Merge pull request #355 from mum4k/release-v0.18.0

Release Termdash v0.18.0.

## v0.18.0 - 08-Feb-2023

### Added

- The `gauge` widget now supports drawing of a vertical threshold bar.
- The `TextInput` widget now supports an OnChange handler that allows user code
  to be notified when the content of the text input changes.

### Changed

- Bump github.com/gdamore/tcell/v2 from 2.5.1 to 2.5.4.
- Bump github.com/mattn/go-runewidth from 0.0.13 to 0.0.14.
- Bump github.com/gdamore/tcell/v2 from 2.5.1 to 2.5.3.
- Bump github.com/gdamore/tcell/v2 from 2.5.1 to 2.5.2
- Change the Go version in `go.mod` to 1.20.
- Executed `go mod tidy`.
- CI now executes tests with Golang v1.20 only.

### Removed

- Removed the `Sourcegraph` badge from the main page.

### Fixed

- Formatted all Go files with `gofmt` from Golang v1.20.
- Fixed line coverage reporting.

.travis.yml

@@ -1,7 +1,6 @@
 language: go
 go:
-        - 1.16.x
+  - 1.20.x
-        - 1.17.x
   - stable
 before_install:
   - go install golang.org/x/tools/cmd/cover@latest
@@ -9,11 +8,8 @@ before_install:
   - go install golang.org/x/lint/golint@latest
 script:
   - go get -t ./...
-        # Temporarily set -mod=mod to allow modification of go.mod and go.sum.
+  - go test -v -covermode=count -coverprofile=coverage.out ./...
-        # This seems to be caused by a sum missing in the tcell dependency and
+  - CGO_ENABLED=1 go test -race ./...
-        # should be removed when no longer needed.
-        - go test -v -covermode=count -coverprofile=coverage.out -mod=mod ./...
-        - CGO_ENABLED=1 go test -mod=mod -race ./...
   - go vet ./...
   - diff -u <(echo -n) <(gofmt -d -s .)
   - diff -u <(echo -n) <(./private/scripts/autogen_licences.sh .)
@@ -22,4 +18,4 @@ script:
 env:
   global:
     - CGO_ENABLED=0
-        - secure: 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
+    - secure: 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

CHANGELOG.md

@@ -7,6 +7,33 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.18.0] - 08-Feb-2023
+
+### Added
+
+- The `gauge` widget now supports drawing of a vertical threshold bar.
+- The `TextInput` widget now supports an OnChange handler that allows user code
+  to be notified when the content of the text input changes.
+
+### Changed
+
+- Bump github.com/gdamore/tcell/v2 from 2.5.1 to 2.5.4.
+- Bump github.com/mattn/go-runewidth from 0.0.13 to 0.0.14.
+- Bump github.com/gdamore/tcell/v2 from 2.5.1 to 2.5.3.
+- Bump github.com/gdamore/tcell/v2 from 2.5.1 to 2.5.2
+- Change the Go version in `go.mod` to 1.20.
+- Executed `go mod tidy`.
+- CI now executes tests with Golang v1.20 only.
+
+### Removed
+
+- Removed the `Sourcegraph` badge from the main page.
+
+### Fixed
+
+- Formatted all Go files with `gofmt` from Golang v1.20.
+- Fixed line coverage reporting.
+
 ## [0.17.0] - 07-Jul-2022
 
 ### Added
@@ -490,6 +517,7 @@ identifiers shouldn't be used externally.
 - The Text widget.
 
 [unreleased]: https://github.com/mum4k/termdash/compare/v0.17.0...devel
+[0.18.0]: https://github.com/mum4k/termdash/compare/v0.17.0...v0.18.0
 [0.17.0]: https://github.com/mum4k/termdash/compare/v0.16.1...v0.17.0
 [0.16.1]: https://github.com/mum4k/termdash/compare/v0.16.0...v0.16.1
 [0.16.0]: https://github.com/mum4k/termdash/compare/v0.15.0...v0.16.0

README.md

@@ -1,6 +1,5 @@
 [![Doc Status](https://godoc.org/github.com/mum4k/termdash?status.png)](https://godoc.org/github.com/mum4k/termdash)
 [![Build Status](https://travis-ci.com/mum4k/termdash.svg?branch=master)](https://travis-ci.com/mum4k/termdash)
-[![Sourcegraph](https://sourcegraph.com/github.com/mum4k/termdash/-/badge.svg)](https://sourcegraph.com/github.com/mum4k/termdash?badge)
 [![Coverage Status](https://coveralls.io/repos/github/mum4k/termdash/badge.svg?branch=master)](https://coveralls.io/github/mum4k/termdash?branch=master)
 [![Go Report Card](https://goreportcard.com/badge/github.com/mum4k/termdash)](https://goreportcard.com/report/github.com/mum4k/termdash)
 [![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/mum4k/termdash/blob/master/LICENSE)

