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# Refs and Click Handling
## Overview
Refs let you hold a reference to a rendered element so you can interact with it from Go code. The most common use is mouse click handling: attach a ref to a button, then check if a click landed on that button. go-tui provides three ref types (`Ref`, `RefList`, and `RefMap[K]`) for single elements, indexed collections, and keyed collections.
## What is a Ref
A `Ref` is a pointer to a single element in the rendered tree. Create one with `tui.NewRef()` and attach it to an element using the `ref` attribute:
```go
type myApp struct {
saveBtn *tui.Ref
}
func MyApp() *myApp {
return &myApp{
saveBtn: tui.NewRef(),
}
}
```
```gsx
templ (a *myApp) Render() {
<button ref={a.saveBtn} class="px-2">Save</button>
}
```
After the first render, `a.saveBtn.El()` returns the `*tui.Element` for that button. Before the first render it returns `nil`, so always check:
```go
if el := a.saveBtn.El(); el != nil {
// safe to use el
}
```
The generated code calls `.Set()` on the ref each render cycle, so the ref always points to the current element instance.
## Ref Types
go-tui provides three ref types for different use cases:
| Type | Constructor | Use When |
|------|------------|----------|
| `*tui.Ref` | `tui.NewRef()` | You have a single element to reference |
| `*tui.RefList` | `tui.NewRefList()` | You have elements in a `for` loop, accessed by index |
| `*tui.RefMap[K]` | `tui.NewRefMap[string]()` | You have elements keyed by a value (string, int, etc.) |
`Ref` stores one element. `RefList` stores elements by their loop index; use `.At(i)` to bind in the template and `.El(i)` to read back. `RefMap[K]` stores elements by an arbitrary key; use `.At(key)` to bind and `.El(key)` to read back.
## Click Handling Pattern
Mouse click handling follows a three-step pattern:
**1. Create refs** in your constructor:
```go
func MyApp() *myApp {
return &myApp{
saveBtn: tui.NewRef(),
cancelBtn: tui.NewRef(),
}
}
```
**2. Bind refs** in your template:
```gsx
<button ref={a.saveBtn} class="px-2">Save</button>
<button ref={a.cancelBtn} class="px-2">Cancel</button>
```
**3. Wire up HandleMouse** with `HandleClicks`:
```go
func (a *myApp) HandleMouse(me tui.MouseEvent) bool {
return tui.HandleClicks(me,
tui.Click(a.saveBtn, a.onSave),
tui.Click(a.cancelBtn, a.onCancel),
)
}
func (a *myApp) onSave() { /* ... */ }
func (a *myApp) onCancel() { /* ... */ }
```
`HandleClicks` checks each `Click` binding in order. When the mouse event is a left-click press that lands within a ref's element bounds, it calls that binding's handler and returns `true`. If no binding matches, it returns `false`.
## HandleClicks Details
`tui.HandleClicks` only responds to left-click press events (`MouseLeft` with `MousePress`). It does not fire on release, drag, or right-click. The bindings are checked in order, and the first match wins.
Each `tui.Click` binding takes a ref (any of the three types) and a `func()` handler. The framework checks whether the click coordinates fall within the element's rendered bounds. For `RefList` and `RefMap`, it checks all stored elements.
The `HandleMouse` method on your component implements the `MouseListener` interface. Return `true` if you handled the event, `false` to let it propagate.
## Refs in Loops
When you use `ref=` inside a `for` loop, the generator automatically uses the right ref type based on whether a `key` attribute is present.
### RefList (no key)
Without a `key`, the ref becomes a `RefList`, an ordered collection populated with `Append` on each iteration:
```go
type listApp struct {
items []string
itemRefs *tui.RefList
}
func ListApp() *listApp {
return &listApp{
items: []string{"Alpha", "Beta", "Gamma"},
itemRefs: tui.NewRefList(),
}
}
```
```gsx
for _, item := range a.items {
<span ref={a.itemRefs} class="p-1">{item}</span>
}
```
The generated code calls `a.itemRefs.Append(el)` for each iteration. Access elements with `.At(i)` or `.All()`.
### RefMap with key
Add a `key` attribute to turn the ref into a `RefMap[K]`. Each element is stored under its key:
```go
type tabApp struct {
presetBtns *tui.RefMap[string]
}
```
```gsx
for _, p := range presets {
<button ref={a.presetBtns} key={p.name} class="px-1">{p.name}</button>
}
```
The generated code calls `a.presetBtns.Put(p.name, el)` for each iteration. Look up elements with `.Get(key)` or iterate with `.All()`.
