Re: [lazarus] Philosophical question: what should trigger OnChange?

[Giuliano Colla]

Mattias Gaertner ha scritto: On Sat, 06 May 2006 13:26:44 +0200 Giuliano Colla <[EMAIL PROTECTED]> wrote: Re-checking the patch I sent yesterday for Qt interface TMemo, I saw that I'm not sending an OnChange Event when the TMemo is programmatically changed. That is OnChange is generated only on user input on the memo. The correction is trivial, just a few lines of code, but the philosophical question arises. Maybe it's already been discussed and settled since a long time, but I'm a newcomer. The OnChange event exists only in controls which may be subject to user input, such as TEdit, TMemo, TComboBox TTrackBar and such. For some of them it's reasonable to think that the same action which must be taken when the user changes something should also be taken when the program changes it (such as TTrackBar): this saves code. For others, as TMemo, TEdit, and perhaps TComboBox, generating the OnChange event when the change comes from the program is IMHO more a nuisance than a feature. In my experience I've always been forced to add code in order to tell apart user input from changes coming from the program. Otherwise unwanted effects and/or unwanted circles are generated. Me2. So the philosophical question: is it right to follow Delphi logic for TEdit and TMemo OnChange, or it would be more reasonable to "improve" the matter, and generate OnChange only on user action? IMHO we need both. For Delphi compatibility we should follow the VCL behaviour here. Maybe a Delphian can test and tell us. In my working copy of Qt TMemo implementation I've added a conditional $IFDEF  DelphiOnChange. If defined it provides Delphi behavior, if not, OnChange is generated only for user actions. I've done that in order to test adequately both conditions, but, if approved, it could become a system wide conditional. As an alternative we might provide, in addition to OnChange, a new event: OnUserChange (or whatever one decides to call it). That way OnChange would provide Delphi behavior, OnUserChange would be triggered only by user actions. Waiting for suggestion before submitting next patch. Thanks Giuliano _________________________________________________________________ To unsubscribe: mail [EMAIL PROTECTED] with "unsubscribe" as the Subject archives at http://www.lazarus.freepascal.org/mailarchives