monkey2/modules/mojo/newdocs/app.md

@manpage Application framework

Application framework

@#### Initialization and the event loop

To initialize mojo, you need to do at least 3 things:

• Create an [[AppInstance]] using 'New AppInstance'. This will automatically initialize the [[App]] global variable.
• Create a [[Window]]. You will generally create a subclass of window you have defined yourself, eg: 'New MyWindow'.
• Start the app using [[AppInstance.Run|App.Run]].

This can all be done inside Main().

Once the app is running, mojo runs a simple event loop that looks like this:

• Get OS events and dispatch corresponding mojo events if necessary.
• Once there are no OS events left to process, any custom [[AppInstance.Idle|App.Idle]] handlers are called.
• If the application has called [[AppInstance.RequestRender|App.RequestRender]], the app is then rendered.

The app will continue executing the event loop until [[AppInstance.Terminate|App.Terminate]] is called.

@#### Subclassing Window

Subclassing the app Window class is easy - just extend the [[Window]] class.

To render to the window, you will also need to override the [[View.OnRender]] method.

The OnRender method is called when the app needs to be rendered, and is passed a [[Canvas|Canvas]] instance for window rendering code to use.

In addition, you may also want to override the [[Window.OnWindowEvent]] method to handle window close, resize etc events.

@#### Handling user input

There are 2 main ways to handle user input, via the [[View.OnKeyEvent]] and [[View.OnMouseEvent]] event handlers or using the [[input.Keyboard]] and [[input.Mouse]] devices.

Key and mouse events are sent to your app as soon they are processed by the event loop, while the keyboard and mouse devices may be 'polled' at any time.

@#### A minimal mojo app.

Ok, time to put it all together!

@example

#Import "" #Import ""

Using std.. Using mojo..

Class MyWindow Extends Windows

Method OnRender( canvas:Canvas ) Override

    canvas.DrawText( "Hello World",Width/2,Height/2,.5,.5 )
End

End

Function Main()

New AppInstance

New MyWindow

App.Run()

End

@end