4D v16.3
Is waiting mouse up
Is waiting mouse up
| Is waiting mouse up -> Function result | ||||||||
| Parameter | Type | Description | ||||||
| Function result | Boolean |
|
True if the object is waiting for a mouse up event, False otherwise | |||||
The Is waiting mouse up command returns True if the current object has been clicked and the mouse button has not been released, while the parent window has the focus. Otherwise, it returns False, in particular if the parent window has lost the focus before the mouse button was released.
The command must be called in the context of the current object. It is designed to be used in conjunction with the On Mouse Up form event which is available for picture fields and variables. It allows your code to handle the cases where the user clicked and started to move something within a form object picture, and this action is interrupted by an external event, such as an alert dialog box. In this case, the internal state of the object can be suspended indefinitely because it is waiting for a mouse up event which will never occur. To prevent this issue, you must protect your mouse moving code within a Is waiting mouse up command which makes you sure that it is executed in a valid context.
The following code can be used to manage a mouse tracking feature in a picture object:
//Object method of the picture object
C_LONGINT(vLtracking) //flag for tracking mode
Case of
:(Form event=On Clicked)
If(Is waiting mouse up) //the mouse button is still not released
vLtracking:=1 //we are in tracking mode
//... Write here initialization code for the tracking feature
End if
:(Form event=On Mouse Move)
If(vLtracking=1) //we are in tracking mode
If(Not(Is waiting mouse up)) //we'll never have the mouse up
vLtracking:=0 //stop the tracking mode
//... Write here the code for handling or canceling user tracking action
Else //the object is still waiting for a mouse up
//... Write here the code for the tracking
End if
End if
:(Form event=On Mouse Up) //the mouse button was released
//... Write here the code to complete the tracking action
vLtracking:=0 //end of the tracking mode
End case
Product: 4D
Theme: Form Events
Number:
1422
Created: 4D v16
4D Language Reference ( 4D v16)
4D Language Reference ( 4D v16.1)
4D Language Reference ( 4D v16.2)
4D Language Reference ( 4D v16.3)
