fix(ui): a drag seen past its page's edge still draws on that page

egui reports a drag once the pointer has moved a few points from the press. A press near a page's
bottom edge, flicked onto the next page in one frame, is seen as a drag only with the pointer on
the next page. Redact (and the area Highlight), the Link tool and Prepare returned before their
drag start unless the pointer was on their own page, and the next page is `Elsewhere`, so the
press drew nothing anywhere. (On main the next page took it, with the box's start on the page
before.)

They now start the gesture from where the press began on their own page, as zoom, snapshot, crop
and Sign area already did, so the box, link rectangle, marquee, field drawn or field moved belongs
to the page the press began on. Tests: one per tool, each seen failing with the fix reverted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/tools/link_ui.rs

@@ -108,7 +108,19 @@ pub(crate) fn page_input(cx: PageToolContext<'_>, free: bool, owner: Option<usiz
         }
         return true;
     }
-    let Some(p) = pointer.filter(|p| xf.rect.contains(*p)) else { return false };
+    // A drag that nobody holds, or from a link (whose hit lets the drag go), draws a new link from
+    // where its press began on this page. egui may see the drag only once the pointer is past the
+    // page's edge.
+    if resp.drag_started()
+        && (free || owner.is_some())
+        && let Some(origin) = ptr.origin.filter(|o| xf.rect.contains(*o))
+    {
+        lv.drag = Some((page, origin));
+        return true;
+    }
+    if !pointer.is_some_and(|p| xf.rect.contains(p)) {
+        return false;
+    }
     // Over a link, its hit claims the hand.
     view.cursor.claim(Layer::ToolArea, egui::CursorIcon::Crosshair);
     if let Some(index) = context {
@@ -128,11 +140,6 @@ pub(crate) fn page_input(cx: PageToolContext<'_>, free: bool, owner: Option<usiz
         }
         return true;
     }
-    if resp.drag_started() && (free || owner.is_some()) {
-        let origin = ptr.origin.unwrap_or(p);
-        lv.drag = Some((page, origin));
-        return true;
-    }
     resp.is_pointer_button_down_on()
 }
 

crates/ui-egui/src/tools/prepare.rs

@@ -378,53 +378,30 @@ pub(crate) fn page_input(
         return out;
     }
 
-    let Some(p) = pointer.filter(|p| xf.rect.contains(*p)) else { return out };
-    if !allowed {
-        return out;
-    }
-    let free = press == PagePress::Free;
-    if let Some(tool) = tool {
-        view.cursor.claim(Layer::ToolArea, egui::CursorIcon::Crosshair);
-        if free && (resp.drag_started() || resp.clicked()) {
-            let origin = ptr.origin.filter(|o| xf.rect.contains(*o)).unwrap_or(p);
-            prep.grab = Some((page, Grab::Draw(origin), origin));
-            out.consumed = true;
-            if resp.clicked() {
-                // A click without a drag: finish at once.
-                prep.grab = None;
-                if tool == FieldTool::TextTable {
-                    out.table = Some((page, table_rect(xf, Rect::from_min_size(p, egui::Vec2::ZERO))));
-                    out.placed = true;
-                    return out;
-                }
-                let at = to_user(xf, info, page, p);
-                let (w, h) = tool.default_size();
-                let join = prep.selected.as_ref().and_then(|(n, _)| form.iter().find(|f| &f.name == n));
-                prep.select_added = Some(form.len());
-                view.pending_edit = Some(Edit::AddField { page, rect: [at[0], at[1] - h, at[0] + w, at[1]], kind: tool.new_field(join), name: None });
-                out.placed = true;
-            }
-        }
-        return out;
-    }
-
     // The Select tool: what the press is on ([`hit`]), a corner handle or a field; a press nobody
-    // holds draws a selection rectangle. A press held by something drawn over the fields (a
-    // comment) is not Prepare's.
+    // holds draws a selection rectangle, or a field with a field tool. A press held by something
+    // drawn over the fields (a comment) is not Prepare's.
+    let free = press == PagePress::Free;
     let held = matches!(press, PagePress::Mine(Owner::PrepareField { .. } | Owner::PrepareCorner { .. }));
     let hit = match press {
         PagePress::Mine(Owner::PrepareField { field, widget }) => form.get(field).map(|f| (f, widget)),
         _ => None,
     };
-    if resp.drag_started() && (held || free) {
-        let origin = ptr.origin.unwrap_or(p);
-        if let PagePress::Mine(Owner::PrepareCorner { left, top }) = press {
+    // A drag starts from where its press began on this page: egui may see it only once the pointer
+    // is past the page's edge.
+    if allowed
+        && resp.drag_started()
+        && (held || free)
+        && let Some(origin) = ptr.origin.filter(|o| xf.rect.contains(*o))
+    {
+        out.consumed = true;
+        if tool.is_some() {
+            prep.grab = Some((page, Grab::Draw(origin), origin));
+        } else if let PagePress::Mine(Owner::PrepareCorner { left, top }) = press {
             prep.grab = Some((page, Grab::Corner(left, top), origin));
-            out.consumed = true;
         } else if let Some((f, wi)) = hit {
             prep.selected = Some((f.name.clone(), wi));
             prep.grab = Some((page, Grab::Move, origin));
-            out.consumed = true;
         } else {
             prep.marquee_before = Some(prep.selected.iter().chain(prep.also.iter()).cloned().collect());
             if !ui.input(|i| i.modifiers.shift || i.modifiers.command) {
@@ -432,7 +409,29 @@ pub(crate) fn page_input(
                 prep.also.clear();
             }
             prep.grab = Some((page, Grab::Select(origin), origin));
+        }
+        return out;
+    }
+    let Some(p) = pointer.filter(|p| xf.rect.contains(*p)) else { return out };
+    if !allowed {
+        return out;
+    }
+    if let Some(tool) = tool {
+        view.cursor.claim(Layer::ToolArea, egui::CursorIcon::Crosshair);
+        // A click without a drag places the field at once.
+        if free && resp.clicked() {
             out.consumed = true;
+            if tool == FieldTool::TextTable {
+                out.table = Some((page, table_rect(xf, Rect::from_min_size(p, egui::Vec2::ZERO))));
+                out.placed = true;
+                return out;
+            }
+            let at = to_user(xf, info, page, p);
+            let (w, h) = tool.default_size();
+            let join = prep.selected.as_ref().and_then(|(n, _)| form.iter().find(|f| &f.name == n));
+            prep.select_added = Some(form.len());
+            view.pending_edit = Some(Edit::AddField { page, rect: [at[0], at[1] - h, at[0] + w, at[1]], kind: tool.new_field(join), name: None });
+            out.placed = true;
         }
         return out;
     }

