Added Alt-Backspace to text area. Also added a text area demo.

demos/textarea/README.md

@@ -0,0 +1 @@
+![Screenshot](screenshot.png)

demos/textarea/main.go

@@ -0,0 +1,133 @@
+// Demo code for the TextArea primitive.
+package main
+
+import (
+	"fmt"
+
+	"github.com/gdamore/tcell/v2"
+	"github.com/rivo/tview"
+)
+
+func main() {
+	app := tview.NewApplication()
+
+	textArea := tview.NewTextArea().
+		SetPlaceholder("Enter text here...")
+	textArea.SetTitle("Text Area").SetBorder(true)
+	helpInfo := tview.NewTextView().
+		SetText(" Press F1 for help, press Ctrl-C to exit")
+	position := tview.NewTextView().
+		SetDynamicColors(true).
+		SetTextAlign(tview.AlignRight)
+	pages := tview.NewPages()
+
+	updateInfos := func() {
+		fromRow, fromColumn, toRow, toColumn := textArea.GetCursor()
+		if fromRow == toRow && fromColumn == toColumn {
+			position.SetText(fmt.Sprintf("Row: [yellow]%d[white], Column: [yellow]%d ", fromRow, fromColumn))
+		} else {
+			position.SetText(fmt.Sprintf("[red]From[white] Row: [yellow]%d[white], Column: [yellow]%d[white] - [red]To[white] Row: [yellow]%d[white], To Column: [yellow]%d ", fromRow, fromColumn, toRow, toColumn))
+		}
+	}
+
+	textArea.SetMovedFunc(updateInfos)
+	updateInfos()
+
+	mainView := tview.NewGrid().
+		SetRows(0, 1).
+		AddItem(textArea, 0, 0, 1, 2, 0, 0, true).
+		AddItem(helpInfo, 1, 0, 1, 1, 0, 0, false).
+		AddItem(position, 1, 1, 1, 1, 0, 0, false)
+
+	help1 := tview.NewTextView().
+		SetDynamicColors(true).
+		SetText(`[green]Navigation
+
+[yellow]Left arrow[white]: Move left.
+[yellow]Right arrow[white]: Move right.
+[yellow]Down arrow[white]: Move down.
+[yellow]Up arrow[white]: Move up.
+[yellow]Ctrl-A, Home[white]: Move to the beginning of the current line.
+[yellow]Ctrl-E, End[white]: Move to the end of the current line.
+[yellow]Ctrl-F, page down[white]: Move down by one page.
+[yellow]Ctrl-B, page up[white]: Move up by one page.
+[yellow]Alt-Up arrow[white]: Scroll the page up.
+[yellow]Alt-Down arrow[white]: Scroll the page down.
+[yellow]Alt-Left arrow[white]: Scroll the page to the left.
+[yellow]Alt-Right arrow[white]:  Scroll the page to the right.
+[yellow]Alt-B, Ctrl-Left arrow[white]: Move back by one word.
+[yellow]Alt-F, Ctrl-Right arrow[white]: Move forward by one word.
+
+[blue]Press Enter for more help, press Escape to return.`)
+	help2 := tview.NewTextView().
+		SetDynamicColors(true).
+		SetText(`[green]Editing[white]
+
+Type to enter text.
+[yellow]Ctrl-H, Backspace[white]: Delete the left character.
+[yellow]Ctrl-D, Delete[white]: Delete the right character.
+[yellow]Ctrl-K[white]: Delete until the end of the line.
+[yellow]Ctrl-W[white]: Delete the rest of the word.
+[yellow]Ctrl-U[white]: Delete the current line.
+
+[blue]Press Enter for more help, press Escape to return.`)
+	help3 := tview.NewTextView().
+		SetDynamicColors(true).
+		SetText(`[green]Selecting Text[white]
+
+Move while holding Shift or drag the mouse.
+Double-click to select a word.
+
+[green]Clipboard
+
+[yellow]Ctrl-Q[white]: Copy.
+[yellow]Ctrl-X[white]: Cut.
+[yellow]Ctrl-V[white]: Paste.
+		
+[green]Undo
+
+[yellow]Ctrl-Z[white]: Undo.
+[yellow]Ctrl-Y[white]: Redo.
+
+[blue]Press Enter for more help, press Escape to return.`)
+	help := tview.NewFrame(help1).
+		SetBorders(1, 1, 0, 0, 2, 2)
+	help.SetBorder(true).
+		SetTitle("Help").
+		SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+			if event.Key() == tcell.KeyEscape {
+				pages.SwitchToPage("main")
+				return nil
+			} else if event.Key() == tcell.KeyEnter {
+				switch {
+				case help.GetPrimitive() == help1:
+					help.SetPrimitive(help2)
+				case help.GetPrimitive() == help2:
+					help.SetPrimitive(help3)
+				case help.GetPrimitive() == help3:
+					help.SetPrimitive(help1)
+				}
+				return nil
+			}
+			return event
+		})
+
+	pages.AddAndSwitchToPage("main", mainView, true).
+		AddPage("help", tview.NewGrid().
+			SetColumns(0, 64, 0).
+			SetRows(0, 22, 0).
+			AddItem(help, 1, 1, 1, 1, 0, 0, true), true, false)
+
+	app.SetInputCapture(func(event *tcell.EventKey) *tcell.EventKey {
+		if event.Key() == tcell.KeyF1 {
+			pages.ShowPage("help") //TODO: Check when clicking outside help window with the mouse. Then clicking help again.
+			return nil
+		}
+		return event
+	})
+
+	if err := app.SetRoot(pages,
+		true).EnableMouse(true).Run(); err != nil {
+		panic(err)
+	}
+}

