[Qt-interest] Fwd: Fwd: decoration role for the tree model subclass

[Scott Aron Bloom]

most of the calls into the model come from views and delegates.

Put a break point in your data method, eventually it will get called with a request for the decoration role
-Scott
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-----Original Message-----
From: "ami guru" <dosto.walla at gmail.com>
Date: Wednesday, Dec 17, 2008 5:09 am
Subject: [Qt-interest] Fwd: Fwd: decoration role for the tree model subclass
To: qt-interest at trolltech.com

Hello Sebastian,

I did according to your hint. 

But the icon is not showing up along with  the item name.

I think the reason is that data() function is called with display role by default.

How to call  that with  the decoration role?

I would to understand the function call hierarchy in the model that i have created

The manual says that for creating a tree model we have to subclass the QAbstractItemModel and must 
reimplement some of the functions. I would like to see how these over-ridden functions are called.

Only then i would probably be able to track and call the data() with the decoration role.


What do you think?


Regards
Sajjad

---------- Forwarded message ----------
 From: Sebastian Fischer <creat at gmx.net>
Date: Wed, Dec 17, 2008 at 6:37 AM
Subject: Re: [Qt-interest] Fwd:  decoration role for the tree model subclass
 To: ami guru <dosto.walla at gmail.com>





Hi, 


 

below is your data() function adapted to correctly handle the decoration role. 

This funtion serves as the source of all information about the item referenced to by the given index. You already handle the Qt::DisplayRole and just have to expand it for the Qt::DecorationRole, since the type of data requested from the view is defined in the role variable, like so: 


 

<<< BEGIN CODE >>> 

QVariant H3DTreeModel::data(const QModelIndex &index, int role) const 

{  

        if (!index.isValid()) 

                return QVariant(); 

         

        H3DTreeItem *item = static_cast<H3DTreeItem*>(index.internalPointer()); 


 

        if (role == Qt::DisplayRole) 

                return item->data(index.column()); 

        else if (role == Qt::DecorationRole) 

                return item->icon(); 

        else 

                return QVariant();         

} 

<<< END CODE >>> 


 

Obviously H3DTreeItem need a (new) member function returning a QIcon (or just can get the icon from somewhere else). 


 

You might want to read through this, the 'Item Roles' section in particular: 

http://doc.trolltech.com/4.4/model-view-model.html 


 

Bye, 

Sebastian Fischer

 


 

on 17.12.2008 at 01:19 you wrote: 
  
  

hello , 


 


 

do i have to overload the data() function for Qt::DecorationRole ? 


 

The link you provided did not make much sense to me 


 

Could you please provide more reference to that? 


 


 

Regards 

Sajjad