Add vim-key navigation to the hexdumper widget

This is a hand-coded widget that does not rely on standard composite
widgets. That was done because constructing the hexdumper widget using
dozens of piles and columns for capturing each hex byte resulted in a
sluggish experience on slow machines like the raspberry pi. So, I need
to manually add vim-key navigation.

widgets/hexdumper2/hexdumper2.go

@@ -15,6 +15,7 @@ import (
 
 	"github.com/gcla/gowid"
 	"github.com/gcla/gowid/gwutil"
+	"github.com/gcla/gowid/vim"
 	"github.com/gcla/gowid/widgets/list"
 	"github.com/gcla/gowid/widgets/styled"
 	"github.com/gcla/termshark/v2/format"
@@ -41,6 +42,10 @@ type Options struct {
 	LineNumUnselected string
 	LineNumSelected   string
 	PaletteIfCopying  string
+	DownKeys          []vim.KeyPress
+	UpKeys            []vim.KeyPress
+	LeftKeys          []vim.KeyPress
+	RightKeys         []vim.KeyPress
 }
 
 type Widget struct {
@@ -53,6 +58,7 @@ type Widget struct {
 	lineNumSelected   string
 	offset            int // scroll position, bit of a hack
 	paletteIfCopying  string
+	opt               Options
 	gowid.AddressProvidesID
 	styled.UsePaletteIfSelectedForCopy
 	Callbacks *gowid.Callbacks
@@ -72,6 +78,19 @@ func New(data []byte, opts ...Options) *Widget {
 		opt = opts[0]
 	}
 
+	if opt.DownKeys == nil {
+		opt.DownKeys = vim.AllDownKeys
+	}
+	if opt.UpKeys == nil {
+		opt.UpKeys = vim.AllUpKeys
+	}
+	if opt.LeftKeys == nil {
+		opt.LeftKeys = vim.AllLeftKeys
+	}
+	if opt.RightKeys == nil {
+		opt.RightKeys = vim.AllRightKeys
+	}
+
 	res := &Widget{
 		data:                        data,
 		layers:                      opt.StyledLayers,
@@ -81,6 +100,7 @@ func New(data []byte, opts ...Options) *Widget {
 		lineNumSelected:             opt.LineNumSelected,
 		paletteIfCopying:            opt.PaletteIfCopying,
 		UsePaletteIfSelectedForCopy: styled.UsePaletteIfSelectedForCopy{Entry: opt.PaletteIfCopying},
+		opt:                         opt,
 		Callbacks:                   gowid.NewCallbacks(),
 	}
 
@@ -459,23 +479,23 @@ func (w *Widget) realUserInput(ev interface{}, size gowid.IRenderSize, focus gow
 	switch ev := ev.(type) {
 	case *tcell.EventKey:
 
-		switch ev.Key() {
-		case tcell.KeyRight, tcell.KeyCtrlF:
+		switch {
+		case vim.KeyIn(ev, w.opt.RightKeys):
 			//res = Scroll(w, 1, w.Wrap(), app)
 			pos := w.Position()
 			if pos < len(w.data) {
 				w.SetPosition(pos+1, app)
 				res = true
 			}
-		case tcell.KeyLeft, tcell.KeyCtrlB:
+		case vim.KeyIn(ev, w.opt.LeftKeys):
 			pos := w.Position()
 			if pos > 0 {
 				w.SetPosition(pos-1, app)
 				res = true
 			}
-		case tcell.KeyDown, tcell.KeyCtrlN:
+		case vim.KeyIn(ev, w.opt.DownKeys):
 			scrollDown = true
-		case tcell.KeyUp, tcell.KeyCtrlP:
+		case vim.KeyIn(ev, w.opt.UpKeys):
 			scrollUp = true
 		}