frame.go

@@ -27,6 +27,9 @@ type Frame struct {
 
 	// Border spacing.
 	top, bottom, header, footer, left, right int
+
+	// Keep a reference in case we need it when we change the primitive.
+	setFocus func(p Primitive)
 }
 
 // NewFrame returns a new frame around the given primitive. The primitive's
@@ -52,7 +55,14 @@ func NewFrame(primitive Primitive) *Frame {
 // SetPrimitive replaces the contained primitive with the given one. To remove
 // a primitive, set it to nil.
 func (f *Frame) SetPrimitive(p Primitive) *Frame {
+	var hasFocus bool
+	if f.primitive != nil {
+		hasFocus = f.primitive.HasFocus()
+	}
 	f.primitive = p
+	if hasFocus && f.setFocus != nil {
+		f.setFocus(p) // Restore focus.
+	}
 	return f
 }
 
@@ -157,6 +167,7 @@ func (f *Frame) Draw(screen tcell.Screen) {
 
 // Focus is called when this primitive receives focus.
 func (f *Frame) Focus(delegate func(p Primitive)) {
+	f.setFocus = delegate
 	if f.primitive != nil {
 		delegate(f.primitive)
 	} else {

textarea.go

@@ -135,6 +135,7 @@ type textAreaUndoItem struct {
 //   - Ctrl-H, Backspace: Delete one character to the left of the cursor.
 //   - Ctrl-D, Delete: Delete the character under the cursor (or the first
 //     character on the next line if the cursor is at the end of a line).
+//   - Alt-Backspace: Delete the word to the left of the cursor.
 //   - Ctrl-K: Delete everything under and to the right of the cursor until the
 //     next newline character.
 //   - Ctrl-W: Delete from the start of the current word to the left of the
@@ -1098,6 +1099,7 @@ func (t *TextArea) reset() {
 	t.truncateLines(0)
 	if t.wrap {
 		t.cursor.row = -1
+		t.selectionStart.row = -1
 	}
 	t.widestLine = 0
 }
@@ -1887,26 +1889,31 @@ func (t *TextArea) InputHandler() func(event *tcell.EventKey, setFocus func(p Pr
 				break
 			}
 
