A widget to translate specific keys into key sequences

This package provides a widget that can map one keypress to a sequence
of keypresses. If the user pnovides as input a key that is mapped, the
sequence of resulting keypresses is played to the subwidget before
control returns. If the key is not mapped, it is passed through as
normal. I'm going to use this to provide a vim-like macro feature in
termshark.

widgets/mapkeys/mapkeys.go

@@ -0,0 +1,75 @@
+// Copyright 2019-2020 Graham Clark. All rights reserved.  Use of this source
+// code is governed by the MIT license that can be found in the LICENSE
+// file.
+
+// Package mapkeys provides a widget that can map one keypress to a sequence of
+// keypresses. If the user pnovides as input a key that is mapped, the sequence of
+// resulting keypresses is played to the subwidget before control returns. If the key is
+// not mapped, it is passed through as normal. I'm going to use this to provide a vim-like
+// macro feature in termshark.
+package mapkeys
+
+import (
+	"github.com/gcla/gowid"
+	"github.com/gcla/gowid/vim"
+	"github.com/gdamore/tcell"
+)
+
+//======================================================================
+
+type Widget struct {
+	gowid.IWidget
+	kmap map[vim.KeyPress]vim.KeySequence
+}
+
+var _ gowid.IWidget = (*Widget)(nil)
+
+func New(w gowid.IWidget) *Widget {
+	res := &Widget{
+		IWidget: w,
+		kmap:    make(map[vim.KeyPress]vim.KeySequence),
+	}
+	return res
+}
+
+func (w *Widget) UserInput(ev interface{}, size gowid.IRenderSize, focus gowid.Selector, app gowid.IApp) bool {
+	switch ev := ev.(type) {
+	case *tcell.EventKey:
+		kp := vim.KeyPressFromTcell(ev)
+		if seq, ok := w.kmap[kp]; ok {
+			var res bool
+			for _, k := range seq {
+				// What should the handled value be??
+				res = w.IWidget.UserInput(tcell.NewEventKey(k.Key, k.Ch, k.Mod), size, focus, app)
+			}
+			return res
+		} else {
+			return w.IWidget.UserInput(ev, size, focus, app)
+		}
+	default:
+		return w.IWidget.UserInput(ev, size, focus, app)
+	}
+}
+
+func (w *Widget) AddMapping(from vim.KeyPress, to vim.KeySequence, app gowid.IApp) {
+	w.kmap[from] = to
+}
+
+func (w *Widget) RemoveMapping(from vim.KeyPress, app gowid.IApp) {
+	delete(w.kmap, from)
+}
+
+// ClearMappings will remove all mappings. I deliberately preserve the same dictionary,
+// though in case I decide in the future it's useful to let clients have direct access to
+// the map (and so maybe store it somewhere).
+func (w *Widget) ClearMappings(app gowid.IApp) {
+	for k := range w.kmap {
+		delete(w.kmap, k)
+	}
+}
+
+//======================================================================
+// Local Variables:
+// mode: Go
+// fill-column: 90
+// End: