Gtk.TreeModelFilter
Description: Reference for Gtk.TreeModelFilter

### Class

# GtkTreeModelFilter

#### Description [src]

    class Gtk.TreeModelFilter : GObject.Object {
      parent: GObject
    }

A `GtkTreeModel` which hides parts of an underlying tree model

A `GtkTreeModelFilter` is a tree model which wraps another tree model, and can do the following things:

- Filter specific rows, based on data from a “visible column”, a column storing booleans indicating whether the row should be filtered or not, or based on the return value of a “visible function”, which gets a model, iter and user_data and returns a boolean indicating whether the row should be filtered or not.

- Modify the “appearance” of the model, using a modify function. This is extremely powerful and allows for just changing some values and also for creating a completely different model based on the given child model.

- Set a different root node, also known as a “virtual root”. You can pass in a `GtkTreePath` indicating the root node for the filter at construction time.

The basic API is similar to `GtkTreeModelSort`. For an example on its usage, see the section on `GtkTreeModelSort`.

When using `GtkTreeModelFilter`, it is important to realize that `GtkTreeModelFilter` maintains an internal cache of all nodes which are visible in its clients. The cache is likely to be a subtree of the tree exposed by the child model. `GtkTreeModelFilter` will not cache the entire child model when unnecessary to not compromise the caching mechanism that is exposed by the reference counting scheme. If the child model implements reference counting, unnecessary signals may not be emitted because of reference counting rule 3, see the `GtkTreeModel` documentation. (Note that e.g. `GtkTreeStore` does not implement reference counting and will always emit all signals, even when the receiving node is not visible).

Because of this, limitations for possible visible functions do apply. In general, visible functions should only use data or properties from the node for which the visibility state must be determined, its siblings or its parents. Usually, having a dependency on the state of any child node is not possible, unless references are taken on these explicitly. When no such reference exists, no signals may be received for these child nodes (see reference counting rule number 3 in the `GtkTreeModel` section).

Determining the visibility state of a given node based on the state of its child nodes is a frequently occurring use case. Therefore, `GtkTreeModelFilter` explicitly supports this. For example, when a node does not have any children, you might not want the node to be visible. As soon as the first row is added to the node’s child level (or the last row removed), the node’s visibility should be updated.

This introduces a dependency from the node on its child nodes. In order to accommodate this, `GtkTreeModelFilter` must make sure the necessary signals are received from the child model. This is achieved by building, for all nodes which are exposed as visible nodes to `GtkTreeModelFilter`‘s clients, the child level (if any) and take a reference on the first node in this level. Furthermore, for every row-inserted, row-changed or row-deleted signal (also these which were not handled because the node was not cached), `GtkTreeModelFilter` will check if the visibility state of any parent node has changed.

Beware, however, that this explicit support is limited to these two cases. For example, if you want a node to be visible only if two nodes in a child’s child level (2 levels deeper) are visible, you are on your own. In this case, either rely on `GtkTreeStore` to emit all signals because it does not implement reference counting, or for models that do implement reference counting, obtain references on these child levels yourself.

#### Ancestors

- GObject

#### Implements

- GtkTreeDragSource
- GtkTreeModel

#### Instance methods

###### gtk_tree_model_filter_clear_cache

This function should almost never be called. It clears the `filter` of any cached iterators that haven’t been reffed with gtk_tree_model_ref_node(). This might be useful if the child model being filtered is static (and doesn’t change often) and there has been a lot of unreffed access to nodes. As a side effect of this function, all unreffed iters will be invalid.

###### gtk_tree_model_filter_convert_child_iter_to_iter

Sets `filter_iter` to point to the row in `filter` that corresponds to the row pointed at by `child_iter`. If `filter_iter` was not set, `FALSE` is returned.

###### gtk_tree_model_filter_convert_child_path_to_path

Converts `child_path` to a path relative to `filter`. That is, `child_path` points to a path in the child model. The rerturned path will point to the same row in the filtered model. If `child_path` isn’t a valid path on the child model or points to a row which is not visible in `filter`, then `NULL` is returned.

###### gtk_tree_model_filter_convert_iter_to_child_iter

Sets `child_iter` to point to the row pointed to by `filter_iter`.

