path: root/widgets/shortcut-bar/e-vscrolled-bar.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */

/* 
 * Author : 
 *  Damon Chaplin <damon@helixcode.com>
 *
 * Copyright 1999, Helix Code, Inc.
 *
 * This program is free software; you can redistribute it and/or 
 * modify it under the terms of the GNU General Public License as 
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
 * USA
 */

/*
 * EVScrolledBar is like GtkScrolledWindow but only scrolls the child widget
 * vertically. It is intended for scrolling narrow vertical bars.
 */

#include <config.h>
#include <gtk/gtkarrow.h>
#include <gtk/gtkbutton.h>
#include <gtk/gtksignal.h>
#include "e-vscrolled-bar.h"

/* These are the offsets of the up & down buttons from the right and top/bottom
   of the widget. */
#define E_VSCROLLED_BAR_BUTTON_X_OFFSET 2
#define E_VSCROLLED_BAR_BUTTON_Y_OFFSET 2

/* This is the time between scrolls. */
#define E_VSCROLLED_BAR_SCROLL_TIMEOUT 20

static void e_vscrolled_bar_class_init (EVScrolledBarClass *class);
static void e_vscrolled_bar_init (EVScrolledBar *vscrolled_bar);
static void e_vscrolled_bar_destroy (GtkObject *object);
static void e_vscrolled_bar_finalize (GtkObject *object);
static void e_vscrolled_bar_map (GtkWidget *widget);
static void e_vscrolled_bar_unmap (GtkWidget *widget);
static void e_vscrolled_bar_size_request (GtkWidget      *widget,
                      GtkRequisition *requisition);
static void e_vscrolled_bar_size_allocate (GtkWidget *widget,
                       GtkAllocation *allocation);
static void e_vscrolled_bar_draw (GtkWidget    *widget,
                  GdkRectangle *area);
static gint e_vscrolled_bar_button_press   (GtkWidget        *widget,
                        GdkEventButton   *event);
static void e_vscrolled_bar_add (GtkContainer *container,
                 GtkWidget    *child);
static void e_vscrolled_bar_remove (GtkContainer *container,
                    GtkWidget    *child);
static void e_vscrolled_bar_forall (GtkContainer *container,
                    gboolean      include_internals,
                    GtkCallback   callback,
                    gpointer      callback_data);
static void e_vscrolled_bar_adjustment_changed (GtkAdjustment *adjustment,
                        gpointer       data);
static void e_vscrolled_bar_button_pressed (GtkWidget *button,
                        EVScrolledBar *vscrolled_bar);
static void e_vscrolled_bar_button_released (GtkWidget *button,
                         EVScrolledBar *vscrolled_bar);
static void e_vscrolled_bar_button_clicked (GtkWidget *button,
                        EVScrolledBar *vscrolled_bar);
static gboolean e_vscrolled_bar_timeout_handler (gpointer data);


static GtkBinClass *parent_class;


GtkType
e_vscrolled_bar_get_type (void)
{
    static GtkType e_vscrolled_bar_type = 0;

    if (!e_vscrolled_bar_type) {
        GtkTypeInfo e_vscrolled_bar_info = {
            "EVScrolledBar",
            sizeof (EVScrolledBar),
            sizeof (EVScrolledBarClass),
            (GtkClassInitFunc) e_vscrolled_bar_class_init,
            (GtkObjectInitFunc) e_vscrolled_bar_init,
            NULL, /* reserved 1 */
            NULL, /* reserved 2 */
            (GtkClassInitFunc) NULL
        };

        parent_class = gtk_type_class (GTK_TYPE_BIN);
        e_vscrolled_bar_type = gtk_type_unique (GTK_TYPE_BIN,
                            &e_vscrolled_bar_info);
    }

    return e_vscrolled_bar_type;
}


static void
e_vscrolled_bar_class_init (EVScrolledBarClass *class)
{
    GtkObjectClass *object_class;
    GtkWidgetClass *widget_class;
    GtkContainerClass *container_class;

    object_class = (GtkObjectClass *) class;
    widget_class = (GtkWidgetClass *) class;
    container_class = (GtkContainerClass *) class;

