DefaultText option for textinput.

CHANGELOG.md

@@ -65,6 +65,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - the `textinput` widget can now be configured to request keyboard events
   exclusively when focused.
+- the `textinput` widget can now be initialized with a default text in the
+  input box.
 
 ## [0.13.0] - 17-Nov-2020
 

widgets/textinput/options.go

@@ -17,6 +17,7 @@ package textinput
 // options.go contains configurable options for TextInput.
 
 import (
+	"errors"
 	"fmt"
 
 	"github.com/mum4k/termdash/align"
@@ -58,6 +59,7 @@ type options struct {
 
 	placeHolder  string
 	hideTextWith rune
+	defaultText  string
 
 	filter                   FilterFn
 	onSubmit                 SubmitFn
@@ -81,6 +83,16 @@ func (o *options) validate() error {
 			return fmt.Errorf("invalid HideTextWidth rune %c(%d), has rune width of %d cells, only runes with width of %d are accepted", r, r, got, want)
 		}
 	}
+	if o.defaultText != "" {
+		if err := wrap.ValidText(o.defaultText); err != nil {
+			return fmt.Errorf("invalid DefaultText: %v", err)
+		}
+		for _, r := range o.defaultText {
+			if r == '\n' {
+				return errors.New("invalid DefaultText: newline characters aren't allowed")
+			}
+		}
+	}
 	return nil
 }
 
@@ -272,3 +284,12 @@ func ExclusiveKeyboardOnFocus() Option {
 		opts.exclusiveKeyboardOnFocus = true
 	})
 }
+
+// DefaultText sets the text to be present in a newly created input field.
+// The text must not contain any control or space characters other than ' '.
+// The user can edit this text as normal.
+func DefaultText(text string) Option {
+	return option(func(opts *options) {
+		opts.defaultText = text
+	})
+}

widgets/textinput/textinput.go

@@ -69,10 +69,15 @@ func New(opts ...Option) (*TextInput, error) {
 	if err := opt.validate(); err != nil {
 		return nil, err
 	}
-	return &TextInput{
+	ti := &TextInput{
 		editor: newFieldEditor(),
 		opts:   opt,
-	}, nil
+	}
+
+	for _, r := range ti.opts.defaultText {
+		ti.editor.insert(r)
+	}
+	return ti, nil
 }
 
 // Vars to be replaced from tests.

widgets/textinput/textinput_test.go

@@ -117,6 +117,20 @@ func TestTextInput(t *testing.T) {
 			},
 			wantNewErr: true,
 		},
+		{
+			desc: "fails on invalid DefaultText which has control characters",
+			opts: []Option{
+				DefaultText("\r"),
+			},
+			wantNewErr: true,
+		},
+		{
+			desc: "fails on invalid DefaultText which has newline",
+			opts: []Option{
+				DefaultText("\n"),
+			},
+			wantNewErr: true,
+		},
 		{
 			desc:   "takes all space without label",
 			canvas: image.Rect(0, 0, 10, 1),
@@ -559,6 +573,62 @@ func TestTextInput(t *testing.T) {
 				return ft
 			},
 		},
+		{
+			desc: "displays default text",
+			opts: []Option{
+				DefaultText("text"),
+			},
+			canvas: image.Rect(0, 0, 10, 1),
+			meta:   &widgetapi.Meta{},
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				cvs := testcanvas.MustNew(ft.Area())
+
+				testcanvas.MustSetAreaCells(
+					cvs,
+					image.Rect(0, 0, 10, 1),
+					textFieldRune,
+					cell.BgColor(cell.ColorNumber(DefaultFillColorNumber)),
+				)
+				testdraw.MustText(
+					cvs,
+					"text",
+					image.Point{0, 0},
+				)
+				testcanvas.MustApply(cvs, ft)
+				return ft
+			},
+		},
+		{
+			desc: "default text can be edited",
+			opts: []Option{
+				DefaultText("text"),
+			},
+			canvas: image.Rect(0, 0, 10, 1),
+			meta:   &widgetapi.Meta{},
+			events: []terminalapi.Event{
+				&terminalapi.Keyboard{Key: keyboard.KeyBackspace},
+				&terminalapi.Keyboard{Key: 'a'},
+			},
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				cvs := testcanvas.MustNew(ft.Area())
+
+				testcanvas.MustSetAreaCells(
+					cvs,
+					image.Rect(0, 0, 10, 1),
+					textFieldRune,
+					cell.BgColor(cell.ColorNumber(DefaultFillColorNumber)),
+				)
+				testdraw.MustText(
+					cvs,
+					"texa",
+					image.Point{0, 0},
+				)
+				testcanvas.MustApply(cvs, ft)
+				return ft
+			},
+		},
 		{
 			desc:   "displays written text",
 			canvas: image.Rect(0, 0, 10, 1),