container/grid/grid.go

@@ -53,11 +53,13 @@ func (b *Builder) Build() ([]container.Option, error) {
 
 // validate recursively validates the elements that were added to the builder.
 // Validates the following per each level of Rows or Columns.:
+//
 //	The subElements are either exactly one Widget or any number of Rows and
 //	Columns.
 //	Each individual width or height is in the range 0 < v < 100.
 //	The sum of all widths is <= 100.
 //	The sum of all heights is <= 100.
+//
 // Argument fixedSizeParent indicates if any of the parent elements uses fixed
 // size splitType.
 func validate(elems []Element, fixedSizeParent bool) error {
@@ -182,14 +184,23 @@ func build(elems []Element, parentHeightPerc, parentWidthPerc int) []container.O
 // E.g. multiple rows would specify that they want the outer split percentage
 // of 25% each, but we are representing them in a tree of containers so the
 // inner splits vary:
+//
 //	╭─────────╮
+//
 // 25% │   25%   │
+//
 //	│╭───────╮│ ---
+//
 // 25% ││  33%  ││
+//
 //	││╭─────╮││
+//
 // 25% │││ 50% │││
+//
 //	││├─────┤││ 75%
+//
 // 25% │││ 50% │││
+//
 //	││╰─────╯││
 //	│╰───────╯│
 //	╰─────────╯ ---

go.mod

@@ -1,11 +1,11 @@
 module github.com/mum4k/termdash
 
-go 1.17
+go 1.20
 
 require (
-	github.com/gdamore/tcell/v2 v2.5.1
+	github.com/gdamore/tcell/v2 v2.5.4
 	github.com/kylelemons/godebug v1.1.0
-	github.com/mattn/go-runewidth v0.0.13
+	github.com/mattn/go-runewidth v0.0.14
 	github.com/nsf/termbox-go v1.1.1
 )
 
@@ -13,7 +13,7 @@ require (
 	github.com/gdamore/encoding v1.0.0 // indirect
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect
 	github.com/rivo/uniseg v0.2.0 // indirect
-	golang.org/x/sys v0.0.0-20220704084225-05e143d24a9e // indirect
+	golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f // indirect
 	golang.org/x/term v0.0.0-20220526004731-065cf7ba2467 // indirect
-	golang.org/x/text v0.3.7 // indirect
+	golang.org/x/text v0.5.0 // indirect
 )

go.sum

@@ -1,27 +1,43 @@
 github.com/gdamore/encoding v1.0.0 h1:+7OoQ1Bc6eTm5niUzBa0Ctsh6JbMW6Ra+YNuAtDBdko=
 github.com/gdamore/encoding v1.0.0/go.mod h1:alR0ol34c49FCSBLjhosxzcPHQbf2trDkoo5dl+VrEg=
-github.com/gdamore/tcell/v2 v2.5.1 h1:zc3LPdpK184lBW7syF2a5C6MV827KmErk9jGVnmsl/I=
+github.com/gdamore/tcell/v2 v2.5.4 h1:TGU4tSjD3sCL788vFNeJnTdzpNKIw1H5dgLnJRQVv/k=
-github.com/gdamore/tcell/v2 v2.5.1/go.mod h1:wSkrPaXoiIWZqW/g7Px4xc79di6FTcpB8tvaKJ6uGBo=
+github.com/gdamore/tcell/v2 v2.5.4/go.mod h1:dZgRy5v4iMobMEcWNYBtREnDZAT9DYmfqIkrgEMxLyw=
 github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
 github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
 github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
 github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
-github.com/mattn/go-runewidth v0.0.13 h1:lTGmDsbAYt5DmK6OnoV7EuIF1wEIFAcxld6ypU4OSgU=
+github.com/mattn/go-runewidth v0.0.14 h1:+xnbZSEeDbOIg5/mE6JF0w6n9duR1l3/WmbinWVwUuU=
-github.com/mattn/go-runewidth v0.0.13/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/mattn/go-runewidth v0.0.14/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
 github.com/nsf/termbox-go v1.1.1 h1:nksUPLCb73Q++DwbYUBEglYBRPZyoXJdrj5L+TkjyZY=
 github.com/nsf/termbox-go v1.1.1/go.mod h1:T0cTdVuOwf7pHQNtfhnEbzHbcNyCEcVU4YPpouCbVxo=
 github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
+github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220318055525-2edf467146b5/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220704084225-05e143d24a9e h1:CsOuNlbOuf0mzxJIefr6Q4uAUetRUwZE4qt7VfzP+xo=
+golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f h1:v4INt8xihDGvnrfjMDVXGxw9wrfxYyCjk0KbXjhR55s=
-golang.org/x/sys v0.0.0-20220704084225-05e143d24a9e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201210144234-2321bbc49cbf/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/term v0.0.0-20220526004731-065cf7ba2467 h1:CBpWXWQpIRjzmkkA+M7q9Fqnwd2mZr3AFqexg8YTfoM=
 golang.org/x/term v0.0.0-20220526004731-065cf7ba2467/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
+golang.org/x/text v0.5.0 h1:OLmvp0KP+FVG99Ct/qFiL/Fhk4zp4QQnZ7b2U+5piUM=
+golang.org/x/text v0.5.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
+golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
+golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

private/draw/vertical_text.go

@@ -75,6 +75,7 @@ func VerticalTextOverrunMode(om OverrunMode) VerticalTextOption {
 
 // VerticalText prints the provided text on the canvas starting at the provided point.
 // The text is printed in a vertical orientation, i.e:
+//
 //	H
 //	e
 //	l

private/numbers/trig/trig.go

@@ -128,6 +128,7 @@ func (ar *angleRange) contains(angle int) bool {
 // normalizeRange normalizes the start and end angles in degrees into ranges of
 // angles. Useful for cases where the 0/360 point falls within the range.
 // E.g:
+//
 //	0,25   => angleRange{0, 26}
 //	0,360  => angleRange{0, 361}
 //	359,20 => angleRange{359, 361}, angleRange{0, 21}
@@ -159,6 +160,7 @@ func normalizeRange(start, end int) ([]*angleRange, error) {
 
