// Read a UTF-16 string value.
static QString read_string( QIODevice *dev, int length )
{
QVarLengthArray<ushort> buf;
buf.reserve( length );
dev->read( (char *)(buf.data()), length * 2 );
return QString::fromUtf16( buf.data(), length );
}
/*
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).
*/
void qGeomCalc(QVector<QLayoutStruct> &chain, int start, int count,
int pos, int space, int spacer)
{
int cHint = 0;
int cMin = 0;
int cMax = 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;
cMax += data->maximumSize;
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 proportionally
if (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 next
if (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 space
int n = count;
int space_left = space - sumSpacing;
// first give to the fixed ones, and handle non-expansiveness
for (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 next
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 (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 much
for (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_DEBUG
qDebug() << "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
}