    /* Method override */
    object_class->destroy       = e_vscrolled_bar_destroy;
    object_class->finalize      = e_vscrolled_bar_finalize;

    widget_class->map       = e_vscrolled_bar_map;
    widget_class->unmap     = e_vscrolled_bar_unmap;
    widget_class->size_request  = e_vscrolled_bar_size_request;
    widget_class->size_allocate = e_vscrolled_bar_size_allocate;
    widget_class->draw      = e_vscrolled_bar_draw;
    widget_class->button_press_event   = e_vscrolled_bar_button_press;

    container_class->add        = e_vscrolled_bar_add;
    container_class->remove     = e_vscrolled_bar_remove;
    container_class->forall     = e_vscrolled_bar_forall;
}


static void
e_vscrolled_bar_init (EVScrolledBar *vscrolled_bar)
{
    GtkWidget *arrow;

    GTK_WIDGET_SET_FLAGS (vscrolled_bar, GTK_NO_WINDOW);

    gtk_container_set_resize_mode (GTK_CONTAINER (vscrolled_bar),
                       GTK_RESIZE_QUEUE);

    gtk_widget_push_composite_child ();

    vscrolled_bar->up_button = gtk_button_new ();
    gtk_widget_set_composite_name (vscrolled_bar->up_button,
                       "up_button");
    gtk_widget_set_parent (vscrolled_bar->up_button,
                   GTK_WIDGET (vscrolled_bar));
    arrow = gtk_arrow_new (GTK_ARROW_UP, GTK_SHADOW_OUT);
    gtk_misc_set_padding (GTK_MISC (arrow), 1, 1);
    gtk_widget_show (arrow);
    gtk_container_add (GTK_CONTAINER (vscrolled_bar->up_button), arrow);
    gtk_widget_show (vscrolled_bar->up_button);
    gtk_signal_connect_after (GTK_OBJECT (vscrolled_bar->up_button), "pressed", GTK_SIGNAL_FUNC (e_vscrolled_bar_button_pressed), vscrolled_bar);
    gtk_signal_connect_after (GTK_OBJECT (vscrolled_bar->up_button), "released", GTK_SIGNAL_FUNC (e_vscrolled_bar_button_released), vscrolled_bar);
    gtk_signal_connect (GTK_OBJECT (vscrolled_bar->up_button), "clicked", GTK_SIGNAL_FUNC (e_vscrolled_bar_button_clicked), vscrolled_bar);

    vscrolled_bar->down_button = gtk_button_new ();
    gtk_widget_set_composite_name (vscrolled_bar->up_button,
                       "down_button");
    gtk_widget_set_parent (vscrolled_bar->down_button,
                   GTK_WIDGET (vscrolled_bar));
    arrow = gtk_arrow_new (GTK_ARROW_DOWN, GTK_SHADOW_OUT);
    gtk_misc_set_padding (GTK_MISC (arrow), 1, 1);
    gtk_widget_show (arrow);
    gtk_container_add (GTK_CONTAINER (vscrolled_bar->down_button), arrow);
    gtk_widget_show (vscrolled_bar->down_button);
    gtk_signal_connect_after (GTK_OBJECT (vscrolled_bar->down_button), "pressed", GTK_SIGNAL_FUNC (e_vscrolled_bar_button_pressed), vscrolled_bar);
    gtk_signal_connect_after (GTK_OBJECT (vscrolled_bar->down_button), "released", GTK_SIGNAL_FUNC (e_vscrolled_bar_button_released), vscrolled_bar);
    gtk_signal_connect (GTK_OBJECT (vscrolled_bar->down_button), "clicked", GTK_SIGNAL_FUNC (e_vscrolled_bar_button_clicked), vscrolled_bar);

    gtk_widget_pop_composite_child ();

    vscrolled_bar->adjustment = NULL;
    vscrolled_bar->timeout_id = 0;
    vscrolled_bar->scrolling_up = FALSE;
    vscrolled_bar->min_distance = -1.0;
    vscrolled_bar->button_pressed = FALSE;
}


/**
 * e_vscrolled_bar_new:
 *
 * @adjustment: The #GtkAdjustment to use for scrolling, or NULL.
 * @Return: A new #EVScrolledBar.
 *
 * Creates a new #EVScrolledBar with the given adjustment.
 **/
GtkWidget *
e_vscrolled_bar_new (GtkAdjustment *adjustment)
{
    GtkWidget *vscrolled_bar;

    vscrolled_bar = GTK_WIDGET (gtk_type_new (e_vscrolled_bar_get_type ()));
    e_vscrolled_bar_set_adjustment (E_VSCROLLED_BAR (vscrolled_bar),
                    adjustment);

    return vscrolled_bar;
}


static void
e_vscrolled_bar_destroy (GtkObject *object)
{
    EVScrolledBar *vscrolled_bar;

    vscrolled_bar = E_VSCROLLED_BAR (object);

    if (vscrolled_bar->timeout_id) {
        g_source_remove (vscrolled_bar->timeout_id);
        vscrolled_bar->timeout_id = 0;
    }

    gtk_widget_unparent (vscrolled_bar->up_button);
    gtk_widget_unparent (vscrolled_bar->down_button);