 // RangeSize returns the size of the degree range.
 // E.g:
+//
 //	0,25  => 25
 //	359,1 => 2
 func RangeSize(start, end int) (int, error) {
@@ -174,6 +176,7 @@ func RangeSize(start, end int) (int, error) {
 
 // RangeMid returns an angle that lies in the middle between start and end.
 // E.g:
+//
 //	0,10   => 5
 //	350,10 => 0
 func RangeMid(start, end int) (int, error) {

private/segdisp/segment/segment.go

@@ -95,14 +95,15 @@ func SkipSlopesLTE(v int) Option {
 // This only has a visible effect when the horizontal segment has height of two
 // or the vertical segment has width of two.
 // Without this option segments with height / width of two look like this:
-//    -   |
+// x  -   |
-//   --- ||
+// x --- ||
-//        |
+// x      |
-//
+// x
-// With this option:
+// x With this option:
-//   ---  |
+// x
-//    -   ||
+// x --- |
-//        |
+// x  -  ||
+// x     |
 func ReverseSlopes() Option {
 	return option(func(opts *options) {
 		opts.reverseSlopes = true

termdashdemo/termdashdemo.go

@@ -976,8 +976,10 @@ func newLayoutButtons(c *container.Container, w *widgets) (*layoutButtons, error
 
 // rotateFloats returns a new slice with inputs rotated by step.
 // I.e. for a step of one:
+//
 //	inputs[0] -> inputs[len(inputs)-1]
 //	inputs[1] -> inputs[0]
+//
 // And so on.
 func rotateFloats(inputs []float64, step int) []float64 {
 	return append(inputs[step:], inputs[:step]...)
@@ -985,8 +987,10 @@ func rotateFloats(inputs []float64, step int) []float64 {
 
 // rotateRunes returns a new slice with inputs rotated by step.
 // I.e. for a step of one:
+//
 //	inputs[0] -> inputs[len(inputs)-1]
 //	inputs[1] -> inputs[0]
+//
 // And so on.
 func rotateRunes(inputs []rune, step int) []rune {
 	return append(inputs[step:], inputs[:step]...)

widgets/gauge/gauge.go

@@ -136,10 +136,12 @@ func (g *Gauge) Percent(p int, opts ...Option) error {
 	return nil
 }
 
-// width determines the required width of the gauge drawn on the provided area
+// width determines the X coordinate that represents point w in rectangle ar.
-// in order to represent the current progress.
+// This is used to calculate the width of the gauge drawn on the provided area
-func (g *Gauge) width(ar image.Rectangle) int {
+// in order to represent the current progress or to figure out the coordinate
-	mult := float32(g.current) / float32(g.total)
+// for the threshold line.
+func (g *Gauge) width(ar image.Rectangle, w int) int {
+	mult := float32(w) / float32(g.total)
 	width := float32(ar.Dx()) * mult
 	return int(width)
 }
@@ -157,6 +159,11 @@ func (g *Gauge) usable(cvs *canvas.Canvas) image.Rectangle {
 	return cvs.Area()
 }
 
+// thresholdVisible determines if the threshold line should be drawn.
+func (g *Gauge) thresholdVisible() bool {
+	return g.opts.threshold > 0 && g.opts.threshold < g.total
+}
+
 // progressText returns the textual representation of the current progress.
 func (g *Gauge) progressText() string {
 	if g.opts.hideTextProgress {
@@ -244,6 +251,26 @@ func (g *Gauge) drawText(cvs *canvas.Canvas, progress image.Rectangle) error {
 	return nil
 }
 
+// drawThreshold draws the threshold line.
+func (g *Gauge) drawThreshold(cvs *canvas.Canvas) error {
+	ar := g.usable(cvs)
+
+	line := draw.HVLine{
+		Start: image.Point{
+			X: ar.Min.X + g.width(ar, g.opts.threshold),
+			Y: cvs.Area().Min.Y,
+		},
+		End: image.Point{
+			X: ar.Min.X + g.width(ar, g.opts.threshold),
+			Y: cvs.Area().Max.Y - 1,
+		},
+	}
+	return draw.HVLines(cvs, []draw.HVLine{line},
+		draw.HVLineStyle(g.opts.thresholdLineStyle),
+		draw.HVLineCellOpts(g.opts.thresholdCellOpts...),
+	)
+}
+
 // Draw draws the Gauge widget onto the canvas.
 // Implements widgetapi.Widget.Draw.
 func (g *Gauge) Draw(cvs *canvas.Canvas, meta *widgetapi.Meta) error {
@@ -273,7 +300,7 @@ func (g *Gauge) Draw(cvs *canvas.Canvas, meta *widgetapi.Meta) error {
 	progress := image.Rect(
 		usable.Min.X,
 		usable.Min.Y,
-		usable.Min.X+g.width(usable),
+		usable.Min.X+g.width(usable, g.current),
 		usable.Max.Y,
 	)
 	if progress.Dx() > 0 {
@@ -284,6 +311,12 @@ func (g *Gauge) Draw(cvs *canvas.Canvas, meta *widgetapi.Meta) error {
 			return err
 		}
 	}
+	if g.thresholdVisible() {
+		if err := g.drawThreshold(cvs); err != nil {
+			return err
+		}
+	}
+
 	return g.drawText(cvs, progress)
 }
 

