gtk/gdk/gdkrectangle.c
Alexander Larsson 3c618f2f1f Avoid integer overflow in gdk_rectangle_intersect
If e.g. the right edge of the leftmost rectangle is near MIN_INT, and
the left edge of the rightmost rectangle is large then subtracting these
can lead to an integer overflow, making the resultant "width" falsely
positive, thus returning a very wide result instead of the expected
no-intersection result.

We avoid the overflow by not doing the subtraction unless we know the
result will be positive. There are still risks for overflow if x + width
or y + width is larger than MAXINT, but we won't ever overflow for valid
rects now.

This may fix #607687
2010-01-22 09:41:17 +01:00

139 lines
3.9 KiB
C

/* GDK - The GIMP Drawing Kit
* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/*
* Modified by the GTK+ Team and others 1997-2000. See the AUTHORS
* file for a list of people on the GTK+ Team. See the ChangeLog
* files for a list of changes. These files are distributed with
* GTK+ at ftp://ftp.gtk.org/pub/gtk/.
*/
#include "config.h"
#include <gdk/gdk.h>
#include "gdkalias.h"
/**
* gdk_rectangle_union:
* @src1: a #GdkRectangle
* @src2: a #GdkRectangle
* @dest: return location for the union of @src1 and @src2
*
* Calculates the union of two rectangles.
* The union of rectangles @src1 and @src2 is the smallest rectangle which
* includes both @src1 and @src2 within it.
* It is allowed for @dest to be the same as either @src1 or @src2.
*/
void
gdk_rectangle_union (const GdkRectangle *src1,
const GdkRectangle *src2,
GdkRectangle *dest)
{
gint dest_x, dest_y;
g_return_if_fail (src1 != NULL);
g_return_if_fail (src2 != NULL);
g_return_if_fail (dest != NULL);
dest_x = MIN (src1->x, src2->x);
dest_y = MIN (src1->y, src2->y);
dest->width = MAX (src1->x + src1->width, src2->x + src2->width) - dest_x;
dest->height = MAX (src1->y + src1->height, src2->y + src2->height) - dest_y;
dest->x = dest_x;
dest->y = dest_y;
}
/**
* gdk_rectangle_intersect:
* @src1: a #GdkRectangle
* @src2: a #GdkRectangle
* @dest: return location for the intersection of @src1 and @src2, or %NULL
*
* Calculates the intersection of two rectangles. It is allowed for
* @dest to be the same as either @src1 or @src2. If the rectangles
* do not intersect, @dest's width and height is set to 0 and its x
* and y values are undefined. If you are only interested in whether
* the rectangles intersect, but not in the intersecting area itself,
* pass %NULL for @dest.
*
* Returns: %TRUE if the rectangles intersect.
*/
gboolean
gdk_rectangle_intersect (const GdkRectangle *src1,
const GdkRectangle *src2,
GdkRectangle *dest)
{
gint dest_x, dest_y;
gint dest_x2, dest_y2;
gint return_val;
g_return_val_if_fail (src1 != NULL, FALSE);
g_return_val_if_fail (src2 != NULL, FALSE);
return_val = FALSE;
dest_x = MAX (src1->x, src2->x);
dest_y = MAX (src1->y, src2->y);
dest_x2 = MIN (src1->x + src1->width, src2->x + src2->width);
dest_y2 = MIN (src1->y + src1->height, src2->y + src2->height);
if (dest_x2 > dest_x && dest_y2 > dest_y)
{
if (dest)
{
dest->x = dest_x;
dest->y = dest_y;
dest->width = dest_x2 - dest_x;
dest->height = dest_y2 - dest_y;
}
return_val = TRUE;
}
else if (dest)
{
dest->width = 0;
dest->height = 0;
}
return return_val;
}
static GdkRectangle *
gdk_rectangle_copy (const GdkRectangle *rectangle)
{
GdkRectangle *result = g_new (GdkRectangle, 1);
*result = *rectangle;
return result;
}
GType
gdk_rectangle_get_type (void)
{
static GType our_type = 0;
if (our_type == 0)
our_type = g_boxed_type_register_static (g_intern_static_string ("GdkRectangle"),
(GBoxedCopyFunc)gdk_rectangle_copy,
(GBoxedFreeFunc)g_free);
return our_type;
}
#define __GDK_RECTANGLE_C__
#include "gdkaliasdef.c"