From 8756ec1846f26537e80d44383b0b6a15d74fca5b Mon Sep 17 00:00:00 2001
From: Camille Moine <ki2pixel@gmail.com>
Date: Mon, 19 Oct 2026 10:25:17 +0200
Subject: [PATCH] Timeline: Preserve Transparency toggles from the clicked row
 (#1849)

layer.setSwitch with no value toggles relative to the first selected layer in
composition order, so with a mixed selection (A checked, C unchecked) clicking
C's box could leave C unchanged. The checkbox now sends the value it toggles
to, as the switches do.
---
 crates/ui-egui/src/panels/timeline.rs     | 11 ++++++++++-
 crates/ui-egui/tests/ui_batch_switches.rs | 17 +++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/crates/ui-egui/src/panels/timeline.rs b/crates/ui-egui/src/panels/timeline.rs
index ebe076dc8..1366b7504 100644
--- a/crates/ui-egui/src/panels/timeline.rs
+++ b/crates/ui-egui/src/panels/timeline.rs
@@ -2241,7 +2241,16 @@ pub fn show(app: &mut EffectcraftApp, ui: &mut egui::Ui, rect: Rect) {
                     let tr = Rect::from_center_size(pos2(cw.mode + 76.0 + 6.0, cy), vec2(14.0, 14.0));
                     app.auto.add(&format!("timeline.layer.{}.preserveTransparency", layer.id.0), tr, "Preserve Transparency");
                     if widgets::checkbox(ui, tr, layer.preserve_transparency, &t, egui::Id::new(("pt", layer.id.0))).clicked() {
-                        actions.push(("layer.setSwitch".into(), json!({"layers": mode_targets(&comp, layer.id, &selected), "switch": "preserveTransparency"})));
+                        // The click gives the selection the state the clicked row toggles to,
+                        // whatever the first selected layer's value (as the switches do).
+                        actions.push((
+                            "layer.setSwitch".into(),
+                            json!({
+                                "layers": mode_targets(&comp, layer.id, &selected),
+                                "switch": "preserveTransparency",
+                                "value": !layer.preserve_transparency
+                            }),
+                        ));
                     }
                     // Track matte: layer picker + kind.
                     let mr = Rect::from_min_size(pos2(cw.trkmat + 2.0, cy - 9.0), vec2(104.0, 18.0));
diff --git a/crates/ui-egui/tests/ui_batch_switches.rs b/crates/ui-egui/tests/ui_batch_switches.rs
index acbc91f87..407ac194e 100644
--- a/crates/ui-egui/tests/ui_batch_switches.rs
+++ b/crates/ui-egui/tests/ui_batch_switches.rs
@@ -225,3 +225,20 @@ fn the_modes_column_sets_the_whole_selection() {
     h.run_steps(2);
     assert_eq!(states(&h, &ids, preserved), [false; 4], "one undo step put both back");
 }
+
+/// Preserve Transparency toggles from the row it is clicked on, not from the first selected layer:
+/// A on and C off, clicking C's box turns both on.
+#[test]
+fn preserve_transparency_toggles_from_the_clicked_row() {
+    let (mut h, ids) = harness();
+    h.state_mut().ui.timeline.show_modes = true;
+    h.run_steps(3);
+    h.state_mut().session.execute("layer.setSwitch", json!({"layers": [ids[0]], "switch": "preserveTransparency", "value": true})).unwrap();
+    h.run_steps(2);
+    select(&mut h, &[ids[0], ids[2]]);
+    click(&mut h, &format!("timeline.layer.{}.preserveTransparency", ids[2]));
+    assert_eq!(states(&h, &ids, preserved), [true, false, true, false]);
+    // The next click turns both off again.
+    click(&mut h, &format!("timeline.layer.{}.preserveTransparency", ids[2]));
+    assert_eq!(states(&h, &ids, preserved), [false; 4]);
+}