UI: Format Shape fill transparency follows the selection

The Fill slider seeded itself at 0% and wrote that when it lost focus, so a
solid fill that was already transparent opened as opaque and could be cleared.

Co-authored-by: Cursor <cursoragent@cursor.com>

ROADMAP.md

@@ -2,7 +2,7 @@
 
 **Stage: alpha** · next: beta, ~20 points and ~120–210 h away
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-10 · **Change:** minor (hours to ~95% per audience added; ready 56% → 55%; stage stays alpha; previous: major, full re-measure against PowerPoint for Mac 16.113.4; restructured to the craftrules progress-docs standard) · **Target:** Microsoft PowerPoint for Mac 16.113 (Microsoft 365)
+> **Last reviewed:** 2026-10-14 · **Last updated:** 2026-10-14 · **Change:** trivial (progress log: Format Shape fill transparency follows the selection; breadth stays 79%; previous: minor, hours to ~95%) · **Target:** Microsoft PowerPoint for Mac 16.113 (Microsoft 365)
 
 DeckCraft aims at full PowerPoint parity, and to be better: faster, open (a documented zip+JSON
 format plus PPTX), scriptable by agents (CLI, JSON control channel, MCP), and available everywhere
@@ -128,6 +128,7 @@ app's JSON control channel (`deckcraft --control PORT`).
 
 | Date | What landed |
 |---|---|
+| 2026-10-14 | Format Shape: the Fill transparency slider shows the selected solid fill, and leaving it no longer clears that transparency |
 | 2026-10-13 | Slide transitions like PowerPoint: every transition and option measured frame by frame against PowerPoint's video export and retuned (curves, directions, soft edges, 3-D perspective, contents moving over backgrounds); PowerPoint's own XML elements and defaults read and written (diagonal Wipe, Zoom, Shape In/Out, Glitter Hexagons, Shred In/Out, Page Curl Single); `deckcraft-cli render-transition` renders frames headless |
 | 2026-10-13 | Wild text cases measured against PowerPoint (102 synthetic slides): bidi by run language, East Asian vertical text upright, mongolianVert/wordArtVert/wordArtVertRtl, underline styles and strikethrough at the font's metrics, centre/right/decimal tabs, East Asian, Thai, Hindi, Arabic and Hebrew numbering, small caps, all-caps "ß", transparent text, soft hyphens, kinsoku, rtlCol and just/dist anchoring, emoji presentation, fallback faces that no longer move the baseline |
 | 2026-10-13 | Render matches PowerPoint more closely on wild shape, picture and table cases: even-odd custom paths, dashes and caps, arrowheads, radial and path gradients, tile rects, rotWithShape, gradient lines, shadows cast by what is drawn (group and perspective too), group fill, picture borders, tiles, reflection, recolour (biLevel, alphaInv, brightness/contrast), table borders and grid default, 20+ preset shapes by their ECMA formulas, default miter joins, and approximate 3-D bevels, cameras and face lighting |
@@ -150,6 +151,7 @@ app's JSON control channel (`deckcraft --control PORT`).
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-14 | trivial | Progress log: Format Shape fill transparency follows the selection |
 | 2026-10-13 | trivial | Progress log: wild text cases |
 | 2026-10-12 | trivial | Progress log: File tab (Backstage, #76) |
 | 2026-10-12 | trivial | Progress log: lines in scaled groups (#233) |

crates/ui-egui/src/panes.rs

@@ -59,6 +59,29 @@ fn run(app: &mut SlideApp, id: &str, p: Value) {
     let _ = app.run(id, p);
 }
 