crates/ui-egui/src/tools/redact_ui.rs

@@ -252,17 +252,17 @@ pub(crate) fn page_input(cx: PageToolContext<'_>, over_text: impl Fn(Pos2) -> bo
         }
         return true;
     }
-    let Some(p) = pointer.filter(|p| xf.rect.contains(*p)) else { return false };
-    if !over_text(p) {
-        view.cursor.claim(Layer::ToolArea, egui::CursorIcon::Crosshair);
+    // The tool's own press, of the primary button: one nobody holds, which began on this page off
+    // its text. egui may see the drag only once the pointer is past the page's edge.
+    if resp.drag_started_by(egui::PointerButton::Primary)
+        && free
+        && let Some(origin) = ptr.origin.filter(|o| xf.rect.contains(*o) && !over_text(*o))
+    {
+        view.redact_drag = Some((page, origin));
+        return true;
     }
-    // The tool's own press, of the primary button: one nobody holds.
-    if resp.drag_started_by(egui::PointerButton::Primary) && free {
-        let origin = ptr.origin.unwrap_or(p);
-        if !over_text(origin) {
-            view.redact_drag = Some((page, origin));
-            return true;
-        }
+    if pointer.is_some_and(|p| xf.rect.contains(p) && !over_text(p)) {
+        view.cursor.claim(Layer::ToolArea, egui::CursorIcon::Crosshair);
     }
     false
 }

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

@@ -1298,3 +1298,61 @@ fn a_fields_tooltip_shows_beside_the_open_palette() {
     rest_at(&mut h, on_field);
     assert!(h.query_all_by_label("Your name").next().is_some(), "the field's tooltip shows");
 }
+
+/// Two blank 300×400 pages.
+fn two_pages_pdf() -> Vec<u8> {
+    pdf(&[
+        CATALOG,
+        "<< /Type /Pages /Kids [3 0 R 4 0 R] /Count 2 /MediaBox [0 0 300 400] >>",
+        "<< /Type /Page /Parent 2 0 R >>",
+        "<< /Type /Page /Parent 2 0 R >>",
+    ])
+}
+
+/// Sets a tool up (`tool`), presses above page 1's bottom edge and drags onto page 2 in one frame,
+/// so egui sees the drag only once the pointer is on page 2, and returns the app after the release.
+fn drag_seen_only_past_page_ones_edge(tool: impl FnOnce(&mut PdfCraftApp)) -> Harness<'static, PdfCraftApp> {
+    let mut h = open(two_pages_pdf(), "100", false);
+    tool(h.state_mut());
+    h.run_steps(4);
+    let (one, two) = {
+        let v = &h.state().views[0];
+        (v.page_screen_rect(0).expect("page 1 on screen"), v.page_screen_rect(1).expect("page 2 on screen"))
+    };
+    let press = egui::pos2(one.min.x + 50.0, one.max.y - 30.0);
+    let release = egui::pos2(one.min.x + 150.0, two.min.y + 20.0);
+    h.hover_at(press);
+    h.run_steps(1);
+    h.drag_at(press);
+    h.run_steps(1);
+    h.hover_at(release);
+    h.run_steps(1);
+    h.drop_at(release);
+    h.run_steps(4);
+    h
+}
+
+// A drag seen only past its page's edge still draws on the page its press began on, as zoom, crop
+// and Sign area do. With these three it used to draw nothing anywhere.
+
+#[test]
+fn a_redaction_box_dragged_off_its_page_is_drawn_on_it() {
+    let h = drag_seen_only_past_page_ones_edge(|app| app.quick_tool = QuickTool::Redact);
+    let s = h.state();
+    let doc = s.session.get(s.views[0].id).unwrap();
+    assert!(doc.info.annotations.iter().any(|a| a.subtype == "Redact" && a.page == 0), "a redaction mark on page 1");
+}
+
+#[test]
+fn a_link_rectangle_dragged_off_its_page_is_drawn_on_it() {
+    let h = drag_seen_only_past_page_ones_edge(|app| app.quick_tool = QuickTool::Link);
+    assert_eq!(h.state().link_draft.as_ref().map(|d| (d.page, d.index)), Some((0, None)), "a new link on page 1");
+}
+
+#[test]
+fn a_field_dragged_off_its_page_is_drawn_on_it() {
+    let h = drag_seen_only_past_page_ones_edge(|app| assert!(app.execute("form.add.text"), "Prepare a form, with the text field tool"));
+    let s = h.state();
+    let doc = s.session.get(s.views[0].id).unwrap();
+    assert!(doc.form.iter().any(|f| f.widgets.iter().any(|w| w.page == Some(0))), "a field on page 1");
+}