Audit keyboard, focus, veils, motion and clocks across all 500

A cross-cutting pass, each fix with a test that failed first.

Veils: MyGo still hands a key to a base that turned off this frame,
so every element key now goes through pixel.Shortcut, which an
archtest enforces. Input handlers record and the build applies them
only while enabled; the editor turns away a veil-frame letter or
copy; value bases get a copy and keep only enabled turns. Popups
give a held focus back to their opener when the veil lifts.

Motion: S5 is enforced at the clock. Every Tick, Since, Step,
Toward and Shot runs at 4-15 fps; blinks keep 1 Hz on 4 fps steps,
fast animations step at 15, and drawn time is quantized to frames.

Clocks stepping back: Since holds at zero without overflow, and
k.Elapsed moves a stored start to now, so nothing goes negative,
runs backward or indexes out of range.

Also: logs count typed text instead of holding it, gallery names
use glyphs the font has, removable rows are keyed, components take
their own Options (archtest), and sweeps over all 508 demos check
veiled keys, clicks, wheels, the clock stepping back and names.

navigation/documenttabs.go

@@ -1,6 +1,7 @@
 package navigation
 
 import (
+	"fmt"
 	"log/slog"
 
 	"github.com/egoist/mygo/ui"
@@ -30,35 +31,48 @@ type DocumentTabsResult struct {
 // DocumentTabs are closable tabs; × or Delete reports Closed.
 func DocumentTabs(c *ui.Context, text string, titles []string, selected *int, o DocumentTabsOptions) DocumentTabsResult {
 	k := pixel.K(c)
+	seen := map[string]bool{}
+	for _, t := range titles {
+		if seen[t] {
+			panic(fmt.Sprintf("navigation: DocumentTabs has %q twice", t))
+		}
+		seen[t] = true
+	}
 	res := DocumentTabsResult{Closed: -1}
-	p := ui.TabsBase(c, selected, len(titles))
+	// The base turns before it learns it is off.
+	v := *selected
+	p := ui.TabsBase(c, &v, len(titles))
 	p.List.Label(text).Children(func() {
 		for i, t := range titles {
-			var x *ui.Element
-			shell, base, st := pixel.Shell(c, func() *ui.Element {
-				tab := p.Tab(i).Label(t).Disabled(o.Disabled)
-				// The × is no Tab stop; Delete closes by keyboard.
-				tab.Children(func() {
-					x = ui.Box(c).Absolute().Right(k.D(4)).Top(k.D(6)).Size(k.D(7), k.D(7)).Role(ui.RoleButton).Label(k.Msg("close") + " " + t)
+			// Keyed by title, so focus follows its tab.
+			ui.Box(c).Key(t).Children(func() {
+				var x *ui.Element
+				shell, base, st := pixel.Shell(c, func() *ui.Element {
+					tab := p.Tab(i).Label(t).Disabled(o.Disabled)
+					// The × is no Tab stop; Delete closes by keyboard.
+					tab.Children(func() {
+						x = ui.Box(c).Absolute().Right(k.D(4)).Top(k.D(6)).Size(k.D(7), k.D(7)).Role(ui.RoleButton).Label(k.Msg("close") + " " + t)
+					})
+					return tab
 				})
-				return tab
-			})
-			if x.Clicked() || base.Shortcut(0, ui.KeyDelete) {
-				res.Closed = i
-			}
-			hot := x.Hovered()
-			shell.Size(k.D(pixel.Measure(t)+24), k.D(pixel.LineHeight+6)).Draw(func(p *ui.Painter, r ui.Rect) {
-				g := k.Canvas(p, r)
-				folder(g, t, i == *selected, false, st)
-				ink := pixel.Faint
-				if hot {
-					ink = pixel.Bad
+				del := pixel.Shortcut(base, 0, ui.KeyDelete)
+				if x.Clicked() || del {
+					res.Closed = i
 				}
-				g.Sprite(g.W-10, 7, cross, 0, ink, 1)
+				hot := x.Hovered()
+				shell.Size(k.D(pixel.Measure(t)+24), k.D(pixel.LineHeight+6)).Draw(func(p *ui.Painter, r ui.Rect) {
+					g := k.Canvas(p, r)
+					folder(g, t, i == *selected, false, st)
+					ink := pixel.Faint
+					if hot {
+						ink = pixel.Bad
+					}
+					g.Sprite(g.W-10, 7, cross, 0, ink, 1)
+				})
 			})
 		}
 	})
-	res.Element, res.Changed = p.List, p.List.Changed()
+	res.Element, res.Changed = p.List, keep(c, v, selected, o.Disabled)
 	if res.Closed >= 0 {
 		slog.Debug("8bit: tab closed", "label", text, "tab", titles[res.Closed])
 	}