Add files components 406-420; Tree opens to a known choice

Fifteen file components: FileExplorer, FileGrid, FileIcon, PathBar,
MemoryCard, DiskUsage, UploadQueue, Trash, RecentFiles, FilePreview,
ArchiveViewer, FileDetails, SharePanel, SyncStatus and QuotaMeter.

FileIcon draws six kinds as hand-placed 12x12 pages and a folder. The
browsers build on data.Tree, List, GridView and Table; ArchiveViewer
owns its sort and keeps the caller's index on its entry. UploadQueue
keys rows by name so focus stays on its row. SharePanel never logs the
link. SyncStatus turns its arrows on Busy steps, so syncing moves under
Reduce Motion.

data.Tree now opens the closed branches above a chosen path it knows,
so a caller's starting path survives the first frame.

files/filepreview.go

@@ -0,0 +1,63 @@
+package files
+
+import (
+	"image"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/display"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/layout"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+// Preview is what a file shows: a picture, else text.
+type Preview struct {
+	Picture image.Image
+	Text    string
+}
+
+type FilePreviewOptions struct {
+	// W and H are dots; zeros mean 160 and 120.
+	W, H int
+}
+
+type previewKey struct{}
+
+// FilePreview shows a picture, else text, in a sunken pane.
+func FilePreview(c *ui.Context, name string, pv Preview, o FilePreviewOptions) *ui.Element {
+	k := pixel.K(c)
+	w, h := pixel.Or("FilePreview W", o.W, 160), pixel.Or("FilePreview H", o.H, 120)
+	return ui.Column(c).Gap(k.D(2)).AlignItems(ui.Start).Role(ui.RoleGroup).Label(name).Children(func() {
+		// The group says the name; the title only shows it.
+		ui.Box(c).Size(k.D(pixel.Measure(name)), k.D(pixel.LineHeight)).Draw(func(p *ui.Painter, r ui.Rect) {
+			k.Canvas(p, r).Text(0, 0, name, pixel.Faint, 1)
+		})
+		layout.Panel(c, layout.PanelOptions{Style: pixel.Sunken, Fill: pixel.Well, Padding: 2}, func() {
+			pane := ui.Column(c).Size(k.D(w), k.D(h)).AlignItems(ui.Center).Justify(ui.Center)
+			pane.Children(func() {
+				switch {
+				case pv.Picture != nil:
+					pw, ph := fit(pv.Picture.Bounds(), w, h)
+					display.Picture(c, pv.Picture, display.PictureOptions{W: pw, H: ph, Label: k.Msg("preview")})
+				case pv.Text != "":
+					s := ui.Local(pane, previewKey{}, func() ui.ScrollState { return ui.ScrollState{} })
+					layout.ScrollArea(c, s, layout.ScrollAreaOptions{Label: k.Msg("preview")}, func() {
+						pixel.Text(c, pv.Text, pixel.TextOptions{Wrap: true})
+					}).Element.Size(k.D(w), k.D(h))
+				default:
+					pixel.Text(c, k.Msg("no_preview"), pixel.TextOptions{Slot: pixel.Faint})
+				}
+			})
+		})
+	})
+}
+
+// fit scales b into w×h: whole steps up, any down.
+func fit(b image.Rectangle, w, h int) (int, int) {
+	bw, bh := max(1, b.Dx()), max(1, b.Dy())
+	s := min(float64(w)/float64(bw), float64(h)/float64(bh))
+	if s >= 1 {
+		s = float64(int(s))
+	}
+	return max(1, int(float64(bw)*s)), max(1, int(float64(bh)*s))
+}