widgets/gauge/gauge_test.go

@@ -70,9 +70,9 @@ func TestGauge(t *testing.T) {
 			wantErr: true,
 		},
 		{
-			desc: "fails on negative height",
+			desc: "fails on negative threshold",
 			opts: []Option{
-				Height(-1),
+				Threshold(-1, linestyle.Light),
 			},
 			canvas: image.Rect(0, 0, 10, 3),
 			want: func(size image.Point) *faketerm.Terminal {
@@ -841,6 +841,157 @@ func TestGauge(t *testing.T) {
 				return ft
 			},
 		},
+		{
+			desc: "threshold with border percentage",
+			opts: []Option{
+				Char('o'),
+				Threshold(20, linestyle.Double),
+			},
+			percent: &percentCall{p: 35},
+			canvas:  image.Rect(0, 0, 10, 3),
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				c := testcanvas.MustNew(ft.Area())
+
+				testdraw.MustRectangle(c, image.Rect(0, 0, 3, 3),
+					draw.RectChar('o'),
+					draw.RectCellOpts(cell.BgColor(cell.ColorGreen)),
+				)
+				testdraw.MustText(c, "35%", image.Point{3, 1})
+				testdraw.MustHVLines(c, []draw.HVLine{{
+					Start: image.Point{X: 2, Y: 0},
+					End:   image.Point{X: 2, Y: 2},
+				}}, draw.HVLineStyle(linestyle.Double))
+				testcanvas.MustApply(c, ft)
+				return ft
+			},
+		},
+		{
+			desc: "threshold without border absolute",
+			opts: []Option{
+				Char('o'),
+				Threshold(3, linestyle.Light, cell.BgColor(cell.ColorRed)),
+				Border(linestyle.None),
+				HideTextProgress(),
+			},
+			absolute: &absoluteCall{done: 4, total: 10},
+			canvas:   image.Rect(0, 0, 10, 3),
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				c := testcanvas.MustNew(ft.Area())
+
+				testdraw.MustRectangle(c, image.Rect(0, 0, 3, 3),
+					draw.RectChar('o'),
+					draw.RectCellOpts(cell.BgColor(cell.ColorGreen)),
+				)
+				testdraw.MustHVLines(c, []draw.HVLine{{
+					Start: image.Point{X: 3, Y: 0},
+					End:   image.Point{X: 3, Y: 2},
+				}}, draw.HVLineStyle(linestyle.Light),
+					draw.HVLineCellOpts(cell.BgColor(cell.ColorRed)))
+				testcanvas.MustApply(c, ft)
+				return ft
+			},
+		},
+		{
+			desc: "threshold outside of bounds (>=max)",
+			opts: []Option{
+				Char('o'),
+				HideTextProgress(),
+				Threshold(100, linestyle.Light), // ignored
+			},
+			percent: &percentCall{p: 35},
+			canvas:  image.Rect(0, 0, 10, 3),
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				c := testcanvas.MustNew(ft.Area())
+
+				testdraw.MustRectangle(c, image.Rect(0, 0, 3, 3),
+					draw.RectChar('o'),
+					draw.RectCellOpts(cell.BgColor(cell.ColorGreen)),
+				)
+				testcanvas.MustApply(c, ft)
+				return ft
+			},
+		},
+		{
+			desc: "progress below threshold",
+			opts: []Option{
+				Char('o'),
+				Threshold(5, linestyle.Light, cell.BgColor(cell.ColorRed)),
+				HideTextProgress(),
+			},
+			absolute: &absoluteCall{done: 4, total: 10},
+			canvas:   image.Rect(0, 0, 10, 3),
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				c := testcanvas.MustNew(ft.Area())
+
+				testdraw.MustRectangle(c, image.Rect(0, 0, 4, 3),
+					draw.RectChar('o'),
+					draw.RectCellOpts(cell.BgColor(cell.ColorGreen)),
+				)
+				testdraw.MustHVLines(c, []draw.HVLine{{
+					Start: image.Point{X: 5, Y: 0},
+					End:   image.Point{X: 5, Y: 2},
+				}}, draw.HVLineStyle(linestyle.Light),
+					draw.HVLineCellOpts(cell.BgColor(cell.ColorRed)))
+				testcanvas.MustApply(c, ft)
+				return ft
+			},
+		},
+		{
+			desc: "progress exactly at threshold",
+			opts: []Option{
+				Char('o'),
+				Threshold(5, linestyle.Light, cell.BgColor(cell.ColorRed)),
+				HideTextProgress(),
+			},
+			absolute: &absoluteCall{done: 5, total: 10},
+			canvas:   image.Rect(0, 0, 10, 3),
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				c := testcanvas.MustNew(ft.Area())
+
+				testdraw.MustRectangle(c, image.Rect(0, 0, 5, 3),
+					draw.RectChar('o'),
+					draw.RectCellOpts(cell.BgColor(cell.ColorGreen)),
+				)
+				testdraw.MustHVLines(c, []draw.HVLine{{
+					Start: image.Point{X: 5, Y: 0},
+					End:   image.Point{X: 5, Y: 2},
+				}}, draw.HVLineStyle(linestyle.Light),
+					draw.HVLineCellOpts(cell.BgColor(cell.ColorRed)))
+				testcanvas.MustApply(c, ft)
+				return ft
+			},
+		},
+		{
+			desc: "progress after threshold",
+			opts: []Option{
+				Char('o'),
+				Threshold(5, linestyle.Light, cell.BgColor(cell.ColorRed)),
+				HideTextProgress(),
+			},
+			absolute: &absoluteCall{done: 6, total: 10},
+			canvas:   image.Rect(0, 0, 10, 3),
+			want: func(size image.Point) *faketerm.Terminal {
+				ft := faketerm.MustNew(size)
+				c := testcanvas.MustNew(ft.Area())
+
+				testdraw.MustRectangle(c, image.Rect(0, 0, 6, 3),
+					draw.RectChar('o'),
+					draw.RectCellOpts(cell.BgColor(cell.ColorGreen)),
+				)
+				testdraw.MustHVLines(c, []draw.HVLine{{
+					Start: image.Point{X: 5, Y: 0},
+					End:   image.Point{X: 5, Y: 2},
+				}}, draw.HVLineStyle(linestyle.Light),
+					draw.HVLineCellOpts(cell.BgColor(cell.ColorRed)))
+				testcanvas.MustApply(c, ft)
+				return ft
+			},
+		},
 	}
 
