1 /* 2 * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved. 3 * 4 * Portions are Copyright (C) 1998 Netscape Communications Corporation. 5 * 6 * Other contributors: 7 * Robert O'Callahan <roc+@cs.cmu.edu> 8 * David Baron <dbaron (at) fas.harvard.edu> 9 * Christian Biesinger <cbiesinger (at) web.de> 10 * Randall Jesup <rjesup (at) wgate.com> 11 * Roland Mainz <roland.mainz (at) informatik.med.uni-giessen.de> 12 * Josh Soref <timeless (at) mac.com> 13 * Boris Zbarsky <bzbarsky (at) mit.edu> 14 * 15 * This library is free software; you can redistribute it and/or 16 * modify it under the terms of the GNU Lesser General Public 17 * License as published by the Free Software Foundation; either 18 * version 2.1 of the License, or (at your option) any later version. 19 * 20 * This library is distributed in the hope that it will be useful, 21 * but WITHOUT ANY WARRANTY; without even the implied warranty of 22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 23 * Lesser General Public License for more details. 24 * 25 * You should have received a copy of the GNU Lesser General Public 26 * License along with this library; if not, write to the Free Software 27 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 28 * 29 * Alternatively, the contents of this file may be used under the terms 30 * of either the Mozilla Public License Version 1.1, found at 31 * http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public 32 * License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html 33 * (the "GPL"), in which case the provisions of the MPL or the GPL are 34 * applicable instead of those above. If you wish to allow use of your 35 * version of this file only under the terms of one of those two 36 * licenses (the MPL or the GPL) and not to allow others to use your 37 * version of this file under the LGPL, indicate your decision by 38 * deletingthe provisions above and replace them with the notice and 39 * other provisions required by the MPL or the GPL, as the case may be. 40 * If you do not delete the provisions above, a recipient may use your 41 * version of this file under any of the LGPL, the MPL or the GPL. 42 */ 43 44 #include "config.h" 45 #include "core/rendering/ScrollAlignment.h" 46 47 #include "platform/geometry/LayoutRect.h" 48 49 namespace blink { 50 51 const ScrollAlignment ScrollAlignment::alignCenterIfNeeded = { ScrollAlignmentNoScroll, ScrollAlignmentCenter, ScrollAlignmentClosestEdge }; 52 const ScrollAlignment ScrollAlignment::alignToEdgeIfNeeded = { ScrollAlignmentNoScroll, ScrollAlignmentClosestEdge, ScrollAlignmentClosestEdge }; 53 const ScrollAlignment ScrollAlignment::alignCenterAlways = { ScrollAlignmentCenter, ScrollAlignmentCenter, ScrollAlignmentCenter }; 54 const ScrollAlignment ScrollAlignment::alignTopAlways = { ScrollAlignmentTop, ScrollAlignmentTop, ScrollAlignmentTop }; 55 const ScrollAlignment ScrollAlignment::alignBottomAlways = { ScrollAlignmentBottom, ScrollAlignmentBottom, ScrollAlignmentBottom }; 56 57 #define MIN_INTERSECT_FOR_REVEAL 32 58 59 LayoutRect ScrollAlignment::getRectToExpose(const LayoutRect& visibleRect, const LayoutRect& exposeRect, const ScrollAlignment& alignX, const ScrollAlignment& alignY) 60 { 61 // Determine the appropriate X behavior. 62 ScrollAlignmentBehavior scrollX; 63 LayoutRect exposeRectX(exposeRect.x(), visibleRect.y(), exposeRect.width(), visibleRect.height()); 64 LayoutUnit intersectWidth = intersection(visibleRect, exposeRectX).width(); 65 if (intersectWidth == exposeRect.width() || intersectWidth >= MIN_INTERSECT_FOR_REVEAL) { 66 // If the rectangle is fully visible, use the specified visible behavior. 67 // If the rectangle is partially visible, but over a certain threshold, 68 // then treat it as fully visible to avoid unnecessary horizontal scrolling 69 scrollX = getVisibleBehavior(alignX); 70 } else if (intersectWidth == visibleRect.width()) { 71 // If the rect is bigger than the visible area, don't bother trying to center. Other alignments will work. 72 scrollX = getVisibleBehavior(alignX); 73 if (scrollX == ScrollAlignmentCenter) 74 scrollX = ScrollAlignmentNoScroll; 75 } else if (intersectWidth > 0) { 76 // If the rectangle is partially visible, but not above the minimum threshold, use the specified partial behavior 77 scrollX = getPartialBehavior(alignX); 78 } else { 79 scrollX = getHiddenBehavior(alignX); 80 } 81 82 if (scrollX == ScrollAlignmentClosestEdge) { 83 // Closest edge is the right in two cases: 84 // (1) exposeRect to the right of and smaller than visibleRect 85 // (2) exposeRect to the left of and larger than visibleRect 86 if ((exposeRect.maxX() > visibleRect.maxX() && exposeRect.width() < visibleRect.width()) 87 || (exposeRect.maxX() < visibleRect.maxX() && exposeRect.width() > visibleRect.width())) { 88 scrollX = ScrollAlignmentRight; 89 } 90 } 91 92 // Given the X behavior, compute the X coordinate. 93 LayoutUnit x; 94 if (scrollX == ScrollAlignmentNoScroll) 95 x = visibleRect.x(); 96 else if (scrollX == ScrollAlignmentRight) 97 x = exposeRect.maxX() - visibleRect.width(); 98 else if (scrollX == ScrollAlignmentCenter) 99 x = exposeRect.x() + (exposeRect.width() - visibleRect.width()) / 2; 100 else 101 x = exposeRect.x(); 102 103 // Determine the appropriate Y behavior. 104 ScrollAlignmentBehavior scrollY; 105 LayoutRect exposeRectY(visibleRect.x(), exposeRect.y(), visibleRect.width(), exposeRect.height()); 106 LayoutUnit intersectHeight = intersection(visibleRect, exposeRectY).height(); 107 if (intersectHeight == exposeRect.height()) { 108 // If the rectangle is fully visible, use the specified visible behavior. 109 scrollY = getVisibleBehavior(alignY); 110 } else if (intersectHeight == visibleRect.height()) { 111 // If the rect is bigger than the visible area, don't bother trying to center. Other alignments will work. 112 scrollY = getVisibleBehavior(alignY); 113 if (scrollY == ScrollAlignmentCenter) 114 scrollY = ScrollAlignmentNoScroll; 115 } else if (intersectHeight > 0) { 116 // If the rectangle is partially visible, use the specified partial behavior 117 scrollY = getPartialBehavior(alignY); 118 } else { 119 scrollY = getHiddenBehavior(alignY); 120 } 121 122 if (scrollY == ScrollAlignmentClosestEdge) { 123 // Closest edge is the bottom in two cases: 124 // (1) exposeRect below and smaller than visibleRect 125 // (2) exposeRect above and larger than visibleRect 126 if ((exposeRect.maxY() > visibleRect.maxY() && exposeRect.height() < visibleRect.height()) 127 || (exposeRect.maxY() < visibleRect.maxY() && exposeRect.height() > visibleRect.height())) { 128 scrollY = ScrollAlignmentBottom; 129 } 130 } 131 132 // Given the Y behavior, compute the Y coordinate. 133 LayoutUnit y; 134 if (scrollY == ScrollAlignmentNoScroll) 135 y = visibleRect.y(); 136 else if (scrollY == ScrollAlignmentBottom) 137 y = exposeRect.maxY() - visibleRect.height(); 138 else if (scrollY == ScrollAlignmentCenter) 139 y = exposeRect.y() + (exposeRect.height() - visibleRect.height()) / 2; 140 else 141 y = exposeRect.y(); 142 143 return LayoutRect(LayoutPoint(x, y), visibleRect.size()); 144 } 145 146 }; // namespace blink 147
