Fix #5750: style-set gallery follows RTL interface direction (#5857)

crates/ui-egui/src/previews.rs

@@ -694,7 +694,7 @@ pub fn style_gallery(app: &mut WordApp, ui: &mut Ui, state: &Value) {
 /// Style sets shown in the Design tab's gallery, in order.
 const STYLE_SETS: [&str; 7] = ["default", "basic", "lines", "shaded", "casual", "centered", "minimalist"];
 /// Width of one gallery thumbnail, points.
-const STYLE_SET_W: f32 = 56.0;
+pub const STYLE_SET_W: f32 = 56.0;
 /// Width the whole gallery takes with the ribbon's 1 pt item spacing.
 pub const STYLE_SET_GALLERY_W: f32 = STYLE_SETS.len() as f32 * (STYLE_SET_W + 1.0) - 1.0;
 

crates/ui-egui/src/ribbon/design.rs

@@ -3,11 +3,12 @@ use super::{CONTENT_H, Rect, Sense, Target, Ui, WordApp, big, group, json, menu_
 
 /// The Design tab's style set gallery in a box of its own, sized from its thumbnails and clipped
 /// to it, with a gap on each side: the Colors and Fonts column can't be drawn over, or cut by,
-/// the thumbnails (#638). Returns the box and the space the thumbnails used.
+/// the thumbnails (#638). In a right-to-left interface, the thumbnails lay out from the right
+/// (#5750). Returns the box and the space the thumbnails used.
 pub(super) fn style_set_box(app: &mut WordApp, ui: &mut Ui) -> (Rect, Rect) {
     ui.add_space(4.0);
     let (gallery, _) = ui.allocate_exact_size(vec2(crate::previews::STYLE_SET_GALLERY_W, CONTENT_H), Sense::hover());
-    let mut gui = ui.new_child(egui::UiBuilder::new().max_rect(gallery).layout(egui::Layout::left_to_right(egui::Align::Min)));
+    let mut gui = ui.new_child(egui::UiBuilder::new().max_rect(gallery).layout(crate::rtl::row_layout(ui, egui::Align::Min)));
     gui.set_clip_rect(gallery.intersect(ui.clip_rect()));
     gui.spacing_mut().item_spacing = vec2(1.0, 1.0);
     crate::previews::style_set_gallery(app, &mut gui);

crates/ui-egui/src/ribbon/tests.rs

@@ -113,6 +113,49 @@ fn design_style_set_gallery_stays_in_its_box() {
     assert!(next_x >= gallery.right() + 8.0 - 0.01, "{next_x} {gallery:?}");
 }
 
+/// #5750: in a right-to-left interface, the Design tab's style-set gallery lays out from the
+/// right: the first style set ("default") is at the right edge, the remaining thumbnails read to
+/// the left, and the next controls start after a gap to the left of the gallery.
+#[test]
+fn design_style_set_gallery_reads_from_the_right_in_rtl() {
+    crate::i18n::set_current(crate::i18n::fixture_lang("ar", "\tHome\tالرئيسية\n"));
+    let mut app = WordApp::new(Session::new(wordcraft_doc::Document::new()), crate::Services::default());
+    let mut seen = None;
+    let mut h = egui_kittest::Harness::builder().with_size(vec2(1440.0, 200.0)).build_ui(|ui| {
+        crate::rtl::root(ui, |ui| {
+            crate::rtl::horizontal_top(ui, |ui| {
+                let (gallery, used) = style_set_box(&mut app, ui);
+                seen = Some((gallery, used, ui.cursor().max.x));
+            });
+        });
+    });
+    h.run_steps(2);
+    let tiles: Vec<Rect> = h.ctx.viewport(|v| {
+        v.prev_pass
+            .widgets
+            .layers()
+            .flat_map(|(_, w)| w.iter())
+            .filter(|w| (w.rect.width() - crate::previews::STYLE_SET_W).abs() < 0.1 && (w.rect.height() - CONTENT_H).abs() < 0.1)
+            .map(|w| w.rect)
+            .collect()
+    });
+    drop(h);
+    crate::i18n::set_current(crate::i18n::Lang::EN);
+
+    let (gallery, used, next_x) = seen.unwrap();
+    assert!((gallery.width() - crate::previews::STYLE_SET_GALLERY_W).abs() < 0.01);
+    assert!(used.left() >= gallery.left() - 0.01, "{used:?} {gallery:?}");
+    assert!(used.right() <= gallery.right() + 0.01, "{used:?} {gallery:?}");
+    assert!(next_x <= gallery.left() - 8.0 + 0.01, "{next_x} {gallery:?}");
+
+    assert_eq!(tiles.len(), 7, "7 style set tiles");
+    assert!((tiles[0].right() - gallery.right()).abs() < 0.01, "default tile at the right edge: {tiles:?} {gallery:?}");
+    assert!((tiles[6].left() - gallery.left()).abs() < 0.01, "minimalist tile at the left edge: {tiles:?} {gallery:?}");
+    for i in 1..tiles.len() {
+        assert!(tiles[i].right() <= tiles[i - 1].left(), "tile {i} is to the left of tile {}", i - 1);
+    }
+}
+
 /// #2738: Home › Underline's drop-down: every line sample is a named entry (assistive
 /// technology, tooltips) that applies its own style; Words only, None and Underline Color ›
 /// Automatic do what they say.