+/// Percent transparency (0 = opaque) of a solid fill, the same number `shape.fill`'s
+/// `transparency` parameter writes as an alpha transform. Anything else — no fill, a
+/// gradient, a picture, a pattern — is 0, because that command only changes a solid.
+fn solid_fill_transparency_percent(fill: Option<&Fill>) -> f32 {
+    let Some(Fill::Solid { color }) = fill else {
+        return 0.0;
+    };
+    ((1.0 - color.alpha()) * 100.0) as f32
+}
+
+/// Fraction to pass to `shape.fill` when the slider moved. An unchanged value (a focus
+/// loss, or switching to another shape) is `None`, so the pane does not rewrite the fill.
+fn fill_transparency_to_apply(shown_percent: f32, seed_percent: f32) -> Option<f64> {
+    if !shown_percent.is_finite() {
+        return None;
+    }
+    let shown = shown_percent.clamp(0.0, 100.0);
+    if (shown - seed_percent).abs() <= 0.01 {
+        return None;
+    }
+    Some(f64::from(shown) / 100.0)
+}
+
 fn scheme(app: &SlideApp) -> deckcraft_color::ColorScheme {
     app.session.active().and_then(|d| d.doc.masters.first().map(|m| m.scheme())).unwrap_or_else(|| deckcraft_model::Theme::default().colors)
 }
@@ -285,12 +308,19 @@ fn format_shape(app: &mut SlideApp, ui: &mut Ui) {
             });
             ui.horizontal(|ui| {
                 ui.label("Transparency");
-                let id = ui.id().with("ftr");
-                let mut v: f32 = ui.data_mut(|d| d.get_temp(id).unwrap_or(0.0));
+                // Seed from this shape. A shared temp defaulted to 0, so a shape that was
+                // already 40% transparent showed as opaque, and leaving the slider wrote 0.
+                let seed = solid_fill_transparency_percent(sh.fill.as_ref());
+                let id = ui.id().with(("ftr", sh.id.0));
+                let mut v: f32 = ui.data_mut(|d| d.get_temp(id).unwrap_or(seed));
                 let r = ui.add(egui::Slider::new(&mut v, 0.0..=100.0).suffix("%"));
-                ui.data_mut(|d| d.insert_temp(id, v));
                 if r.drag_stopped() || r.lost_focus() {
-                    let _ = app.run("shape.fill", json!({"transparency": v as f64 / 100.0}));
+                    if let Some(t) = fill_transparency_to_apply(v, seed) {
+                        let _ = app.run("shape.fill", json!({"transparency": t}));
+                    }
+                    ui.data_mut(|d| d.remove::<f32>(id));
+                } else if r.dragged() || r.changed() {
+                    ui.data_mut(|d| d.insert_temp(id, v));
                 }
             });
             if let Some(Fill::Gradient(g)) = &sh.fill {
@@ -635,3 +665,92 @@ fn designer(app: &mut SlideApp, ui: &mut Ui) {
         ui.add_space(8.0);
     }
 }
+
+#[cfg(test)]
+mod tests {
+    #![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+
+    use deckcraft_color::{ColorTransform, SchemeSlot};
+    use deckcraft_engine::Session;
+    use deckcraft_model::{ColorRef, Fill, ShapeId};
+    use egui_kittest::Harness;
+    use egui_kittest::kittest::{NodeT, Queryable};
+    use serde_json::json;
+
+    use super::{fill_transparency_to_apply, solid_fill_transparency_percent};
+    use crate::{Services, SlideApp};
+
+    #[test]
+    fn solid_fill_transparency_reads_the_alpha_shape_fill_writes() {
+        assert_eq!(solid_fill_transparency_percent(None), 0.0);
+        assert_eq!(solid_fill_transparency_percent(Some(&Fill::None)), 0.0);
+        assert_eq!(solid_fill_transparency_percent(Some(&Fill::Group)), 0.0);
+        let plain = Fill::solid(ColorRef::scheme(SchemeSlot::Accent1));
+        assert_eq!(solid_fill_transparency_percent(Some(&plain)), 0.0);
+        // `shape.fill` transparency 0.4 stores Alpha((1 - 0.4) * 100_000).
+        let forty = Fill::solid(ColorRef::scheme(SchemeSlot::Accent1).with(ColorTransform::Alpha(60_000)));
+        let p = solid_fill_transparency_percent(Some(&forty));
+        assert!((p - 40.0).abs() < 0.01, "{p}");
+        let clear = Fill::solid(ColorRef::scheme(SchemeSlot::Accent1).with(ColorTransform::Alpha(0)));
+        assert!((solid_fill_transparency_percent(Some(&clear)) - 100.0).abs() < 0.01);
+        // A later alpha wins, matching ColorRef::alpha.
+        let layered = Fill::solid(ColorRef::scheme(SchemeSlot::Accent1).with(ColorTransform::Alpha(0)).with(ColorTransform::Alpha(60_000)));
+        assert!((solid_fill_transparency_percent(Some(&layered)) - 40.0).abs() < 0.01);
+
+        assert_eq!(fill_transparency_to_apply(40.0, 40.0), None);
+        assert_eq!(fill_transparency_to_apply(40.005, 40.0), None);
+        assert_eq!(fill_transparency_to_apply(f32::NAN, 40.0), None);
+        assert_eq!(fill_transparency_to_apply(55.0, 40.0), Some(0.55));
+        assert_eq!(fill_transparency_to_apply(0.0, 40.0), Some(0.0));
+    }
+
+    fn solid_alpha(app: &SlideApp, id: u32) -> Option<i32> {
+        let sh = app.session.active()?.shape(ShapeId(id))?;
+        let Fill::Solid { color } = sh.fill.as_ref()? else { return None };
+        color.mods.iter().find_map(|m| match m {
+            ColorTransform::Alpha(v) => Some(*v),
+            _ => None,
+        })
+    }
+
+    fn slider_values(h: &Harness<'_, SlideApp>) -> Vec<f64> {
+        h.query_all_by_role(egui::accesskit::Role::Slider).filter_map(|n| n.accesskit_node().numeric_value()).collect()
+    }
+
+    /// The Fill slider shows the selected solid's transparency, and opening the pane
+    /// (or looking at another shape first) does not write 0% over it.
+    #[test]
+    fn fill_transparency_slider_follows_the_selection() {
+        let mut s = Session::with_new();
+        s.execute("slide.new", &json!({"layout": "blank"})).unwrap();
+        let a = s.execute("shape.insert", &json!({"preset": "rect", "rect": [40.0, 40.0, 120.0, 80.0]})).unwrap()["id"].as_u64().unwrap() as u32;
+        let b = s.execute("shape.insert", &json!({"preset": "rect", "rect": [200.0, 40.0, 120.0, 80.0]})).unwrap()["id"].as_u64().unwrap() as u32;
+        s.execute("shape.fill", &json!({"id": a, "color": "accent1", "transparency": 0.0})).unwrap();
+        s.execute("shape.fill", &json!({"id": b, "color": "accent1", "transparency": 0.4})).unwrap();
+        s.execute("edit.select", &json!({"ids": [a]})).unwrap();
+        let mut app = SlideApp::new(s, Services::default());
+        app.ui.pane = Some("format".into());
+        app.ui.format_tab = "fill".into();
+        let mut h = Harness::builder().with_size(egui::vec2(1400.0, 900.0)).build_ui_state(
+            |ui, app: &mut SlideApp| {
+                app.logic(ui.ctx());
+                app.ui(ui);
+            },
+            app,
+        );
+        h.run_steps(3);
+        let opaque: Vec<f64> = slider_values(&h);
+        assert!(opaque.iter().any(|v| (*v - 0.0).abs() < 0.5), "opaque shape should show 0%, got {opaque:?}");
+        assert!(opaque.iter().all(|v| (*v - 40.0).abs() > 0.5), "opaque shape should not show 40%, got {opaque:?}");
+
+        h.state_mut().session.execute("edit.select", &json!({"ids": [b]})).unwrap();
+        h.run_steps(3);
+        let clear: Vec<f64> = slider_values(&h);
+        assert!(clear.iter().any(|v| (*v - 40.0).abs() < 0.5), "40% fill should show 40%, got {clear:?}");
+        assert_eq!(solid_alpha(h.state(), b), Some(60_000));
+
+        h.get_by_label("Transparency").click();
+        h.run_steps(2);
+        assert_eq!(solid_alpha(h.state(), b), Some(60_000));
+    }
+}

