path: root/src/widgets/kernel/qlayoutengine.cpp

// Copyright (C) 2016 The Qt Company Ltd.// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only#include"qlayout.h"#include"private/qlayoutengine_p.h"#include"qlist.h"#include"qwidget.h"#include <qvarlengtharray.h>#include <qdebug.h>#include <algorithm> QT_BEGIN_NAMESPACE //#define QLAYOUT_EXTRA_DEBUGtypedef qint64 Fixed64;staticinline Fixed64 toFixed(int i) {return(Fixed64)i *256; }staticinlineintfRound(Fixed64 i) {return(i %256<128) ? i /256:1+ i /256;}/* This is the main workhorse of the QGridLayout. It portions out available space to the chain's children. The calculation is done in fixed point: "fixed" variables are scaled by a factor of 256. If the layout runs "backwards" (i.e. RightToLeft or Up) the layout is computed mirror-reversed, and it's the caller's responsibility do reverse the values before use. 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).*/voidqGeomCalc(QList<QLayoutStruct> &chain,int start,int count,int pos,int space,int spacer){int cHint =0;int cMin =0;int sumStretch =0;int sumSpacing =0;int expandingCount =0;bool allEmptyNonstretch =true;int pendingSpacing = -1;int spacerCount =0;int i;for(i = start; i < start + count; i++) { QLayoutStruct *data = &chain[i]; data->done =false; cHint += data->smartSizeHint(); cMin += data->minimumSize; sumStretch += data->stretch;if(!data->empty) {/* Using pendingSpacing, we ensure that the spacing for the last (non-empty) item is ignored. */if(pendingSpacing >=0) { sumSpacing += pendingSpacing;++spacerCount;} pendingSpacing = data->effectiveSpacer(spacer);}if(data->expansive) expandingCount++; allEmptyNonstretch = allEmptyNonstretch && data->empty && !data->expansive && data->stretch <=0;}int extraspace =0;if(space < cMin + sumSpacing) {/* Less space than minimumSize; take from the biggest first */int minSize = cMin + sumSpacing;// shrink the spacers proportionallyif(spacer >=0) { spacer = minSize >0? spacer * space / minSize :0; sumSpacing = spacer * spacerCount;} QVarLengthArray<int,32> minimumSizes; minimumSizes.reserve(count);for(i = start; i < start + count; i++) minimumSizes << chain.at(i).minimumSize;std::sort(minimumSizes.begin(), minimumSizes.end());int space_left = space - sumSpacing;int sum =0;int idx =0;int space_used=0;int current =0;while(idx < count && space_used < space_left) { current = minimumSizes.at(idx); space_used = sum + current * (count - idx); sum += current;++idx;}--idx;int deficit = space_used - space_left;int items = count - idx;/* * If we truncate all items to "current", we would get "deficit" too many pixels. Therefore, we have to remove * deficit/items from each item bigger than maxval. The actual value to remove is deficitPerItem + remainder/items * "rest" is the accumulated error from using integer arithmetic. */int deficitPerItem = deficit/items;int remainder = deficit % items;int maxval = current - deficitPerItem;int rest =0;for(i = start; i < start + count; i++) {int maxv = maxval; rest += remainder;if(rest >= items) { maxv--; rest-=items;} QLayoutStruct *data = &chain[i]; data->size =qMin(data->minimumSize, maxv); data->done =true;}}else if(space < cHint + sumSpacing) {/* 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;int space_left = space - sumSpacing;int overdraft = cHint - space_left;// first give to the fixed ones:for(i = start; i < start + count; i++) { QLayoutStruct *data = &chain[i];if(!data->done && data->minimumSize >= data->smartSizeHint()) { data->size = data->smartSizeHint(); data->done =true; space_left -= data->smartSizeHint();// sumStretch -= data->stretch; n--;}}bool finished = n ==0;while(!finished) { finished =true; Fixed64 fp_over =toFixed(overdraft); Fixed64 fp_w =0;for(i = start; i < start+count; i++) { QLayoutStruct *data = &chain[i];if(data->done)continue;// if (sumStretch <= 0) fp_w += fp_over / n;// else// fp_w += (fp_over * data->stretch) / sumStretch;int w =fRound(fp_w); data->size = data->smartSizeHint() - w; fp_w -=toFixed(w);// give the difference to the nextif(data->size < data->minimumSize) { data->done =true; data->size = data->minimumSize; finished =false; overdraft -= data->smartSizeHint() - data->minimumSize;// sumStretch -= data->stretch; n--;break;}}}}else{// extra spaceint n = count;int space_left = space - sumSpacing;// first give to the fixed ones, and handle non-expansivenessfor(i = start; i < start + count; i++) { QLayoutStruct *data = &chain[i];if(!data->done && (data->maximumSize <= data->smartSizeHint()|| (!allEmptyNonstretch && data->empty &&!data->expansive && data->stretch ==0))) { data->size = data->smartSizeHint(); data->done =true; space_left -= data->size; sumStretch -= data->stretch;if(data->expansive) expandingCount--; n--;}} extraspace = space_left;/* 