path: root/e-util/e-cell-tree.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
/*
 * e-cell-tree.c - Tree cell object.
 * Copyright (C) 1999-2008 Novell, Inc. (www.novell.com)
 *
 * Authors:
 *   Chris Toshok <toshok@ximian.com>
 *
 * A majority of code taken from:
 *
 * the ECellText renderer.
 * Copyright 1998, The Free Software Foundation
 * Copyright (C) 1999-2008 Novell, Inc. (www.novell.com)
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <ctype.h>
#include <math.h>
#include <stdio.h>

#include <gdk/gdkkeysyms.h>
#include <gtk/gtk.h>
#include <libgnomecanvas/libgnomecanvas.h>

#include "gal-a11y-e-cell-registry.h"
#include "gal-a11y-e-cell-tree.h"

#include "e-cell-tree.h"
#include "e-table-item.h"
#include "e-tree.h"
#include "e-tree-model.h"
#include "e-tree-table-adapter.h"

G_DEFINE_TYPE (ECellTree, e_cell_tree, E_TYPE_CELL)

typedef struct {
    ECellView    cell_view;
    ECellView   *subcell_view;

    GnomeCanvas *canvas;
    gboolean prelit;
    gint animate_timeout;

} ECellTreeView;

#define INDENT_AMOUNT 16

ECellView *
e_cell_tree_view_get_subcell_view (ECellView *ect)
{
    return ((ECellTreeView *) ect)->subcell_view;
}

static ETreePath
e_cell_tree_get_node (ETableModel *table_model,
                      gint row)
{
    return e_table_model_value_at (table_model, -1, row);
}

static ETreeModel *
e_cell_tree_get_tree_model (ETableModel *table_model,
                            gint row)
{
    return e_table_model_value_at (table_model, -2, row);
}

static ETreeTableAdapter *
e_cell_tree_get_tree_table_adapter (ETableModel *table_model,
                                    gint row)
{
    return e_table_model_value_at (table_model, -3, row);
}

static gint
visible_depth_of_node (ETableModel *model,
                       gint row)
{
    ETreeModel *tree_model = e_cell_tree_get_tree_model (model, row);
    ETreeTableAdapter *adapter = e_cell_tree_get_tree_table_adapter (model, row);
    ETreePath path = e_cell_tree_get_node (model, row);
    return (e_tree_model_node_depth (tree_model, path)
        - (e_tree_table_adapter_root_node_is_visible (adapter) ? 0 : 1));
}

/* If this is changed to not include the width of the expansion pixmap
 * if the path is not expandable, then max_width needs to change as
 * well. */
static gint
offset_of_node (ETableModel *table_model,
                gint row)
{
    ETreeModel *tree_model = e_cell_tree_get_tree_model (table_model, row);
    ETreePath path = e_cell_tree_get_node (table_model, row);

    if (visible_depth_of_node (table_model, row) >= 0 ||
        e_tree_model_node_is_expandable (tree_model, path)) {
        return (visible_depth_of_node (table_model, row) + 1) * INDENT_AMOUNT;
    } else {
        return 0;
    }
}

/*
 * ECell::new_view method
 */
static ECellView *
ect_new_view (ECell *ecell,
              ETableModel *table_model,
              gpointer e_table_item_view)
{
    ECellTree *ect = E_CELL_TREE (ecell);
    ECellTreeView *tree_view = g_new0 (ECellTreeView, 1);
    GnomeCanvas *canvas = GNOME_CANVAS_ITEM (e_table_item_view)->canvas;

    tree_view->cell_view.ecell = ecell;
    tree_view->cell_view.e_table_model = table_model;
    tree_view->cell_view.e_table_item_view = e_table_item_view;
    tree_view->cell_view.kill_view_cb = NULL;
    tree_view->cell_view.kill_view_cb_data = NULL;

    /* create our subcell view */
    tree_view->subcell_view = e_cell_new_view (ect->subcell, table_model, e_table_item_view /* XXX */);

    tree_view->canvas = canvas;

    return (ECellView *) tree_view;
}

/*
 * ECell::kill_view method
 */
static void
ect_kill_view (ECellView *ecv)
{
    ECellTreeView *tree_view = (ECellTreeView *) ecv;

    if (tree_view->cell_view.kill_view_cb)
        (tree_view->cell_view.kill_view_cb)(ecv, tree_view->cell_view.kill_view_cb_data);

    if (tree_view->cell_view.kill_view_cb_data)
        g_list_free (tree_view->cell_view.kill_view_cb_data);

