fix(ui): a picture's grip and knob take their drag from the press

Found in review. On `main` the selected picture's grips and rotate knob
were drag-only widgets of their own, so their drag began at the press.
Their widgets went, and the page's response is click-and-drag, which calls
it a drag only past egui's click distance: a move of a few pixels resized
nothing. They take their drag from the press again. A click that doesn't
move edits nothing, as before; a drag of the picture itself still waits,
since a click selects.

Tests: `a_short_drag_from_a_picture_grip_resizes_it` (seen failing with
the fix reverted), `a_click_on_a_picture_grip_changes_nothing` (a pin,
seen failing with the release planted to edit always).

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

crates/ui-egui/src/tools/edit_text_ui/image.rs

@@ -782,13 +782,16 @@ pub(crate) fn image_input(cx: &ImageCx<'_>, images: &[pdfcraft_engine::PageImage
         }
 
         // A drag of the selected picture takes what its press was on ([`body_hit`], [`handle_hit`]):
-        // the rotate knob turns it, a grip resizes it, the picture itself moves.
+        // the rotate knob turns it, a grip resizes it, the picture itself moves. The knob and the
+        // grips take it from the press, so a move too short to be a drag of the page counts; the
+        // picture waits for that, as a click selects.
+        let at_press = |part| matches!(part, PicturePart::Knob | PicturePart::Corner(_));
         if gate
-            && ptr.drag_started
             && let Some(o) = ptr.origin
             && let PagePress::Mine(Owner::Picture { index, part }) = press
             && (index == i || part == PicturePart::OverSelected)
-            && let Some(s) = view.image_selection.as_mut()
+            && (ptr.drag_started || at_press(part) && ptr.pressed().is_some())
+            && let Some(s) = view.image_selection.as_mut().filter(|s| s.drag.is_none())
         {
             match part {
                 PicturePart::Knob => {

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

@@ -7435,6 +7435,39 @@ fn a_drag_from_the_selected_picture_under_another_moves_the_selected_one() {
     assert_eq!(selected, Some(1), "a click selects the one on top");
 }
 
+/// A move too short to be a drag of the page still resizes the selected picture from its grip, as
+/// the grip takes its drag from the press.
+#[test]
+fn a_short_drag_from_a_picture_grip_resizes_it() {
+    let mut h = picture_pages(false);
+    let id = h.state().views[0].id;
+    let before = h.state().session.get(id).unwrap().page_images(0)[0].matrix;
+    // The picture shows at x 30..160, y 170..250: its lower right grip, moved 3 px.
+    let grip = page_at(&h, 0, 160.0, 170.0);
+    h.hover_at(grip);
+    h.run_steps(1);
+    h.drag_at(grip);
+    h.run_steps(1);
+    h.hover_at(grip + egui::vec2(3.0, 0.0));
+    h.run_steps(1);
+    h.drop_at(grip + egui::vec2(3.0, 0.0));
+    h.run_steps(3);
+    assert_ne!(h.state().session.get(id).unwrap().page_images(0)[0].matrix, before, "the picture is resized");
+}
+
+/// A click on a selected picture's grip that doesn't move resizes nothing: no edit, and the picture
+/// stays selected.
+#[test]
+fn a_click_on_a_picture_grip_changes_nothing() {
+    let mut h = picture_pages(false);
+    let id = h.state().views[0].id;
+    let before = h.state().session.get(id).unwrap().edit_generation();
+    let grip = page_at(&h, 0, 160.0, 170.0);
+    slipping_click(&mut h, grip, grip);
+    assert_eq!(h.state().session.get(id).unwrap().edit_generation(), before, "no edit");
+    assert!(h.state().views[0].image_selection.is_some(), "the picture stays selected");
+}
+
 /// In the page grid, Delete deletes the page chosen there. The picture selected before the grid
 /// opened is not on screen, and stays.
 #[test]