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# Creating a Dialog Handler

Next to assigning macros to events or creating event listeners, one can use dialog handlers, whose principle is to define UNO keywords, or methods, that are mapped to events to watch for. The event handler is responsible for executing methods using the vnd.sun.star.UNO:<method_name> protocol. Unlike listeners that require to define all supported methods, even if unused, dialog handlers require only two methods on top of intended control hook scripts.

The advantages of this approach are:

- It packs the code that handles event-driven macros,

- it decorrelates events from macros names which facilitates maintenance or updates, in particular when moving macros or modules.

This mechanism is illustrated herewith for Basic and Python languages using an imported copy of Access2Base dlgTrace dialog. Exception handling and localisation are omitted for clarity.

## Assigning Dialog methods

Export Access2Base dlgTrace dialog and import it into MyLib application library.

Inside the control properties pane of the Dialog Editor, use the Events tab to replace macro assignments by component assignments, and type in the intended method names:

- Set Dump to file dialog button component method name to _dump2File

- Optionally define txtTracelog key pressed and mouse button pressed events component method names as _openHelp

- Optionally define Ok button receiving focus event component method name as onOkHasfocus

Events assigned actions should mention the vnd.sun.star.UNO: protocol.

## Creating the handler

createDialogWithHandler method of com.sun.star.awt.DialogProvider2 service is used to set the dialog and its handler. The handler is responsible for implementing com.sun.star.awt.XDialogEventHandler interface.

All component method names must be explicitly declared when using a dialog handler.

### With Python

In this example the dialog is located on the computer.

          # -*- coding: utf-8 -*-
          from __future__ import unicode_literals

          import uno, unohelper
          from com.sun.star.awt import XDialogEventHandler

          _DLG_PROVIDER = "com.sun.star.awt.DialogProvider2"

          class Console(unohelper.Base, XDialogEventHandler):
              """ Access2Base Console Handler """
              ''' adapted from « Créer un dialogue avec gestionnaire d'événements » by JM Zambon
              https://wiki.openoffice.org/wiki/FR/Documentation/Python/Creating_Dialog_with_Handler '''
              def show(self):
                  dialog = self.getDialog("MyLib.dlgTrace", embedded=True)
                  dialog.Title = "Konsole"
                  dialog.execute()

              def callHandlerMethod(self, dialog, event, method):
                  if method == '_dump2File':
                      event.Source.setLabel("dump requested")
                      scr = getBasicScript(script="_DumpToFile", module="Trace",
                          library='Access2Base')
                      scr.invoke((event,), (), ())
                  elif method == '_openHelp':
                      _msgbox('Not yet implemented')
                      dialog.endDialog(1)
                  else:
                      return False

              def getSupportedMethodNames(self):
                  return ('_dump2File', '_openHelp')

              def getDialog(self, libr_dlg: str, embedded=False):
                  """ Create a Dialog from its location """
                  smgr = XSCRIPTCONTEXT.getComponentContext().ServiceManager
                  if embedded:
                      model = XSCRIPTCONTEXT.getDocument()
                      dp = smgr.createInstanceWithArguments(_DLG_PROVIDER, (model,))
                      location = "?location=document"
                  else:
                      dp = smgr.createInstanceWithContext(_DLG_PROVIDER, ctx)
                      location = "?location=application"
                  dlg = dp.createDialogWithHandler("vnd.sun.star.script:"+libr_dlg+location, self)
                  return dlg

          # def getBasicScript()  # see note

          def _msgbox(prompt='', title=''):
              ''' Ugly MsgBox '''
              import msgbox
              mb = msgbox.MsgBox(uno.getComponentContext())
              mb.addButton('Howdy')
              mb.show(prompt,0,title)

          def ConsoleHandler():
              Console().show()

          g_exportedScripts = (ConsoleHandler,)

As expected, onOkHasFocus missing method throws an exception.

Refer to Python calls to LibreOffice Basic page for getBasicScript routine description and for details about cross-language scripting execution.

### With LibreOffice Basic

In this example the dialog is embedded in a document, and can equally be located on the computer.

          ' <MyLib>.<Handler> module

          Public Sub Console_Show()
              Dim dp as Object ' com.sun.star.awt.DialogProvider2
              Dim dialog As Object ' com.sun.star.awt.XDialog, com.sun.star.awt.XDialogEventHandler
              Dim eventHandler As Object ' com.sun.star.awt.XDialogEventHandler
              dp = CreateUnoService("com.sun.star.awt.DialogProvider2")
              dp.Initialize(Array(ThisComponent)) ' if doc-embedded dialog
              eventHandler = CreateUnoListener("Console_", "com.sun.star.awt.XDialogEventHandler")
              dialog = dp.createDialogWithHandler("vnd.sun.star.script:MyLib.dlgTrace?location=document", eventHandler)
              dialog.Title = "Konsole"
              dialog.execute()
          End Sub ' <Handler>.Console_Show()

          Private Function Console_callHandlerMethod(dialog as Object, _
                  event As com.sun.star.document.DocumentEvent, _
                  method As String) As Boolean
              ''' Intercept dialog events using .UNO protocol '''
              Console_callHandlerMethod = True
              Select Case method
                  Case "_dump2File"
                      event.Source.setLabel("dump requested")
                      With GlobalScope.BasicLibraries
                          If Not .IsLibraryLoaded("Access2Base") Then .LoadLibrary("Access2Base")
                      End With
                      Access2Base.Trace._DumpToFile
                  Case "_openHelp"
                      MsgBox "Not yet implemented",0 , "Howdy"
                      'dialog.endDialog(1) if computer-based dialog
                  Case Else : Console_callHandlerMethod = False
              End Select
          End Function ' <Handler>.Console_callHandlerMethod

          Private Function Console_getSupportedMethodNames()
              Console_getSupportedMethodNames = Array("_dump2File", "_openHelp")
          End Function ' <Handler>.Console _getSupportedMethodNames

          ' adapted from « Créer un dialogue avec gestionnaire d'événements » by JM Zambon
          ' https://wiki.openoffice.org/wiki/FR/Documentation/Python/Creating_Dialog_with_Handler

As expected, onOkHasFocus missing method throws an exception.

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