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.

data/treevalue_test.go

@@ -0,0 +1,40 @@
+package data_test
+
+import (
+	"testing"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/data"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+func TestTreeDrawsValuesInTheirSlot(t *testing.T) {
+	sel := "0"
+	roots := []data.TreeNode{{Label: "name", Value: `"Aria"`, Slot: pixel.Good}, {Label: "hp", Value: "42", Slot: pixel.Warn}}
+	tt := view(300, 200, newClock(), false, func(c *ui.Context) {
+		data.Tree(c, "Doc", roots, &sel, data.TreeOptions{})
+	})
+	r, img := find(t, tt, "Doc"), tt.Image()
+	count := func(row int, s pixel.Slot) int {
+		n, want := 0, pixel.SpringDay.Colors[s]
+		for y := int(r.Y) + row*2*pixel.LineHeight; y < int(r.Y)+(row+1)*2*pixel.LineHeight; y++ {
+			for x := int(r.X); x < int(r.X+r.W); x++ {
+				if c := img.RGBAAt(x, y); c.R == want.R && c.G == want.G && c.B == want.B {
+					n++
+				}
+			}
+		}
+		return n
+	}
+	// The chosen row inks its value; the other keeps Warn.
+	if count(0, pixel.Good) != 0 || count(1, pixel.Warn) == 0 {
+		t.Fatalf("values: Good on the chosen row %d, Warn below %d", count(0, pixel.Good), count(1, pixel.Warn))
+	}
+	// A click on the middle chooses the second row.
+	click(t, tt, "Doc")
+	img = tt.Image()
+	if sel != "1" || count(0, pixel.Good) == 0 || count(1, pixel.Warn) != 0 {
+		t.Fatalf("choosing hp (%q) did not swap which value is inked", sel)
+	}
+}