flowlayout.cpp

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/*
 
Pencil2D - Traditional Animation Software
Copyright (C) 2005-2007 Patrick Corrieri & Pascal Naidon
Copyright (C) 2012-2020 Matthew Chiawen Chang
 
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; version 2 of the License.
 
This program 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 General Public License for more details.
 
*/
 
#include <QWidget>
#include <QLayout>
#include <QtMath>
#include <QDebug>
#include <QDockWidget>
 
#include "flowlayout.h"
 
FlowLayout::FlowLayout(QWidget *parent, int margin, int hSpacing, int vSpacing)
    : QLayout(parent), m_hSpace(hSpacing), m_vSpace(vSpacing)
{
    setContentsMargins(margin, margin, margin, margin);
}
 
FlowLayout::FlowLayout(int margin, int hSpacing, int vSpacing)
    : FlowLayout(nullptr, margin, hSpacing, vSpacing)
{}
 
FlowLayout::~FlowLayout()
{
    QLayoutItem *item;
    while ((item = takeAt(0)))
        delete item;
}
 
void FlowLayout::addItem(QLayoutItem *item)
{
    itemList.append(item);
}
 
int FlowLayout::horizontalSpacing() const
{
    if (m_hSpace >= 0) {
        return m_hSpace;
    } else {
        return smartSpacing(QStyle::PM_LayoutHorizontalSpacing);
    }
}
 
int FlowLayout::verticalSpacing() const
{
    if (m_vSpace >= 0) {
        return m_vSpace;
    } else {
        return smartSpacing(QStyle::PM_LayoutVerticalSpacing);
    }
}
 
int FlowLayout::count() const
{
    return itemList.size();
}
 
QLayoutItem *FlowLayout::itemAt(int index) const
{
    return itemList.value(index);
}
 
QLayoutItem *FlowLayout::takeAt(int index)
{
    if (index >= 0 && index < itemList.size())
        return itemList.takeAt(index);
    else
        return nullptr;
}
 
bool FlowLayout::hasHeightForWidth() const
{
    return true;
}
 
Qt::Orientations FlowLayout::expandingDirections() const
{
    return {};
}
 
int FlowLayout::heightForWidth(int width) const
{
    return calculateHeightForWidth(width);
}
 
void FlowLayout::setGeometry(const QRect &rect)
{
    QLayout::setGeometry(rect);
    mNumberOfRows = applyLayout(rect);
}
 
QSize FlowLayout::sizeHint() const
{
    return minimumSize();
}
 
QSize FlowLayout::minimumSize() const
{
    QSize size;
    QLayoutItem *item;
    foreach (item, itemList)
        size = size.expandedTo(item->minimumSize());
    int left, top, right, bottom;
    getContentsMargins(&left, &top, &right, &bottom);
    size += QSize(left + right, top + bottom);
    return size;
}
 
RowLayoutInfo FlowLayout::alignJustifiedRow(int startIndex, int count, const QRect& effectiveRect, int spaceX) const
{
 
    int spacing = 0;
    if (count > 0) {
        int gapCount = count + 1;
        int rowWidth = calculateRowWidth(startIndex, count, spaceX);
        int availableSpace = effectiveRect.width() - rowWidth;
 
        spacing = (gapCount > 0 && availableSpace > 0)
                  ? availableSpace / gapCount
                  : 0;
    }
 
    int itemX = effectiveRect.left() + spacing;
 
    RowLayoutInfo row;
 
    row.startX = itemX;
    row.startIndex = startIndex;
    row.spacing = spaceX + spacing;
 
    for (int j = startIndex; j < startIndex + count; j += 1) {
        QLayoutItem *rowItem = itemList.at(j);
        const QSize& itemSize = rowItem->sizeHint();
        rowItem->setGeometry(QRect(QPoint(itemX, rowItem->geometry().y()), itemSize));
        itemX += row.spacing + itemSize.width();
    }
 
    return row;
}
 
RowLayoutInfo FlowLayout::alignHCenterRow(int startIndex, int count, const QRect &effectiveRect, int spaceX) const
{
    int rowWidth = calculateRowWidth(startIndex, count, spaceX);
    int offset = (effectiveRect.width() - rowWidth) / 2;
    int rowOffsetX = effectiveRect.left() + offset;
 
