From 1ae11a4bb1c3c5f7125ab16bf7b3c1c3838266a3 Mon Sep 17 00:00:00 2001
From: Brandon Thomas <echelon@gmail.com>
Date: Thu, 8 Oct 2026 03:17:44 -0400
Subject: [PATCH] Shape tools: Shift and Alt pressed during the drag constrain
 it, as in Photoshop (#668) (#984)

Shape drags only read the modifiers held at the press, so pressing Shift
mid-drag (the usual way) didn't square a rectangle or keep a polygon's
proportions, and Alt mid-drag didn't draw from the centre. They now follow
the modifiers held at each pointer event, like the marquees.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
---
 crates/ui-egui/src/canvas.rs    |  4 ++--
 crates/ui-egui/src/vector_ui.rs | 24 ++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/crates/ui-egui/src/canvas.rs b/crates/ui-egui/src/canvas.rs
index 260d6a41..56e959f3 100644
--- a/crates/ui-egui/src/canvas.rs
+++ b/crates/ui-egui/src/canvas.rs
@@ -2293,7 +2293,7 @@ fn draw_drag_preview(app: &mut PhotocraftApp, painter: &egui::Painter, xf: &View
             trail.feed(&d.points, app.session.tools.brush.size);
             trail.draw(painter, doc_rect, xf.flip, col);
         }
-        t if crate::vector_ui::is_shape_tool(t) => crate::vector_ui::draw_shape_preview(app, painter, xf, t, d.start, last, d.modifiers),
+        t if crate::vector_ui::is_shape_tool(t) => crate::vector_ui::draw_shape_preview(app, painter, xf, t, d.start, last, d.live),
         Tool::RectMarquee | Tool::EllipseMarquee | Tool::ObjectSelection => {
             // Marching ants, visible on any pixels (#172).
             let (a, b) = marquee.unwrap_or((d.start, last));
@@ -2714,7 +2714,7 @@ pub(crate) fn finish_gesture(app: &mut PhotocraftApp, d: Drag) {
     }
     match d.tool {
         Tool::ObjectSelection => crate::retouch_ui::finish_object_selection(app, d.start, [end[0], end[1]], d.modifiers),
-        t if crate::vector_ui::is_shape_tool(t) => crate::vector_ui::finish_shape(app, t, d.start, [end[0], end[1]], d.modifiers),
+        t if crate::vector_ui::is_shape_tool(t) => crate::vector_ui::finish_shape(app, t, d.start, [end[0], end[1]], d.live),
         Tool::PathSelection => crate::vector_ui::path_selection_finish(app, d.start, [end[0], end[1]]),
         Tool::Type | Tool::VerticalType => crate::type_tool::pointer_up(app, d.start, [end[0], end[1]]),
         Tool::Brush | Tool::Pencil | Tool::Eraser => {
diff --git a/crates/ui-egui/src/vector_ui.rs b/crates/ui-egui/src/vector_ui.rs
index 61951501..f6d258a9 100644
--- a/crates/ui-egui/src/vector_ui.rs
+++ b/crates/ui-egui/src/vector_ui.rs
@@ -938,6 +938,30 @@ mod tests {
         assert_eq!(app.session.active().unwrap().doc.layers.len(), 4);
     }
 
+    #[test]
+    fn shift_pressed_during_a_shape_drag_constrains_it() {
+        // #668: ⇧ only counted when held at the press; Photoshop constrains when it is pressed
+        // mid-drag (and stops when it is released).
+        use crate::canvas::{ToolEvent, tool_event};
+        for (tool, sides) in [(Tool::Polygon, 6), (Tool::Rectangle, 4), (Tool::EllipseShape, 0)] {
+            let mut app = app();
+            app.ui.tool = tool;
+            app.ui.tool_options.polygon_sides = 6;
+            let none = egui::Modifiers::NONE;
+            tool_event(&mut app, ToolEvent::Down { x: 10.0, y: 10.0, pressure: 1.0 }, none);
+            tool_event(&mut app, ToolEvent::Move { x: 40.0, y: 30.0, pressure: 1.0 }, none);
+            tool_event(&mut app, ToolEvent::Move { x: 70.0, y: 40.0, pressure: 1.0 }, egui::Modifiers::SHIFT);
+            tool_event(&mut app, ToolEvent::Up { x: 70.0, y: 40.0 }, egui::Modifiers::SHIFT);
+            let st = app.session.active().unwrap();
+            let l = st.doc.layer(st.active_layer.unwrap()).unwrap();
+            assert!(matches!(l.content, LayerContent::Shape(_)), "{tool:?} ({sides} sides): a shape layer");
+            let b = l.surface().unwrap().content_bounds();
+            // The drag is 60 × 30; constrained, the shape's box is 60 × 60 (a hexagon is narrower
+            // than its box, so the height tells).
+            assert!(b.height().abs_diff(60) <= 1 && b.width() <= 61, "{tool:?}: ⇧ mid-drag keeps proportions: {b:?}");
+        }
+    }
+
     #[test]
     fn shape_preview_is_the_committed_path() {
         let mut app = app();