add LimitedWidthEntry widget

README.md

@@ -94,6 +94,11 @@ entry.OnChanged = func(s string) {
   <img src="img/widget-completion-entry.png" width="825" height="634" alt="CompletionEntry Widget" style="max-width: 100%" />
 </p>
 
+### LimitedWidthEntry
+
+An extended Entry widget that sets the width, and limits entry of a given number of chars.
+
+
 ### 7-Segment ("Hex") Display
 
 A skeuomorphic widget simulating a 7-segment "hex" display. Supports setting

widget/limited_width_entry.go

@@ -0,0 +1,65 @@
+package widget
+
+import (
+	"strings"
+
+	"fyne.io/fyne/v2"
+	"fyne.io/fyne/v2/theme"
+	"fyne.io/fyne/v2/widget"
+)
+
+// LimitedWidthEntry is an extended entry that sets a minimum width, and
+// limits the entry/pasting to a given number of characters `CharsWide`
+type LimitedWidthEntry struct {
+	widget.Entry
+	CharsWide int
+}
+
+// NewLimitedWidthEntry returns an extended entry that has a minimum width and is limited
+// to a CharsWide number of characters
+func NewLimitedWidthEntry() *LimitedWidthEntry {
+	entry := &LimitedWidthEntry{}
+	entry.ExtendBaseWidget(entry)
+	return entry
+}
+
+// MinSize returns the size that this widget should not shrink below.
+//
+// Implements: fyne.Widget
+func (e *LimitedWidthEntry) MinSize() fyne.Size {
+	min := e.Entry.MinSize()
+	if e.CharsWide > 0 {
+		width := fyne.MeasureText(strings.Repeat("W", e.CharsWide), theme.TextSize(), e.TextStyle).Width
+		if e.Validator != nil {
+			width += theme.IconInlineSize() + theme.Padding()
+		}
+		if min.Width < width {
+			min.Width = width
+		}
+	}
+	return min
+}
+
+// TypedRune is called when this item receives a char event.
+//
+// Implements: fyne.Focusable
+func (e *LimitedWidthEntry) TypedRune(r rune) {
+	if e.CharsWide < 1 || len(e.Text) < e.CharsWide {
+		e.Entry.TypedRune(r)
+		return
+	}
+}
+
+// TypedShortcut handles the registered shortcuts.
+//
+// Implements: fyne.Shortcutable
+func (e *LimitedWidthEntry) TypedShortcut(shortcut fyne.Shortcut) {
+	e.Entry.TypedShortcut(shortcut)
+	if e.CharsWide > 0 {
+		// Limit the text length after the paste as the paste might
+		// have inserted or appended to existing content
+		if len(e.Text) > e.CharsWide {
+			e.SetText(e.Text[:e.CharsWide])
+		}
+	}
+}

widget/limited_width_entry_test.go

@@ -0,0 +1,33 @@
+package widget
+
+import (
+	"testing"
+
+	"fyne.io/fyne/v2"
+	"fyne.io/fyne/v2/test"
+	"github.com/stretchr/testify/assert"
+)
+
+// Check typed chars are limited
+func TestLimitedWidthEntry_TypedRune(t *testing.T) {
+	entry := NewLimitedWidthEntry()
+
+	win := test.NewWindow(entry)
+	win.Resize(fyne.NewSize(200, 100))
+	defer win.Close()
+
+	for i := 1; i < 20; i++ {
+		// reset the widget for `i` chars
+		entry.CharsWide = i
+		entry.SetText("")
+
+		// Get the width before we add runes
+		width := entry.Size().Width
+
+		for j := 0; j < 30; j++ {
+			entry.TypedRune(rune('W' + j))
+			assert.LessOrEqual(t, len(entry.Text), i)
+			assert.EqualValues(t, width, entry.Size().Width)
+		}
+	}
+}