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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 "third_party/blink/renderer/core/scroll/scroll_alignment.h"
#include "third_party/blink/renderer/core/layout/geometry/physical_rect.h"
namespace blink {
const ScrollAlignment ScrollAlignment::kAlignCenterIfNeeded = {
kScrollAlignmentNoScroll, kScrollAlignmentCenter,
kScrollAlignmentClosestEdge};
const ScrollAlignment ScrollAlignment::kAlignToEdgeIfNeeded = {
kScrollAlignmentNoScroll, kScrollAlignmentClosestEdge,
kScrollAlignmentClosestEdge};
const ScrollAlignment ScrollAlignment::kAlignCenterAlways = {
kScrollAlignmentCenter, kScrollAlignmentCenter, kScrollAlignmentCenter};
const ScrollAlignment ScrollAlignment::kAlignTopAlways = {
kScrollAlignmentTop, kScrollAlignmentTop, kScrollAlignmentTop};
const ScrollAlignment ScrollAlignment::kAlignBottomAlways = {
kScrollAlignmentBottom, kScrollAlignmentBottom, kScrollAlignmentBottom};
const ScrollAlignment ScrollAlignment::kAlignLeftAlways = {
kScrollAlignmentLeft, kScrollAlignmentLeft, kScrollAlignmentLeft};
const ScrollAlignment ScrollAlignment::kAlignRightAlways = {
kScrollAlignmentRight, kScrollAlignmentRight, kScrollAlignmentRight};
#define MIN_INTERSECT_FOR_REVEAL 32
ScrollOffset ScrollAlignment::GetScrollOffsetToExpose(
const PhysicalRect& scroll_snapport_rect,
const PhysicalRect& expose_rect,
const ScrollAlignment& align_x,
const ScrollAlignment& align_y,
const ScrollOffset& current_scroll_offset) {
// Prevent degenerate cases by giving the visible rect a minimum non-0 size.
PhysicalRect non_zero_visible_rect = scroll_snapport_rect;
LayoutUnit minimum_layout_unit;
minimum_layout_unit.SetRawValue(1);
if (non_zero_visible_rect.Width() == LayoutUnit())
non_zero_visible_rect.SetWidth(minimum_layout_unit);
if (non_zero_visible_rect.Height() == LayoutUnit())
non_zero_visible_rect.SetHeight(minimum_layout_unit);
// Determine the appropriate X behavior.
ScrollAlignmentBehavior scroll_x;
PhysicalRect expose_rect_x(expose_rect.X(), non_zero_visible_rect.Y(),
expose_rect.Width(),
non_zero_visible_rect.Height());
LayoutUnit intersect_width =
Intersection(non_zero_visible_rect, expose_rect_x).Width();
if (intersect_width == expose_rect.Width() ||
intersect_width >= 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
scroll_x = GetVisibleBehavior(align_x);
} else if (intersect_width == non_zero_visible_rect.Width()) {
// If the rect is bigger than the visible area, don't bother trying to
// center. Other alignments will work.
scroll_x = GetVisibleBehavior(align_x);
if (scroll_x == kScrollAlignmentCenter)
scroll_x = kScrollAlignmentNoScroll;
} else if (intersect_width > 0) {
// If the rectangle is partially visible, but not above the minimum
// threshold, use the specified partial behavior
scroll_x = GetPartialBehavior(align_x);
} else {
scroll_x = GetHiddenBehavior(align_x);
}
if (scroll_x == kScrollAlignmentClosestEdge) {
// 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 ((expose_rect.Right() > non_zero_visible_rect.Right() &&
expose_rect.Width() < non_zero_visible_rect.Width()) ||
(expose_rect.Right() < non_zero_visible_rect.Right() &&
expose_rect.Width() > non_zero_visible_rect.Width())) {
scroll_x = kScrollAlignmentRight;
}
}
// Determine the appropriate Y behavior.
ScrollAlignmentBehavior scroll_y;
PhysicalRect expose_rect_y(non_zero_visible_rect.X(), expose_rect.Y(),
non_zero_visible_rect.Width(),
expose_rect.Height());
LayoutUnit intersect_height =
Intersection(non_zero_visible_rect, expose_rect_y).Height();
if (intersect_height == expose_rect.Height()) {
// If the rectangle is fully visible, use the specified visible behavior.
scroll_y = GetVisibleBehavior(align_y);
} else if (intersect_height == non_zero_visible_rect.Height()) {
// If the rect is bigger than the visible area, don't bother trying to
// center. Other alignments will work.
scroll_y = GetVisibleBehavior(align_y);
if (scroll_y == kScrollAlignmentCenter)
scroll_y = kScrollAlignmentNoScroll;
} else if (intersect_height > 0) {
// If the rectangle is partially visible, use the specified partial behavior
scroll_y = GetPartialBehavior(align_y);
} else {
scroll_y = GetHiddenBehavior(align_y);
}
if (scroll_y == kScrollAlignmentClosestEdge) {
// Closest edge is the bottom in two cases:
// (1) exposeRect below and smaller than nonZeroVisibleRect
// (2) exposeRect above and larger than nonZeroVisibleRect
if ((expose_rect.Bottom() > non_zero_visible_rect.Bottom() &&
expose_rect.Height() < non_zero_visible_rect.Height()) ||
(expose_rect.Bottom() < non_zero_visible_rect.Bottom() &&
expose_rect.Height() > non_zero_visible_rect.Height())) {
scroll_y = kScrollAlignmentBottom;
}
}
// We would like calculate the ScrollPosition to move |expose_rect| inside
// the scroll_snapport, which is based on the scroll_origin of the scroller.
non_zero_visible_rect.Move(
-PhysicalOffset::FromFloatSizeRound(current_scroll_offset));
// Given the X behavior, compute the X coordinate.
float x;
if (scroll_x == kScrollAlignmentNoScroll) {
x = current_scroll_offset.Width();
} else if (scroll_x == kScrollAlignmentRight) {
x = (expose_rect.Right() - non_zero_visible_rect.Right()).ToFloat();
} else if (scroll_x == kScrollAlignmentCenter) {
x = ((expose_rect.X() + expose_rect.Right() -
(non_zero_visible_rect.X() + non_zero_visible_rect.Right())) /
2)
.ToFloat();
} else {
x = (expose_rect.X() - non_zero_visible_rect.X()).ToFloat();
}
// Given the Y behavior, compute the Y coordinate.
float y;
if (scroll_y == kScrollAlignmentNoScroll) {
y = current_scroll_offset.Height();
} else if (scroll_y == kScrollAlignmentBottom) {
y = (expose_rect.Bottom() - non_zero_visible_rect.Bottom()).ToFloat();
} else if (scroll_y == kScrollAlignmentCenter) {
y = ((expose_rect.Y() + expose_rect.Bottom() -
(non_zero_visible_rect.Y() + non_zero_visible_rect.Bottom())) /
2)
.ToFloat();
} else {
y = (expose_rect.Y() - non_zero_visible_rect.Y()).ToFloat();
}
return ScrollOffset(x, y);
}
} // namespace blink
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