libservo: Add a very simple libservo API test (#36440)

libservo: Add a very simple `libservo` API test

This is the first step toward adding full testing for the `WebView` API.
The test added here simply starts up a Servo instance and verifies that
it does not crash when shutting down.

Testing: This change is a test, so there are tests for these changes.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/servo/tests/common/mod.rs

@@ -0,0 +1,86 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use std::rc::Rc;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::time::Duration;
+
+use compositing::windowing::{EmbedderMethods, WindowMethods};
+use compositing_traits::rendering_context::{RenderingContext, SoftwareRenderingContext};
+use dpi::PhysicalSize;
+use embedder_traits::EventLoopWaker;
+use euclid::Scale;
+use servo::Servo;
+use servo_geometry::DeviceIndependentPixel;
+use webrender_api::units::DevicePixel;
+
+pub struct ServoTest {
+    servo: Servo,
+}
+
+impl ServoTest {
+    pub fn new() -> Self {
+        let rendering_context = Rc::new(
+            SoftwareRenderingContext::new(PhysicalSize {
+                width: 500,
+                height: 500,
+            })
+            .expect("Could not create SoftwareRenderingContext"),
+        );
+        assert!(rendering_context.make_current().is_ok());
+
+        #[derive(Clone)]
+        struct EmbedderMethodsImpl(Arc<AtomicBool>);
+        impl EmbedderMethods for EmbedderMethodsImpl {
+            fn create_event_loop_waker(&mut self) -> Box<dyn embedder_traits::EventLoopWaker> {
+                Box::new(EventLoopWakerImpl(self.0.clone()))
+            }
+        }
+
+        struct WindowMethodsImpl;
+        impl WindowMethods for WindowMethodsImpl {
+            fn hidpi_factor(&self) -> Scale<f32, DeviceIndependentPixel, DevicePixel> {
+                Scale::new(1.0)
+            }
+        }
+
+        #[derive(Clone)]
+        struct EventLoopWakerImpl(Arc<AtomicBool>);
+        impl EventLoopWaker for EventLoopWakerImpl {
+            fn clone_box(&self) -> Box<dyn EventLoopWaker> {
+                Box::new(self.clone())
+            }
+
+            fn wake(&self) {
+                self.0.store(true, Ordering::Relaxed);
+            }
+        }
+
+        let user_event_triggered = Arc::new(AtomicBool::new(false));
+        let servo = Servo::new(
+            Default::default(),
+            Default::default(),
+            rendering_context.clone(),
+            Box::new(EmbedderMethodsImpl(user_event_triggered)),
+            Rc::new(WindowMethodsImpl),
+            Default::default(),
+        );
+        Self { servo }
+    }
+
+    pub fn servo(&self) -> &Servo {
+        &self.servo
+    }
+}
+
+impl Drop for ServoTest {
+    fn drop(&mut self) {
+        self.servo.start_shutting_down();
+        while self.servo.spin_event_loop() {
+            std::thread::sleep(Duration::from_millis(1));
+        }
+        self.servo.deinit();
+    }
+}

components/servo/tests/servo.rs

@@ -0,0 +1,13 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+mod common;
+
+use common::*;
+
+#[test]
+fn test_simple_servo_start_and_stop() {
+    let shared_test = ServoTest::new();
+    assert!(!shared_test.servo().animating());
+}