    GTK_OBJECT_CLASS (parent_class)->destroy (object);
}


static void
e_vscrolled_bar_finalize (GtkObject *object)
{
    EVScrolledBar *vscrolled_bar;

    vscrolled_bar = E_VSCROLLED_BAR (object);

    gtk_object_unref (GTK_OBJECT (vscrolled_bar->adjustment));

    GTK_OBJECT_CLASS (parent_class)->finalize (object);
}


static void
e_vscrolled_bar_map (GtkWidget *widget)
{
    EVScrolledBar *vscrolled_bar;
    GtkAdjustment *adjustment;

    g_return_if_fail (widget != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (widget));

    vscrolled_bar = E_VSCROLLED_BAR (widget);

    /* chain parent class handler to map self and child */
    GTK_WIDGET_CLASS (parent_class)->map (widget);
  
    adjustment = vscrolled_bar->adjustment;

    if (GTK_WIDGET_VISIBLE (vscrolled_bar->up_button)
        && adjustment->value != adjustment->lower
        && !GTK_WIDGET_MAPPED (vscrolled_bar->up_button))
        gtk_widget_map (vscrolled_bar->up_button);
  
    if (GTK_WIDGET_VISIBLE (vscrolled_bar->down_button)
        && adjustment->value < adjustment->upper - adjustment->page_size
        && !GTK_WIDGET_MAPPED (vscrolled_bar->down_button))
        gtk_widget_map (vscrolled_bar->down_button);
}


static void
e_vscrolled_bar_unmap (GtkWidget *widget)
{
    EVScrolledBar *vscrolled_bar;

    g_return_if_fail (widget != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (widget));

    vscrolled_bar = E_VSCROLLED_BAR (widget);

    /* chain parent class handler to unmap self and child */
    GTK_WIDGET_CLASS (parent_class)->unmap (widget);
  
    if (GTK_WIDGET_MAPPED (vscrolled_bar->up_button))
        gtk_widget_unmap (vscrolled_bar->up_button);
  
    if (GTK_WIDGET_MAPPED (vscrolled_bar->down_button))
        gtk_widget_unmap (vscrolled_bar->down_button);
}


static void
e_vscrolled_bar_size_request (GtkWidget      *widget,
                  GtkRequisition *requisition)
{
    EVScrolledBar *vscrolled_bar;
    GtkBin *bin;
    GtkRequisition child_requisition;

    g_return_if_fail (widget != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (widget));
    g_return_if_fail (requisition != NULL);

    vscrolled_bar = E_VSCROLLED_BAR (widget);
    bin = GTK_BIN (widget);

    requisition->width = 0;
    requisition->height = 0;

    /* We just return the requisition of the child widget, plus the
       border width. */
    if (bin->child && GTK_WIDGET_VISIBLE (bin->child)) {
        gtk_widget_size_request (bin->child, &child_requisition);
        *requisition = child_requisition;
    }

    /* We remember the requested heights of the up & down buttons. */
    gtk_widget_size_request (vscrolled_bar->up_button,
                 &child_requisition);
    vscrolled_bar->up_button_width = child_requisition.width;
    vscrolled_bar->up_button_height = child_requisition.height;

    gtk_widget_size_request (vscrolled_bar->down_button,
                 &child_requisition);
    vscrolled_bar->down_button_width = child_requisition.width;
    vscrolled_bar->down_button_height = child_requisition.height;

