package cview import ( "sync" "github.com/gdamore/tcell" ) // The size of the event/update/redraw channels. const queueSize = 100 // Application represents the top node of an application. // // It is not strictly required to use this class as none of the other classes // depend on it. However, it provides useful tools to set up an application and // plays nicely with all widgets. // // The following command displays a primitive p on the screen until Ctrl-C is // pressed: // // if err := cview.NewApplication().SetRoot(p, true).Run(); err != nil { // panic(err) // } type Application struct { sync.RWMutex // The application's screen. Apart from Run(), this variable should never be // set directly. Always use the screenReplacement channel after calling // Fini(), to set a new screen (or nil to stop the application). screen tcell.Screen // The primitive which currently has the keyboard focus. focus Primitive // The root primitive to be seen on the screen. root Primitive // Whether or not the application resizes the root primitive. rootFullscreen bool // An optional capture function which receives a key event and returns the // event to be forwarded to the default input handler (nil if nothing should // be forwarded). inputCapture func(event *tcell.EventKey) *tcell.EventKey // An optional callback function which is invoked just before the root // primitive is drawn. beforeDraw func(screen tcell.Screen) bool // An optional callback function which is invoked after the root primitive // was drawn. afterDraw func(screen tcell.Screen) // Used to send screen events from separate goroutine to main event loop events chan tcell.Event // Functions queued from goroutines, used to serialize updates to primitives. updates chan func() // An object that the screen variable will be set to after Fini() was called. // Use this channel to set a new screen object for the application // (screen.Init() and draw() will be called implicitly). A value of nil will // stop the application. screenReplacement chan tcell.Screen } // NewApplication creates and returns a new application. func NewApplication() *Application { return &Application{ events: make(chan tcell.Event, queueSize), updates: make(chan func(), queueSize), screenReplacement: make(chan tcell.Screen, 1), } } // SetInputCapture sets a function which captures all key events before they are // forwarded to the key event handler of the primitive which currently has // focus. This function can then choose to forward that key event (or a // different one) by returning it or stop the key event processing by returning // nil. // // Note that this also affects the default event handling of the application // itself: Such a handler can intercept the Ctrl-C event which closes the // application. func (a *Application) SetInputCapture(capture func(event *tcell.EventKey) *tcell.EventKey) *Application { a.inputCapture = capture return a } // GetInputCapture returns the function installed with SetInputCapture() or nil // if no such function has been installed. func (a *Application) GetInputCapture() func(event *tcell.EventKey) *tcell.EventKey { return a.inputCapture } // SetScreen allows you to provide your own tcell.Screen object. For most // applications, this is not needed and you should be familiar with // tcell.Screen when using this function. // // This function is typically called before the first call to Run(). Init() need // not be called on the screen. func (a *Application) SetScreen(screen tcell.Screen) *Application { if screen == nil { return a // Invalid input. Do nothing. } a.Lock() if a.screen == nil { // Run() has not been called yet. a.screen = screen a.Unlock() return a } // Run() is already in progress. Exchange screen. oldScreen := a.screen a.Unlock() oldScreen.Fini() a.screenReplacement <- screen return a } // Run starts the application and thus the event loop. This function returns // when Stop() was called. func (a *Application) Run() error { var err error a.Lock() // Make a screen if there is none yet. if a.screen == nil { a.screen, err = tcell.NewScreen() if err != nil { a.Unlock() return err } if err = a.screen.Init(); err != nil { a.Unlock() return err } } // We catch panics to clean up because they mess up the terminal. defer func() { if p := recover(); p != nil { if a.screen != nil { a.screen.Fini() } panic(p) } }() // Draw the screen for the first time. a.Unlock() a.draw() // Separate loop to wait for screen events. var wg sync.WaitGroup wg.Add(1) go func() { defer wg.Done() for { a.RLock() screen := a.screen a.RUnlock() if screen == nil { // We have no screen. Let's stop. a.QueueEvent(nil) break } // Wait for next event and queue it. event := screen.PollEvent() if event != nil { // Regular event. Queue. a.QueueEvent(event) continue } // A screen was finalized (event is nil). Wait for a new scren. screen = <-a.screenReplacement if screen == nil { // No new screen. We're done. a.QueueEvent(nil) return } // We have a new screen. Keep going. a.Lock() a.screen = screen a.Unlock() // Initialize and draw this screen. if err := screen.Init(); err != nil { panic(err) } a.draw() } }() // Start event loop. EventLoop: for { select { case event := <-a.events: if event == nil { break EventLoop } switch event := event.(type) { case *tcell.EventKey: a.RLock() p := a.focus inputCapture := a.inputCapture a.RUnlock() // Intercept keys. if inputCapture != nil { event = inputCapture(event) if event == nil { a.draw() continue // Don't forward event. } } // Ctrl-C closes the application. if event.Key() == tcell.KeyCtrlC { a.Stop() } // Pass other key events to the currently focused primitive. if p != nil { if handler := p.InputHandler(); handler != nil { handler(event, func(p Primitive) { a.SetFocus(p) }) a.draw() } } case *tcell.EventResize: a.RLock() screen := a.screen a.RUnlock() if screen == nil { continue } screen.Clear() a.draw() } // If we have updates, now is the time to execute them. case updater := <-a.updates: updater() } } // Wait for the event loop to finish. wg.Wait() a.screen = nil return nil } // Stop stops the application, causing Run() to return. func (a *Application) Stop() { a.Lock() defer a.Unlock() screen := a.screen if screen == nil { return } a.screen = nil screen.Fini() a.screenReplacement <- nil } // Suspend temporarily suspends the application by exiting terminal UI mode and // invoking the provided function "f". When "f" returns, terminal UI mode is // entered again and the application resumes. // // A return value of true indicates that the application was suspended and "f" // was called. If false is returned, the application was already suspended, // terminal UI mode was not exited, and "f" was not called. func (a *Application) Suspend(f func()) bool { a.RLock() screen := a.screen a.RUnlock() if screen == nil { return false // Screen has not yet been initialized. } // Enter suspended mode. screen.Fini() // Wait for "f" to return. f() // Make a new screen. var err error screen, err = tcell.NewScreen() if err != nil { panic(err) } a.screenReplacement <- screen // One key event will get lost, see https://github.com/gdamore/tcell/issues/194 // Continue application loop. return true } // Draw refreshes the screen (during the next update cycle). It calls the Draw() // function of the application's root primitive and then syncs the screen // buffer. func (a *Application) Draw() *Application { a.QueueUpdate(func() { a.draw() }) return a } // ForceDraw refreshes the screen immediately. Use this function with caution as // it may lead to race conditions with updates to primitives in other // goroutines. It is always preferrable to use Draw() instead. Never call this // function from a goroutine. // // It is safe to call this function during queued updates and direct event // handling. func (a *Application) ForceDraw() *Application { return a.draw() } // draw actually does what Draw() promises to do. func (a *Application) draw() *Application { a.Lock() defer a.Unlock() screen := a.screen root := a.root fullscreen := a.rootFullscreen before := a.beforeDraw after := a.afterDraw // Maybe we're not ready yet or not anymore. if screen == nil || root == nil { return a } // Resize if requested. if fullscreen && root != nil { width, height := screen.Size() root.SetRect(0, 0, width, height) } // Call before handler if there is one. if before != nil { if before(screen) { screen.Show() return a } } // Draw all primitives. root.Draw(screen) // Call after handler if there is one. if after != nil { after(screen) } // Sync screen. screen.Show() return a } // SetBeforeDrawFunc installs a callback function which is invoked just before // the root primitive is drawn during screen updates. If the function returns // true, drawing will not continue, i.e. the root primitive will not be drawn // (and an after-draw-handler will not be called). // // Note that the screen is not cleared by the application. To clear the screen, // you may call screen.Clear(). // // Provide nil to uninstall the callback function. func (a *Application) SetBeforeDrawFunc(handler func(screen tcell.Screen) bool) *Application { a.beforeDraw = handler return a } // GetBeforeDrawFunc returns the callback function installed with // SetBeforeDrawFunc() or nil if none has been installed. func (a *Application) GetBeforeDrawFunc() func(screen tcell.Screen) bool { return a.beforeDraw } // SetAfterDrawFunc installs a callback function which is invoked after the root // primitive was drawn during screen updates. // // Provide nil to uninstall the callback function. func (a *Application) SetAfterDrawFunc(handler func(screen tcell.Screen)) *Application { a.afterDraw = handler return a } // GetAfterDrawFunc returns the callback function installed with // SetAfterDrawFunc() or nil if none has been installed. func (a *Application) GetAfterDrawFunc() func(screen tcell.Screen) { return a.afterDraw } // SetRoot sets the root primitive for this application. If "fullscreen" is set // to true, the root primitive's position will be changed to fill the screen. // // This function must be called at least once or nothing will be displayed when // the application starts. // // It also calls SetFocus() on the primitive. func (a *Application) SetRoot(root Primitive, fullscreen bool) *Application { a.Lock() a.root = root a.rootFullscreen = fullscreen if a.screen != nil { a.screen.Clear() } a.Unlock() a.SetFocus(root) return a } // ResizeToFullScreen resizes the given primitive such that it fills the entire // screen. func (a *Application) ResizeToFullScreen(p Primitive) *Application { a.RLock() width, height := a.screen.Size() a.RUnlock() p.SetRect(0, 0, width, height) return a } // SetFocus sets the focus on a new primitive. All key events will be redirected // to that primitive. Callers must ensure that the primitive will handle key // events. // // Blur() will be called on the previously focused primitive. Focus() will be // called on the new primitive. func (a *Application) SetFocus(p Primitive) *Application { a.Lock() if a.focus != nil { a.focus.Blur() } a.focus = p if a.screen != nil { a.screen.HideCursor() } a.Unlock() if p != nil { p.Focus(func(p Primitive) { a.SetFocus(p) }) } return a } // GetFocus returns the primitive which has the current focus. If none has it, // nil is returned. func (a *Application) GetFocus() Primitive { a.RLock() defer a.RUnlock() return a.focus } // QueueUpdate is used to synchronize access to primitives from non-main // goroutines. The provided function will be executed as part of the event loop // and thus will not cause race conditions with other such update functions or // the Draw() function. // // Note that Draw() is not implicitly called after the execution of f as that // may not be desirable. You can call Draw() from f if the screen should be // refreshed after each update. Alternatively, use QueueUpdateDraw() to follow // up with an immediate refresh of the screen. func (a *Application) QueueUpdate(f func()) *Application { a.updates <- f return a } // QueueUpdateDraw works like QueueUpdate() except it refreshes the screen // immediately after executing f. func (a *Application) QueueUpdateDraw(f func()) *Application { a.QueueUpdate(func() { f() a.draw() }) return a } // QueueEvent sends an event to the Application event loop. // // It is not recommended for event to be nil. func (a *Application) QueueEvent(event tcell.Event) *Application { a.events <- event return a }