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. */int surplus, deficit;do{ surplus = deficit =0; Fixed64 fp_space =toFixed(space_left); Fixed64 fp_w =0;for(i = start; i < start + count; i++) { QLayoutStruct *data = &chain[i];if(data->done)continue; extraspace =0;if(sumStretch >0) { fp_w += (fp_space * data->stretch) / sumStretch;}else if(expandingCount >0) { fp_w += (fp_space * (data->expansive ?1:0)) / expandingCount;}else{ fp_w += fp_space *1/ n;}int w =fRound(fp_w); data->size = w; fp_w -=toFixed(w);// give the difference to the nextif(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 littlefor(i = start; i < start+count; i++) { QLayoutStruct *data = &chain[i];if(!data->done && data->size < data->smartSizeHint()) { data->size = data->smartSizeHint(); data->done =true; space_left -= data->smartSizeHint(); sumStretch -= data->stretch;if(data->expansive) expandingCount--; n--;}}}if(surplus >0&& surplus >= deficit) {// take from the ones that have too muchfor(i = start; i < start + count; i++) { QLayoutStruct *data = &chain[i];if(!data->done && data->size > data->maximumSize) { data->size = data->maximumSize; data->done =true; space_left -= data->maximumSize; sumStretch -= data->stretch;if(data->expansive) expandingCount--; n--;}}}}while(n >0&& surplus != deficit);if(n ==0) extraspace = space_left;}/* 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. */int extra = extraspace / (spacerCount +2);int p = pos + extra;for(i = start; i < start+count; i++) { QLayoutStruct *data = &chain[i]; data->pos = p; p += data->size;if(!data->empty) p += data->effectiveSpacer(spacer) + extra;}#ifdef QLAYOUT_EXTRA_DEBUGqDebug() <<"qGeomCalc"<<"start"<< start <<"count"<< count <<"pos"<< pos <<"space"<< space <<"spacer"<< spacer;for(i = start; i < start + count; ++i) {qDebug() << i <<':'<< chain[i].minimumSize << chain[i].smartSizeHint()<< chain[i].maximumSize <<"stretch"<< chain[i].stretch <<"empty"<< chain[i].empty <<"expansive"<< chain[i].expansive <<"spacing"<< chain[i].spacing;qDebug() <<"result pos"<< chain[i].pos <<"size"<< chain[i].size;}#endif} Q_WIDGETS_EXPORT QSize qSmartMinSize(const QSize &sizeHint,const QSize &minSizeHint,const QSize &minSize,const QSize &maxSize,const QSizePolicy &sizePolicy){ QSize s(0,0);if(sizePolicy.horizontalPolicy() !=QSizePolicy::Ignored) {if(sizePolicy.horizontalPolicy() &QSizePolicy::ShrinkFlag) s.setWidth(minSizeHint.width());else s.setWidth(qMax(sizeHint.width(), minSizeHint.width()));}if(sizePolicy.verticalPolicy() !=QSizePolicy::Ignored) {if(sizePolicy.verticalPolicy() &QSizePolicy::ShrinkFlag) { s.setHeight(minSizeHint.height());}else{ s.setHeight(qMax(sizeHint.height(), minSizeHint.height()));}} s = s.boundedTo(maxSize);if(minSize.width() >0) s.setWidth(minSize.width());if(minSize.height() >0) s.setHeight(minSize.height());return s.expandedTo(QSize(0,0));} Q_WIDGETS_EXPORT QSize qSmartMinSize(const QWidgetItem *i){ QWidget *w = i->widget();returnqSmartMinSize(w->sizeHint(), w->minimumSizeHint(), w->minimumSize(), w->maximumSize(), w->sizePolicy());} Q_WIDGETS_EXPORT QSize qSmartMinSize(const QWidget *w){returnqSmartMinSize(w->sizeHint(), w->minimumSizeHint(), w->minimumSize(), w->maximumSize(), w->sizePolicy());} Q_WIDGETS_EXPORT QSize qSmartMaxSize(const QSize &sizeHint,const QSize &minSize,const QSize &maxSize,const QSizePolicy &sizePolicy,Qt::Alignment align){if(align &Qt::AlignHorizontal_Mask && align &Qt::AlignVertical_Mask)returnQSize(QLAYOUTSIZE_MAX, QLAYOUTSIZE_MAX); QSize s = maxSize; QSize hint = sizeHint.expandedTo(minSize);if(s.width() == QWIDGETSIZE_MAX && !(align &Qt::AlignHorizontal_Mask))if(!(sizePolicy.horizontalPolicy() &QSizePolicy::GrowFlag)) s.setWidth(hint.width());if(s.height() == QWIDGETSIZE_MAX && !(align &Qt::AlignVertical_Mask))if(!(sizePolicy.verticalPolicy() &QSizePolicy::GrowFlag)) s.setHeight(hint.height());if(align &Qt::AlignHorizontal_Mask) s.setWidth(QLAYOUTSIZE_MAX);if(align &Qt::AlignVertical_Mask) s.setHeight(QLAYOUTSIZE_MAX);return s;} Q_WIDGETS_EXPORT QSize qSmartMaxSize(const QWidgetItem *i,Qt::Alignment align){ QWidget *w = i->widget();returnqSmartMaxSize(w->sizeHint().expandedTo(w->minimumSizeHint()), w->minimumSize(), w->maximumSize(), w->sizePolicy(), align);} Q_WIDGETS_EXPORT QSize qSmartMaxSize(const QWidget *w,Qt::Alignment align){returnqSmartMaxSize(w->sizeHint().expandedTo(w->minimumSizeHint()), w->minimumSize(), w->maximumSize(), w->sizePolicy(), align);} Q_WIDGETS_EXPORT intqSmartSpacing(const QLayout *layout,QStyle::PixelMetric pm){ QObject *parent = layout->parent();if(!parent) {return-1;}else if(parent->isWidgetType()) { QWidget *pw =static_cast<QWidget *>(parent);return pw->style()->pixelMetric(pm,nullptr, pw);}else{return static_cast<QLayout *>(parent)->spacing();}} QT_END_NAMESPACE