    /* Add on the standard container border widths. */
    requisition->width += GTK_CONTAINER (widget)->border_width * 2;
    requisition->height += GTK_CONTAINER (widget)->border_width * 2;
}


static void
e_vscrolled_bar_size_allocate (GtkWidget *widget,
                   GtkAllocation *allocation)
{
    EVScrolledBar *vscrolled_bar;
    GtkBin *bin;
    GtkAllocation button_allocation, child_allocation;
    gint border_width;

    g_return_if_fail (widget != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (widget));
    g_return_if_fail (allocation != NULL);

    vscrolled_bar = E_VSCROLLED_BAR (widget);
    bin = GTK_BIN (widget);

    widget->allocation = *allocation;

    border_width = GTK_CONTAINER (widget)->border_width;

    child_allocation.x = border_width;
    child_allocation.y = border_width;
    child_allocation.width = allocation->width - 2 * border_width;
    child_allocation.height = allocation->height - 2 * border_width;
    gtk_widget_size_allocate (bin->child, &child_allocation);

    button_allocation.x = allocation->width - border_width
        - vscrolled_bar->up_button_width
        - E_VSCROLLED_BAR_BUTTON_X_OFFSET;
    button_allocation.y = border_width + E_VSCROLLED_BAR_BUTTON_Y_OFFSET;
    button_allocation.width = vscrolled_bar->up_button_width;
    button_allocation.height = vscrolled_bar->up_button_height;
    gtk_widget_size_allocate (vscrolled_bar->up_button,
                  &button_allocation);

    button_allocation.x = allocation->width - border_width
        - vscrolled_bar->down_button_width
        - E_VSCROLLED_BAR_BUTTON_X_OFFSET;
    button_allocation.y = allocation->height - border_width
        - vscrolled_bar->down_button_height
        - E_VSCROLLED_BAR_BUTTON_Y_OFFSET;
    button_allocation.width = vscrolled_bar->down_button_width;
    button_allocation.height = vscrolled_bar->down_button_height;
    gtk_widget_size_allocate (vscrolled_bar->down_button,
                  &button_allocation);
}


static void
e_vscrolled_bar_draw (GtkWidget    *widget,
              GdkRectangle *area)
{
    EVScrolledBar *vscrolled_bar;
    GtkBin *bin;
    GdkRectangle child_area;

    g_return_if_fail (widget != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (widget));
    g_return_if_fail (area != NULL);
  
    vscrolled_bar = E_VSCROLLED_BAR (widget);
    bin = GTK_BIN (widget);

    if (bin->child && GTK_WIDGET_VISIBLE (bin->child) &&
        gtk_widget_intersect (bin->child, area, &child_area))
        gtk_widget_draw (bin->child, &child_area);
  
    if (GTK_WIDGET_DRAWABLE (vscrolled_bar->up_button) &&
        gtk_widget_intersect (vscrolled_bar->up_button, area, &child_area))
        gtk_widget_draw (vscrolled_bar->up_button, &child_area);
  
    if (GTK_WIDGET_DRAWABLE (vscrolled_bar->down_button) &&
        gtk_widget_intersect (vscrolled_bar->down_button, area, &child_area))
        gtk_widget_draw (vscrolled_bar->down_button, &child_area);
}


static gint
e_vscrolled_bar_button_press (GtkWidget      *widget,
                  GdkEventButton *event)
{
    EVScrolledBar *vscrolled_bar;
    GtkAdjustment *adjustment;
    gfloat new_value, step;

    vscrolled_bar = E_VSCROLLED_BAR (widget);
    adjustment = vscrolled_bar->adjustment;

    step = adjustment->page_size;

    if (event->button == 4) {
        new_value = adjustment->value - step;
        if (new_value <= adjustment->lower) {
            new_value = adjustment->lower;
        }
    } else if (event->button == 5) {
        new_value = adjustment->value + step;
        if (new_value >= adjustment->upper - adjustment->page_size) {
            new_value = adjustment->upper - adjustment->page_size;
        }
    } else
        return FALSE;

    if (adjustment->value != new_value) {
        adjustment->value = new_value;
        gtk_signal_emit_by_name (GTK_OBJECT (adjustment),
                     "value_changed");
        return TRUE;
    }

    return FALSE;
}


static void
e_vscrolled_bar_add (GtkContainer *container,
             GtkWidget    *child)
{
    EVScrolledBar *vscrolled_bar;
    GtkBin *bin;

    g_return_if_fail (container != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (container));
  
    vscrolled_bar = E_VSCROLLED_BAR (container);
    bin = GTK_BIN (container);

    g_return_if_fail (bin->child == NULL);

    bin->child = child;
    gtk_widget_set_parent (child, GTK_WIDGET (bin));

    gtk_widget_set_scroll_adjustments (child, NULL,
                       vscrolled_bar->adjustment);

