MS Dialog Check Box "OnClick" Observation

[JRL]

Just discovered that changing the "Checked" property of a Macro Scheduler dialog check box programmatically, will trigger the "OnClick" event for that check box. In other words, if you create a dialog with a check box and also create a dialog handler for that check box that triggers on the "OnClick" event, when you use SetDialogProperty to alter the "Checked" property of the check box, the "OnClick" event's subroutine will be processed.

I would have thought that a check box "OnClick" would require an actual mouse click but apparently it simply requires a status change. This makes some sense since a user could also alter the state of a check box by tabbing to it and pressing the space bar.

Here is a script to demonstrate. Roughly once per second the check box will be checked or unchecked by the program. There is an adddialoghandler function for the check box's OnClick event. Each time the check box's status is changed, the OnClick event will be triggered and a message box with a counter will open. If the word "True" at the end of Line 40 is changed to "False", the check box state will no longer change and the OnClick event will not be triggered.

Code: Select all

Dialog>Dialog1
object Dialog1: TForm
  object CheckBox1: TCheckBox
    Left = 50
    Top = 100
    Width = 97
    Height = 17
    Caption = 'CheckBox1'
    TabOrder = 8
  end
end
EndDialog>Dialog1

AddDialogHandler>Dialog1,,OnCLose,Quit
AddDialogHandler>Dialog1,checkbox1,OnClick,Report
Let>RepCount=0

SRT>Report
  Add>RepCount,1
  Message>RepCount
END>Report

SRT>Quit
  Exit>0
END>Quit

Show>Dialog1

Let>kk=0

Label>Loop
  Wait>0.01
  Add>kk,1
  Let>test={%kk% mod 100}
  If>test=0
    GetDialogProperty>Dialog1,checkbox1,Checked,res
    If>res=True
      SetDialogProperty>Dialog1,checkbox1,Checked,False
    Else
      SetDialogProperty>Dialog1,checkbox1,Checked,True
    EndIf
  EndIf
Goto>Loop

[Marcus Tettmar]

Yes, as you know these objects are inherited Delphi controls, and I recently discovered this to my peril in Delphi and managed to put myself into an infinite loop

Before someone says "why isn't it documented" the answer is "it isn't." I also only discovered this by accident myself and I guess it suggests that OnClick is badly named - OnChangeCheckedStatus might be more accurate and it would then be logical why this happens. We'd have to ask CodeGear.

[JRL]

Before someone says "why isn't it documented" the answer is...

I thought I just documented it.

[jpuziano]

Before someone says "why isn't it documented" the answer is "it isn't." I also only discovered this by accident myself and I guess it suggests that OnClick is badly named - OnChangeCheckedStatus might be more accurate and it would then be logical why this happens. We'd have to ask CodeGear.

CodeGear? Don't you mean Embarcadero? Googling...

http://en.wikipedia.org/wiki/Embarcadero_Delphi

"Embarcadero Delphi, formerly CodeGear Delphi, Inprise Delphi and Borland Delphi, is an integrated development environment for Microsoft Windows applications..."

Ahh... an old name of the company. If you do ask them, please share what they say. I wonder if they would agree and rename the event?

Before someone says "why isn't it documented" the answer is...

I thought I just documented it.

By George, I think you just did... thanks for sharing... no wonder we're past 30,000 forum posts!

Take care