This is useful when you need to identify *which* element was clicked by its key rather than by position.
## Combining Keyboard and Mouse
The color mixer example wires both keyboard shortcuts and clickable buttons to the same actions:
```go
func (c *colorMixer) KeyMap() tui.KeyMap {
return tui.KeyMap{
tui.On(tui.KeyEscape, func(ke tui.KeyEvent) { ke.App().Stop() }),
tui.On(tui.Rune('r'), func(ke tui.KeyEvent) { c.adjustRed(16) }),
tui.On(tui.Rune('R'), func(ke tui.KeyEvent) { c.adjustRed(-16) }),
tui.On(tui.Rune('g'), func(ke tui.KeyEvent) { c.adjustGreen(16) }),
tui.On(tui.Rune('G'), func(ke tui.KeyEvent) { c.adjustGreen(-16) }),
tui.On(tui.Rune('b'), func(ke tui.KeyEvent) { c.adjustBlue(16) }),
tui.On(tui.Rune('B'), func(ke tui.KeyEvent) { c.adjustBlue(-16) }),
}
}
func (c *colorMixer) HandleMouse(me tui.MouseEvent) bool {
// Check single-ref button clicks
if tui.HandleClicks(me,
tui.Click(c.redUpBtn, func() { c.adjustRed(16) }),
tui.Click(c.redDnBtn, func() { c.adjustRed(-16) }),
tui.Click(c.greenUpBtn, func() { c.adjustGreen(16) }),
tui.Click(c.greenDnBtn, func() { c.adjustGreen(-16) }),
tui.Click(c.blueUpBtn, func() { c.adjustBlue(16) }),
tui.Click(c.blueDnBtn, func() { c.adjustBlue(-16) }),
) {
return true
}
// Check keyed-ref preset button clicks via RefMap
if me.Button == tui.MouseLeft && me.Action == tui.MousePress {
for name, el := range c.presetBtns.All() {
if el != nil && el.ContainsPoint(me.X, me.Y) {
c.applyPreset(name)
return true
}
}
}
return false
}
```
Both input methods call the same `adjust*` methods, so the behavior stays consistent. The preset buttons use `RefMap.All()` to iterate and hit-test by key, letting us identify which preset was clicked by name.
## Click Handling in Modals
Modals handle mouse clicks internally. You don't need refs or `HandleMouse` for buttons inside a modal. Use the `onActivate` attribute on focusable elements instead:
```gsx
<modal open={s.showDialog} class="justify-center items-center">
<div class="border-rounded p-2 flex-col gap-1 w-40">
<span class="font-bold">Delete Item?</span>
<div class="flex gap-2 justify-center">
<button class="px-2 border-rounded focusable" onActivate={s.onDelete}>Delete</button>
<button class="px-2 border-rounded focusable" onActivate={s.onCancel}>Cancel</button>
</div>
</div>
</modal>
```
Clicking a button fires its `onActivate` callback. Clicking the backdrop (the dimmed area outside the dialog) closes the modal by setting the `open` state to `false`.
Enter does the same thing as a click: it fires `onActivate` on whichever button is focused. Tab and Shift+Tab cycle between focusable elements inside the modal. Escape closes it.
Outside of modals, use refs and `HandleClicks` for click targets. Inside modals, `onActivate` is all you need.
