Add a test that verifies that grab_window() returns something when using

the Skia OpenGL or FemtoVG renderer

internal/renderers/femtovg/Cargo.toml

@@ -52,3 +52,12 @@ core-text = { version = "20.1.0" }
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 web-sys = { version = "0.3", features=["console", "WebGlContextAttributes", "CanvasRenderingContext2d", "HtmlInputElement", "HtmlCanvasElement", "Window", "Document"] }
 wasm-bindgen = { version = "0.2" }
+
+[dev-dependencies]
+slint = { workspace = true, default-features = true }
+i-slint-backend-winit = { workspace = true, features = ["renderer-femtovg"] }
+
+[[test]]
+name = "screenshot"
+path = "tests/screenshot.rs"
+harness = false

internal/renderers/femtovg/tests/screenshot.rs

@@ -0,0 +1,48 @@
+// Copyright © SixtyFPS GmbH <[email protected]>
+// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
+
+fn main() {
+    slint::platform::set_platform(Box::new(
+        i_slint_backend_winit::Backend::new_with_renderer_by_name(Some("femtovg")).unwrap(),
+    ))
+    .unwrap();
+
+    slint::slint! {
+        export component App inherits Window {
+            Text { text: "Ok"; }
+        }
+    }
+
+    let app = App::new().unwrap();
+    let slint_window = app.window();
+    let app_weak = app.as_weak();
+
+    let mut rendered_once = false;
+    let screenshot = std::rc::Rc::new(std::cell::RefCell::new(None));
+
+    slint_window
+        .set_rendering_notifier({
+            let screenshot = screenshot.clone();
+            move |state, _| match state {
+                slint::RenderingState::BeforeRendering => {
+                    if rendered_once {
+                        *screenshot.borrow_mut() = Some(app_weak.unwrap().window().grab_window());
+                        slint::quit_event_loop().unwrap();
+                    }
+                }
+                slint::RenderingState::AfterRendering => {
+                    rendered_once = true;
+                    app_weak.unwrap().window().request_redraw();
+                }
+                _ => {}
+            }
+        })
+        .unwrap();
+
+    app.show().unwrap();
+    app.run().unwrap();
+
+    let screenshot = screenshot.borrow_mut().take().unwrap().unwrap();
+    assert!(screenshot.width() > 0);
+    assert!(screenshot.height() > 0);
+}

internal/renderers/skia/Cargo.toml

@@ -75,3 +75,12 @@ skia-safe = { version = "0.75.0", features = ["gl"] }
 
 [build-dependencies]
 cfg_aliases = { workspace = true }
+
+[dev-dependencies]
+slint = { workspace = true, default-features = true }
+i-slint-backend-winit = { workspace = true, features = ["renderer-skia"] }
+
+[[test]]
+name = "screenshot"
+path = "tests/screenshot.rs"
+harness = false

internal/renderers/skia/tests/screenshot.rs

@@ -0,0 +1,48 @@
+// Copyright © SixtyFPS GmbH <[email protected]>
+// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
+
+fn main() {
+    slint::platform::set_platform(Box::new(
+        i_slint_backend_winit::Backend::new_with_renderer_by_name(Some("skia-opengl")).unwrap(),
+    ))
+    .unwrap();
+
+    slint::slint! {
+        export component App inherits Window {
+            Text { text: "Ok"; }
+        }
+    }
+
+    let app = App::new().unwrap();
+    let slint_window = app.window();
+    let app_weak = app.as_weak();
+
+    let mut rendered_once = false;
+    let screenshot = std::rc::Rc::new(std::cell::RefCell::new(None));
+
+    slint_window
+        .set_rendering_notifier({
+            let screenshot = screenshot.clone();
+            move |state, _| match state {
+                slint::RenderingState::BeforeRendering => {
+                    if rendered_once {
+                        *screenshot.borrow_mut() = Some(app_weak.unwrap().window().grab_window());
+                        slint::quit_event_loop().unwrap();
+                    }
+                }
+                slint::RenderingState::AfterRendering => {
+                    rendered_once = true;
+                    app_weak.unwrap().window().request_redraw();
+                }
+                _ => {}
+            }
+        })
+        .unwrap();
+
+    app.show().unwrap();
+    app.run().unwrap();
+
+    let screenshot = screenshot.borrow_mut().take().unwrap().unwrap();
+    assert!(screenshot.width() > 0);
+    assert!(screenshot.height() > 0);
+}