QFileSystemModel - iterating through current index children
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bq. If the state is “determined by children”, then iterate over the (existing!) child nodes. If they are all the same, then the state is that state, otherwise the state is the ambivalent PartlyChecked state.
Thanks for your response. However, a concern I have is that I will still have to fetchMore (an indefinite procedure) to iterate over the (existing) child nodes.
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No, you don't. That's the whole beauty of the idea. :-)
You only need to iterate over the children that you already have. Potential children that have not been loaded yet, will have the default Determined by parent state.
Edit:
Perhaps there could be a slight snag though, if you are in a large directory, perhaps it could occur that not all files in that directory are loaded yet when you start modifying check boxes in it. That might be a point of breakdown. That could be solved by introducing something like a "default state for child nodes" for all branch nodes. Set that, and have nodes that have just been added take over that state. -
Can you provide code snippets to resolve this issue? I cannot get this to work... I´ve also been searching the web for sample but have not had any luck... Thanks!
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I could in principle, but I don't think I will have time to provide one within the next two days.
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any help would greatly be appreciated!!! I´ve tried but cannot seem to get things to work properly. Thank you for your continual support!
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Please do remind me (by replying in this topic) if I don't respond before the end of the week. In the meantime, of course everyone else is welcome to pitch in as well ;-)
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Just so that we are on the same page because the topic doesn´t describe my issue in details. I am using a QTreeView populated with a subclassed QFileSystemModel. I´ve been successful at integrating a checkbox in column 0 of each tree node (a row) and have also added another column to my treeview. I am running into the issue of propagating the state of the parent node to the children when it´s state change as well as propagating the state of the parent node to uncheck if any of its child is unchecked or to check if all of its child is checked. Eventually, my goal will be to iterate through all of the check nodes (files) in the treeview and process them.
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Andre... this is a reminder to respond on request for code snippets for propagating QTreeView using subclassed QFileSystemModel with checkboxes. Thanks!
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It is still on my radar, but time is flying and to be honest, I'm also a bit bussy enjoying the excellent weather out here for a bit ;-) Thanks for the reminder though!
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Hi Andre... Any progress?
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I am making good progress. I am just trying to find some last issues, but the basics are working just fine. I guess I also need to bolt some kind of API onto it for modifying and querying the checked items from code, but that is for later.
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The snippets you requested have turned into a complete class. The principle works, -but there is still an issue to iron out that sometimes, an infinate recursion is triggered and the application crashes. That, of course, is not acceptable.-
Still, working with a QFileSystemModel as the base model, the proxy nicely manages to add checkboxes to each node, and make branch nodes work as expected (checking or unchecking them will do the same for the whole subtree, while having both checked and unchecked nodes in the subtree results in the Partially Checked checkbox state). That works with a minimum number of items that are actually tracked. In a realistic scenario on a pretty big file system, I still only had a few dozen items in the internal data store that tracks the check state of each node. The proxy model automatically reduces the number of size of the internal data store to a minimum. Obviously, all that works without recursing into the base model more deeply than the user already has, let alone trying to iterate over all children and trying to make the model fetch all of them. :-)
Now that I have a complete class, the question arises under what licence to publish it. Do you need it for an open source project, or do you need something compatible with a closed source application? It turned out to be quite a bit of work to get working, even though the principles are actually the same as I described on the previous page of this topic. That makes me a bit reluctant to just dump it into the public domain...
Edit:
I have managed to resolve the issue, I think. At least the class now seems to work reliably under my tests. See screenshot below for how it looks:
!http://dl.dropbox.com/u/16442531/CheckableProxyModelDemo.png(Screenshot of CheckableProxyModel class applied to a QFileSystemModel)!What kind of additional API would be needed, you think? I am thinking along these lines:
An API to set the default state of all the nodes to either checked or unchecked (done)
An API to list the checked subtrees (QModelIndexList with the top nodes that have everything under them checked) (done)
An API to list the checked branch nodes (also a QModelIndexList) (done)
Signals to indicate when 1 or 2 changes (done, though only one change signal for now)
... ?
Will we need convenience API to set the check-state programatically? I mean, you can already do that of course by using QAbstractItemModel::setData() just like the view does, but perhaps that could be made easier. What might be handy is to be able to specify the check state based on the source models QModelIndex-es. That way, it would be easy to set for instance the check state based on the file path when using a QFileSystemModel as the source model.
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OK, I guess the class is pretty much done. All the ideas in my previous post have been implemented, and the class seems to behave nicely even when you also use the sort capabilities of the QSortFilterProxyModel it is based on.
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Hi Andre,
did you think of making this class a contribution to Qt? Or a QtSolution or something. It sounds really interesting.
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I am thinking of the best way to do this, yes. I'm not sure if it should be a Qt contribution, or some other third party component, nor I am sure if I could perhaps make some kind of dual licence for it.
Edit: a suggestion at #qt-labs was to make it into a Qt example. That might work.
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Hi Andre, it looks great and I can´t wait to see its implementation!!! I do not need it to be closed source, thus, any license you see fit should work.
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OK. I guess I will start by tagging the files as GPL for now, and then put the whole project into a git repository somewhere, and I'll put the link here.
phamtv: do you think you will be needing other API than what's already available?
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How hard will it be to get a list of unchecked files from the root directory filtered by a certain extention.
For instance, you´ve filter the model to show all .txt file in the tree. I see that you have all of the checked .txt file listed in the snapshot shown above. How hard will it to be to get all the .txt file that is NOT checked from your model?
edit: The goal is to get a list of all UNCHECKED filtered files from -partially checked/checked- all directory.
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Hmmm... That is actually not trivial. I guess you can do the filtering on .txt files using the QFileSystemModel itself, by using the setNameFilter.
In principle, getting the unchecked items from the tree is about the same complexity as getting the checked ones: doable. That is: you would get a list of unchecked files, and of unchecked branches.
However, it is not really feasable to get all the unchecked .txt files inside the unchecked branches. That would bring you back to having to populate the entire tree and potentially recurse through the whole file system to find them all. That would be outside the scope of this class, and should be done using QDirIterator, I think (if you really can't avoid this) or using system dependent methods if your system supports more efficient search of files than just scanning the complete file system. You can still use the results of the selection to limit the search scope though. -
You read my mind. It is very specific to my project. I have been researching and I think that QDirIterator along with your class will be the solution to my problem. I will basically use QDirIterator to get all my filtered files and compare it to your model/class result and determine if it is unchecked.. Thanks!