-			// Move the cursor back by one grapheme cluster.
-			endPos := t.cursor.pos
-			if t.cursor.actualColumn == 0 {
-				// Move to the end of the previous row.
-				if t.cursor.row > 0 {
-					t.moveCursor(t.cursor.row-1, -1)
+			beforeCursor := t.cursor
+			if event.Modifiers()&tcell.ModAlt == 0 {
+				// Move the cursor back by one grapheme cluster.
+				if t.cursor.actualColumn == 0 {
+					// Move to the end of the previous row.
+					if t.cursor.row > 0 {
+						t.moveCursor(t.cursor.row-1, -1)
+					}
+				} else {
+					// Move one grapheme cluster to the left.
+					t.moveCursor(t.cursor.row, t.cursor.actualColumn-1)
 				}
+				newLastAction = taActionBackspace
 			} else {
-				// Move one grapheme cluster to the left.
-				t.moveCursor(t.cursor.row, t.cursor.actualColumn-1)
+				// Move the cursor back by one word.
+				t.moveWordLeft(false)
 			}
 
 			// Remove that last grapheme cluster.
-			if t.cursor.pos != endPos {
-				t.cursor.pos = t.replace(t.cursor.pos, endPos, "", t.lastAction == taActionBackspace) // Delete the character.
-				t.cursor.pos[2] = endPos[2]
+			if t.cursor.pos != beforeCursor.pos {
+				t.cursor, beforeCursor = beforeCursor, t.cursor                                                 // So we put the right position on the stack.
+				t.cursor.pos = t.replace(beforeCursor.pos, t.cursor.pos, "", t.lastAction == taActionBackspace) // Delete the character.
 				t.cursor.row = -1
-				t.truncateLines(t.cursor.row - 1)
-				t.findCursor(true, t.cursor.row-1)
-				newLastAction = taActionBackspace
+				t.truncateLines(beforeCursor.row - 1)
+				t.findCursor(true, beforeCursor.row-1)
 			}
 			t.selectionStart = t.cursor
 		case tcell.KeyDelete, tcell.KeyCtrlD: // Delete forward.
@@ -2002,7 +2009,7 @@ func (t *TextArea) InputHandler() func(event *tcell.EventKey, setFocus func(p Pr
 				t.spans[undo.originalBefore], t.spans[undo.before] = t.spans[undo.before], t.spans[undo.originalBefore]
 				t.spans[undo.originalAfter], t.spans[undo.after] = t.spans[undo.after], t.spans[undo.originalAfter]
 				t.cursor.pos, t.undoStack[t.nextUndo].pos = undo.pos, t.cursor.pos
-				t.length = undo.length
+				t.length, t.undoStack[t.nextUndo].length = undo.length, t.length
 				if !undo.continuation {
 					break
 				}
@@ -2023,7 +2030,7 @@ func (t *TextArea) InputHandler() func(event *tcell.EventKey, setFocus func(p Pr
 				t.spans[undo.originalBefore], t.spans[undo.before] = t.spans[undo.before], t.spans[undo.originalBefore]
 				t.spans[undo.originalAfter], t.spans[undo.after] = t.spans[undo.after], t.spans[undo.originalAfter]
 				t.cursor.pos, t.undoStack[t.nextUndo].pos = undo.pos, t.cursor.pos
-				t.length = undo.length
+				t.length, t.undoStack[t.nextUndo].length = undo.length, t.length
 				t.nextUndo++
 				if t.nextUndo < len(t.undoStack) && !t.undoStack[t.nextUndo].continuation {
 					break
@@ -2040,7 +2047,7 @@ func (t *TextArea) InputHandler() func(event *tcell.EventKey, setFocus func(p Pr
 	})
 }
 
-// THIS FUNCTION WILL BE REMOVED ONCE WE DEEM THE TEXT AREA STABLE!
+// THIS FUNCTION WILL BE REMOVED ONCE WE DEEM THE TEXT AREA STABLE! DO NOT USE!
 func (t *TextArea) Dump() string {
 	var buf strings.Builder