    /* kill our subcell view */
    e_cell_kill_view (tree_view->subcell_view);

    g_free (tree_view);
}

/*
 * ECell::realize method
 */
static void
ect_realize (ECellView *ecell_view)
{
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;

    /* realize our subcell view */
    e_cell_realize (tree_view->subcell_view);

    if (E_CELL_CLASS (e_cell_tree_parent_class)->realize)
        (* E_CELL_CLASS (e_cell_tree_parent_class)->realize) (ecell_view);
}

/*
 * ECell::unrealize method
 */
static void
ect_unrealize (ECellView *ecv)
{
    ECellTreeView *tree_view = (ECellTreeView *) ecv;

    /* unrealize our subcell view. */
    e_cell_unrealize (tree_view->subcell_view);

    if (E_CELL_CLASS (e_cell_tree_parent_class)->unrealize)
        (* E_CELL_CLASS (e_cell_tree_parent_class)->unrealize) (ecv);
}

static void
draw_expander (ECellTreeView *ectv,
               cairo_t *cr,
               GtkExpanderStyle expander_style,
               GtkStateType state,
               GdkRectangle *rect)
{
    GtkStyleContext *style_context;
    GtkWidget *tree;
    GtkStateFlags flags = 0;
    gint exp_size;

    tree = gtk_widget_get_parent (GTK_WIDGET (ectv->canvas));
    style_context = gtk_widget_get_style_context (tree);

    gtk_style_context_save (style_context);

    gtk_style_context_add_class (style_context, GTK_STYLE_CLASS_EXPANDER);

    switch (state) {
        case GTK_STATE_PRELIGHT:
            flags |= GTK_STATE_FLAG_PRELIGHT;
            break;
        case GTK_STATE_SELECTED:
            flags |= GTK_STATE_FLAG_SELECTED;
            break;
        case GTK_STATE_INSENSITIVE:
            flags |= GTK_STATE_FLAG_INSENSITIVE;
            break;
        default:
            break;
    }

    if (expander_style == GTK_EXPANDER_EXPANDED)
        flags |= GTK_STATE_FLAG_ACTIVE;

    gtk_style_context_set_state (style_context, flags);

    gtk_widget_style_get (tree, "expander_size", &exp_size, NULL);

    cairo_save (cr);

    gtk_render_expander (
        style_context, cr,
        (gdouble) rect->x + rect->width - exp_size,
        (gdouble) (rect->y + rect->height / 2) - (exp_size / 2),
        (gdouble) exp_size,
        (gdouble) exp_size);

    cairo_restore (cr);

    gtk_style_context_restore (style_context);
}

/*
 * ECell::draw method
 */
static void
ect_draw (ECellView *ecell_view,
          cairo_t *cr,
          gint model_col,
          gint view_col,
          gint row,
          ECellFlags flags,
          gint x1,
          gint y1,
          gint x2,
          gint y2)
{
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;
    ETreeModel *tree_model = e_cell_tree_get_tree_model (ecell_view->e_table_model, row);
    ETreeTableAdapter *tree_table_adapter = e_cell_tree_get_tree_table_adapter (ecell_view->e_table_model, row);
    ETreePath node;
    GdkRectangle rect;
    gint offset, subcell_offset;

    cairo_save (cr);

    /* only draw the tree effects if we're the active sort */
    if (/* XXX */ TRUE) {
        tree_view->prelit = FALSE;

        node = e_cell_tree_get_node (ecell_view->e_table_model, row);

        offset = offset_of_node (ecell_view->e_table_model, row);
        subcell_offset = offset;

        /*
         * Be a nice citizen: clip to the region we are supposed to draw on
         */
        rect.x = x1;
        rect.y = y1;
        rect.width = subcell_offset;
        rect.height = y2 - y1;

