENCE_PATH = pathlib.Path(__file__).parent / "reference_images"
+GENERATE_REFERENCE_IMAGES = False
+
+
+@pytest.fixture(scope="session")
+def qapp() -> QtGui.QGuiApplication:
+    return QtGui.QGuiApplication([])
+
+
+@pytest.mark.parametrize("example_path", EXAMPLE_PATHS, ids=lambda p: str(p.stem))
+def test_export(
+    example_path: pathlib.Path, qapp: QtGui.QGuiApplication, tmp_path: pathlib.Path
+) -> None:
+    image_path = tmp_path / f"{example_path.stem}.png"
+    engine = QtQml.QQmlApplicationEngine()
+    engine.setInitialProperties(
+        {
+            "exampleUrl": QtCore.QUrl.fromLocalFile(example_path),
+            "outputUrl": QtCore.QUrl.fromLocalFile(image_path),
+        }
+    )
+    engine.addImportPath(QuickGraphLib.QML_IMPORT_PATH)
+    engine.loadData(
+        rb"""
+import QtQuick
+Window {
+    id: root
+    required property url exampleUrl
+    required property url outputUrl
+    width: 800
+    height: 600
+    visible: true
+    Loader {
+        id: loader
+        source: exampleUrl
+        anchors.fill: parent
+    }
+    Component.onCompleted: {
+        let res = loader.item.grabToImage(result => {
+           result.saveToFile(root.outputUrl);
+            Qt.exit(0);
+        });
+        if (!res) {
+            Qt.exit(1);
+        }
+    }
+}
+"""
+    )
+    assert len(engine.rootObjects()) != 0
+    engine.quit.connect(qapp.quit)
+    assert qapp.exec() == 0
+
+    reference_path = REFERENCE_PATH / image_path.name
+    if GENERATE_REFERENCE_IMAGES:
+        if reference_path.exists():
+            reference_path.unlink()
+        image_path.rename(reference_path)
+
+    else:
+        reference_img = QtGui.QImage(str(reference_path))
+        output_img = QtGui.QImage(str(image_path))
+        assert reference_img.width() == output_img.width() == 800
+        assert reference_img.height() == output_img.height() == 600
+        shape = (reference_img.height(), reference_img.width(), 4)
+        reference_arr = np.asarray(reference_img.bits()).reshape(shape).astype(int)
+        output_arr = np.asarray(output_img.bits()).reshape(shape).astype(int)
+        difference = np.abs(reference_arr - output_arr).sum() / shape[0] / shape[1]
+        print(difference)
+        assert difference < 0.01