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Jump to: navigation, search dialogs and forms are based on an event-oriented programming model where you can assign event handlers to the control elements. An event handler runs a predefined procedure when a particular action occurs. You can also edit documents or open databases with event handling as well as access other control elements. control elements recognize different types of events that can be triggered in different situations. These event types can be divided into four groups:

  • Mouse control: Events that correspond to mouse actions (for example, simple mouse movements or a click on a particular screen location).
  • Keyboard control: Events that are triggered by keyboard strokes.
  • Focus modification: Events that performs when control elements are activated or deactivated.
  • Control element-specific events: Events that only occur in relation to certain control elements.

When you work with events, make sure that you create the associated dialog in the development environment and that it contains the required control elements or documents (if you apply the events to a form).

The Basic development environment

The figure above shows the Basic development environment with a dialog window that contains two list boxes. You can move the data from one list to the other using the buttons between the two list boxes.

If you want to display the layout on screen, then you should create the associated Basic procedures so that they can be called up by the event handlers. Even though you can use these procedures in any module, it is best to limit their use to two modules. To make your code easier to read, you should assign meaningful names to these procedures. Jumping directly to a general program procedure from a macro can result in unclear code. Instead, to simplify code maintenance and troubleshooting, you should create another procedure to serve as an entry point for event handling - even if it only executes a single call to the target procedure.

The code in the following example moves an entry from the left to the right list box of a dialog.

Sub cmdSelect_Initiated
   Dim lstEntries As Object
   Dim lstSelection As Object
   lstEntries = Dlg.getControl("lstEntries")
   lstSelection = Dlg.getControl("lstSelection")
   If lstEntries.SelectedItem > 0 Then
     lstSelection.AddItem(lstEntries.SelectedItem, 0)
     lstEntries.removeItems(lstEntries.SelectItemPos, 1)
   End If
End Sub

If this procedure was created in Basic, you can assign it to an event required using the property window of the dialog editor.

The Assign Action dialog

The Assign Action dialog lists all of the available Events. To assign a macro to an event:

  1. Select the event
  2. Click Macro...
  3. Browse to and select the macro you want to assign
  4. Click OK


The occurrence of a particular event is not always enough for an appropriate response. Additional information may be required. For example, to process a mouse click, you may need the screen position where the mouse button was pressed.

In Basic, you can use object parameters to provide more information about an event to a procedure, for example:

Sub ProcessEvent(Event As Object)
End Sub

The structure and properties of the Event object depend on the type of event that triggers the procedure call.

Regardless of the type of event, all objects provide access to the relevant control element and its model. The control element can be reached using Event.Source and its model using Event.Source.Model. The dialog can be reached using Event.Source.Context.

You can use these properties to trigger an event within an event handler.

Mouse Events Basic recognizes the following mouse events:

Mouse moved
user moves mouse
Mouse moved while key pressed
user drags mouse while holding down a key
Mouse button pressed
user presses a mouse button
Documentation note.png This event is also used for notifying requests for a popup context menu on the control. In this case, the member PopupTrigger of the event passed to your macro function will be TRUE. In particular, if such a request is made by pressing the right mouse button on the control, the event will be fired twice: once for the popup menu request, and once for the real mouse event. If you are interested in only the mouse click, your macro should ignore all calls where PopupTrigger is TRUE.
Mouse button released
user releases a mouse button
Mouse outside
user moves mouse outside of the current window

The structure of the associated event objects is defined in the structure which provides the following information:

Buttons (short)
button pressed (one or more constants in accordance with
X (long)
X-coordinate of mouse, measured in pixels from the top left corner of the control element
Y (long)
Y-coordinate of mouse, measured in pixels from the top left corner of the control element
ClickCount (long)
number of clicks associated with the mouse event (if can respond fast enough, ClickCount is also 1 for a double-click because only an individual event is initiated)

The constants defined in for the mouse buttons are:

left mouse button
right mouse button
middle mouse button

The following example outputs the mouse position as well as the mouse button that was pressed:

Sub MouseUp(Event As Object)
   Dim Msg As String
   Msg = "Keys: "
   If Event.Buttons AND Then
     Msg = Msg & "LEFT "
   End If
   If Event.Buttons AND Then
     Msg = Msg & "RIGHT "
   End If
   If Event.Buttons AND Then
     Msg = Msg & "MIDDLE "
   End If
   Msg = Msg & Chr(13) & "Position: "
   Msg = Msg & Event.X & "/" & Event.Y
   MsgBox Msg
End Sub
Documentation note.png VBA : The VBA Click and Doubleclick events are not available in Basic. Instead use the Basic MouseUp event for the click event and imitate the Doubleclick event by changing the application logic.

Keyboard Events

The following keyboard events are available in Basic:

Key pressed
user presses a key.
Key released
user releases a key

Both events relate to logical key actions and not to physical actions. If the user presses several keys to output a single character (for example, to add an accent to a character), then Basic only creates one event.

A single key action on a modification key, such as the Shift key or the Alt key does not create an independent event.

Information about a pressed key is provided by the event object that Basic supplies to the procedure for event handling. It contains the following properties:

KeyCode (short)
code of the pressed key (default values in accordance with
KeyChar (String)
character that is entered (taking the modification keys into consideration)

The following example uses the KeyCode property to establish if the Enter key, the Tab key, or one of the other control keys has been pressed. If one of these keys has been pressed, the name of the key is returned, otherwise the character that was typed is returned:

Sub KeyPressed(Event As Object)
   Dim Msg As String
   Select Case Event.KeyCode
     Msg = "Return pressed"
     Msg = "Tab pressed"
     Msg = "Delete pressed"
     Msg = "Escape pressed"
     Msg = "Down pressed"
     Msg = "Up pressed"
     Msg = "Left pressed"
     Msg = "Right pressed"
   Case Else
     Msg = "Character " & Event.KeyChar & " entered"
   End Select
   MsgBox Msg
End Sub

Information about other keyboard constants can be found in the API Reference under the group of constants.

Focus Events

Focus events indicate if a control element receives or loses focus. You can use these events to, for example, determine if a user has finished processing a control element so that you can update other elements of a dialog. The following focus events are available:

When receiving focus
element receives focus
When losing focus
element loses focus

The Event objects for the focus events are structured as follows:

FocusFlags (short)
cause of focus change (default value in accordance with )
NextFocus (Object)
object that receives focus (only for the When losing focus event)
Temporary (Boolean)
the focus is temporarily lost

Control Element-Specific Events

In addition to the preceding events, which are supported by all control elements, there are also some control element-specific events that are only defined for certain control elements. The most important of these events are:

When Item Changed
the value of a control element changes
Item Status Changed
the status of a control element changes
Text modified
the text of a control element changes
When initiating
an action that can be performed when the control element is triggered (for example, a button is pressed)

When you work with events, note that some events, such as the When initiating event, can be initiated each time you click the mouse on some control elements (for example, on radio buttons). No action is performed to check if the status of the control element has actually changed. To avoid such “blind events”, save the old control element value in a global variable, and then check to see if the value has changed when an event is executing.

The When initiating event is also noteworthy for the following reasons:

  • This event is initiated by either a key-press or a mouse button. Thus, it provides a consistent interface for users who navigate by mouse or by keyboard.
  • When the Repeat property of a command button is set to True, this event is the one which is repeatedly sent, as long as the triggering action (key down or mouse-button down) remains in effect.

The properties for the Item Status Changed event are:

Selected (long)
currently selected entry
Highlighted (long)
currently highlighted entry
ItemId (long)
ID of entry

Content on this page is licensed under the Public Documentation License (PDL).
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