        /* now draw our icon if we're expandable */
        if (e_tree_model_node_is_expandable (tree_model, node)) {
            gboolean expanded = e_tree_table_adapter_node_is_expanded (tree_table_adapter, node);
            GdkRectangle r;

            r = rect;
            r.width -= 2;
            draw_expander (tree_view, cr, expanded ? GTK_EXPANDER_EXPANDED : GTK_EXPANDER_COLLAPSED, GTK_STATE_NORMAL, &r);
        }
    }

    /* Now cause our subcell to draw its contents, shifted by
     * subcell_offset pixels */
    e_cell_draw (
        tree_view->subcell_view, cr,
        model_col, view_col, row, flags,
        x1 + subcell_offset, y1, x2, y2);

    cairo_restore (cr);
}

static void
adjust_event_position (GdkEvent *event,
                       gint offset)
{
    switch (event->type) {
    case GDK_BUTTON_PRESS:
    case GDK_BUTTON_RELEASE:
    case GDK_2BUTTON_PRESS:
    case GDK_3BUTTON_PRESS:
        event->button.x += offset;
        break;
    case GDK_MOTION_NOTIFY:
        event->motion.x += offset;
        break;
    default:
        break;
    }
}

static gboolean
event_in_expander (GdkEvent *event,
                   gint offset,
                   gint height)
{
    switch (event->type) {
    case GDK_BUTTON_PRESS:
        return (event->button.x > (offset - INDENT_AMOUNT) && event->button.x < offset);
    case GDK_MOTION_NOTIFY:
        return (event->motion.x > (offset - INDENT_AMOUNT) && event->motion.x < offset &&
            event->motion.y > 2 && event->motion.y < (height - 2));
    default:
        break;
    }

    return FALSE;
}

/*
 * ECell::height method
 */
static gint
ect_height (ECellView *ecell_view,
            gint model_col,
            gint view_col,
            gint row)
{
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;

    return (((e_cell_height (tree_view->subcell_view, model_col, view_col, row)) + 1) / 2) * 2;
}

typedef struct {
    ECellTreeView *ectv;
    ETreeTableAdapter *etta;
    ETreePath node;
    gboolean expanded;
    gboolean finish;
    GdkRectangle area;
} animate_closure_t;

static gboolean
animate_expander (gpointer data)
{
    GtkLayout *layout;
    GdkWindow *window;
    animate_closure_t *closure = (animate_closure_t *) data;
    cairo_t *cr;

    if (closure->finish) {
        e_tree_table_adapter_node_set_expanded (closure->etta, closure->node, !closure->expanded);
        closure->ectv->animate_timeout = 0;
        g_free (data);
        return FALSE;
    }

    layout = GTK_LAYOUT (closure->ectv->canvas);
    window = gtk_layout_get_bin_window (layout);

    cr = gdk_cairo_create (window);

    draw_expander (
        closure->ectv, cr, closure->expanded ?
        GTK_EXPANDER_SEMI_COLLAPSED :
        GTK_EXPANDER_SEMI_EXPANDED,
        GTK_STATE_NORMAL, &closure->area);
    closure->finish = TRUE;

    cairo_destroy (cr);

    return TRUE;
}

/*
 * ECell::event method
 */
static gint
ect_event (ECellView *ecell_view,
           GdkEvent *event,
           gint model_col,
           gint view_col,
           gint row,
           ECellFlags flags,
           ECellActions *actions)
{
    GtkLayout *layout;
    GdkWindow *window;
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;
    ETreeModel *tree_model = e_cell_tree_get_tree_model (ecell_view->e_table_model, row);
    ETreeTableAdapter *etta = e_cell_tree_get_tree_table_adapter (ecell_view->e_table_model, row);
    ETreePath node = e_cell_tree_get_node (ecell_view->e_table_model, row);
    gint offset = offset_of_node (ecell_view->e_table_model, row);
    gint result;

    layout = GTK_LAYOUT (tree_view->canvas);
    window = gtk_layout_get_bin_window (layout);

    switch (event->type) {
    case GDK_BUTTON_PRESS:

        if (event_in_expander (event, offset, 0)) {
            if (e_tree_model_node_is_expandable (tree_model, node)) {
                gboolean expanded = e_tree_table_adapter_node_is_expanded (etta, node);
                gint tmp_row = row;
                GdkRectangle area;
                animate_closure_t *closure = g_new0 (animate_closure_t, 1);
                cairo_t *cr;
                gint hgt;