## Complete Example
This color mixer uses ref-based click handling for the +/- buttons and presets, plus a modal confirmation dialog for the reset action. Each color channel has a visual bar, a value readout, and clickable buttons. Preset colors use `RefMap` with `key`:
```gsx
package main
import (
"fmt"
tui "github.com/grindlemire/go-tui"
)
type colorMixer struct {
red *tui.State[int]
green *tui.State[int]
blue *tui.State[int]
redUpBtn *tui.Ref
redDnBtn *tui.Ref
greenUpBtn *tui.Ref
greenDnBtn *tui.Ref
blueUpBtn *tui.Ref
blueDnBtn *tui.Ref
presetBtns *tui.RefMap[string]
activePreset *tui.State[string]
showReset *tui.State[bool]
}
func ColorMixer() *colorMixer {
return &colorMixer{
red: tui.NewState(128),
green: tui.NewState(64),
blue: tui.NewState(200),
redUpBtn: tui.NewRef(),
redDnBtn: tui.NewRef(),
greenUpBtn: tui.NewRef(),
greenDnBtn: tui.NewRef(),
blueUpBtn: tui.NewRef(),
blueDnBtn: tui.NewRef(),
presetBtns: tui.NewRefMap[string](),
activePreset: tui.NewState(""),
showReset: tui.NewState(false),
}
}
type preset struct {
name string
r, g, b int
}
var presets = []preset{
{"Sunset", 255, 128, 0},
{"Ocean", 0, 100, 255},
{"Forest", 34, 180, 34},
{"Rose", 255, 64, 128},
}
func clamp(v, min, max int) int {
if v < min {
return min
}
if v > max {
return max
}
return v
}
func (c *colorMixer) adjustRed(delta int) {
c.red.Set(clamp(c.red.Get()+delta, 0, 255))
c.activePreset.Set("")
}
func (c *colorMixer) adjustGreen(delta int) {
c.green.Set(clamp(c.green.Get()+delta, 0, 255))
c.activePreset.Set("")
}
func (c *colorMixer) adjustBlue(delta int) {
c.blue.Set(clamp(c.blue.Get()+delta, 0, 255))
c.activePreset.Set("")
}
func (c *colorMixer) confirmReset() {
c.showReset.Set(false)
c.red.Set(128)
c.green.Set(64)
c.blue.Set(200)
c.activePreset.Set("")
}
func (c *colorMixer) cancelReset() {
c.showReset.Set(false)
}
func (c *colorMixer) applyPreset(name string) {
for _, p := range presets {
if p.name == name {
c.red.Set(p.r)
c.green.Set(p.g)
c.blue.Set(p.b)
c.activePreset.Set(name)
return
}
}
}
func (c *colorMixer) KeyMap() tui.KeyMap {
return tui.KeyMap{
tui.On(tui.KeyEscape, func(ke tui.KeyEvent) { ke.App().Stop() }),
tui.On(tui.Rune('q'), func(ke tui.KeyEvent) { ke.App().Stop() }),
tui.On(tui.Rune('r'), func(ke tui.KeyEvent) { c.adjustRed(16) }),
tui.On(tui.Rune('R'), func(ke tui.KeyEvent) { c.adjustRed(-16) }),
tui.On(tui.Rune('g'), func(ke tui.KeyEvent) { c.adjustGreen(16) }),
tui.On(tui.Rune('G'), func(ke tui.KeyEvent) { c.adjustGreen(-16) }),
tui.On(tui.Rune('b'), func(ke tui.KeyEvent) { c.adjustBlue(16) }),
tui.On(tui.Rune('B'), func(ke tui.KeyEvent) { c.adjustBlue(-16) }),
tui.On(tui.Rune('x'), func(ke tui.KeyEvent) { c.showReset.Set(true) }),
}
}
func (c *colorMixer) HandleMouse(me tui.MouseEvent) bool {
// Check single-ref button clicks
if tui.HandleClicks(me,
tui.Click(c.redUpBtn, func() { c.adjustRed(16) }),
tui.Click(c.redDnBtn, func() { c.adjustRed(-16) }),
tui.Click(c.greenUpBtn, func() { c.adjustGreen(16) }),
tui.Click(c.greenDnBtn, func() { c.adjustGreen(-16) }),
tui.Click(c.blueUpBtn, func() { c.adjustBlue(16) }),
tui.Click(c.blueDnBtn, func() { c.adjustBlue(-16) }),
) {
return true
}
// Check keyed-ref preset button clicks via RefMap
if me.Button == tui.MouseLeft && me.Action == tui.MousePress {
for name, el := range c.presetBtns.All() {
if el != nil && el.ContainsPoint(me.X, me.Y) {
c.applyPreset(name)
return true
}
}
}
return false
}
func colorBar(value int) string {
filled := value * 20 / 255
bar := ""
for i := 0; i < 20; i++ {
if i < filled {
bar += "█"
} else {
bar += "░"
}
}
return bar
}
templ (c *colorMixer) Render() {
<div class="flex-col p-1 border-rounded border-cyan">
<span class="text-gradient-cyan-magenta font-bold">Color Mixer</span>
// Color preview
<div class="flex-col items-center border-rounded p-1">
<span class="text-gradient-cyan-magenta font-bold">Preview</span>
<div backgroundGradient={tui.NewGradient(tui.Black, tui.RGBColor(uint8(c.red.Get()), uint8(c.green.Get()), uint8(c.blue.Get())))} height={2} width={30}>