    if (GTK_WIDGET_REALIZED (child->parent))
        gtk_widget_realize (child);

    if (GTK_WIDGET_VISIBLE (child->parent) && GTK_WIDGET_VISIBLE (child)) {
        if (GTK_WIDGET_MAPPED (child->parent))
            gtk_widget_map (child);

        gtk_widget_queue_resize (child);
    }
}


static void
e_vscrolled_bar_remove (GtkContainer *container,
            GtkWidget    *child)
{
    g_return_if_fail (container != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (container));
    g_return_if_fail (child != NULL);
    g_return_if_fail (GTK_BIN (container)->child == child);

    gtk_widget_set_scroll_adjustments (child, NULL, NULL);

    /* chain parent class handler to remove child */
    GTK_CONTAINER_CLASS (parent_class)->remove (container, child);
}


static void
e_vscrolled_bar_forall (GtkContainer *container,
            gboolean      include_internals,
            GtkCallback   callback,
            gpointer      callback_data)
{
    g_return_if_fail (container != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (container));
    g_return_if_fail (callback != NULL);

    GTK_CONTAINER_CLASS (parent_class)->forall (container,
                            include_internals,
                            callback,
                            callback_data);
    if (include_internals) {
        EVScrolledBar *vscrolled_bar;

        vscrolled_bar = E_VSCROLLED_BAR (container);
      
        if (vscrolled_bar->up_button)
            callback (vscrolled_bar->up_button, callback_data);
        if (vscrolled_bar->down_button)
            callback (vscrolled_bar->down_button, callback_data);
    }
}


/**
 * e_vscrolled_bar_get_adjustment:
 *
 * @vscrolled_bar: An #EVScrolledBar.
 * @Return: The #GtkAdjustment used for scrolling @vscrolled_bar.
 *
 * Returns the #GtkAdjustment used for scrolling the #EVscrolledBar.
 **/
GtkAdjustment*
e_vscrolled_bar_get_adjustment (EVScrolledBar *vscrolled_bar)
{
    g_return_val_if_fail (vscrolled_bar != NULL, NULL);
    g_return_val_if_fail (E_IS_VSCROLLED_BAR (vscrolled_bar), NULL);

    return vscrolled_bar->adjustment;
}


/**
 * e_vscrolled_bar_set_adjustment:
 *
 * @vscrolled_bar: An #EVScrolledBar.
 * @adjustment: The #GtkAdjustment to use for scrolling @vscrolled_bar.
 *
 * Sets the #GtkAdjustment to use for scrolling the #EVscrolledBar.
 **/
void
e_vscrolled_bar_set_adjustment (EVScrolledBar     *vscrolled_bar,
                GtkAdjustment     *adjustment)
{
    g_return_if_fail (vscrolled_bar != NULL);
    g_return_if_fail (E_IS_VSCROLLED_BAR (vscrolled_bar));

    if (adjustment)
        g_return_if_fail (GTK_IS_ADJUSTMENT (adjustment));
    else
        adjustment = (GtkAdjustment*) gtk_object_new (GTK_TYPE_ADJUSTMENT, NULL);

    if (vscrolled_bar->adjustment == adjustment)
        return;

    if (vscrolled_bar->adjustment) {
        gtk_signal_disconnect_by_func (GTK_OBJECT (vscrolled_bar->adjustment),
                           GTK_SIGNAL_FUNC (e_vscrolled_bar_adjustment_changed),
                           vscrolled_bar);
        gtk_object_unref (GTK_OBJECT (vscrolled_bar->adjustment));
    }

    vscrolled_bar->adjustment = adjustment;
    gtk_object_ref (GTK_OBJECT (vscrolled_bar->adjustment));
    gtk_object_sink (GTK_OBJECT (vscrolled_bar->adjustment));

    /* I've used connect_after here to avoid a problem when using a
       GnomeCanvas as the child widget. When just using connect it would
       leave a blank space when one of the buttons is hidden. We want
       the GtkLayout to handle the scrolling before we hide any buttons. */
    gtk_signal_connect_after (GTK_OBJECT (adjustment), "changed",
                  GTK_SIGNAL_FUNC (e_vscrolled_bar_adjustment_changed),
                  vscrolled_bar);
    gtk_signal_connect_after (GTK_OBJECT (adjustment), "value_changed",
                  GTK_SIGNAL_FUNC (e_vscrolled_bar_adjustment_changed),
                  vscrolled_bar);