                e_table_item_get_cell_geometry (
                    tree_view->cell_view.e_table_item_view,
                    &tmp_row, &view_col, &area.x, &area.y, NULL, &area.height);
                area.width = offset - 2;
                hgt = e_cell_height (ecell_view, model_col, view_col, row);

                if (hgt != area.height) /* Composite cells */
                    area.height += hgt;

                cr = gdk_cairo_create (window);
                draw_expander (
                    tree_view, cr, expanded ?
                    GTK_EXPANDER_SEMI_EXPANDED :
                    GTK_EXPANDER_SEMI_COLLAPSED,
                    GTK_STATE_NORMAL, &area);
                cairo_destroy (cr);

                closure->ectv = tree_view;
                closure->etta = etta;
                closure->node = node;
                closure->expanded = expanded;
                closure->area = area;
                tree_view->animate_timeout = g_timeout_add (50, animate_expander, closure);
                return TRUE;
            }
        }
        else if (event->button.x < (offset - INDENT_AMOUNT))
            return FALSE;
        break;

    case GDK_MOTION_NOTIFY:

        if (e_tree_model_node_is_expandable (tree_model, node)) {
            gint height = ect_height (ecell_view, model_col, view_col, row);
            GdkRectangle area;
            gboolean in_expander = event_in_expander (event, offset, height);

            if (tree_view->prelit ^ in_expander) {
                gint tmp_row = row;
                cairo_t *cr;

                e_table_item_get_cell_geometry (
                    tree_view->cell_view.e_table_item_view,
                    &tmp_row, &view_col, &area.x, &area.y, NULL, &area.height);
                area.width = offset - 2;

                cr = gdk_cairo_create (window);
                draw_expander (
                    tree_view, cr,
                    e_tree_table_adapter_node_is_expanded (etta, node) ?
                    GTK_EXPANDER_EXPANDED : GTK_EXPANDER_COLLAPSED,
                    in_expander ? GTK_STATE_PRELIGHT : GTK_STATE_NORMAL, &area);
                cairo_destroy (cr);

                tree_view->prelit = in_expander;
                return TRUE;
            }

        }
        break;

    case GDK_LEAVE_NOTIFY:

        if (tree_view->prelit) {
            gint tmp_row = row;
            GdkRectangle area;
            cairo_t *cr;

            e_table_item_get_cell_geometry (
                tree_view->cell_view.e_table_item_view,
                &tmp_row, &view_col, &area.x, &area.y, NULL, &area.height);
            area.width = offset - 2;

            cr = gdk_cairo_create (window);
            draw_expander (
                tree_view, cr,
                e_tree_table_adapter_node_is_expanded (etta, node) ?
                GTK_EXPANDER_EXPANDED : GTK_EXPANDER_COLLAPSED,
                GTK_STATE_NORMAL, &area);
            cairo_destroy (cr);

            tree_view->prelit = FALSE;
        }
        return TRUE;

    default:
        break;
    }

    adjust_event_position (event, -offset);
    result = e_cell_event (tree_view->subcell_view, event, model_col, view_col, row, flags, actions);
    adjust_event_position (event, offset);

    return result;
}

/*
 * ECell::max_width method
 */
static gint
ect_max_width (ECellView *ecell_view,
               gint model_col,
               gint view_col)
{
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;
    gint row;
    gint number_of_rows;
    gint max_width = 0;
    gint width = 0;
    gint subcell_max_width = 0;
    gboolean per_row = e_cell_max_width_by_row_implemented (tree_view->subcell_view);

    number_of_rows = e_table_model_row_count (ecell_view->e_table_model);

    if (!per_row)
        subcell_max_width = e_cell_max_width (tree_view->subcell_view, model_col, view_col);

    for (row = 0; row < number_of_rows; row++) {
        gint offset, subcell_offset;
#if 0
        gboolean expanded, expandable;
        ETreeTableAdapter *tree_table_adapter = e_cell_tree_get_tree_table_adapter (ecell_view->e_table_model, row);
#endif

        offset = offset_of_node (ecell_view->e_table_model, row);
        subcell_offset = offset;

        width = subcell_offset;

        if (per_row)
            width += e_cell_max_width_by_row (tree_view->subcell_view, model_col, view_col, row);
        else
            width += subcell_max_width;