docs/ui-parity.md

@@ -1,6 +1,6 @@
 # UI parity with PowerPoint
 
-> **Last reviewed:** 2026-10-10 · **Last updated:** 2026-10-12 · **Change:** minor (File tab / Backstage, #76; previous: off-slide objects in Normal view, #270) · **Target:** Microsoft PowerPoint for Mac 16.113 (Microsoft 365)
+> **Last reviewed:** 2026-10-14 · **Last updated:** 2026-10-14 · **Change:** trivial (Format Shape fill transparency follows the selection; previous: minor, File tab / Backstage, #76) · **Target:** Microsoft PowerPoint for Mac 16.113 (Microsoft 365)
 
 > **Last reviewed:** 2026-10-12 · **Last updated:** 2026-10-12 · **Change:** minor (text editing keys observed in PowerPoint for Windows, #268) · **Target:** Microsoft PowerPoint for Mac 16.113 (Microsoft 365)
 
@@ -58,7 +58,7 @@ menu colours taken from the theme tokens (menu `chrome`, page `card`).
 
 | Pane / dialog | PowerPoint | DeckCraft |
 |---|---|---|
-| Format Shape / Picture / Text pane (Fill & Line, Effects, Size & Properties, Picture, Text Box) | full | partial: fill, gradient editor, line, some effects, size; no 3-D, thin picture/texture options |
+| Format Shape / Picture / Text pane (Fill & Line, Effects, Size & Properties, Picture, Text Box) | full | partial: fill (solid transparency follows the selection), gradient editor, line, some effects, size; no 3-D, thin picture/texture options |
 | Format Background pane | yes | yes |
 | Selection Pane | front-most first, groups fold, drag to restack, Bring Forward / Send Backward arrows, Show All / Hide All, eye, padlock (Lock), rename in place | same: drag restacks among siblings (a child stays in its group), Ctrl+click toggles, Shift+click selects a run, arrows / Home / End / F2 / Esc in the list, right-click menu |
 | Animation Pane | list + advanced timeline | list, reorder, timing; no timeline |
@@ -148,6 +148,7 @@ imitate Microsoft's. No pixel comparison against PowerPoint screenshots has been
 
 | Date | Change | Summary |
 |---|---|---|
+| 2026-10-14 | trivial | Format Shape Fill transparency slider follows the selected solid fill and does not clear it on focus loss |
 | 2026-10-12 | minor | File tab (Backstage) observed in PowerPoint for Windows and matched (#76); the start screen is File › Home |
 | 2026-10-12 | minor | Off-slide objects drawn and editable around the slide in Normal view (#270) |
 | 2026-10-12 | minor | Selection Pane matched to PowerPoint (#133): drag and drop, arrows, groups, eye, Lock |