[Kommander-devel] Making a Kommander editor using Designer 4

[Andras Mantia]

Hi Eric,

On Wednesday 16 April 2008, Eric Laffoon wrote:
> QWidget *ButtonGroupKmdrDesignerPlugin::createWidget(QWidget *parent)
> {
>   return new ButtonGroup(parent);
> }
>
> The compiler rightly points out this is not correct as the
> constructor requires another vairable, the name variable. However I
> added this locally so it calls

Assuming it is about the ButtonGroup widget inside 
kde-trunk/kdewebdev/widgets the compiler was right. ;) But somehow I 
don't understand why you want to create a ButtonGroup widget in a 
plugin when there is one in the main Kommander. Ah, I see, this is 
about the designer plugin.
First of all, I'm not happy at all that these classed ended up in the 
widgets directory and the libkommanderwidgets plugin.
This plugin should have ONLY the widgets themselves. Otherwise we would 
bloat the executor with designer (editor) specific code, and will make 
moving of the executor to kdebase close to impossible.
If the problem is that you need access to the classes, we will find some 
other solution.

> The changes to headers were made and everything is right... Except of
> course that I'm mucking with not just the widget constructor, but the
> virtual function in the QDesigner plugin. Now it is not happy...
>
> /home/eric/kdesvn/kdewebdev/kommander/widgets/kmdrdesignerwidgets.cpp
>:18: error: cannot allocate an object of abstract
> type 'ButtonGroupKmdrDesignerPlugin'
> /home/eric/kdesvn/kdewebdev/kommander/widgets/buttongroupkmdrdesigner
>plugin.h:26: note:   because the following virtual functions are pure
> within 'ButtonGroupKmdrDesignerPlugin':
> /usr/local/Trolltech/Qt-4.4.0-beta1/include/QtDesigner/customwidget.h
>:73: note: virtual QWidget*
> QDesignerCustomWidgetInterface::createWidget(QWidget*)

This means that you inherit from an "abstract" class, that has abstract 
(pure virtual) methods. Those are the methods declared as:
 void methodName() = 0; 
(or similar).

These methods are not implemented at all in the base class, this is why 
they are abstract. The class also cannot be instantiated as an object. 
So you need to subclass it (as I understood you did), and write the 
implementation of the abstract methods (all of them!). So you need a 
QWidget* createWidget(QWidget*);
declaration in the class header file, and the impelementation of this 
method in the cpp file.

Now that I see this code, I'm wondering what is wrong. :)
Ok, so the problem here was only the (first) compiler error. There is no 
complain about the pure virtual methods. So maybe you messed your local 
checkout up by adding a name argument to the createWidget declaration?

> So what is happening with the name in the constructor?
Name is the object name assigned to the widget. In Qt3 all widgets had a 
name argument. In Qt4 none of them has and you have to use 
widget->setObjectName(name).
They are useful to find/identify an widget (or to be more precise, 
QObject).

> Is Kommander 
> being passed the widget name here? 
No.

I hope this helps, I committed the "fixed" buttongroup stuff, but others 
still failing. They need the same change though.

Andras


-- 
Quanta Plus developer - http://quanta.kdewebdev.org
K Desktop Environment - http://www.kde.org
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