Hi,
First of all, my question:
I have an "RDF content tree" (ie generated from an RDF datasource, but
without the 'dont-build-content' flag. Is it possible to support UI
feedback when dragging things over the tree? (ie. horizontal insertion
bars between tree elements)
To show what I mean, I've implemented the DnD using the nsdraganddrop
wrapper as follows:
---
var treeObserver = {
getSupportedFlavours : function () {
var flavours = new FlavourSet();
flavours.appendFlavour("text/x-moz-url");
return flavours;
},
onDragOver: function (evt,flavour,session) {
session.canDrop=true;
},
onDrop: function (evt,dropdata,session) {
var tree = document.getElementById("UpdateTree");
var col={};
var row={};
var child={};
tree.treeBoxObject.getCellAt(evt.pageX, evt.pageY, row, col, child);
split = dropdata.data.indexOf("\n");
url = dropdata.data.substring(0, split);
title = dropdata.data.substring(split);
openNewDialogNoRefresh(title, url, row.value);
}
};
---
This works fine, but doesn't provide any feedback when an item is
dragged over the tree.
So I tried a different approach, adding the dont-build-content flag, and
assigning the builder manually. I then added the following observer to
the builder:
---
var dragService =
Components.classes["@mozilla.org/widget/dragservice;1"].getService().QueryInterface(Components.interfaces.nsIDragService);
var treeBuilderObserver = {
canDrop : function(idx, orient) {
if (orient == Components.interfaces.nsITreeView.DROP_ON)
return false;
else
return true;
},
onDrop : function(index, orient) {
data = getDragData("text/x-moz-url").data.split("\n");
url = data[0];
title = data[1];
openNewDialogNoRefresh(title, url, index);
},
};
function getDragData(flavour)
{
var dragSession = dragService.getCurrentSession();
if (!dragSession)
return false;
var trans =
Components.classes["@mozilla.org/widget/transferable;1"].
createInstance(Components.interfaces.nsITransferable);
trans.addDataFlavor(flavour);
var dataObj = new Object();
var flavor = new Object();
var len = new Object();
for (var i = 0; i < dragSession.numDropItems; i++)
{
dragSession.getData(trans, i);
trans.getAnyTransferData(flavor, dataObj, len);
if (!dataObj)
continue;
return dataObj.value.QueryInterface(
Components.interfaces.nsISupportsString);
}
return null;
}
---
This provided the UI feedback I was after (an insertion bar appears when
dragging something over the tree), but introduced other problems:
* The openNewDialogNoRefresh function brings up a dialog window, to
allow the user to edit the new item. This doesn't work when called from
the new observer callback function - the dialog isn't drawn correctly,
and doesn't respond to user input. I'm guessing I need to return
immediately from the builder callback.
* Other parts of my code rely on the content builder for getting the
currently selected item, etc. I should be able to work around this, but
results in many changes to my code
* I saw some strange behaviour, with elements of the tree changing
position randomly. Again, I can probably work around this, but it is
pretty weird!
So for these reasons (the first one in particular), I would like to use
the content builder and nsdraganddrop wrapper. Which takes me back to my
original question:
Is it possible to support UI feedback with a content builder? (I'm still
learning about how trees work in XUL, so any hints are appreciated!)
Thanks,
Pete
--
http://www.fastmail.fm - I mean, what is it about a decent email service?
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