[test] add e2e egui test

egui/src/lib.rs

@@ -82,3 +82,21 @@ pub use {
     ui::Ui,
     widgets::*,
 };
+
+#[test]
+pub fn text_egui_e2e() {
+    let mut demo_app = crate::demos::DemoApp::default();
+    let mut ctx = crate::Context::new();
+    let raw_input = crate::RawInput {
+        screen_size: crate::vec2(1280.0, 1024.0),
+        ..Default::default()
+    };
+
+    const NUM_FRAMES: usize = 5;
+    for _ in 0..NUM_FRAMES {
+        let mut ui = ctx.begin_frame(raw_input.clone());
+        demo_app.ui(&mut ui, "");
+        let (_output, paint_jobs) = ctx.end_frame();
+        assert!(!paint_jobs.is_empty());
+    }
+}

egui/src/paint/color.rs

@@ -426,6 +426,7 @@ pub fn rgb_from_hsv((h, s, v): (f32, f32, f32)) -> (f32, f32, f32) {
 }
 
 #[test]
+#[ignore] // a bit expensive
 fn test_hsv_roundtrip() {
     for r in 0..=255 {
         for g in 0..=255 {

egui/src/paint/font.rs

@@ -193,6 +193,9 @@ impl Font {
         scale_in_points: f32,
         pixels_per_point: f32,
     ) -> Font {
+        assert!(scale_in_points > 0.0);
+        assert!(pixels_per_point > 0.0);
+
         let font = rusttype::Font::try_from_bytes(font_data).expect("Error constructing Font");
         let scale_in_pixels = pixels_per_point * scale_in_points;