GTK+ 3 Reference Manual: GtkTreeModelFilter

## GtkTreeModelFilter GtkTreeModelFilter — A GtkTreeModel which hides parts of an underlying tree model |

## Functions

gboolean | (*GtkTreeModelFilterVisibleFunc) ()
void | (*GtkTreeModelFilterModifyFunc) ()
GtkTreeModel * | gtk_tree_model_filter_new ()
void | gtk_tree_model_filter_set_visible_func ()
void | gtk_tree_model_filter_set_modify_func ()
void | gtk_tree_model_filter_set_visible_column ()
GtkTreeModel * | gtk_tree_model_filter_get_model ()
gboolean | gtk_tree_model_filter_convert_child_iter_to_iter ()
void | gtk_tree_model_filter_convert_iter_to_child_iter ()
GtkTreePath * | gtk_tree_model_filter_convert_child_path_to_path ()
GtkTreePath * | gtk_tree_model_filter_convert_path_to_child_path ()
void | gtk_tree_model_filter_refilter ()
void | gtk_tree_model_filter_clear_cache ()

## Properties

GtkTreeModel * | child-model | Read / Write / Construct Only
GtkTreePath * | virtual-root | Read / Write / Construct Only

## Types and Values

struct | GtkTreeModelFilter

## Object Hierarchy

        GObject
        ╰── GtkTreeModelFilter

## Implemented Interfaces

GtkTreeModelFilter implements GtkTreeModel and GtkTreeDragSource.

## Includes

    #include <gtk/gtk.h>

## Description

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 couting 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 necesary 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.

## Functions

### GtkTreeModelFilterVisibleFunc ()

    gboolean
    (*GtkTreeModelFilterVisibleFunc) (GtkTreeModel *model,
                                      GtkTreeIter *iter,
                                      gpointer data);

A function which decides whether the row indicated by `iter` is visible.

#### Parameters

model | the child model of the GtkTreeModelFilter |
iter | a GtkTreeIter pointing to the row in `model` whose visibility is determined |
data | user data given to `gtk_tree_model_filter_set_visible_func()`. | [closure]

#### Returns

Whether the row indicated by `iter` is visible.

### GtkTreeModelFilterModifyFunc ()

    void
    (*GtkTreeModelFilterModifyFunc) (GtkTreeModel *model,
                                     GtkTreeIter *iter,
                                     GValue *value,
                                     gint column,
                                     gpointer data);

A function which calculates display values from raw values in the model. It must fill `value` with the display value for the column `column` in the row indicated by `iter` .

Since this function is called for each data access, it's not a particularly efficient operation.

#### Parameters

model | the GtkTreeModelFilter |
iter | a GtkTreeIter pointing to the row whose display values are determined |
value | A GValue which is already initialized for with the correct type for the column `column` . |
column | the column whose display value is determined |
data | user data given to `gtk_tree_model_filter_set_modify_func()`. | [closure]

### gtk_tree_model_filter_new ()

    GtkTreeModel *
    gtk_tree_model_filter_new (GtkTreeModel *child_model,
                               GtkTreePath *root);

Creates a new GtkTreeModel, with `child_model` as the child_model and `root` as the virtual root.

#### Parameters

child_model | A GtkTreeModel. |
root | A GtkTreePath or `NULL`. | [allow-none]

#### Returns

A new GtkTreeModel.

[transfer full]

Since 2.4

### gtk_tree_model_filter_set_visible_func ()

    void
    gtk_tree_model_filter_set_visible_func
                                   (GtkTreeModelFilter *filter,
                                    GtkTreeModelFilterVisibleFunc func,
                                    gpointer data,
                                    GDestroyNotify destroy);

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.

If the condition calculated by the function changes over time (e.g. because it depends on some global parameters), you must call `gtk_tree_model_filter_refilter()` to keep the visibility information of the model uptodate.

Note that `func` is called whenever a row is inserted, when it may still be empty. The visible function should therefore take special care of empty rows, like in the example below.

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    static gboolean
    visible_func (GtkTreeModel *model,
                  GtkTreeIter  *iter,
                  gpointer      data)
    {
      /* Visible if row is non-empty and first column is "HI" */
      gchar *str;
      gboolean visible = FALSE;

      gtk_tree_model_get (model, iter, 0, &str, -1);
      if (str && strcmp (str, "HI") == 0)
        visible = TRUE;
      g_free (str);

      return visible;
    }

#### Parameters

filter | A GtkTreeModelFilter. |
func | A GtkTreeModelFilterVisibleFunc, the visible function. |
data | User data to pass to the visible function, or `NULL`. | [allow-none]
destroy | Destroy notifier of `data` , or `NULL`. | [allow-none]

Since 2.4

### gtk_tree_model_filter_set_modify_func ()

    void
    gtk_tree_model_filter_set_modify_func (GtkTreeModelFilter *filter,
                                           gint n_columns,
                                           GType *types,
                                           GtkTreeModelFilterModifyFunc func,
                                           gpointer data,
                                           GDestroyNotify destroy);

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.