 	for _, tc := range tests {

widgets/gauge/gaugedemo/gaugedemo.go

@@ -101,6 +101,7 @@ func main() {
 		gauge.Color(cell.ColorNumber(33)),
 		gauge.Border(linestyle.Light),
 		gauge.BorderTitle("Absolute progress"),
+		gauge.Threshold(43, linestyle.Light, cell.FgColor(cell.ColorRed)),
 	)
 	if err != nil {
 		panic(err)
@@ -124,6 +125,7 @@ func main() {
 		gauge.Color(cell.ColorRed),
 		gauge.FilledTextColor(cell.ColorBlack),
 		gauge.EmptyTextColor(cell.ColorYellow),
+		gauge.Threshold(20, linestyle.Double),
 	)
 	if err != nil {
 		panic(err)

widgets/gauge/options.go

@@ -47,6 +47,10 @@ type options struct {
 	borderCellOpts    []cell.Option
 	borderTitle       string
 	borderTitleHAlign align.Horizontal
+	// If set draws a vertical line representing the threshold.
+	threshold          int
+	thresholdCellOpts  []cell.Option
+	thresholdLineStyle linestyle.LineStyle
 }
 
 // newOptions returns options with the default values set.
@@ -66,6 +70,9 @@ func (o *options) validate() error {
 	if got, min := o.height, 0; got < min {
 		return fmt.Errorf("invalid Height %d, must be %d <= Height", got, min)
 	}
+	if got, min := o.threshold, 0; got < min {
+		return fmt.Errorf("invalid Threshold %d, must be %d <= Threshold", got, min)
+	}
 	return nil
 }
 
@@ -201,3 +208,17 @@ func BorderTitleAlign(h align.Horizontal) Option {
 		opts.borderTitleHAlign = h
 	})
 }
+
+// Threshold configures the Gauge to display a vertical threshold line at value
+// t. If the progress is set by a call to Percent(), t represents a percentage,
+// e.g. "40" means line is displayed at 40%. If the progress is set by a call to
+// Absolute(), the threshold is considered an absolute number.
+// Threshold must be positive to be displayed. If the threshold is zero or
+// greater than total, it won't be displayed. Defaults to zero.
+func Threshold(t int, ls linestyle.LineStyle, cOpts ...cell.Option) Option {
+	return option(func(opts *options) {
+		opts.threshold = t
+		opts.thresholdLineStyle = ls
+		opts.thresholdCellOpts = cOpts
+	})
+}

widgets/linechart/internal/axes/scale.go

@@ -328,6 +328,7 @@ func (xs *XScale) CellLabel(x int) (*Value, error) {
 // the position. Positions grow up, coordinates grow down.
 //
 // Positions     Y Coordinates
+//
 //	2  |  0
 //	1  |  1
 //	0  |  2

widgets/segmentdisplay/segmentdisplaydemo/segmentdisplaydemo.go

@@ -62,8 +62,10 @@ func clock(ctx context.Context, sd *segmentdisplay.SegmentDisplay) {
 
 // rotate returns a new slice with inputs rotated by step.
 // I.e. for a step of one:
+//
 //	inputs[0] -> inputs[len(inputs)-1]
 //	inputs[1] -> inputs[0]
+//
 // And so on.
 func rotate(inputs []rune, step int) []rune {
 	return append(inputs[step:], inputs[:step]...)

widgets/text/text.go

@@ -105,7 +105,9 @@ func (t *Text) contentCells() int {
 // Write writes text for the widget to display. Multiple calls append
 // additional text. The text contain cannot control characters
 // (unicode.IsControl) or space character (unicode.IsSpace) other than:
+//
 //	' ', '\n'
+//
 // Any newline ('\n') characters are interpreted as newlines when displaying
 // the text.
 func (t *Text) Write(text string, wOpts ...WriteOption) error {

widgets/textinput/editor.go

@@ -274,11 +274,14 @@ type fieldEditor struct {
 
 	// width is the width of the text input field last time viewFor was called.
 	width int
+
+	// onChange if provided is the handler called when fieldData changes
+	onChange ChangeFn
 }
 
