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+/****************************************************************************
+**
+** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the examples of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+** * Redistributions of source code must retain the above copyright
+** notice, this list of conditions and the following disclaimer.
+** * Redistributions in binary form must reproduce the above copyright
+** notice, this list of conditions and the following disclaimer in
+** the documentation and/or other materials provided with the
+** distribution.
+** * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
+** of its contributors may be used to endorse or promote products derived
+** from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qquicklayoutengine_p.h"
+
+
+/*
+ This function is a modification of qGeomCalc() included in "QtCore/kernel/qlayoutengine_p.h".
+ It is used as a helper function to handle linear layout recalculations for QQuickItems.
+
+ chain contains input and output parameters describing the geometry.
+ count is the count of items in the chain; pos and space give the
+ interval (relative to parentWidget topLeft).
+*/
+void qDeclarativeLayoutCalculate(QVector<QQuickComponentsLayoutInfo> &chain, int start,
+ int count, qreal pos, qreal space, qreal spacer)
+{
+ if (chain.count() == 0)
+ return;
+
+ bool wannaGrow = false;
+ qreal totalStretch = 0;
+ qreal totalSpacing = 0;
+ qreal totalSizeHint = 0;
+ qreal totalMinimumSize = 0;
+
+ const int end = start + count;
+ const int spacerCount = chain.count() - 1;
+
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+
+ data->done = false;
+
+ totalStretch += data->stretch;
+ totalSizeHint += data->smartSizeHint();
+ totalMinimumSize += data->minimumSize;
+
+ // don't count last spacing
+ if (i < end - 1)
+ totalSpacing += data->effectiveSpacer(spacer);
+
+ wannaGrow = (wannaGrow || data->expansive || data->stretch > 0);
+ }
+
+ qreal extraSpace = 0;
+
+ if (space < totalMinimumSize + totalSpacing) {
+ // Less space than minimumSize; take from the biggest first
+ qreal minSize = totalMinimumSize + totalSpacing;
+
+ // shrink the spacers proportionally
+ if (spacer >= 0) {
+ spacer = minSize > 0 ? spacer * space / minSize : 0;
+ totalSpacing = spacer * spacerCount;
+ }
+
+ QList<qreal> list;
+
+ for (int i = start; i < end; i++)
+ list << chain.at(i).minimumSize;
+
+ qSort(list);
+
+ qreal spaceLeft = space - totalSpacing;
+
+ qreal sum = 0;
+ int idx = 0;
+ qreal spaceUsed = 0;
+ qreal current = 0;
+
+ while (idx < count && spaceUsed < spaceLeft) {
+ current = list.at(idx);
+ spaceUsed = sum + current * (count - idx);
+ sum += current;
+ ++idx;
+ }
+
+ --idx;
+
+ int items = count - idx;
+ qreal deficit = spaceUsed - spaceLeft;
+ qreal deficitPerItem = deficit / items;
+ qreal maxval = current - deficitPerItem;
+
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+ data->done = true;
+
+ if (data->minimumSize > 0)
+ data->size = data->minimumSize;
+ else
+ data->size = qMin<qreal>(data->minimumSize, maxval);
+ }
+ } else if (space < totalSizeHint + totalSpacing) {
+ /*
+ Less space than smartSizeHint(), but more than minimumSize.
+ Currently take space equally from each, as in Qt 2.x.
+ Commented-out lines will give more space to stretchier
+ items.
+ */
+ int n = count;
+ qreal spaceLeft = space - totalSpacing;
+ qreal overdraft = totalSizeHint - spaceLeft;
+
+ // first give to the fixed ones
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+
+ if (!data->done && data->minimumSize >= data->smartSizeHint()) {
+ data->done = true;
+ data->size = data->smartSizeHint();
+ spaceLeft -= data->smartSizeHint();
+ n--;
+ }
+ }
+
+ bool finished = (n == 0);
+
+ while (!finished) {
+ finished = true;
+
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+
+ if (data->done)
+ continue;
+
+ qreal w = overdraft / n;
+ data->size = data->smartSizeHint() - w;
+
+ if (data->size < data->minimumSize) {
+ data->done = true;
+ data->size = data->minimumSize;
+ finished = false;
+ overdraft -= data->smartSizeHint() - data->minimumSize;
+ n--;
+ break;
+ }
+ }
+ }
+ } else { // extra space
+ int n = count;
+ qreal spaceLeft = space - totalSpacing;
+
+ // first give to the fixed ones, and handle non-expansiveness
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+
+ if (data->done)
+ continue;
+
+ if (data->maximumSize <= data->smartSizeHint()
+ || (wannaGrow && !data->expansive && data->stretch == 0)
+ || (!data->expansive && data->stretch == 0)) {
+ data->done = true;
+ data->size = data->smartSizeHint();
+ spaceLeft -= data->size;
+ totalStretch -= data->stretch;
+ n--;
+ }
+ }
+
+ extraSpace = spaceLeft;
+
+ /*
+ Do a trial distribution and calculate how much it is off.
+ If there are more deficit pixels than surplus pixels, give
+ the minimum size items what they need, and repeat.
+ Otherwise give to the maximum size items, and repeat.
+
+ Paul Olav Tvete has a wonderful mathematical proof of the
+ correctness of this principle, but unfortunately this
+ comment is too small to contain it.
+ */
+ qreal surplus, deficit;
+
+ do {
+ surplus = deficit = 0;
+
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+
+ if (data->done)
+ continue;
+
+ extraSpace = 0;
+
+ qreal w;
+
+ if (totalStretch <= 0)
+ w = (spaceLeft / n);
+ else
+ w = (spaceLeft * data->stretch) / totalStretch;
+
+ data->size = w;
+
+ if (w < data->smartSizeHint())
+ deficit += data->smartSizeHint() - w;
+ else if (w > data->maximumSize)
+ surplus += w - data->maximumSize;
+ }
+
+ if (deficit > 0 && surplus <= deficit) {
+ // give to the ones that have too little
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+
+ if (!data->done && data->size < data->smartSizeHint()) {
+ data->done = true;
+ data->size = data->smartSizeHint();
+ spaceLeft -= data->smartSizeHint();
+ totalStretch -= data->stretch;
+ n--;
+ }
+ }
+ }
+
+ if (surplus > 0 && surplus >= deficit) {
+ // take from the ones that have too much
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+
+ if (!data->done && data->size > data->maximumSize) {
+ data->done = true;
+ data->size = data->maximumSize;
+ spaceLeft -= data->maximumSize;
+ totalStretch -= data->stretch;
+ n--;
+ }
+ }
+ }
+ } while (n > 0 && surplus != deficit);
+
+ if (n == 0)
+ extraSpace = spaceLeft;
+ }
+
+ /*
+ As a last resort, we distribute the unwanted space equally
+ among the spacers (counting the start and end of the chain). We
+ could, but don't, attempt a sub-pixel allocation of the extra
+ space.
+ */
+ qreal extra = extraSpace / (spacerCount + 2);
+ qreal p = pos + extra;
+
+ for (int i = start; i < end; i++) {
+ QQuickComponentsLayoutInfo *data = &chain[i];
+ data->pos = p;
+ p += data->size;
+ p += data->effectiveSpacer(spacer) + extra;
+ }
+}
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