M1, #1758: a primary drag let go during a pan still ends

crates/ui-egui/src/canvas/input.rs

@@ -148,6 +148,31 @@ fn import_dropped(app: &mut FigApp, ctx: &egui::Context, hover_pos: Option<egui:
     }
 }
 
+/// One frame of a pan (the middle or a side button held, or Space + drag): the view follows the
+/// pointer from where the pan began, and the pan ends once no button that pans is held.
+fn pan_view(app: &mut FigApp, ctx: &egui::Context, pos: Pos2, mods: &egui::Modifiers, middle_down: bool) {
+    if let Ok(ds) = app.session.ds_mut() {
+        match app.canvas.middle_pan {
+            None => app.canvas.middle_pan = Some((pos, ds.view.cx, ds.view.cy)),
+            Some((p0, cx, cy)) => {
+                let z = ds.view.zoom.max(1e-6);
+                ds.view.cx = cx - f64::from(pos.x - p0.x) / z;
+                ds.view.cy = cy - f64::from(pos.y - p0.y) / z;
+                ds.revision += 1;
+            }
+        }
+    }
+    // A primary drag under way when the pan began ends when its button is let go, pan or
+    // not: the engine gets its release here, as it does over the canvas or off it.
+    if app.canvas.dragging && !ctx.input(|i| i.pointer.primary_down()) {
+        app.canvas.dragging = false;
+        send(app, PointerKind::Up, pos, mods);
+    }
+    if !middle_down && !ctx.input(|i| i.pointer.primary_down()) {
+        app.canvas.middle_pan = None;
+    }
+}
+
 /// The pointer and keys on the canvas. False when something on it with a cursor of its own has
 /// the pointer (a comment pin, a ruler guide, a gradient or padding handle): the tool's cursor
 /// then doesn't show.
@@ -224,20 +249,7 @@ pub(super) fn input(app: &mut FigApp, ui: &mut Ui, resp: &egui::Response) -> boo
     // Middle-button (or side-button) / space panning.
     let middle_down = ctx.input(pan_button_down);
     if (middle_down || (app.canvas.space_pan && ctx.input(|i| i.pointer.primary_down()))) && resp.hovered() || app.canvas.middle_pan.is_some() {
-        if let Ok(ds) = app.session.ds_mut() {
-            match app.canvas.middle_pan {
-                None => app.canvas.middle_pan = Some((pos, ds.view.cx, ds.view.cy)),
-                Some((p0, cx, cy)) => {
-                    let z = ds.view.zoom.max(1e-6);
-                    ds.view.cx = cx - f64::from(pos.x - p0.x) / z;
-                    ds.view.cy = cy - f64::from(pos.y - p0.y) / z;
-                    ds.revision += 1;
-                }
-            }
-        }
-        if !middle_down && !ctx.input(|i| i.pointer.primary_down()) {
-            app.canvas.middle_pan = None;
-        }
+        pan_view(app, &ctx, pos, &mods, middle_down);
         return true;
     }
     // A handle drag whose button went up ends first, wherever on the canvas the pointer is: over a

crates/ui-egui/tests/it/canvas_pan_release.rs

@@ -109,3 +109,25 @@ fn side_buttons_pan_like_the_middle_button() {
         check_button(b, false, true);
     }
 }
+
+/// A primary drag under way when a pan starts (a side or the middle button pressed mid-drag) ends
+/// when the primary button is let go during the pan: the engine gets the release, so its gesture
+/// isn't left open once the pan is over.
+#[test]
+fn a_primary_drag_released_during_a_pan_ends() {
+    for pan in [PointerButton::Middle, PointerButton::Extra1] {
+        let mut u = Frames::new();
+        let rect = u.app.canvas.rect;
+        let start = Pos2::new(rect.min.x + 200.0, rect.center().y);
+        let moved = Pos2::new(rect.min.x + 400.0, rect.center().y);
+        u.frame(vec![Event::PointerMoved(start)]);
+        u.frame(vec![button(start, PointerButton::Primary, true)]);
+        u.frame(vec![Event::PointerMoved(moved)]);
+        assert!(u.app.session.tool.busy(), "{pan:?}: a primary drag is under way");
+        u.frame(vec![button(moved, pan, true)]);
+        u.frame(vec![button(moved, PointerButton::Primary, false)]);
+        u.frame(vec![button(moved, pan, false)]);
+        u.frame(vec![]);
+        assert!(!u.app.session.tool.busy(), "{pan:?}: the primary release reached the engine");
+    }
+}