 // newFieldEditor returns a new fieldEditor instance.
-func newFieldEditor() *fieldEditor {
+func newFieldEditor(onChange ChangeFn) *fieldEditor {
-	return &fieldEditor{}
+	return &fieldEditor{onChange: onChange}
 }
 
 // minFieldWidth is the minimum supported width of the text input field.
@@ -326,7 +329,7 @@ func (fe *fieldEditor) content() string {
 
 // reset resets the content back to zero.
 func (fe *fieldEditor) reset() {
-	*fe = *newFieldEditor()
+	*fe = *newFieldEditor(fe.onChange)
 }
 
 // insert inserts the rune at the current position of the cursor.
@@ -338,6 +341,9 @@ func (fe *fieldEditor) insert(r rune) {
 	}
 	fe.data.insertAt(fe.curDataPos, r)
 	fe.curDataPos++
+	if fe.onChange != nil {
+		fe.onChange(string(fe.data))
+	}
 }
 
 // delete deletes the rune at the current position of the cursor.
@@ -347,6 +353,9 @@ func (fe *fieldEditor) delete() {
 		return
 	}
 	fe.data.deleteAt(fe.curDataPos)
+	if fe.onChange != nil {
+		fe.onChange(string(fe.data))
+	}
 }
 
 // deleteBefore deletes the rune that is immediately to the left of the cursor.

