lazarus

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History

juha 8abfe4423f LCL: Refactor RegisterWSComponent parameter ANewRegistration into a procedure RegisterNewWSComp. git-svn-id: trunk@63671 -		2020-07-29 18:28:57 +00:00
..
README.txt
wsbuttons.pp
wscalendar.pp	LCL/Calendar: Remove option dsStartMonday from Calendar.DisplaySettings and replace it by Delphi-compatible Calendar.FirstDayOfWeek	2020-05-25 14:16:57 +00:00
wschecklst.pp
wscomctrls.pp	bug #36281 . Merged revision(s) 62516-62547 from branches/listviewsortindicator:	2020-01-17 01:49:23 +00:00
wscontrols.pp	LCL-QT5: Remove and cleanup recently added debug code. Issue #36773 was fixed faster than expected.	2020-03-08 16:33:55 +00:00
wsdesigner.pp
wsdialogs.pp
wsextctrls.pp
wsextdlgs.pp
wsfactory.pas
wsforms.pp	LCL: implement MDI for win32. Issue #36582 , based on patch by Kostas Michalopoulos, attempt 2	2020-03-12 09:28:38 +00:00
wsgrids.pp	lcl: less hints	2020-01-31 14:10:00 +00:00
wsimglist.pp
wslazdeviceapis.pas
wslclclasses.pp	LCL: Refactor RegisterWSComponent parameter ANewRegistration into a procedure RegisterNewWSComp.	2020-07-29 18:28:57 +00:00
wsmenus.pp
wspairsplitter.pp	LCL/PairSplitter: Fix Position parameter and panel widths being out of sync under some circumstances (https://forum.lazarus.freepascal.org/index.php/topic,46726.msg333773.html#msg333773 ).	2019-09-21 20:48:04 +00:00
wsproc.pp
wsreferences.pp
wsspin.pp
wsstdctrls.pp	LCL: Prevent scrolling in the default Widgetset implementation of ListBox.SelectRange. Fix off by 1 error. Part of issue #0036929 .	2020-06-10 09:52:40 +00:00
wstoolwin.pp

README.txt

This directory contains all skeleton widget set component 
classes. These classes will never get instantiated and may 
only contain class functions.
  
=========  
IMPORTANT
=========  

Derivation and inheritance of classes is different then one
might be used to. It will be explained by the following 
examples.

Suppose the following LCL class hierarchy:

 TLCLComponent
     |
  TControl
     |
 TWinControl
 
the corresponding WS skeleton would be

 TWSLCLComponent
      |
  TWSControl
      |
 TWSWinControl


When method X of TWSControl gets implemented by 
widgetset Q the hierarchy looks like

 TWSLCLComponent
      |
  TWSControl.X --> TQWSControl.X
      |
 TWSWinControl


Calling TWSWinControl.X doesn't call TQWSControl.X since
it's parent is TWSControl. This problem is solved by 
modifying the class hierarchy at runtime.
When a component class is registered by RegisterWSComponent,
the class is copied and the vmt entries are adjusted so 
that the hierarchy looks like:


 TWSLCLComponent
      |
  TWSControl.X --> TQWSControl.X
                        |
                   TWSWinControl

In this case, calling TWSWinControl.X will call the overridden 
TQWSControl.X. The only thing which doesn't get handled is the 
inherited statement. Suppose there is also a TQWSWinControl.X 
which implements a few extra steps. In a normal situation one 
would have called "inherited". The call to inherited is
resolved at compile time and would in this example to a call to
TWSControl.X. That is not what we want.
To get around this, call the parent yourself:
  TWSWinControlClass(ClassParent).X