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/*
* Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
*
* Portions are Copyright (C) 1998 Netscape Communications Corporation.
*
* Other contributors:
* Robert O'Callahan <roc+@cs.cmu.edu>
* David Baron <dbaron@fas.harvard.edu>
* Christian Biesinger <cbiesinger@web.de>
* Randall Jesup <rjesup@wgate.com>
* Roland Mainz <roland.mainz@informatik.med.uni-giessen.de>
* Josh Soref <timeless@mac.com>
* Boris Zbarsky <bzbarsky@mit.edu>
*
* 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 2.1 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
*
* Alternatively, the contents of this file may be used under the terms
* of either the Mozilla Public License Version 1.1, found at
* http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public
* License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html
* (the "GPL"), in which case the provisions of the MPL or the GPL are
* applicable instead of those above. If you wish to allow use of your
* version of this file only under the terms of one of those two
* licenses (the MPL or the GPL) and not to allow others to use your
* version of this file under the LGPL, indicate your decision by
* deletingthe provisions above and replace them with the notice and
* other provisions required by the MPL or the GPL, as the case may be.
* If you do not delete the provisions above, a recipient may use your
* version of this file under any of the LGPL, the MPL or the GPL.
*/
#include "core/layout/ScrollAlignment.h"
#include "platform/geometry/LayoutRect.h"
namespace blink {
const ScrollAlignment ScrollAlignment::alignCenterIfNeeded = {
ScrollAlignmentNoScroll, ScrollAlignmentCenter, ScrollAlignmentClosestEdge};
const ScrollAlignment ScrollAlignment::alignToEdgeIfNeeded = {
ScrollAlignmentNoScroll, ScrollAlignmentClosestEdge,
ScrollAlignmentClosestEdge};
const ScrollAlignment ScrollAlignment::alignCenterAlways = {
ScrollAlignmentCenter, ScrollAlignmentCenter, ScrollAlignmentCenter};
const ScrollAlignment ScrollAlignment::alignTopAlways = {
ScrollAlignmentTop, ScrollAlignmentTop, ScrollAlignmentTop};
const ScrollAlignment ScrollAlignment::alignBottomAlways = {
ScrollAlignmentBottom, ScrollAlignmentBottom, ScrollAlignmentBottom};
#define MIN_INTERSECT_FOR_REVEAL 32
LayoutRect ScrollAlignment::getRectToExpose(const LayoutRect& visibleRect,
const LayoutRect& exposeRect,
const ScrollAlignment& alignX,
const ScrollAlignment& alignY) {
// Prevent degenerate cases by giving the visible rect a minimum non-0 size.
LayoutRect nonZeroVisibleRect(visibleRect);
LayoutUnit minimumLayoutUnit;
minimumLayoutUnit.setRawValue(1);
if (nonZeroVisibleRect.width() == LayoutUnit())
nonZeroVisibleRect.setWidth(minimumLayoutUnit);
if (nonZeroVisibleRect.height() == LayoutUnit())
nonZeroVisibleRect.setHeight(minimumLayoutUnit);
// Determine the appropriate X behavior.
ScrollAlignmentBehavior scrollX;
LayoutRect exposeRectX(exposeRect.x(), nonZeroVisibleRect.y(),
exposeRect.width(), nonZeroVisibleRect.height());
LayoutUnit intersectWidth =
intersection(nonZeroVisibleRect, exposeRectX).width();
if (intersectWidth == exposeRect.width() ||
intersectWidth >= MIN_INTERSECT_FOR_REVEAL) {
// If the rectangle is fully visible, use the specified visible behavior.
// If the rectangle is partially visible, but over a certain threshold,
// then treat it as fully visible to avoid unnecessary horizontal scrolling
scrollX = getVisibleBehavior(alignX);
} else if (intersectWidth == nonZeroVisibleRect.width()) {
// If the rect is bigger than the visible area, don't bother trying to
// center. Other alignments will work.
scrollX = getVisibleBehavior(alignX);
if (scrollX == ScrollAlignmentCenter)
scrollX = ScrollAlignmentNoScroll;
} else if (intersectWidth > 0) {
// If the rectangle is partially visible, but not above the minimum
// threshold, use the specified partial behavior
scrollX = getPartialBehavior(alignX);
} else {
scrollX = getHiddenBehavior(alignX);
}
if (scrollX == ScrollAlignmentClosestEdge) {
// Closest edge is the right in two cases:
// (1) exposeRect to the right of and smaller than nonZeroVisibleRect
// (2) exposeRect to the left of and larger than nonZeroVisibleRect
if ((exposeRect.maxX() > nonZeroVisibleRect.maxX() &&
exposeRect.width() < nonZeroVisibleRect.width()) ||
(exposeRect.maxX() < nonZeroVisibleRect.maxX() &&
exposeRect.width() > nonZeroVisibleRect.width())) {
scrollX = ScrollAlignmentRight;
}
}
// Given the X behavior, compute the X coordinate.
LayoutUnit x;
if (scrollX == ScrollAlignmentNoScroll)
x = nonZeroVisibleRect.x();
else if (scrollX == ScrollAlignmentRight)
x = exposeRect.maxX() - nonZeroVisibleRect.width();
else if (scrollX == ScrollAlignmentCenter)
x = exposeRect.x() + (exposeRect.width() - nonZeroVisibleRect.width()) / 2;
else
x = exposeRect.x();
// Determine the appropriate Y behavior.
ScrollAlignmentBehavior scrollY;
LayoutRect exposeRectY(nonZeroVisibleRect.x(), exposeRect.y(),
nonZeroVisibleRect.width(), exposeRect.height());
LayoutUnit intersectHeight =
intersection(nonZeroVisibleRect, exposeRectY).height();
if (intersectHeight == exposeRect.height()) {
// If the rectangle is fully visible, use the specified visible behavior.
scrollY = getVisibleBehavior(alignY);
} else if (intersectHeight == nonZeroVisibleRect.height()) {
// If the rect is bigger than the visible area, don't bother trying to
// center. Other alignments will work.
scrollY = getVisibleBehavior(alignY);
if (scrollY == ScrollAlignmentCenter)
scrollY = ScrollAlignmentNoScroll;
} else if (intersectHeight > 0) {
// If the rectangle is partially visible, use the specified partial behavior
scrollY = getPartialBehavior(alignY);
} else {
scrollY = getHiddenBehavior(alignY);
}
if (scrollY == ScrollAlignmentClosestEdge) {
// Closest edge is the bottom in two cases:
// (1) exposeRect below and smaller than nonZeroVisibleRect
// (2) exposeRect above and larger than nonZeroVisibleRect
if ((exposeRect.maxY() > nonZeroVisibleRect.maxY() &&
exposeRect.height() < nonZeroVisibleRect.height()) ||
(exposeRect.maxY() < nonZeroVisibleRect.maxY() &&
exposeRect.height() > nonZeroVisibleRect.height())) {
scrollY = ScrollAlignmentBottom;
}
}
// Given the Y behavior, compute the Y coordinate.
LayoutUnit y;
if (scrollY == ScrollAlignmentNoScroll)
y = nonZeroVisibleRect.y();
else if (scrollY == ScrollAlignmentBottom)
y = exposeRect.maxY() - nonZeroVisibleRect.height();
else if (scrollY == ScrollAlignmentCenter)
y = exposeRect.y() +
(exposeRect.height() - nonZeroVisibleRect.height()) / 2;
else
y = exposeRect.y();
return LayoutRect(LayoutPoint(x, y), nonZeroVisibleRect.size());
}
} // namespace blink
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