###### gtk_tree_model_filter_convert_path_to_child_path

Converts `filter_path` to a path on the child model of `filter`. That is, `filter_path` points to a location in `filter`. The returned path will point to the same location in the model not being filtered. If `filter_path` does not point to a location in the child model, `NULL` is returned.

###### gtk_tree_model_filter_get_model

Returns a pointer to the child model of `filter`.

###### gtk_tree_model_filter_refilter

Emits ::row_changed for each row in the child model, which causes the filter to re-evaluate whether a row is visible or not.

###### gtk_tree_model_filter_set_modify_func

With the `n_columns` and `types` parameters, you give an array of column types for this model (which will be exposed to the parent model/view). The `func`, `data` and `destroy` parameters are for specifying the modify function. The modify function will get called for each data access, the goal of the modify function is to return the data which should be displayed at the location specified using the parameters of the modify function.

###### gtk_tree_model_filter_set_visible_column

Sets `column` of the child_model to be the column where `filter` should look for visibility information. `columns` should be a column of type `G_TYPE_BOOLEAN`, where `TRUE` means that a row is visible, and `FALSE` if not.

###### gtk_tree_model_filter_set_visible_func

Sets the visible function used when filtering the `filter` to be `func`. The function should return `TRUE` if the given row should be visible and `FALSE` otherwise.

##### Methods inherited from GObject (43)

Please see GObject for a full list of methods.

##### Methods inherited from GtkTreeDragSource (3)

###### gtk_tree_drag_source_drag_data_delete

Asks the `GtkTreeDragSource` to delete the row at `path`, because it was moved somewhere else via drag-and-drop. Returns `FALSE` if the deletion fails because `path` no longer exists, or for some model-specific reason. Should robustly handle a `path` no longer found in the model!

###### gtk_tree_drag_source_drag_data_get

Asks the `GtkTreeDragSource` to return a `GdkContentProvider` representing the row at `path`. Should robustly handle a `path` no longer found in the model!

###### gtk_tree_drag_source_row_draggable

Asks the `GtkTreeDragSource` whether a particular row can be used as the source of a DND operation. If the source doesn’t implement this interface, the row is assumed draggable.

##### Methods inherited from GtkTreeModel (28)

Please see GtkTreeModel for a full list of methods.

#### Properties

###### Gtk.TreeModelFilter:child-model

No description available.

###### Gtk.TreeModelFilter:virtual-root

No description available.

#### Signals

##### Signals inherited from GObject (1)

###### GObject.Object::notify

The notify signal is emitted on an object when one of its properties has its value set through g_object_set_property(), g_object_set(), et al.

##### Signals inherited from GtkTreeModel (5)

###### Gtk.TreeModel::row-changed

This signal is emitted when a row in the model has changed.

###### Gtk.TreeModel::row-deleted

This signal is emitted when a row has been deleted.

###### Gtk.TreeModel::row-has-child-toggled

This signal is emitted when a row has gotten the first child row or lost its last child row.

###### Gtk.TreeModel::row-inserted

This signal is emitted when a new row has been inserted in the model.

###### Gtk.TreeModel::rows-reordered

This signal is emitted when the children of a node in the `GtkTreeModel` have been reordered.

#### Class structure

    struct GtkTreeModelFilterClass {
      GObjectClass parent_class;
      gboolean (* visible) (
        GtkTreeModelFilter* self,
        GtkTreeModel* child_model,
        GtkTreeIter* iter
      );
      void (* modify) (
        GtkTreeModelFilter* self,
        GtkTreeModel* child_model,
        GtkTreeIter* iter,
        GValue* value,
        int column
      );

    }

###### Class members

`parent_class` |
    GObjectClass
| No description available.
`visible` |
    gboolean (* visible) (
        GtkTreeModelFilter* self,
        GtkTreeModel* child_model,
        GtkTreeIter* iter
      )
| No description available.
`modify` |
    void (* modify) (
        GtkTreeModelFilter* self,
        GtkTreeModel* child_model,
        GtkTreeIter* iter,
        GValue* value,
        int column
      )
| No description available.

#### Virtual methods

###### Gtk.TreeModelFilterClass.modify

No description available.

###### Gtk.TreeModelFilterClass.visible

No description available.