widgets/textinput/editor_test.go

@@ -309,7 +309,7 @@ func TestCurCell(t *testing.T) {
 
 	for _, tc := range tests {
 		t.Run(tc.desc, func(t *testing.T) {
-			fe := newFieldEditor()
+			fe := newFieldEditor(nil)
 			fe.data = tc.data
 			fe.firstRune = tc.firstRune
 			fe.curDataPos = tc.curDataPos
@@ -330,6 +330,7 @@ func TestFieldEditor(t *testing.T) {
 		wantContent       string
 		wantCurIdx        int
 		wantErr           bool
+		wantOnChangeCalls int
 	}{
 		{
 			desc:    "fails for width too small",
@@ -355,6 +356,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "longer data than the width, cursor at the end",
@@ -369,6 +371,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd",
 			wantContent:       "abcd",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "longer data than the width, cursor at the end, has full-width runes",
@@ -383,6 +386,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦世",
 			wantContent:       "abc世",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "width decreased, adjusts cursor and shifts data",
@@ -400,6 +404,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd",
 			wantContent:       "abcd",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "cursor won't go right beyond the end of the data",
@@ -417,6 +422,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd",
 			wantContent:       "abcd",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "moves cursor to the left",
@@ -435,6 +441,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd",
 			wantContent:       "abcd",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "scrolls content to the left, start becomes visible",
@@ -455,6 +462,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc⇨",
 			wantContent:       "abcd",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "scrolls content to the left, both ends invisible",
@@ -476,6 +484,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "scrolls left, then back right to make end visible again",
@@ -503,6 +512,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦de",
 			wantContent:       "abcde",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "scrolls left, won't go beyond the start of data",
@@ -527,6 +537,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        0,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "scrolls left, then back right won't go beyond the end of data",
@@ -555,6 +566,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦de",
 			wantContent:       "abcde",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "have less data than width, all fits",
@@ -571,6 +583,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "moves cursor to the start",
@@ -590,6 +603,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        0,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "moves cursor to the end",
@@ -613,6 +627,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦de",
 			wantContent:       "abcde",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "deletesBefore when cursor after the data",
@@ -632,6 +647,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd",
 			wantContent:       "abcd",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 6,
 		},
 		{
 			desc:  "deletesBefore when cursor after the data, text has full-width rune",
@@ -651,6 +667,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦世",
 			wantContent:       "abc世",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 6,
 		},
 		{
 			desc:  "deletesBefore when cursor in the middle",
@@ -676,6 +693,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "acd⇨",
 			wantContent:       "acde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 6,
 		},
 		{
 			desc:  "deletesBefore when cursor in the middle, full-width runes",
@@ -701,6 +719,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "世c⇨",
 			wantContent:       "世cde",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 6,
 		},
 		{
 			desc:  "deletesBefore does nothing when cursor at the start",
@@ -724,6 +743,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        0,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "delete does nothing when cursor at the end",
@@ -743,6 +763,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦de",
 			wantContent:       "abcde",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "delete in the middle, last rune remains hidden",
@@ -767,6 +788,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "acd⇨",
 			wantContent:       "acde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 6,
 		},
 		{
 			desc:  "delete in the middle, last rune becomes visible",
@@ -792,6 +814,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "ade",
 			wantContent:       "ade",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 7,
 		},
 		{
 			desc:  "delete in the middle, last full-width rune would be invisible, shifts to keep cursor in window",
@@ -818,6 +841,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦世",
 			wantContent:       "ab世",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 7,
 		},
 		{
 			desc:  "delete in the middle, last rune was and is visible",
@@ -840,6 +864,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "ac",
 			wantContent:       "ac",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "delete in the middle, last full-width rune was and is visible",
@@ -862,6 +887,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "a世",
 			wantContent:       "a世",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "delete last rune, contains full-width runes",
@@ -885,6 +911,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "",
 			wantContent:       "",
 			wantCurIdx:        0,
+			wantOnChangeCalls: 6,
 		},
 		{
 			desc:  "half-width runes only, exact fit",
@@ -901,6 +928,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "full-width runes only, exact fit",
@@ -917,6 +945,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "你好世",
 			wantContent:       "你好世",
 			wantCurIdx:        6,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "half-width runes only, both ends hidden",
@@ -938,6 +967,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "half-width runes only, both ends invisible, scrolls to make start visible",
@@ -960,6 +990,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "half-width runes only, both ends invisible, deletes to make start visible",
@@ -982,6 +1013,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "acd⇨",
 			wantContent:       "acde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 6,
 		},
 		{
 			desc:  "half-width runes only, deletion on second page refills the field",
@@ -1004,6 +1036,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦df",
 			wantContent:       "abcdf",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 7,
 		},
 		{
 			desc:  "half-width runes only, both ends invisible, scrolls to make end visible",
@@ -1030,6 +1063,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦de",
 			wantContent:       "abcde",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "half-width runes only, both ends invisible, deletes to make end visible",
@@ -1055,6 +1089,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦de",
 			wantContent:       "abde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 6,
 		},
 		{
 			desc:  "full-width runes only, both ends invisible",
@@ -1074,6 +1109,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦世⇨",
 			wantContent:       "你好世界",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "full-width runes only, both ends invisible, scrolls to make start visible",
@@ -1097,6 +1133,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "你好⇨",
 			wantContent:       "你好世界",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "full-width runes only, both ends invisible, deletes to make start visible",
@@ -1120,6 +1157,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "你世⇨",
 			wantContent:       "你世界",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "full-width runes only, both ends invisible, scrolls to make end visible",
@@ -1143,6 +1181,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦界",
 			wantContent:       "你好世界",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "full-width runes only, both ends invisible, deletes to make end visible",
@@ -1166,6 +1205,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦界",
 			wantContent:       "你好界",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "scrolls to make full-width rune appear at the beginning",
@@ -1186,6 +1226,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "你b⇨",
 			wantContent:       "你bcd",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "scrolls to make full-width rune appear at the end",
@@ -1207,6 +1248,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦你",
 			wantContent:       "abc你",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "inserts after last full width rune, first is half-width",
@@ -1225,6 +1267,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦c你e",
 			wantContent:       "abc你e",
 			wantCurIdx:        5,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "inserts after last full width rune, first is half-width",
@@ -1242,6 +1285,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦你d",
 			wantContent:       "世b你d",
 			wantCurIdx:        4,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "inserts after last full width rune, hidden rune is full-width",
@@ -1259,6 +1303,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦cd",
 			wantContent:       "世你cd",
 			wantCurIdx:        4,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "scrolls right, first is full-width, last are half-width",
@@ -1285,6 +1330,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦def⇨",
 			wantContent:       "a你世defgh",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 8,
 		},
 		{
 			desc:  "scrolls right, first is half-width, last is full-width",
@@ -1311,6 +1357,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦你世⇨",
 			wantContent:       "abc你世fgh",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 8,
 		},
 		{
 			desc:  "scrolls right, first and last are full-width",
@@ -1331,6 +1378,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦世⇨",
 			wantContent:       "你好世界",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "scrolls right, first and last are half-width",
@@ -1357,6 +1405,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cdef⇨",
 			wantContent:       "abcdefg",
 			wantCurIdx:        4,
+			wantOnChangeCalls: 7,
 		},
 		{
 			desc:  "scrolls left, first is full-width, last are half-width",
@@ -1383,6 +1432,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦def⇨",
 			wantContent:       "a你世defgh",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 8,
 		},
 		{
 			desc:  "scrolls left, first is half-width, last is full-width",
@@ -1409,6 +1459,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦你世⇨",
 			wantContent:       "abc你世fgh",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 8,
 		},
 		{
 			desc:  "scrolls left, first and last are full-width",
@@ -1428,6 +1479,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦世⇨",
 			wantContent:       "你好世界",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 4,
 		},
 		{
 			desc:  "scrolls left, first and last are half-width",
@@ -1453,6 +1505,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cdef⇨",
 			wantContent:       "abcdefg",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 7,
 		},
 		{
 			desc:  "resets the field editor",
@@ -1470,6 +1523,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "",
 			wantContent:       "",
 			wantCurIdx:        0,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "doesn't insert runes with rune width of zero",
@@ -1486,6 +1540,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "ac",
 			wantContent:       "ac",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 2,
 		},
 		{
 			desc:  "all text visible, moves cursor to position zero",
@@ -1503,6 +1558,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        0,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "all text visible, moves cursor to position in the middle",
@@ -1520,6 +1576,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "all text visible, moves cursor back to the last character",
@@ -1538,6 +1595,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "all text visible, moves cursor to the appending space",
@@ -1556,6 +1614,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "all text visible, moves cursor before the beginning of data",
@@ -1574,6 +1633,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        0,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "all text visible, moves cursor after the appending space",
@@ -1592,6 +1652,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "abc",
 			wantContent:       "abc",
 			wantCurIdx:        3,
+			wantOnChangeCalls: 3,
 		},
 		{
 			desc:  "moves cursor when there is no text",
@@ -1629,6 +1690,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "both ends hidden, moves cursor onto the first character",
@@ -1655,6 +1717,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        1,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "both ends hidden, moves cursor onto the right arrow",
@@ -1680,6 +1743,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "both ends hidden, moves cursor onto the last character",
@@ -1705,6 +1769,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦cd⇨",
 			wantContent:       "abcde",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "moves cursor onto the first cell containing a full-width rune",
@@ -1730,6 +1795,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦世界⇨",
 			wantContent:       "你好世界你",
 			wantCurIdx:        4,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "moves cursor onto the second cell containing a full-width rune",
@@ -1755,6 +1821,7 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦世界⇨",
 			wantContent:       "你好世界你",
 			wantCurIdx:        4,
+			wantOnChangeCalls: 5,
 		},
 		{
 			desc:  "moves cursor onto the second right arrow",
@@ -1780,12 +1847,17 @@ func TestFieldEditor(t *testing.T) {
 			wantView:          "⇦⇦世界⇨",
 			wantContent:       "你好世界你",
 			wantCurIdx:        2,
+			wantOnChangeCalls: 5,
 		},
 	}
 