#if 0
        expandable = e_tree_model_node_is_expandable (tree_model, node);
        expanded = e_tree_table_adapter_node_is_expanded (tree_table_adapter, node);

        /* This is unnecessary since this is already handled
         * by the offset_of_node function.  If that changes,
         * this will have to change too. */

        if (expandable) {
            GdkPixbuf *image;

            image = (expanded
                 ? E_CELL_TREE (tree_view->cell_view.ecell)->open_pixbuf
                 : E_CELL_TREE (tree_view->cell_view.ecell)->closed_pixbuf);

            width += gdk_pixbuf_get_width (image);
        }
#endif

        max_width = MAX (max_width, width);
    }

    return max_width;
}

/*
 * ECellView::get_bg_color method
 */
static gchar *
ect_get_bg_color (ECellView *ecell_view,
                  gint row)
{
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;

    return e_cell_get_bg_color (tree_view->subcell_view, row);
}

/*
 * ECellView::enter_edit method
 */
static gpointer
ect_enter_edit (ECellView *ecell_view,
                gint model_col,
                gint view_col,
                gint row)
{
    /* just defer to our subcell's view */
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;

    return e_cell_enter_edit (tree_view->subcell_view, model_col, view_col, row);
}

/*
 * ECellView::leave_edit method
 */
static void
ect_leave_edit (ECellView *ecell_view,
                gint model_col,
                gint view_col,
                gint row,
                gpointer edit_context)
{
    /* just defer to our subcell's view */
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;

    e_cell_leave_edit (tree_view->subcell_view, model_col, view_col, row, edit_context);
}

static void
ect_print (ECellView *ecell_view,
           GtkPrintContext *context,
           gint model_col,
           gint view_col,
           gint row,
           gdouble width,
           gdouble height)
{
    ECellTreeView *tree_view = (ECellTreeView *) ecell_view;
    cairo_t *cr = gtk_print_context_get_cairo_context (context);

    cairo_save (cr);

    if (/* XXX only if we're the active sort */ TRUE) {
        ETreeModel *tree_model = e_cell_tree_get_tree_model (ecell_view->e_table_model, row);
        ETreeTableAdapter *tree_table_adapter = e_cell_tree_get_tree_table_adapter (ecell_view->e_table_model, row);
        ETreePath node = e_cell_tree_get_node (ecell_view->e_table_model, row);
        gint offset = offset_of_node (ecell_view->e_table_model, row);
        gint subcell_offset = offset;
        gboolean expandable = e_tree_model_node_is_expandable (tree_model, node);

        /* draw our lines */
        if (E_CELL_TREE (tree_view->cell_view.ecell)->draw_lines) {
            gint depth;

            if (!e_tree_model_node_is_root (tree_model, node)
                || e_tree_model_node_get_n_children (tree_model, node) > 0) {
                cairo_move_to (
                    cr,
                    offset - INDENT_AMOUNT / 2,
                    height / 2);
                cairo_line_to (cr, offset, height / 2);
            }

            if (visible_depth_of_node (ecell_view->e_table_model, row) != 0) {
                cairo_move_to (
                    cr,
                    offset - INDENT_AMOUNT / 2, height);
                cairo_line_to (
                    cr,
                    offset - INDENT_AMOUNT / 2,
                    e_tree_table_adapter_node_get_next
                    (tree_table_adapter, node) ? 0 :
                    height / 2);
            }

            /* now traverse back up to the root of the tree, checking at
             * each level if the node has siblings, and drawing the
             * correct vertical pipe for it's configuration. */
            node = e_tree_model_node_get_parent (tree_model, node);
            depth = visible_depth_of_node (ecell_view->e_table_model, row) - 1;
            offset -= INDENT_AMOUNT;
            while (node && depth != 0) {
                if (e_tree_table_adapter_node_get_next (tree_table_adapter, node)) {
                    cairo_move_to (
                        cr,
                        offset - INDENT_AMOUNT / 2,
                        height);
                    cairo_line_to (
                        cr,
                        offset - INDENT_AMOUNT / 2, 0);
                }
                node = e_tree_model_node_get_parent (tree_model, node);
                depth--;
                offset -= INDENT_AMOUNT;
            }
        }

