Merge remote-tracking branch 'origin/main' into finish-836

The live on-canvas filter preview runs the real command on a downsampled
proxy of the document, but the proxy dropped the selection, so on documents
large enough to need a proxy (over ~5 MP) the preview filtered the whole
layer while OK only changed the selection. The proxy now downsamples the
selection with the pixels, so the preview is limited to the (feathered)
selection exactly like the result.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/compose/src/proxy.rs

@@ -62,7 +62,9 @@ fn shrink_layer(l: &mut Layer, k: u32) {
     }
 }
 
-/// A copy of `doc` scaled down by `k` (same layer ids, so adjustments can be swapped in).
+/// A copy of `doc` scaled down by `k` (same layer ids, so adjustments can be swapped in). The
+/// selection scales with it, so a filter previewed on the proxy stays inside the (feathered)
+/// selection exactly as the full-size result does.
 pub fn proxy_document(doc: &Document, k: u32) -> Document {
     let mut p = doc.clone();
     if k <= 1 {
@@ -76,7 +78,7 @@ pub fn proxy_document(doc: &Document, k: u32) -> Document {
     for c in &mut p.channels {
         c.surface = downsample(&c.surface, k);
     }
-    p.selection = None;
+    p.selection = p.selection.as_ref().map(|s| downsample(s, k));
     p
 }
 
@@ -120,4 +122,16 @@ mod tests {
         assert_eq!(p.layers[0].surface().unwrap().pixel(999, 749), vec![1.0; 4]);
         assert!(proxy_faithful(&doc));
     }
+
+    #[test]
+    fn proxy_scales_the_selection() {
+        let mut doc = Document::with_background("d", Size::new(64, 64), ColorMode::Rgb, SampleType::U8, Color::WHITE);
+        let mut sel = Surface::new(PixelFormat::GRAY8);
+        sel.fill_rect(Rect::new(0, 0, 32, 64), &[1.0]);
+        doc.selection = Some(sel);
+        let p = proxy_document(&doc, 4);
+        let s = p.selection.as_ref().expect("selection kept");
+        assert_eq!((s.pixel(7, 15)[0], s.pixel(8, 0)[0]), (1.0, 0.0));
+        assert!(proxy_document(&Document::new("n", Size::new(8, 8), ColorMode::Rgb, SampleType::U8), 4).selection.is_none());
+    }
 }

crates/ui-egui/src/filter_dialog.rs

@@ -550,4 +550,25 @@ mod tests {
         assert!(p[0] > 0.2 && p[0] < 0.8, "edge blurred: {p:?}");
         assert_eq!(label("wavelengthMin"), "Wavelength Min");
     }
+
+    #[test]
+    fn preview_stays_inside_the_selection_at_every_proxy_factor() {
+        use photocraft_doc::SampleType;
+        for depth in [SampleType::U8, SampleType::U16, SampleType::F32] {
+            let mut doc =
+                Document::with_background("p", photocraft_doc::Size::new(64, 64), photocraft_doc::ColorMode::Rgb, depth, photocraft_doc::Color::gray(0.5));
+            let bg = doc.layers[0].id;
+            let mut sel = photocraft_raster::Surface::new(photocraft_doc::PixelFormat::GRAY8);
+            sel.fill_rect(photocraft_geom::Rect::new(0, 0, 32, 64), &[1.0]);
+            doc.selection = Some(sel);
+            for k in [1, 2, 4] {
+                let out = preview_document(&doc, Some(bg), "filter.noise.addNoise", &json!({"amount": 100.0}), k).unwrap();
+                let s = out.layers[0].surface().unwrap();
+                let half = 32 / k as i32;
+                let changed = |x0: i32, x1: i32| (0..64 / k as i32).any(|y| (x0..x1).any(|x| s.pixel(x, y) != doc.layers[0].surface().unwrap().pixel(0, 0)));
+                assert!(changed(0, half), "{depth:?} k={k}: noise inside the selection");
+                assert!(!changed(half, 64 / k as i32), "{depth:?} k={k}: nothing outside the selection");
+            }
+        }
+    }
 }