Luigi Castelli

after studying the dbviewer.c example and much experimenting with the jdataview API I am gaining a pretty good grasp of it.

I can now build a complete dataview with different components and options, display values and menus, edit the data, etc... Great.

However, there's still one last thing that escapes me:

How to have cells respond to drag'n'drop operations ?

I would like to be able to drag from cells of my dataview to objects and patchers and be able to have Max automatically select the right action to perform (load an image or soundfile, create a message, create a patcher, etc...). This is the same behavior that I see implemented in filebrowser.

I have been looking and looking through the jdataview API, but the only clue I could find is a 

 function, which I set when I create and initialize my dataview.

Needless to say, I am clueless as to what direction to go from here.

after studying the dbviewer.c example and much experimenting with the jdataview API I am gaining a pretty good grasp of it.
I can now build a complete dataview with different components and options, display values and menus, edit the data, etc... Great.

How to have cells respond to drag'n'drop operations ?
I would like to be able to drag from cells of my dataview to objects and patchers and be able to have Max automatically select the right action to perform (load an image or soundfile, create a message, create a patcher, etc...). This is the same behavior that I see implemented in filebrowser.

I have been looking and looking through the jdataview API, but the only clue I could find is a jdataview_setdragenabled() function, which I set when I create and initialize my dataview.
Needless to say, I am clueless as to what direction to go from here.

dragndrop-in-jdataview

We aren't officially supporting this. The mechanism is not incredibly simple. But, I can try to point you in the right direction...

In a dataview, various methods are called, and they often indicate what row using a t_rowref.

In the filebrowser we map the t_rowrefs to instances of nobox class we created that represents the data for a row.

So when our dataview-based object receives a "getrowobject" method we implement something like this:

// called when we start a drag
t_object *filebrowser_getrowobject(t_filebrowser *x, t_rowref rr)
{
    t_filerow *f = (t_filerow *)rr;
    if (!f->d_dragrole)
        f->d_dragrole = filebrowser_getdragrole(x, rr);
    // if there is no role, could return NULL here, indicating the item is not draggable...
    return (t_object *)rr;
}


Max will then take the object (if not NULL) returned by this method and query the "dragrole" attribute

       // this is for the t_filerow object
    CLASS_ATTR_SYM(c, "dragrole", 0, t_filerow, d_dragrole);


If the target of the drag knows what to do with a given dragrole (the kinds you see in the filebrowser), then Max will proceed to call a "getname" message on the object returned by "getrowobject". This should return e.g. the name of the audiofile or whatever.

We aren't officially supporting this.  The mechanism is not incredibly simple.  But, I can try to point you in the right direction...

In a dataview, various methods are called, and they often indicate what row using a t_rowref.  

So when our dataview-based object receives a "getrowobject" method we implement something like this: 

// called when we start a drag
t_object *filebrowser_getrowobject(t_filebrowser *x, t_rowref rr)
{
	t_filerow *f = (t_filerow *)rr;
	if (!f->d_dragrole)
		f->d_dragrole = filebrowser_getdragrole(x, rr);
	// if there is no role, could return NULL here, indicating the item is not draggable...
	return (t_object *)rr;
}


       // this is for the t_filerow object
	CLASS_ATTR_SYM(c, "dragrole", 0, t_filerow, d_dragrole);


If the target of the drag knows what to do with a given dragrole (the kinds you see in the filebrowser), then Max will proceed to call a "getname" message on the object returned by "getrowobject".  This should return e.g. the name of the audiofile or whatever.

sorry it took me a while to digest all the explicit and implicit information in your reply, but I think I now understand the basic structure of this mechanism.

I also assume you are using the sqlite object and the facilities exposed in ext_database.h to query folders and files in different locations.

So - as you suggested - I have created a t_filerow nobox class and mapped it to every t_rowref.

The t_filerow class has a "dragrole" attribute for Max to query.

Now - if I understand the whole mechanism correctly - I am still missing a step.

When the "getrowobject" method is called as I drag an item from my dataview, Max has still no notion of what's draggable and what's not. In other words the dragrole attribute of each filerow still needs to be set. So, for each file/folder found by the database query I need to create a filerow object and set its dragrole attribute to represent the role of the found file/folder. I am guessing that's done for each query, when the columns and rows of the dataview are created and initialized.

If so, how do I make each filerow object represent the 'draggability' state of each file/folder?

Where do I find the role of each file/folder found?

sorry it took me a while to digest all the explicit and implicit information in your reply, but I think I now understand the basic structure of this mechanism.
I also assume you are using the sqlite object and the facilities exposed in ext_database.h  to query folders and files in different locations.

So - as you suggested - I have created a t_filerow nobox class and mapped it to every t_rowref.
The t_filerow class has a "dragrole" attribute for Max to query.

Now - if I understand the whole mechanism correctly - I am still missing a step.
When the "getrowobject" method is called as I drag an item from my dataview, Max has still no notion of what's draggable and what's not. In other words the dragrole attribute of each filerow still needs to be set. So, for each file/folder found by the database query I need to create a filerow object and set its dragrole attribute to represent the role of the found file/folder. I am guessing that's done for each query, when the columns and rows of the dataview are created and initialized.
Is my reasoning correct?

If so, how do I make each filerow object represent the 'draggability' state of each file/folder?
Where do I find the role of each file/folder found?
That's where I am stuck...

drag'n'drop in jdataview