BlitzMax/Modules/Events/Hook functions

This module provides a generic way to hook into various BlitzMax commands, and to add support for hooks into your own code.

The following hook ids are currently used by BlitzMax modules:

Hook id	Description	Data
FlipHook	A Max2D Flip is about to occur	Null
EmitEventHook	An event has been emitted by a call to EmitEvent	A TEvent object

To hook into any of these functions, use AddHook with the specified hook id and your hook function.

To provide hook support for your own code, use AllocHookId to generate a valid integer hook id somewhere in your program's startup code. Then, when the section of code you would like to be 'hookable' is about to execute, simply call RunHooks with the previously generated hook id and your own custom 'data' object.

Functions

AllocHookId

Function AllocHookId()

Description: Allocate a hook id

Returns: An integer hook id

Information: The returned hook id can be used with AddHook, RunHooks and RemoveHook.

AddHook

Function AddHook( id,func:Object( id,data:Object,context:Object )

Description: Add a hook function

Returns: A hook object that can be used with the RemoveHook command.

Information: Add a hook function to be executed when RunHooks is called with the specified hook id.

Example:

'This function will be automagically called every Flip
Function MyHook:Object( id,data:Object,context:Object )
	Global count
	
	count:+1
	If count Mod 10=0 Print "Flips="+count
	
End Function

'Add our hook to the system
AddHook FlipHook,MyHook

'Some simple graphics
Graphics 640,480,0

While Not KeyHit( KEY_ESCAPE )

	Cls
	DrawText MouseX()+","+MouseY(),0,0
	Flip

Wend

RunHooks

Function RunHooks:Object( id,data:Object )

Description: Run hook functions

Returns: The data produced by the last hook function

Information: RunHooks runs all hook functions that have been added for the specified hook id.

The first hook function is called with the provided data object. The object returned by this function is then passed as the data parameter to the next hook function and so on. Therefore, hook functions should generally return the data parameter when finished.

RemoveHook

Function RemoveHook( id,func:Object( id,data:Object,context:Object )

Description: Remove a hook function

Information: Removes the hook function specified by id, func and context.