test: 同帧按下/松开绘制从按下点开始的回归用例

crates/ui-egui/src/canvas_fixes_tests.rs

@@ -6,7 +6,7 @@ use std::sync::Arc;
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::time::{Duration, Instant};
 
-use egui::{Pos2, Shape};
+use egui::{Event, Modifiers, PointerButton, Pos2, Shape};
 use figcraft_engine::Session;
 use serde_json::json;
 
@@ -25,6 +25,29 @@ fn dashes_along(shapes: &[Shape], a: Pos2, b: Pos2) -> usize {
     shapes.iter().filter(|s| matches!(s, Shape::LineSegment { points: [p, q], .. } if on(*p) && on(*q))).count()
 }
 
+#[test]
+fn a_press_and_release_in_one_frame_draw_from_the_press() {
+    // A quick drag (or a slow frame) puts both in one frame, where the hover position is the end:
+    // the press must still use its own position, or the shape starts where the pointer let go.
+    let mut u = Ui::new(Session::new());
+    u.app.run("tool.set", json!({"tool": "rectangle"}));
+    u.frame(vec![]);
+    let press = u.app.to_screen(100.0, 100.0);
+    let release = u.app.to_screen(260.0, 220.0);
+    u.frame(vec![
+        Event::PointerMoved(release),
+        Event::PointerButton { pos: press, button: PointerButton::Primary, pressed: true, modifiers: Modifiers::NONE },
+        Event::PointerButton { pos: release, button: PointerButton::Primary, pressed: false, modifiers: Modifiers::NONE },
+    ]);
+    for _ in 0..3 {
+        u.frame(vec![]);
+    }
+    let doc = u.app.session.doc().unwrap();
+    let drawn = u.app.session.selection().first().copied().expect("the press drew a shape");
+    let b = doc.world_bounds(drawn).expect("the shape has bounds");
+    assert!((b.x0 - 100.0).abs() < 1.0 && (b.y0 - 100.0).abs() < 1.0, "drawn from the press, not the release: {b:?}");
+}
+
 #[test]
 fn frame_outlines_and_slices_draw_when_shown() {
     let mut s = Session::new();