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package main
import (
"log"
"os"
"strconv"
"gioui.org/app" // app contains Window handling.
"gioui.org/font/gofont" // gofont is used for loading the default font.
"gioui.org/io/key" // key is used for keyboard events.
"gioui.org/io/system" // system is used for system events (e.g. closing the window).
"gioui.org/layout" // layout is used for layouting widgets.
"gioui.org/op" // op is used for recording different operations.
"gioui.org/unit" // unit is used to define pixel-independent sizes
"gioui.org/widget" // widget contains state handling for widgets.
"gioui.org/widget/material" // material contains material design widgets.
)
func main() {
// The ui loop is separated from the application window creation
// such that it can be used for testing.
ui := NewUI()
// This creates a new application window and starts the UI.
go func() {
w := app.NewWindow(
app.Title("Counter"),
app.Size(unit.Dp(240), unit.Dp(70)),
)
if err := ui.Run(w); err != nil {
log.Println(err)
os.Exit(1)
}
os.Exit(0)
}()
// This starts Gio main.
app.Main()
}
// defaultMargin is a margin applied in multiple places to give
// widgets room to breathe.
var defaultMargin = unit.Dp(10)
// UI holds all of the application state.
type UI struct {
// Theme is used to hold the fonts used throughout the application.
Theme *material.Theme
// Counter displays and keeps the state of the counter.
Counter Counter
}
// NewUI creates a new UI using the Go Fonts.
func NewUI() *UI {
ui := &UI{}
ui.Theme = material.NewTheme(gofont.Collection())
return ui
}
// Run handles window events and renders the application.
func (ui *UI) Run(w *app.Window) error {
var ops op.Ops
// listen for events happening on the window.
for e := range w.Events() {
// detect the type of the event.
switch e := e.(type) {
// this is sent when the application should re-render.
case system.FrameEvent:
// gtx is used to pass around rendering and event information.
gtx := layout.NewContext(&ops, e)
// render and handle UI.
ui.Layout(gtx)
// render and handle the operations from the UI.
e.Frame(gtx.Ops)
// handle a global key press.
case key.Event:
switch e.Name {
// when we click escape, let's close the window.
case key.NameEscape:
return nil
}
// this is sent when the application is closed.
case system.DestroyEvent:
return e.Err
}
}
return nil
}
// Layout displays the main program layout.
func (ui *UI) Layout(gtx layout.Context) layout.Dimensions {
// inset is used to add padding around the window border.
inset := layout.UniformInset(defaultMargin)
return inset.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
return ui.Counter.Layout(ui.Theme, gtx)
})
}
// Counter is a component that keeps track of it's state and
// displays itself as a label and a button.
type Counter struct {
// Count is the current value.
Count int
// increase is used to track button clicks.
increase widget.Clickable
}
// Layout lays out the counter and handles input.
func (counter *Counter) Layout(th *material.Theme, gtx layout.Context) layout.Dimensions {
// Flex layout lays out widgets from left to right by default.
return layout.Flex{}.Layout(gtx,
// We use weight 1 for both text and count to make them the same size.
layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
// We center align the text to the area available.
return layout.Center.Layout(gtx,
// Body1 is the default text size for reading.
material.Body1(th, strconv.Itoa(counter.Count)).Layout)
}),
// We use an empty widget to add spacing between the text
// and the button.
layout.Rigid(layout.Spacer{Height: defaultMargin}.Layout),
layout.Flexed(1, func(gtx layout.Context) layout.Dimensions {
// For every click on the button increment the count.
for range counter.increase.Clicks() {
counter.Count++
}
// Finally display the button.
return material.Button(th, &counter.increase, "Count").Layout(gtx)
}),
)
}