Plasmacore:Applications and Screens
From Plasmaworks
Contents |
Class Application
In a Plasmacore program, class Application acts as the primary event dispatcher and program manager. You generally do not need to interact with it directly, though you may wish to install a custom ExitRequestHandler. Type "gogo doc Application::exit_request_handler" for more information.
Class Screen
A Plasmacore Screen provides program state, view, and control. The application maintains a Screen stack, with the topmost screen on the stack having active control. Your main class (topmost or specified with [main {classname}]) should extend class Screen; the program will start there.
Each Screen has the following methods.
Class Methods
- current()
- This method returns the active screen (same as Application.screen).
Lifecycle Events
- init(...)
- As with any class, the initializer is called when you first create an object of the class.
- on_activate()
- This method is called when a screen is about to have update() and/or draw() called on it for the first time. This is sometimes a while after the screen is created, so on_activate() is a good place to put timing-sensitive commands.
- on_suspend()
- This method is called whenever a screen is about to become inactive.
- on_deactivate()
- This method is called when a screen is about to become permanently replaced.
Examples assuming screen 1 is the active screen:
| Action | Events |
|---|---|
| screen1.push(screen2) | screen1.on_suspend()
screen2.on_activate() |
| screen1.replace_with(screen2) | screen1.on_suspend()
screen1.on_deactivate() |
| screen2.pop | screen2.on_suspend()
screen2.on_deactivate() |
- on_resume()
- Called when another active screen that was push()ed on this one relinquishes control (via advance() or pop()) and this screen becomes active once more. Note that if the resumed screen has never had an update or draw, its on_activate() is called instead of its on_resume().
- on_images_lost()
- Called on all screens when image data has been irrevocably lost. Currently only happens on Android due to app switching. Generally you don't need to do anything, but if you're using any OffscreenBuffer object or Image objects created with custom Bitmap data then you'll need to recreate them.
Update Cycle and Input
- update()
- When a screen is the active screen on the stack, its update() method is called 60 times per second. Update your game state in this method.
- draw()
- When a screen is the active screen on the stack, its draw() method is called up to 60 times per second. Draw the current game state here.
- on(MouseEvent e)
- Called for each kind of mouse input.
# TECHNIQUE 1
method on( MouseEvent e )
if (e.is_button_press)
println( "button #$ of mouse #$ pressed at position $." (e.button,e.mouse_id,e.position) )
elseIf (e.is_button_release or e.is_movement)
println( "Similar stuff" )
else
println( "Something else" )
endIf
# TECHNIQUE 2
method on( MouseEvent e )
which (e.type)
case MouseEvent.button_press
println( "button #$ of mouse #$ pressed at position $." (e.button,e.mouse_id,e.position) )
case MouseEvent.button_release, MouseEvent.movement
println( "Similar stuff" )
others
println( "Something else" )
endWhich
- For multitouch devices, each different touch registers as a different mouse id.
- See class Input for other mouse-related info.
- on(KeyEvent e)
- Called for each keyboard event type (press, release, repeat - e.g. key.type == KeyEvent.type_press).
- Compare e.keycode to Key.keycode_escape, etc.
- Compare e.unicode to 'A', '!', etc.
- Use e.is_press('A') or e.is_press(Key.keycode_a), etc.
- See class Input for other keyboard-related info and methods, including "Input.keyboard_visible = true" for virtual keyboards.
- on(AccelerationEvent e)
- Called on platforms that have accelerometer input.
- Use the gravity readings of e.x, e.y, and e.z.
- Call e.orientation() to obtain RollPitchYaw orientation data with roll, pitch, and yaw.
Transfer of Control
- push(Screen,[Int32 fade_style])
- Push another screen on top of this one, allowing it to assume control. You can pass Screen.fade_none (the default), Screen.fade_between (the most common fade), Screen.fade_in, or Screen.fade_out.
- pop([Int32 fade_style])
- Removes this screen from the stack and allows the previous screen to resume control.
- replace_with(Screen,[Int32 fade_style])
- Replaces this screen with the given screen.
- chain(Screen)
- Specifies a screen to be the "next" screen after this one. See advance(), below.
- advance([Int32 fade_style])
- If a "next" screen is specified, performs a replace_with(). Otherwise performs a pop().
Example
# Demonstrates using Screens as game states. A Title Screen alternates
# with a Controls Screen until a tap (aka click). The app then transitions
# to a Game Screen that can become a Pause Screen with a tap.
class TitleScreen : Screen
PROPERTIES
stopwatch() : Stopwatch
METHODS
method init
method on_activate
Display.background_color = Color.red
method update
if (stopwatch.elapsed_seconds > 2) replace_with( ControlsScreen() )
method draw
SystemFont.handle = Handle.center
SystemFont.draw( "TITLE SCREEN\n\nTap to Start", Display.center )
method on( MouseEvent e )
if (e.is_button_press) replace_with( GameScreen(), Screen.fade_between )
endClass
class ControlsScreen : Screen
PROPERTIES
stopwatch() : Stopwatch
METHODS
method init
method on_activate
Display.background_color = Color.yellow
method update
if (stopwatch.elapsed_seconds > 2) replace_with( TitleScreen() )
method draw
SystemFont.handle = Handle.center
SystemFont.draw( "CONTROLS SCREEN\n\nTap to Start", Display.center )
method on( MouseEvent e )
if (e.is_button_press) replace_with( GameScreen(), Screen.fade_between )
endClass
class GameScreen : Screen
METHODS
method init
method on_activate
on_resume
method on_resume
Display.background_color = Color.blue
method draw
SystemFont.handle = Handle.center
SystemFont.draw( "GAME PLAY\n\nTap to Pause", Display.center )
method on( MouseEvent e )
if (e.is_button_press) push( PauseScreen() )
endClass
class PauseScreen : Screen
METHODS
method init
method on_activate
on_resume
method on_resume
Display.background_color = Color.gray
method draw
SystemFont.handle = Handle.center
SystemFont.draw( "PAUSED\n\nTap to Resume", Display.center )
method on( MouseEvent e )
if (e.is_button_press) pop
endClass
