Add code components 366-385; ScrollArea Follow, editor sync

A terminal with history, a Go-colored code block, a log viewer that
follows, a hex viewer, a memory map, a JSON tree, a line diff, a GAME
OVER crash screen, an FPS meter, profiler bars, breakpoints,
variables, command history, a shortcut list, a debug grid, a pixel
editor that exports string art, a palette editor, a sprite sheet, a
glyph map and a 6502 register view.

layout.ScrollArea takes Follow, and ChatLog now uses it. data.TreeNode
takes a Value drawn in its Slot. pixel gains Has, and Sprite.Art
writes MustSprite art. pixel.Editor takes the caller's value at each
input event, so a value changed between frames is never typed onto.

code/breakpoints.go

@@ -0,0 +1,77 @@
+package code
+
+import (
+	"fmt"
+	"log/slog"
+	"strconv"
+	"strings"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type BreakpointsOptions struct {
+	Disabled bool
+}
+
+type BreakpointsResult struct {
+	Element *ui.Element
+	Changed bool
+}
+
+type lineKey struct{}
+
+// Breakpoints shows code; a click or Enter toggles a dot.
+func Breakpoints(c *ui.Context, text, src string, marks map[int]bool, o BreakpointsOptions) BreakpointsResult {
+	k := pixel.K(c)
+	if marks == nil {
+		panic("code: Breakpoints needs a map of marks")
+	}
+	src = tidy(src)
+	lines, slots := strings.Split(src, "\n"), paint(src)
+	gutter := 10 + pixel.Measure(strconv.Itoa(len(lines))) + 6
+	w := 0
+	for _, l := range lines {
+		w = max(w, gutter+pixel.Measure(l)+4)
+	}
+	res := BreakpointsResult{Element: ui.Box(c)}
+	cur := ui.Local(res.Element, lineKey{}, func() int { return 0 })
+	*cur = min(*cur, len(lines)-1)
+	res.Element.Children(func() {
+		shell, base, st, picked := pixel.Pad(c, text, 1, len(lines), w, pixel.LineHeight, cur, o.Disabled)
+		if picked >= 0 {
+			n := picked + 1
+			marks[n], res.Changed = !marks[n], true
+			if !marks[n] {
+				delete(marks, n)
+			}
+			slog.Debug("8bit: breakpoints", "label", text, "line", n, "on", marks[n])
+		}
+		say := strconv.Itoa(*cur + 1)
+		if marks[*cur+1] {
+			say += ", " + k.Msg("breakpoint")
+		}
+		base.Description(fmt.Sprintf("%s: %s", say, lines[*cur]))
+		at := *cur
+		shell.Draw(func(p *ui.Painter, r ui.Rect) {
+			g := k.Canvas(p, r)
+			off := 0
+			for i, l := range lines {
+				y, from := i*pixel.LineHeight, off
+				off += len(l) + 1
+				if i == at && st.Focus {
+					g.Cursor(0, y, w, pixel.LineHeight)
+				}
+				if marks[i+1] {
+					g.Disc(5, y+6, 3, pixel.Bad)
+				}
+				n := strconv.Itoa(i + 1)
+				g.Text(gutter-6-pixel.Measure(n), y, n, pixel.Faint, 1)
+				colored(g, gutter, y, l, slots[from:from+len(l)])
+			}
+			g.Finish(st)
+		})
+	})
+	return res
+}