    e_vscrolled_bar_adjustment_changed (adjustment, vscrolled_bar);

    if (GTK_BIN (vscrolled_bar)->child)
        gtk_widget_set_scroll_adjustments (GTK_BIN (vscrolled_bar)->child, NULL, adjustment);
}


static void
e_vscrolled_bar_adjustment_changed (GtkAdjustment *adjustment,
                    gpointer       data)
{
    EVScrolledBar *vscrolled_bar;

    g_return_if_fail (adjustment != NULL);
    g_return_if_fail (data != NULL);
#if 0
    g_print ("Adjustment changed to: %g\n", adjustment->value);
#endif
    vscrolled_bar = E_VSCROLLED_BAR (data);

    if (!GTK_WIDGET_MAPPED (vscrolled_bar))
        return;

    /* If the adjustment value is not 0, show the up button. */
    if (adjustment->value != adjustment->lower) {
        gtk_widget_map (vscrolled_bar->up_button);
        gdk_window_raise (vscrolled_bar->up_button->window);
    } else {
        gtk_widget_unmap (vscrolled_bar->up_button);
    }

    /* If the adjustment value is less than the maximum value, show the
       down button. */
    if (adjustment->value < adjustment->upper - adjustment->page_size) {
        gtk_widget_map (vscrolled_bar->down_button);
        gdk_window_raise (vscrolled_bar->down_button->window);
    } else {
        gtk_widget_unmap (vscrolled_bar->down_button);
    }
}


static void
e_vscrolled_bar_button_pressed (GtkWidget *button,
                EVScrolledBar *vscrolled_bar)
{
    if (vscrolled_bar->timeout_id != 0)
        g_source_remove (vscrolled_bar->timeout_id);

    vscrolled_bar->timeout_id = g_timeout_add (E_VSCROLLED_BAR_SCROLL_TIMEOUT, e_vscrolled_bar_timeout_handler, vscrolled_bar);
    vscrolled_bar->scrolling_up = (button == vscrolled_bar->up_button) ? TRUE : FALSE;
    vscrolled_bar->min_distance = vscrolled_bar->adjustment->page_size / 4;
    vscrolled_bar->button_pressed = TRUE;

    e_vscrolled_bar_timeout_handler (vscrolled_bar);
}


static void
e_vscrolled_bar_button_released (GtkWidget *button,
                 EVScrolledBar *vscrolled_bar)
{
    vscrolled_bar->button_pressed = FALSE;
}


/* This will be called when the user hits the space key to activate the button.
   It will also be called just before button_released() is called, but since
   we already handle that we simply return if the button is pressed. */
static void
e_vscrolled_bar_button_clicked (GtkWidget *button,
                EVScrolledBar *vscrolled_bar)
{
    if (vscrolled_bar->button_pressed)
        return;

    /* We act as if the button is pressed and released immediately. */
    e_vscrolled_bar_button_pressed (button, vscrolled_bar);
    vscrolled_bar->button_pressed = FALSE;
}


static gboolean
e_vscrolled_bar_timeout_handler (gpointer data)
{
    EVScrolledBar *vscrolled_bar;
    GtkAdjustment *adjustment;
    gfloat new_value;
    gboolean retval = TRUE;

    vscrolled_bar = E_VSCROLLED_BAR (data);
    adjustment = vscrolled_bar->adjustment;

    GDK_THREADS_ENTER ();

    /* Check if the user has released the button and we have already
       scrolled the minimum distance. */
    if (vscrolled_bar->button_pressed == FALSE
        && vscrolled_bar->min_distance <= 0) {
        GDK_THREADS_LEAVE ();
        return FALSE;
    }

    vscrolled_bar->min_distance -= adjustment->step_increment;

    if (vscrolled_bar->scrolling_up) {
        new_value = adjustment->value - adjustment->step_increment;
        if (new_value <= adjustment->lower) {
            new_value = adjustment->lower;
            retval = FALSE;
        }
    } else {
        new_value = adjustment->value + adjustment->step_increment;
        if (new_value >= adjustment->upper - adjustment->page_size) {
            new_value = adjustment->upper - adjustment->page_size;
            retval = FALSE;
        }
    }

    if (adjustment->value != new_value) {
        adjustment->value = new_value;
        gtk_signal_emit_by_name (GTK_OBJECT (adjustment),
                     "value_changed");
    }

    GDK_THREADS_LEAVE ();
    return retval;
}