        /* now draw our icon if we're expandable */
        if (expandable) {
            gboolean expanded;
            GdkRectangle r;
            gint exp_size = 0;

            gtk_widget_style_get (GTK_WIDGET (gtk_widget_get_parent (GTK_WIDGET (tree_view->canvas))), "expander_size", &exp_size, NULL);

            node = e_cell_tree_get_node (ecell_view->e_table_model, row);
            expanded = e_tree_table_adapter_node_is_expanded (tree_table_adapter, node);

            r.x = 0;
            r.y = 0;
            r.width = MIN (width, exp_size);
            r.height = height;

            draw_expander (tree_view, cr, expanded ? GTK_EXPANDER_EXPANDED : GTK_EXPANDER_COLLAPSED, GTK_STATE_NORMAL, &r);
        }

        cairo_stroke (cr);

        cairo_translate (cr, subcell_offset, 0);
        width -= subcell_offset;
    }

    cairo_restore (cr);

    e_cell_print (tree_view->subcell_view, context, model_col, view_col, row, width, height);
}

static gdouble
ect_print_height (ECellView *ecell_view,
                  GtkPrintContext *context,
                  gint model_col,
                  gint view_col,
                  gint row,
                  gdouble width)
{
    return 12; /* XXX */
}

/*
 * GObject::dispose method
 */
static void
ect_dispose (GObject *object)
{
    ECellTree *ect = E_CELL_TREE (object);

    /* destroy our subcell */
    if (ect->subcell)
        g_object_unref (ect->subcell);
    ect->subcell = NULL;

    G_OBJECT_CLASS (e_cell_tree_parent_class)->dispose (object);
}

static void
e_cell_tree_class_init (ECellTreeClass *class)
{
    GObjectClass *object_class = G_OBJECT_CLASS (class);
    ECellClass *ecc = E_CELL_CLASS (class);

    object_class->dispose = ect_dispose;

    ecc->new_view         = ect_new_view;
    ecc->kill_view        = ect_kill_view;
    ecc->realize          = ect_realize;
    ecc->unrealize        = ect_unrealize;
    ecc->draw             = ect_draw;
    ecc->event            = ect_event;
    ecc->height           = ect_height;
    ecc->enter_edit       = ect_enter_edit;
    ecc->leave_edit       = ect_leave_edit;
    ecc->print            = ect_print;
    ecc->print_height     = ect_print_height;
    ecc->max_width        = ect_max_width;
    ecc->get_bg_color     = ect_get_bg_color;

    gal_a11y_e_cell_registry_add_cell_type (NULL, E_TYPE_CELL_TREE, gal_a11y_e_cell_tree_new);
}

static void
e_cell_tree_init (ECellTree *ect)
{
    /* nothing to do */
}

/**
 * e_cell_tree_construct:
 * @ect: the ECellTree we're constructing.
 * @draw_lines: whether or not to draw the lines between parents/children/siblings.
 * @subcell: the ECell to render to the right of the tree effects.
 *
 * Constructs an ECellTree.  used by subclasses that need to
 * initialize a nested ECellTree.  See e_cell_tree_new() for more info.
 *
 **/
void
e_cell_tree_construct (ECellTree *ect,
                       gboolean draw_lines,
                       ECell *subcell)
{
    ect->subcell = subcell;
    if (subcell)
        g_object_ref_sink (subcell);

    ect->draw_lines = draw_lines;
}

/**
 * e_cell_tree_new:
 * @draw_lines: whether or not to draw the lines between parents/children/siblings.
 * @subcell: the ECell to render to the right of the tree effects.
 *
 * Creates a new ECell renderer that can be used to render tree
 * effects that come from an ETreeModel.  Various assumptions are made
 * as to the fact that the ETableModel the ETable this cell is
 * associated with is in fact an ETreeModel.  The cell uses special
 * columns to get at structural information (needed to draw the
 * lines/icons.
 *
 * Return value: an ECell object that can be used to render trees.
 **/
ECell *
e_cell_tree_new (gboolean draw_lines,
                 ECell *subcell)
{
    ECellTree *ect = g_object_new (E_TYPE_CELL_TREE, NULL);

    e_cell_tree_construct (ect, draw_lines, subcell);

    return (ECell *) ect;
}