added a small text about IDE plugins

git-svn-id: trunk@4186 -

.gitattributes

@@ -182,6 +182,7 @@ designer/sizecompsdlg.pp svneol=native#text/pascal
 designer/taborderdlg.lfm svneol=native#text/plain
 designer/taborderdlg.lrs svneol=native#text/pascal
 designer/taborderdlg.pas svneol=native#text/pascal
+docs/ExtendingTheIDE.txt svneol=native#text/plain
 docs/LazarusIDEInternals.pdf -text svneol=unset#application/pdf
 docs/Packages.txt svneol=native#text/plain
 examples/bitbtnform.pp svneol=native#text/pascal

docs/ExtendingTheIDE.txt

@@ -0,0 +1,119 @@
+Extending the IDE (Overview)
+============================
+
+The IDE supports several types of plugins:
+
+Components
+  These are the items in the component palette. For a example TButton can be
+  used to create Buttons.
+    
+Component Editors
+  Component editors are used when you double click on a component in the
+  designer or to add some extra items to the popup menu of the designer, when
+  you right click on a component.
+
+Property Editors
+  These are used by the rows in the object inspector.
+
+Experts
+  These are all other types.
+
+-------------------------------------------------------------------------------
+There are two possibilities to add your own plugins to Lazarus:
+
+1. Write a package, install it and register your plugins in the 'Register'
+   procedure of a unit.
+2. Extend the lazarus code, and send your cvs diff to the lazarus mailing list.
+
+
+
+-------------------------------------------------------------------------------
+Writing components:
+
+ToDo
+Hint: Create a new component via the package editor.
+
+
+
+-------------------------------------------------------------------------------
+Writing component editors:
+
+ToDo
+Hint: see componenteditors.pas for examples
+
+
+-------------------------------------------------------------------------------
+Writing property editors
+
+ToDo
+Hint: see propedits.pp for examples
+
+
+-------------------------------------------------------------------------------
+Register event handlers
+
+There are several events in the IDE, where plugins can add their own handlers.
+In propedits.pp there is a GlobalDesignHook object, maintains several events
+for designing. Each event calls a list of handlers. The default handlers are
+added by the IDE. You can add your own handlers with the AddHandlerXXX and
+RemoveHandlerXXX methods. They will be called before the default handlers.
+Examples:
+
+  Adding your handler (this is normally done in the constructor of your object):
+    GlobalDesignHook.AddHandlerComponentAdded(@YourOnComponentAdded);
+    
+  Removing your handler:
+    GlobalDesignHook.RemoveHandlerComponentAdded(@YourOnComponentAdded);
+
+  You can remove all handlers at once. For example, it is a good idea to add
+  this line in the destructor of object:
+    GlobalDesignHook.RemoveAllHandlersForObject(Self);
+
+
+The handlers of GlobalDesignHook:
+
+  // lookup root
+  ChangeLookupRoot
+    Called when the LookupRoot changed.
+    The LookupRoot is the owner object of the currently selected components.
+    Normally this is a TForm.
+
+  // methods
+  CreateMethod
+  GetMethodName
+  GetMethods
+  MethodExists
+  RenameMethod
+  ShowMethod
+    Called
+  MethodFromAncestor
+  ChainCall
+
+  // components
+  GetComponent
+  GetComponentName
+  GetComponentNames
+  GetRootClassName
+  ComponentRenamed
+    Called when a component was renamed
+  ComponentAdded
+    Called when a new component was added to the LookupRoot
+  ComponentDeleting
+    Called before a component is freed.
+  DeleteComponent
+    Called by the IDE to delete a component.
+  GetSelectedComponents
+    Get the current selection of components.
+
+  // persistent objects
+  GetObject
+  GetObjectName
+  GetObjectNames
+
+  // modifing
+  Modified
+  Revert
+  RefreshPropertyValues
+
+
+