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Diffstat (limited to 'chromium/third_party/WebKit/Source/core/rendering/ScrollAlignment.cpp')
| -rw-r--r-- | chromium/third_party/WebKit/Source/core/rendering/ScrollAlignment.cpp | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/chromium/third_party/WebKit/Source/core/rendering/ScrollAlignment.cpp b/chromium/third_party/WebKit/Source/core/rendering/ScrollAlignment.cpp new file mode 100644 index 00000000000..433a0864815 --- /dev/null +++ b/chromium/third_party/WebKit/Source/core/rendering/ScrollAlignment.cpp @@ -0,0 +1,146 @@ +/* + * 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 "config.h" +#include "core/rendering/ScrollAlignment.h" + +#include "platform/geometry/LayoutRect.h" + +namespace WebCore { + +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) +{ + // Determine the appropriate X behavior. + ScrollAlignmentBehavior scrollX; + LayoutRect exposeRectX(exposeRect.x(), visibleRect.y(), exposeRect.width(), visibleRect.height()); + LayoutUnit intersectWidth = intersection(visibleRect, 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 == visibleRect.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 visibleRect + // (2) exposeRect to the left of and larger than visibleRect + if ((exposeRect.maxX() > visibleRect.maxX() && exposeRect.width() < visibleRect.width()) + || (exposeRect.maxX() < visibleRect.maxX() && exposeRect.width() > visibleRect.width())) { + scrollX = ScrollAlignmentRight; + } + } + + // Given the X behavior, compute the X coordinate. + LayoutUnit x; + if (scrollX == ScrollAlignmentNoScroll) + x = visibleRect.x(); + else if (scrollX == ScrollAlignmentRight) + x = exposeRect.maxX() - visibleRect.width(); + else if (scrollX == ScrollAlignmentCenter) + x = exposeRect.x() + (exposeRect.width() - visibleRect.width()) / 2; + else + x = exposeRect.x(); + + // Determine the appropriate Y behavior. + ScrollAlignmentBehavior scrollY; + LayoutRect exposeRectY(visibleRect.x(), exposeRect.y(), visibleRect.width(), exposeRect.height()); + LayoutUnit intersectHeight = intersection(visibleRect, exposeRectY).height(); + if (intersectHeight == exposeRect.height()) { + // If the rectangle is fully visible, use the specified visible behavior. + scrollY = getVisibleBehavior(alignY); + } else if (intersectHeight == visibleRect.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 visibleRect + // (2) exposeRect above and larger than visibleRect + if ((exposeRect.maxY() > visibleRect.maxY() && exposeRect.height() < visibleRect.height()) + || (exposeRect.maxY() < visibleRect.maxY() && exposeRect.height() > visibleRect.height())) { + scrollY = ScrollAlignmentBottom; + } + } + + // Given the Y behavior, compute the Y coordinate. + LayoutUnit y; + if (scrollY == ScrollAlignmentNoScroll) + y = visibleRect.y(); + else if (scrollY == ScrollAlignmentBottom) + y = exposeRect.maxY() - visibleRect.height(); + else if (scrollY == ScrollAlignmentCenter) + y = exposeRect.y() + (exposeRect.height() - visibleRect.height()) / 2; + else + y = exposeRect.y(); + + return LayoutRect(LayoutPoint(x, y), visibleRect.size()); +} + +}; // namespace WebCore |