About: refit credits tables when what they measure changes

The columns became resizable, so the table keeps its own widths. A longer
name, a changed cell or a resized window left the old widths in place and
clipped text. The table now goes back to its fit when a column measure or
the clip rect width changes, which scrolling never moves.

Adds tests that drag every column edge, change the fit and scroll a
widened table, as CodeRabbit asked for the drag.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/dialogs/credits.rs

@@ -343,15 +343,17 @@ fn column_width<'a>(ui: &egui::Ui, header: &str, cells: impl Iterator<Item = &'a
 }
 
 /// A credits table: columns of `widths`, the `None` one taking what the others leave (at least
-/// `flex_min`). The header stays put while the rows scroll, within `height` (header included). Too
+/// [`NAME_MIN_W`]). The header stays put while the rows scroll, within `height` (header included). Too
 /// narrow for every column, it scrolls sideways rather than clip one. Every
-/// column edge can be dragged, down to [`MIN_COLUMN`] (the `None` column to `flex_min`): widening
-/// a column grows the table, as in a spreadsheet, and only then does it scroll sideways.
+/// column edge can be dragged, down to [`MIN_COLUMN`] (the `None` column to [`NAME_MIN_W`]): widening
+/// a column grows the table, as in a spreadsheet, and only then does it scroll sideways. When the
+/// window, a column's width or `flex_text` (the width the `None` column's text needs) changes, the
+/// columns go back to this fit, dropping any dragged widths.
 fn credits_table(
     ui: &mut egui::Ui,
     id: &str,
     widths: &[Option<f32>],
-    flex_min: f32,
+    flex_text: f32,
     height: f32,
     header: impl FnOnce(egui_extras::TableRow<'_, '_>),
     body: impl FnOnce(egui_extras::TableBody<'_>),
@@ -362,9 +364,16 @@ fn credits_table(
     // The table puts a row gap under its header.
     let body_h = (height - TABLE_HEADER_H - ui.spacing().item_spacing.y).max(TABLE_ROW_H);
     egui::ScrollArea::horizontal().id_salt((id, "h")).auto_shrink([false, true]).show(ui, |ui| {
-        let flex = (ui.available_width() - fixed).max(flex_min);
+        let flex = (ui.available_width() - fixed).max(NAME_MIN_W);
         // No gaps between cells: their padding spaces them, and the header rule runs unbroken.
         ui.spacing_mut().item_spacing.x = 0.0;
+        // The table keeps its own column widths, so a change in what they were fitted to has to clear
+        // them. Scrolling can nudge the available width, so this compares the clip rect, which scrolling
+        // never moves.
+        let fit = egui::Id::unique(("credits_fit", id));
+        let measured = (widths.to_vec(), flex_text, ui.clip_rect().width());
+        let refit = ui.data_mut(|d| d.get_temp::<(Vec<Option<f32>>, f32, f32)>(fit)).as_ref() != Some(&measured);
+        ui.data_mut(|d| d.insert_temp(fit, measured));
         let mut b = egui_extras::TableBuilder::new(ui)
             .id_salt(id)
             .striped(true)
@@ -373,10 +382,13 @@ fn credits_table(
             .min_scrolled_height(body_h)
             .max_scroll_height(body_h)
             .cell_layout(egui::Layout::left_to_right(egui::Align::Center));
+        if refit {
+            b.reset();
+        }
         for w in widths {
             b = b.column(match w {
                 Some(w) => egui_extras::Column::initial(*w).at_least(MIN_COLUMN).clip(true),
-                None => egui_extras::Column::initial(flex).at_least(flex_min).clip(true),
+                None => egui_extras::Column::initial(flex).at_least(NAME_MIN_W).clip(true),
             });
         }
         b.header(TABLE_HEADER_H, header).body(body);
@@ -399,11 +411,13 @@ fn table(ui: &mut egui::Ui, list: &[&Contributor], v: &mut View, height: f32) {
     let t = Tokens::get(ui.ctx());
     let names = v.names;
     let widths = contributor_widths(ui, list);
+    let shown: Vec<String> = list.iter().map(|c| c.name(names)).collect();
+    let name_text = column_width(ui, SortKey::Name.label().1, shown.iter().map(String::as_str));
     credits_table(
         ui,
         "credits_table",
         &widths,
-        NAME_MIN_W,
+        name_text,
         height,
         |mut header| {
             for k in SortKey::ALL {
@@ -526,12 +540,13 @@ fn models_in(ui: &mut egui::Ui, models: &[Model], total_commits: u64) {
     let total = total_commits.max(models.iter().map(|m| m.commits).max().unwrap_or(0));
     let rows: Vec<[String; 6]> = models.iter().map(|m| model_cells(m, total)).collect();
     let widths = model_widths(ui, &rows);
+    let model_text = column_width(ui, tr(MODEL_HEADS[1]), rows.iter().filter_map(|r| r.get(1)).map(String::as_str));
     let numeric = |i: usize| i >= 3;
     credits_table(
         ui,
         "credits_models",
         &widths,
-        NAME_MIN_W,
+        model_text,
         table_height(ui, rows.len()),
         |mut header| {
             for (i, h) in MODEL_HEADS.iter().enumerate() {