    RowLayoutInfo row;
 
    row.startX = rowOffsetX;
    row.startIndex = startIndex;
    row.spacing = spaceX;
 
    for (int i = startIndex; i < startIndex + count; i += 1) {
        QLayoutItem *rowItem = itemList.at(i);
 
        const QSize& itemSize = rowItem->sizeHint();
        rowItem->setGeometry(QRect(QPoint(rowOffsetX, rowItem->geometry().y()), itemSize));
        rowOffsetX += row.spacing + itemSize.width();
    }
 
    return row;
}
 
int FlowLayout::calculateHeightForWidth(int width) const
{
    int left, top, right, bottom;
    getContentsMargins(&left, &top, &right, &bottom);
    int lineHeight = 0;
    int rowCount = 0;
    int totalRows = 0;
 
    int spaceX = horizontalSpacing();
    int spaceY = verticalSpacing();
 
    int y = 0;
 
    for (int i = 0; i < itemList.length(); i++) {
        QLayoutItem* item = itemList.at(i);
        QWidget *wid = item->widget();
        int rowWidth = calculateRowWidth(0, rowCount, spaceX);
 
        if (spaceX == -1)
            spaceX = wid->style()->layoutSpacing(
                QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Horizontal);
        if (spaceY == -1)
            spaceY = wid->style()->layoutSpacing(
                QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Vertical);
 
        if (rowWidth + item->sizeHint().width() + spaceX >= width && lineHeight > 0) {
            totalRows++;
 
            y += lineHeight + spaceY;
            lineHeight = 0;
            rowCount = 0;
        }
 
        lineHeight = qMax(lineHeight, item->sizeHint().height());
        rowCount++;
    }
 
 
    return lineHeight + y + top + bottom;
}
 
int FlowLayout::applyLayout(const QRect &rect) const
{
    int left, top, right, bottom;
    getContentsMargins(&left, &top, &right, &bottom);
 
    int spaceX = horizontalSpacing();
    int spaceY = verticalSpacing();
 
    QRect effectiveRect = rect.adjusted(+left, +top, -right, -bottom);
    int x = effectiveRect.x();
    int y = effectiveRect.y();
    int lineHeight = 0;
 
    QLayoutItem *item;
 
    QVector<RowLayoutInfo> rowAlignments;
 
    int currentRowCount = 0;
    int maxRowCount = 0;
 
    for (int i = 0; i < itemList.length(); i += 1) {
        item = itemList.at(i);
        QWidget *wid = item->widget();
 
        if (spaceX == -1)
            spaceX = wid->style()->layoutSpacing(
                QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Horizontal);
        if (spaceY == -1)
            spaceY = wid->style()->layoutSpacing(
                QSizePolicy::PushButton, QSizePolicy::PushButton, Qt::Vertical);
 
        int startRowIndex = i - currentRowCount;
        int rowWidth = calculateRowWidth(startRowIndex, currentRowCount, spaceX);
 
        if (currentRowCount > 0) {
            maxRowCount = qMax(currentRowCount, maxRowCount);
 
            if (rowWidth + item->sizeHint().width() + spaceX >= effectiveRect.width()) {
                if (alignment() & Qt::AlignHCenter) {
                    rowAlignments.append(alignHCenterRow(startRowIndex, currentRowCount, effectiveRect, spaceX));
                } else if (alignment() & Qt::AlignJustify) {
                    rowAlignments.append(alignJustifiedRow(startRowIndex, currentRowCount, effectiveRect, spaceX));
                }
 
                y = y + lineHeight + spaceY;
                lineHeight = 0;
                currentRowCount = 0;
            }
        }
 
        item->setGeometry(QRect(QPoint(x, y), item->sizeHint()));
 
        lineHeight = qMax(lineHeight, item->sizeHint().height());
        currentRowCount += 1;
    }
 
    if (maxRowCount == itemList.length() - 1) {
        alignHCenterRow(itemList.length() - currentRowCount, currentRowCount, effectiveRect, spaceX);
    } else if (currentRowCount > 0) {
        lastLineAlignment(itemList.length() - currentRowCount, currentRowCount, rowAlignments.last(), effectiveRect);
    }
 
    return maxRowCount;
}
 
void FlowLayout::lastLineAlignment(int startIndex, int count, RowLayoutInfo rowInfo, const QRect& effectiveRect) const
{
    if (alignment() & Qt::AlignHCenter) {
        alignHCenterRow(startIndex, count, effectiveRect, rowInfo.spacing);
    } else if (alignment() & Qt::AlignJustify) {
        alignJustifiedRow(startIndex, count, effectiveRect, rowInfo.spacing);
    }
}
 
int FlowLayout::calculateRowWidth(int start, int end, int spacing) const
{
    if (itemList.isEmpty()) { return 0; }
 
    int totalWidth = 0;
    // Calculate the total width of all item in row including spacing
    for (int i = start; i < start + end; i += 1) {
        totalWidth += itemList.at(i)->sizeHint().width();
    }
 
    return totalWidth + (spacing * (end - 1));
}
 
int FlowLayout::smartSpacing(QStyle::PixelMetric pm) const
{
    QObject* parent = this->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();
    }
}