WIP components (as built)

remote_cursor.go

@@ -0,0 +1,85 @@
+package mujica
+
+import (
+	"fmt"
+	"hash/fnv"
+	"strings"
+
+	"github.com/egoist/mygo/ui"
+
+	"mujicaui/internal"
+	"mujicaui/theme"
+)
+
+// RemoteCaret describes a collaborator's caret and selection offsets.
+type RemoteCaret struct {
+	ID, Name string
+	// Offset and Anchor bound the selection, equal for a caret.
+	Offset, Anchor int
+}
+
+// RemoteCursorOptions configure RemoteCursor.
+type RemoteCursorOptions struct {
+	// Caret maps text offsets into overlay-relative rectangles; required.
+	Caret func(offset int) ui.Rect
+	// Selection maps offset ranges into overlay-relative rectangles; optional.
+	Selection func(from, to int) []ui.Rect
+}
+
+// RemoteCursor overlays collaborator carets, selections and names; input passes through.
+// Place it filling the editor's box, after the editor.
+func RemoteCursor(c *ui.Context, carets []RemoteCaret, opts RemoteCursorOptions) *ui.Element {
+	if opts.Caret == nil {
+		panic("mujica: RemoteCursor needs Caret")
+	}
+	k := Tokens(c)
+	names := make([]string, len(carets))
+	for i, rc := range carets {
+		if rc.ID == "" || rc.Offset < 0 || rc.Anchor < 0 {
+			panic("mujica: RemoteCaret needs an ID and offsets not negative")
+		}
+		names[i] = rc.Name
+	}
+	size := FontSize(c, theme.CaptionSize)
+	e := ui.Box(c).Absolute().Top(0).Left(0).Right(0).Bottom(0).PassThrough().Clip().Role(ui.RoleNone)
+	if len(carets) > 0 {
+		e.Role(ui.RoleStatus).Label(fmt.Sprintf(msg(c, "remote_cursor.label"), strings.Join(names, ", ")))
+	}
+	return e.Draw(func(p *ui.Painter, r ui.Rect) {
+		for _, rc := range carets {
+			col := remoteColor(k, rc.ID)
+			if opts.Selection != nil && rc.Anchor != rc.Offset {
+				for _, b := range opts.Selection(min(rc.Anchor, rc.Offset), max(rc.Anchor, rc.Offset)) {
+					p.Fill(remoteRect(p, ui.Rect{X: r.X + b.X, Y: r.Y + b.Y, W: b.W, H: b.H}), col.Alpha(0.22), 2)
+				}
+			}
+			cb := opts.Caret(rc.Offset)
+			x, y := internal.Snap(p, r.X+cb.X), internal.Snap(p, r.Y+cb.Y)
+			p.Fill(ui.Rect{X: x - 1, Y: y, W: 2, H: cb.H}, col, 0)
+			// Keep the name flag inside the overlay.
+			tw, th := p.MeasureText(0, ui.Span{Text: rc.Name, Size: size})
+			flag := ui.Rect{X: x - 1, Y: y - th - 2, W: min(tw+8, r.W), H: th + 2}
+			if flag.Y < r.Y {
+				flag.Y = y + cb.H
+			}
+			flag.X = max(r.X, min(flag.X, r.X+r.W-flag.W))
+			flag.Y = max(r.Y, min(flag.Y, r.Y+r.H-flag.H))
+			flag = remoteRect(p, flag)
+			p.Fill(flag, col, 2)
+			p.Clip(flag, 2, func() { p.Text(flag.X+4, flag.Y+1, rc.Name, size, k.Surface) })
+		}
+	})
+}
+
+func remoteRect(p *ui.Painter, r ui.Rect) ui.Rect {
+	x, y := internal.Snap(p, r.X), internal.Snap(p, r.Y)
+	return ui.Rect{X: x, Y: y, W: internal.Snap(p, r.X+r.W) - x, H: internal.Snap(p, r.Y+r.H) - y}
+}
+
+// remoteColor assigns a palette color by collaborator ID.
+func remoteColor(k theme.Tokens, id string) ui.Color {
+	h := fnv.New32a()
+	h.Write([]byte(id))
+	pal := flamegraphPalette(k)
+	return pal[h.Sum32()%uint32(len(pal))]
+}