crates/ui-egui/src/dialogs/credits/ui_tests.rs

@@ -267,3 +267,121 @@ fn the_about_window_draws_every_tab() {
         assert_eq!(app.ui.about_tab, tab);
     }
 }
+
+const WINDOW: f32 = 640.5;
+const WIDTHS: [Option<f32>; 3] = [None, Some(80.0), Some(80.0)];
+const NAME: f32 = 120.0;
+
+/// One frame of a table long enough to scroll, in a window `width` wide; the rects of its header cells.
+fn table_frame(ctx: &egui::Context, width: f32, widths: &[Option<f32>], name: f32, events: Vec<egui::Event>) -> Vec<Rect> {
+    let screen_rect = Some(Rect::from_min_size(egui::Pos2::ZERO, vec2(width, 300.0)));
+    let raw = egui::RawInput { screen_rect, events, ..Default::default() };
+    let mut cells = Vec::new();
+    let out = ctx.run_ui(raw, |ui| {
+        cells.clear();
+        credits_table(
+            ui,
+            "test",
+            widths,
+            name,
+            240.0,
+            |mut header| {
+                for _ in widths {
+                    header.col(|ui| cells.push(ui.max_rect()));
+                }
+            },
+            |body| {
+                body.rows(TABLE_ROW_H, 40, |mut row| {
+                    for _ in widths {
+                        row.col(|ui| {
+                            ui.label("x");
+                        });
+                    }
+                });
+            },
+        );
+    });
+    out.drop_without_applying_deltas();
+    cells
+}
+
+/// [`table_frame`] at the usual size.
+fn settled_frame(ctx: &egui::Context) -> Vec<Rect> {
+    table_frame(ctx, WINDOW, &WIDTHS, NAME, Vec::new())
+}
+
+/// A new context with the table open and settled, and the rects of its header cells.
+fn opened_table() -> (egui::Context, Vec<Rect>) {
+    let ctx = egui::Context::default();
+    settled_frame(&ctx);
+    let cells = settled_frame(&ctx);
+    (ctx, cells)
+}
+
+/// Drags a column's right edge (cells have no gap between them), then lets go.
+fn drag_edge(ctx: &egui::Context, cell: Rect, by: f32) {
+    let start = egui::pos2(cell.right(), cell.center().y);
+    let halfway = start + vec2(by / 2.0, 0.0);
+    let end = start + vec2(by, 0.0);
+    let moved = egui::Event::PointerMoved;
+    let button = |pos, pressed| egui::Event::PointerButton { pos, button: egui::PointerButton::Primary, pressed, modifiers: egui::Modifiers::NONE };
+    for event in [moved(start), button(start, true), moved(halfway), moved(end), button(end, false)] {
+        table_frame(ctx, WINDOW, &WIDTHS, NAME, vec![event]);
+    }
+}
+
+#[test]
+fn every_column_can_be_dragged_at_its_right_edge_and_stays_there() {
+    let (_, opened) = opened_table();
+    for (dragged, cell) in opened.iter().enumerate() {
+        let (ctx, _) = opened_table();
+        drag_edge(&ctx, *cell, -30.0);
+        settled_frame(&ctx);
+        let after = settled_frame(&ctx);
+        for (column, (was, now)) in opened.iter().zip(&after).enumerate() {
+            let want = if column == dragged { was.width() - 30.0 } else { was.width() };
+            assert!((now.width() - want).abs() < 1.0, "dragging column {dragged}: column {column} is {now:?}, was {was:?}");
+        }
+    }
+}
+
+#[test]
+fn a_changed_fit_replaces_the_column_widths() {
+    let (ctx, opened) = opened_table();
+    drag_edge(&ctx, opened[0], -30.0);
+    let longer_name = table_frame(&ctx, WINDOW, &WIDTHS, NAME + 80.0, Vec::new());
+    assert!((longer_name[0].width() - opened[0].width()).abs() < 1.0, "a longer name drops a dragged width: {longer_name:?}");
+    let wider = table_frame(&ctx, WINDOW, &[None, Some(200.0), Some(80.0)], NAME, Vec::new());
+    let widths: Vec<f32> = wider.iter().map(|c| c.width().round()).collect();
+    assert!(widths.ends_with(&[200.0, 80.0]), "a longer cell widens its column: {widths:?}");
+    assert!(wider[2].right() < WINDOW, "the table still fits the window: {wider:?}");
+    let narrower = table_frame(&ctx, 400.0, &WIDTHS, NAME, Vec::new());
+    assert!(narrower[2].right() < 400.0, "a narrower window refits the table: {narrower:?}");
+}
+
+#[test]
+fn scrolling_sideways_keeps_dragged_widths() {
+    let (ctx, opened) = opened_table();
+    drag_edge(&ctx, opened[0], 100.0);
+    settled_frame(&ctx);
+    let dragged = settled_frame(&ctx);
+    assert!((dragged[0].width() - opened[0].width() - 100.0).abs() < 1.0, "the drag took: {dragged:?}");
+    table_frame(&ctx, WINDOW, &WIDTHS, NAME, vec![egui::Event::PointerMoved(dragged[0].center())]);
+    let mut scrolled = false;
+    for delta in [-13.3, -27.77, -41.1, 30.6] {
+        let wheel = egui::Event::MouseWheel {
+            source: egui::MouseWheelSource::Unknown,
+            unit: egui::MouseWheelUnit::Point,
+            delta: vec2(delta, 0.0),
+            modifiers: egui::Modifiers::NONE,
+            phase: egui::TouchPhase::Move,
+        };
+        table_frame(&ctx, WINDOW, &WIDTHS, NAME, vec![wheel]);
+        for _ in 0..8 {
+            let cells = settled_frame(&ctx);
+            assert!((cells[0].width() - dragged[0].width()).abs() < 1.0, "scrolled by {delta}: {cells:?}");
+            scrolled |= cells[0].left() < dragged[0].left() - 1.0;
+        }
+    }
+    assert!(scrolled, "the wheel never moved the table sideways");
+}