 	for _, tc := range tests {
 		t.Run(tc.desc, func(t *testing.T) {
-			fe := newFieldEditor()
+			var changeCount int
+			fe := newFieldEditor(func(data string) {
+				changeCount++
+			})
+
 			if tc.ops != nil {
 				if err := tc.ops(fe); err != nil {
 					t.Fatalf("ops => unexpected error: %v", err)
@@ -1808,6 +1880,10 @@ func TestFieldEditor(t *testing.T) {
 			if gotContent != tc.wantContent {
 				t.Errorf("content -> %q, want %q", gotContent, tc.wantContent)
 			}
+
+			if tc.wantOnChangeCalls != changeCount {
+				t.Errorf("unexpected number of onChange calls -> %d, want %d", changeCount, tc.wantOnChangeCalls)
+			}
 		})
 	}
 }

widgets/textinput/options.go

@@ -63,6 +63,7 @@ type options struct {
 
 	filter                   FilterFn
 	onSubmit                 SubmitFn
+	onChange                 ChangeFn
 	clearOnSubmit            bool
 	exclusiveKeyboardOnFocus bool
 }
@@ -269,6 +270,21 @@ func OnSubmit(fn SubmitFn) Option {
 	})
 }
 
+// ChangeFn when passed to OnChage will be called with all the text in the text
+// input each time it gets modified.
+//
+// This function must be thread-safe as the keyboard event that
+// triggers the submission comes from a separate goroutine.
+type ChangeFn func(data string)
+
+// OnChange sets a function that will be called when the content of the text input
+// field changes.
+func OnChange(fn ChangeFn) Option {
+	return option(func(opts *options) {
+		opts.onChange = fn
+	})
+}
+
 // ClearOnSubmit sets the text input to be cleared when a submit of the content
 // is triggered by the user pressing the Enter key.
 func ClearOnSubmit() Option {

widgets/textinput/textinput.go

@@ -70,10 +70,9 @@ func New(opts ...Option) (*TextInput, error) {
 		return nil, err
 	}
 	ti := &TextInput{
-		editor: newFieldEditor(),
+		editor: newFieldEditor(opt.onChange),
 		opts:   opt,
 	}
-
 	for _, r := range ti.opts.defaultText {
 		ti.editor.insert(r)
 	}

widgets/textinput/textinputdemo/textinputdemo.go

@@ -29,13 +29,16 @@ import (
 	"github.com/mum4k/termdash/terminal/tcell"
 	"github.com/mum4k/termdash/widgets/button"
 	"github.com/mum4k/termdash/widgets/segmentdisplay"
+	"github.com/mum4k/termdash/widgets/text"
 	"github.com/mum4k/termdash/widgets/textinput"
 )
 
 // rotate returns a new slice with inputs rotated by step.
 // I.e. for a step of one:
+//
 //	inputs[0] -> inputs[len(inputs)-1]
 //	inputs[1] -> inputs[0]
+//
 // And so on.
 func rotate(inputs []rune, step int) []rune {
 	return append(inputs[step:], inputs[:step]...)
@@ -126,11 +129,20 @@ func main() {
 	updateText := make(chan string)
 	go rollText(ctx, rollingSD, updateText)
 
+	mirror, err := text.New()
+	if err != nil {
+		panic(err)
+	}
+
 	input, err := textinput.New(
 		textinput.Label("New text:", cell.FgColor(cell.ColorNumber(33))),
 		textinput.MaxWidthCells(20),
 		textinput.Border(linestyle.Light),
 		textinput.PlaceHolder("Enter any text"),
+		textinput.OnChange(func(data string) {
+			mirror.Reset()
+			mirror.Write(data)
+		}),
 	)
 	if err != nil {
 		panic(err)
@@ -177,7 +189,8 @@ func main() {
 		),
 	)
 	builder.Add(
-		grid.RowHeightPerc(20,
+		grid.RowHeightPerc(40,
+			grid.RowHeightPerc(50,
 				grid.Widget(
 					input,
 					container.AlignHorizontal(align.HorizontalCenter),
@@ -185,10 +198,21 @@ func main() {
 					container.MarginBottom(1),
 				),
 			),
+			grid.RowHeightPerc(50,
+				grid.Widget(
+					mirror,
+					container.Border(linestyle.Light),
+					container.BorderTitle("Text"),
+					container.AlignHorizontal(align.HorizontalCenter),
+					container.AlignHorizontal(align.Horizontal(align.VerticalBottom)),
+					container.MarginBottom(1),
+				),
+			),
+		),
 	)
 
 	builder.Add(
-		grid.RowHeightPerc(40,
+		grid.RowHeightPerc(20,
 			grid.ColWidthPerc(20),
 			grid.ColWidthPerc(20,
 				grid.Widget(