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