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app.go
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app.go
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// Copyright 2018 The Tcell Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use file except in compliance with the License.
// You may obtain a copy of the license at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package views
import (
"sync"
"github.com/gdamore/tcell"
)
// Application represents an event-driven application running on a screen.
type Application struct {
widget Widget
screen tcell.Screen
style tcell.Style
err error
wg sync.WaitGroup
}
// SetRootWidget sets the primary (root, main) Widget to be displayed.
func (app *Application) SetRootWidget(widget Widget) {
app.widget = widget
}
// initialize initializes the application. It will normally attempt to
// allocate a default screen if one is not already established.
func (app *Application) initialize() error {
if app.screen == nil {
if app.screen, app.err = tcell.NewScreen(); app.err != nil {
return app.err
}
app.screen.SetStyle(app.style)
}
return nil
}
// Quit causes the application to shutdown gracefully. It does not wait
// for the application to exit, but returns immediately.
func (app *Application) Quit() {
ev := &eventAppQuit{}
ev.SetEventNow()
if scr := app.screen; scr != nil {
go func() { scr.PostEventWait(ev) }()
}
}
// Refresh causes the application forcibly redraw everything. Use this
// to clear up screen corruption, etc.
func (app *Application) Refresh() {
ev := &eventAppRefresh{}
ev.SetEventNow()
if scr := app.screen; scr != nil {
go func() { scr.PostEventWait(ev) }()
}
}
// Update asks the application to draw any screen updates that have not
// been drawn yet.
func (app *Application) Update() {
ev := &eventAppUpdate{}
ev.SetEventNow()
if scr := app.screen; scr != nil {
go func() { scr.PostEventWait(ev) }()
}
}
// PostFunc posts a function to be executed in the context of the
// application's event loop. Functions that need to update displayed
// state, etc. can do this to avoid holding locks.
func (app *Application) PostFunc(fn func()) {
ev := &eventAppFunc{fn: fn}
ev.SetEventNow()
if scr := app.screen; scr != nil {
go func() { scr.PostEventWait(ev) }()
}
}
// SetScreen sets the screen to use for the application. This must be
// done before the application starts to run or is initialized.
func (app *Application) SetScreen(scr tcell.Screen) {
if app.screen == nil {
app.screen = scr
app.err = nil
}
}
// SetStyle sets the default style (background) to be used for Widgets
// that have not specified any other style.
func (app *Application) SetStyle(style tcell.Style) {
app.style = style
if app.screen != nil {
app.screen.SetStyle(style)
}
}
func (app *Application) run() {
screen := app.screen
widget := app.widget
if widget == nil {
app.wg.Done()
return
}
if screen == nil {
if e := app.initialize(); e != nil {
app.wg.Done()
return
}
screen = app.screen
}
defer func() {
screen.Fini()
app.wg.Done()
}()
screen.Init()
screen.Clear()
widget.SetView(screen)
loop:
for {
if widget = app.widget; widget == nil {
break
}
widget.Draw()
screen.Show()
ev := screen.PollEvent()
switch nev := ev.(type) {
case *eventAppQuit:
break loop
case *eventAppUpdate:
screen.Show()
case *eventAppRefresh:
screen.Sync()
case *eventAppFunc:
nev.fn()
case *tcell.EventResize:
screen.Sync()
widget.Resize()
default:
widget.HandleEvent(ev)
}
}
}
// Start starts the application loop, initializing the screen
// and starting the Event loop. The application will run in a goroutine
// until Quit is called.
func (app *Application) Start() {
app.wg.Add(1)
go app.run()
}
// Wait waits until the application finishes.
func (app *Application) Wait() error {
app.wg.Wait()
return app.err
}
// Run runs the application, waiting until the application loop exits.
// It is equivalent to app.Start() followed by app.Wait()
func (app *Application) Run() error {
app.Start()
return app.Wait()
}
type eventAppUpdate struct {
tcell.EventTime
}
type eventAppQuit struct {
tcell.EventTime
}
type eventAppRefresh struct {
tcell.EventTime
}
type eventAppFunc struct {
tcell.EventTime
fn func()
}