#### Parameters

filter | A GtkTreeModelFilter. |
n_columns | The number of columns in the filter model. |
types | The GTypes of the columns. | [array length=n_columns]
func | A GtkTreeModelFilterModifyFunc |
data | User data to pass to the modify function, or `NULL`. | [allow-none]
destroy | Destroy notifier of `data` , or `NULL`. | [allow-none]

Since 2.4

### gtk_tree_model_filter_set_visible_column ()

    void
    gtk_tree_model_filter_set_visible_column
                                   (GtkTreeModelFilter *filter,
                                    gint 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.

#### Parameters

filter | A GtkTreeModelFilter. |
column | A gint which is the column containing the visible information. |

Since 2.4

### gtk_tree_model_filter_get_model ()

    GtkTreeModel *
    gtk_tree_model_filter_get_model (GtkTreeModelFilter *filter);

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

#### Parameters

filter | A GtkTreeModelFilter. |

#### Returns

A pointer to a GtkTreeModel.

[transfer none]

Since 2.4

### gtk_tree_model_filter_convert_child_iter_to_iter ()

    gboolean
    gtk_tree_model_filter_convert_child_iter_to_iter
                                   (GtkTreeModelFilter *filter,
                                    GtkTreeIter *filter_iter,
                                    GtkTreeIter *child_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.

#### Parameters

filter | A GtkTreeModelFilter. |
filter_iter | An uninitialized GtkTreeIter. | [out]
child_iter | A valid GtkTreeIter pointing to a row on the child model. |

#### Returns

`TRUE`, if `filter_iter` was set, i.e. if `child_iter` is a valid iterator pointing to a visible row in child model.

Since 2.4

### gtk_tree_model_filter_convert_iter_to_child_iter ()

    void
    gtk_tree_model_filter_convert_iter_to_child_iter
                                   (GtkTreeModelFilter *filter,
                                    GtkTreeIter *child_iter,
                                    GtkTreeIter *filter_iter);

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

#### Parameters

filter | A GtkTreeModelFilter. |
child_iter | An uninitialized GtkTreeIter. | [out]
filter_iter | A valid GtkTreeIter pointing to a row on `filter` . |

Since 2.4

### gtk_tree_model_filter_convert_child_path_to_path ()

    GtkTreePath *
    gtk_tree_model_filter_convert_child_path_to_path
                                   (GtkTreeModelFilter *filter,
                                    GtkTreePath *child_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.

#### Parameters

filter | A GtkTreeModelFilter. |
child_path | A GtkTreePath to convert. |

#### Returns

A newly allocated GtkTreePath, or `NULL`.

Since 2.4

### gtk_tree_model_filter_convert_path_to_child_path ()

    GtkTreePath *
    gtk_tree_model_filter_convert_path_to_child_path
                                   (GtkTreeModelFilter *filter,
                                    GtkTreePath *filter_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.

#### Parameters

filter | A GtkTreeModelFilter. |
filter_path | A GtkTreePath to convert. |

#### Returns

A newly allocated GtkTreePath, or `NULL`.

Since 2.4

### gtk_tree_model_filter_refilter ()

    void
    gtk_tree_model_filter_refilter (GtkTreeModelFilter *filter);

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

#### Parameters

filter | A GtkTreeModelFilter. |

Since 2.4

### gtk_tree_model_filter_clear_cache ()

    void
    gtk_tree_model_filter_clear_cache (GtkTreeModelFilter *filter);

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.

#### Parameters

filter | A GtkTreeModelFilter. |

Since 2.4

## Types and Values

### struct GtkTreeModelFilter

    struct GtkTreeModelFilter;

## Property Details

### The `“child-model”` property

      “child-model”              GtkTreeModel *

The model for the filtermodel to filter.

Flags: Read / Write / Construct Only

### The `“virtual-root”` property

      “virtual-root”             GtkTreePath *

The virtual root (relative to the child model) for this filtermodel.

Flags: Read / Write / Construct Only

## See Also

GtkTreeModelSort