<span>{" "}</span>
</div>
<div class="flex gap-2 justify-center">
<span class="text-red font-bold">{fmt.Sprintf("R: %d", c.red.Get())}</span>
<span class="text-green font-bold">{fmt.Sprintf("G: %d", c.green.Get())}</span>
<span class="text-blue font-bold">{fmt.Sprintf("B: %d", c.blue.Get())}</span>
</div>
</div>
// Color bars
<div class="flex-col border-rounded p-1">
<div class="flex gap-1">
<span class="text-red font-bold w-5">Red</span>
<span class="text-red">{colorBar(c.red.Get())}</span>
<span class="text-red font-bold">{fmt.Sprintf("%3d", c.red.Get())}</span>
</div>
<div class="flex gap-1">
<span class="text-green font-bold w-5">Grn</span>
<span class="text-green">{colorBar(c.green.Get())}</span>
<span class="text-green font-bold">{fmt.Sprintf("%3d", c.green.Get())}</span>
</div>
<div class="flex gap-1">
<span class="text-blue font-bold w-5">Blu</span>
<span class="text-blue">{colorBar(c.blue.Get())}</span>
<span class="text-blue font-bold">{fmt.Sprintf("%3d", c.blue.Get())}</span>
</div>
</div>
// Channel controls with refs
<div class="flex gap-1">
<div class="flex-col border-rounded p-1 items-center" flexGrow={1.0}>
<span class="font-bold text-red">Red</span>
<div class="flex gap-1 items-center">
<button ref={c.redDnBtn} class="px-1">{"-"}</button>
<span class="font-bold text-red">{fmt.Sprintf("%3d", c.red.Get())}</span>
<button ref={c.redUpBtn} class="px-1">{"+"}</button>
</div>
</div>
<div class="flex-col border-rounded p-1 items-center" flexGrow={1.0}>
<span class="font-bold text-green">Green</span>
<div class="flex gap-1 items-center">
<button ref={c.greenDnBtn} class="px-1">{"-"}</button>
<span class="font-bold text-green">{fmt.Sprintf("%3d", c.green.Get())}</span>
<button ref={c.greenUpBtn} class="px-1">{"+"}</button>
</div>
</div>
<div class="flex-col border-rounded p-1 items-center" flexGrow={1.0}>
<span class="font-bold text-blue">Blue</span>
<div class="flex gap-1 items-center">
<button ref={c.blueDnBtn} class="px-1">{"-"}</button>
<span class="font-bold text-blue">{fmt.Sprintf("%3d", c.blue.Get())}</span>
<button ref={c.blueUpBtn} class="px-1">{"+"}</button>
</div>
</div>
</div>
// Preset colors using RefMap with key
<div class="flex gap-1 border-rounded p-1 items-center">
<span class="font-bold">Presets:</span>
for _, p := range presets {
if p.name == c.activePreset.Get() {
<button ref={c.presetBtns} key={p.name} class="px-1 font-bold text-cyan">{p.name}</button>
} else {
<button ref={c.presetBtns} key={p.name} class="px-1 font-dim">{p.name}</button>
}
}
</div>
<div class="flex justify-center">
<span class="font-dim">r/g/b increase | R/G/B decrease | x reset | click buttons/presets | q quit</span>
</div>
</div>
// Reset confirmation modal (uses onActivate, not refs)
<modal open={c.showReset} class="justify-center items-center">
<div class="border-rounded p-2 flex-col gap-1 w-40 border-cyan">
<span class="font-bold text-cyan">Reset Colors?</span>
<span>This restores the default RGB values.</span>
<div class="flex gap-2 justify-center">
<button class="px-2 border-rounded focusable" onActivate={c.confirmReset}>Yes</button>
<button class="px-2 border-rounded focusable" onActivate={c.cancelReset}>No</button>
</div>
</div>
</modal>
}
```
With `main.go`:
```go
package main
import (
"fmt"
"os"
tui "github.com/grindlemire/go-tui"
)
func main() {
app, err := tui.NewApp(
tui.WithRootComponent(ColorMixer()),
)
if err != nil {
fmt.Fprintf(os.Stderr, "Failed to create app: %v\n", err)
os.Exit(1)
}
defer app.Close()
if err := app.Run(); err != nil {
fmt.Fprintf(os.Stderr, "App error: %v\n", err)
os.Exit(1)
}
}
```
Generate and run:
```bash
tui generate ./...
go run .
```
Click the +/- buttons, use r/g/b keys to adjust colors, or click a preset to apply it:
Click "reset" to open the confirmation dialog and click on an option.
## Next Steps
- [Built-in Elements](elements) - Reference guide to every HTML-like element in go-tui
- [Streaming Data](streaming) - Build a live data viewer with channels and auto-scroll
|