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QUESTION:
When I use buttons in my components I usually let Visual DataFlex underline one of the characters to indicate the hotkey (accelerator key) that executes the same functionality as the button. But often I forget to add the appropriate On_Key statement in the button's parent object. Can't this key assigment be automated?
ANSWER:
Yes, it can be automated. In the following code - subclass of button - the set label method is augmented. In this method we remove the current key definition - if any - and assign the new key definition. The trick is that a part of the code is executed as if it was executed in the key definition object.
Class cAcceleratorKeyMixin Is A Mixin
//****************************************************************************
// $Module name: DefineAccKeyProperties
// $Author : VO
// Created : 15-09-96 @ 16:33
//
// Description
// Add two properties to the object.
// 1. phoKeyDestination: We can store the accelerator key destination object
// in this property. If not assigned by you, the key destination (the
// on_key location) will be the parent object.
// 2. piKeyModifier: Default is the Key_Ctrl plus your underlined character
// but you can also store key_alt or key_shift in the property. Note that
// a menubar overrides a key_alt+<char> combination if present.
//
// $Rev History
// 15-09-96 Module header created
//****************************************************************************
Procedure DefineAccKeyProperties
Property Handle phoKeyDestination (Parent (Self))
Property Integer piKeyModifier Key_Ctrl
End_Procedure
//****************************************************************************
// $Module name: AcceleratorKeyDef
// $Author : VO
// Created : 24-05-07 @ 14:33
//
// Description
// This method will find the underlined key in the value of the button (the
// label). If present, a keymapping based on the keymodifier (usually
// key_ctrl) and the underlined character will be created. If possible - the
// key exists - the key id will be returned in the byref variable. The message
// property value will be returned as the message to be send. Finally, the
// aux_value property is read and returned. If the latter one is 0 the current
// object ID will be used instead.
//
// The function returns true if the function created a key mapping.
//
// $Rev History
// 24-05-07 Module header created
//****************************************************************************
Function AcceleratorKeyDef Integer BYREF iKey Integer BYREF iMsg Handle BYREF hoDestination Returns Boolean
String sItemValue sKeyChar
Integer iKeyChar iKeyModifier iPos
Boolean bSuccess
Get Value Item 0 To sItemValue
Move (Pos ("&", sItemValue)) To iPos
If (iPos > 0) Begin
Move (Uppercase ("KEY_" - Mid (sItemValue, 1, iPos + 1))) To sKeyChar
Move (Eval (sKeyChar)) To iKeyChar
If (iKeyChar > 0) Begin
Get piKeyModifier To iKeyModifier
Move (iKeyModifier + iKeyChar) To iKey
Get Message Item 0 To iMsg
Get Aux_Value Item 0 To hoDestination
If (hoDestination = 0) Begin
Move Self To hoDestination
End
Move True To bSuccess
End
End
Function_Return bSuccess
End_Function
//****************************************************************************
// $Module name: AssignAcceleratorKey
// $Author : VO
// Created : 15-09-96 @ 16:33
//
// Description
// This method constructs a keymapping (via AccelatorKeyDef) and if successful,
// the key mapping will be added or removed from the key destination object.
// The trick in this routine is that a part of the code is executed as if
// the code was part of the key destination object.
//
// $Rev History
// 15-09-96 Module header created
//****************************************************************************
Procedure AssignAcceleratorKey Boolean bRemove
Integer iKey iMsg
Boolean bKeyDefined
Handle hoDestination hoSelf hoKeyDestination
Get AcceleratorKeyDef (&iKey) (&iMsg) (&hoDestination) To bKeyDefined
If (bKeyDefined) Begin
Get phoKeyDestination To hoKeyDestination
If (hoKeyDestination > 0) Begin
Move Self To hoSelf
Move hoKeyDestination To Self
If (bRemove) Begin
On_Key iKey Send Default_Key Of hoDestination
End
Else Begin
On_Key iKey Send iMsg Of hoDestination
End
Move hoSelf To Self
End
End
End_Procedure
//****************************************************************************
// $Module name: Set Label
// $Author : VO
// Created : 15-09-96 @ 16:33
//
// Description
// This method is augmented to assign an accelerator key for execution of
// the object's message.
//
// $Rev History
// 15-09-96 Module header created
//****************************************************************************
Procedure Set Label String sLabelText
Send AssignAcceleratorKey True
Forward Set Label To sLabelText
Send AssignAcceleratorKey False
End_Procedure
End_Class
Class cMyButton Is A Button
Import_Class_Protocol cAcceleratorKeyMixin
//****************************************************************************
// $Module name: Construct_Object
// $Author : VO
// Created : 15-09-96 @ 16:33
//
// Description
// Send a message to define extra properties.
//
// $Rev History
// 15-09-96 Module header created
//****************************************************************************
Procedure Construct_Object
Forward Send Construct_Object
Send DefineAccKeyProperties
End_Procedure
End_Class
To test the above code either directly use it in your own system or use the enclosed test view to see the results.
Contributed By:
Vincent Oorsprong
Company: Data Access Worldwide
email: vincent.oorsprong@dataaccess.eu
Web Site: http://www.dataaccess.eu
Web Links Related to this Article
File testacckey.vw
URL=http://www.dataaccess.com/KBasePublic/Files/2316.testacckey.vw
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