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| GwyNullStore * | gwy_null_store_new () |
| guint | gwy_null_store_get_n_rows () |
| void | gwy_null_store_set_n_rows () |
| void | gwy_null_store_row_changed () |
| void | gwy_null_store_rows_changed () |
| gboolean | gwy_null_store_iter_is_valid () |
| void | gwy_clear_null_store_tree_view () |
GwyNullStore is a very simple GtkTreeModel which pretents to have a single column of type G_TYPE_UINT. Values in
the column are equal to row numbers (counted from 0). In reality the column is purely virtual and the store always
takes up only a small constant amount of memory.
The purpose of GwyNullStore is to provide a low-overhead GtkTreeModel interface for array-like (and other indexed) data structures.
A new null store can be created with gwy_null_store_new(), then number of virtual rows can be controlled with
gwy_null_store_set_n_rows(). For convenience, methods to emit "row-changed" signal on a row or a range of rows by
their indices are provided: gwy_null_store_row_changed() and gwy_null_store_rows_changed().
A simple example to create a multiplication table with null storage:
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GtkWidget *treeview; GtkTreeViewColumn *column; GtkCellRenderer *renderer; GwyNullStore *store; gint i; store = gwy_null_store_new(10); treeview = gtk_tree_view_new_with_model(GTK_TREE_MODEL(store)); gtk_tree_view_set_headers_visible(GTK_TREE_VIEW(treeview), FALSE); column = gtk_tree_view_column_new(); for (i = 1; i <= 10; i++) { renderer = gtk_cell_renderer_text_new(); g_object_set(renderer, "xalign", 1.0, "width-chars", 4, NULL); gtk_tree_view_column_pack_start(column, renderer, TRUE); gtk_tree_view_column_set_cell_data_func(column, renderer, multiply, GINT_TO_POINTER(i), NULL); } gtk_tree_view_append_column(GTK_TREE_VIEW(treeview), column); |
The cell data function multiply() just multiplies the column number with the number of (virtual) null store row:
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static void multiply(GtkTreeViewColumn *column, GtkCellRenderer *renderer, GtkTreeModel *model, GtkTreeIter *iter, gpointer data) { gchar buf[20]; gint i; gtk_tree_model_get(model, iter, 0, &i, -1); g_snprintf(buf, sizeof(buf), "%d", (i + 1)*GPOINTER_TO_INT(data)); g_object_set(renderer, "text", buf, NULL); } |
To extend the multiplication table to 20 rows, one only needs
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gwy_null_store_set_n_rows(store, 20); |
GwyNullStore *
gwy_null_store_new (guint n);
Creates a new GtkTreeModel wrapper around nothing.
guint
gwy_null_store_get_n_rows (GwyNullStore *store);
Gets the number of imaginary rows in a null store.
This is a convenience function, the same information can be obtained with gtk_tree_model_iter_n_children().
void gwy_null_store_set_n_rows (GwyNullStore *store,guint n);
Sets the number of imaginary rows in a null store.
If the new number of rows is larger than the current one, rows will be sequentially and virtually appended to the end of the store until the requested number of rows is reached.
Similarly, if the new number of rows is smaller then the current one, rows will be sequentially and virtually deleted from the end of the store until the requested number of rows is reached.
Note for radical changes it is usually more useful to disconnect the model from its view(s), change the number of rows, and then reconnect.
void gwy_null_store_row_changed (GwyNullStore *store,guint i);
Emits "GtkTreeModel::row-changed" signal on a null store.
This is a convenience method, with a bit more work the same effect can be achieved with
gtk_tree_model_row_changed().
void gwy_null_store_rows_changed (GwyNullStore *store,guint ifrom,guint ito);
Emits "GtkTreeModel::row-changed" signal on a block of rows in a null store.
This is a convenience method, with a bit more work the same effect can be achieved with
gtk_tree_model_row_changed().
It is possible to pass ifrom
larger than ito
. The signal is then emitted for the same rows, but in the opposite
order.
gboolean gwy_null_store_iter_is_valid (GwyNullStore *store,GtkTreeIter *iter);
Checks if the given iter is a valid iter for this null store.
void
gwy_clear_null_store_tree_view (GtkTreeView *treeview);
Clears a tree view backed by a null store.
The tree view treeview
must have a GwyNullStore as its model.
The function does not remove the rows one by one. It unsets the model, clears the store and sets it back as the
model. This is, of course, efficient only if treeview
is the only view backed by the null store because other
views will still see the individual row removals. If the store is already empty, the function is a no-op.