Writing Simba Extensions
========================

Simba extensions are scripts written in PascalScript that can be embedded into
Simba. Purposes vary from updaters to full blown dtm and bitmap editors.

.. FIXME link to dtm and bitmap

How they work
-------------

Extensions are event based. This means you don't have some ``loop`` in your
program that never ends and does all the logic for you. When a system is event
based, you implement some functions and those are called on a certain event.

Hooks overview
--------------

.. references

Extension core hooks
--------------------

Simba offers several core hooks: init, free, attach and detach. These are used
to initialize, show, hide and free your extension. GetName and GetVersion are
called to retreive the name and version of an extension.

init
~~~~

Called when the Extension is initialized. 

.. code-block:: pascal
    :linenos:

    procedure init;
    begin;
        Writeln('Init your extension here.');
    end;    

If you want to add a button to the menu, do it now.
From the SRL updater extension:

.. code-block:: pascal
    :linenos:

    procedure Init;
    begin;
      MainMenuItem := TMenuItem.Create(Simba_MainMenu);  
      MainMenuItem.Caption := 'SRL';
      Simba_MainMenu.Items.Add(MainMenuItem);
    
      MenuCheck := TMenuItem.Create(MainMenuItem);
      MenuCheck.Caption := 'Check for new SRL';
      MenuCheck.OnClick := @OnSRLCheckClick;
      MainMenuItem.Add(MenuCheck);
    
      MenuUpdate := TMenuItem.Create(MainMenuItem);
      MenuUpdate.Caption := 'Update SRL';
      MenuUpdate.OnClick := @OnSRLUpdateClick;
      MainMenuItem.Add(MenuUpdate);
      
      AutoUpdate := TMenuItem.Create(MainMenuItem);
      AutoUpdate.Caption := 'Automatically update';
      AutoUpdate.OnClick := @SetAutoUpdate;
      AutoUpdate.Checked := LowerCase(Settings.GetKeyValueDef('AutoUpdate',
                                    'True')) = 'true';
      MainMenuItem.Add(AutoUpdate);
     
      Timer := TTimer.Create(Simba);
      Timer.Interval := 5000;
      Timer.OnTimer := @OnUpdateTimer;
      Timer.Enabled :=AutoUpdate.Checked;
    
      started := True;
    end;     

free
~~~~

Called upon freeing the extension. Usually this means that Simba is closed.

.. code-block:: pascal
    :linenos:
    
    procedure free;
    begin
        if started then
            writeln('Init was called');
    end;

From the SRL updater extension:

.. code-block:: pascal
    :linenos:

    procedure Free;
    begin
      if (started) then
        Timer.Enabled := False;
        { Freeing the components is not needed, as they will be freed
           upon the freeing of Simba. }
    end;    

attach
~~~~~~

Called when your extension has been enabled.

From the SRL updater extension:

.. code-block:: pascal
    :linenos:
      
    procedure Attach;
    begin;
      Writeln('From now on, you shall be alerted as to when your SRL is out of date!');
      MainMenuItem.Visible := True;
      Timer.Enabled := AutoUpdate.Checked;
    end;        



detach
~~~~~~

Called when your extension has been disabled. (This is not the same as freeing)

.. code-block:: pascal
    :linenos:

    Procedure Detach;
    begin
      Timer.Enabled := False;
      MainMenuItem.Visible := False;
    end;    

GetName
~~~~~~~

Called when Simba requests the name of your extension.

.. code-block:: pascal
    :linenos:

    function GetName : string;
    begin;
      result := 'SRL Updater';
    end;   

GetVersion
~~~~~~~~~~

Called when Simba requests the version of the extension.

.. code-block:: pascal
    :linenos:

    function GetVersion : string;
    begin;
      result := '1.0';
    end;    

More extension hooks
~~~~~~~~~~~~~~~~~~~~

The following hooks are called upon if the event that the name describes has happened.


onOpenConnection
~~~~~~~~~~~~~~~~

onWriteFile
~~~~~~~~~~~

onOpenFile
~~~~~~~~~~

onColourPick
~~~~~~~~~~~~

onScriptStart
~~~~~~~~~~~~~


Example code
------------

Explanatory code for all:

.. literalinclude:: extraextensionhooks.sex
    :language: pascal
    :linenos: