how to set long label beyond axis widget's extent?

[pptux]

Hi,

I need to set rotated long labels on the x axis, but the left end aligns with the y axis. The scales is compressed as below.
01.png

Is there any way to make the label extend beyond the end of its axis, like this
02.png

Thanks.

[Uwe]

What happens if you set:

plot->plotLayout()->setAlignCanvasToScale( QwtPlot::yLeft, true );

plot->plotLayout()->setAlignCanvasToScale( QwtPlot::yLeft, true );

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Uwe

[pptux]

Thanks for your reply. It's not the problem of canvas alignment. After many tries, it already works. But I still don't understand;-)

I want the labels to rotate to avoid overlap when resizing. The minimum working code is below:

#include "qwt_plot.h"
 
class QwtPlotBarChart;
class LabelScaleDraw;
 
class Widget : public QWidget
{
    Q_OBJECT
 
public:
    explicit Widget(QWidget *parent = 0);
 
    bool eventFilter(QObject *watched, QEvent *ev);
 
private:
    void setLabels(qreal step, const QList<QwtText> &labels, LabelScaleDraw &scaleDraw);
 
private slots:
    void setData();
 
private:
    QwtPlot *_plot;
    QwtPlotBarChart *_barChart;
    LabelScaleDraw *_scaleDraw;
};

#include "qwt_plot.h"

class QwtPlotBarChart;
class LabelScaleDraw;

class Widget : public QWidget
{
    Q_OBJECT

public:
    explicit Widget(QWidget *parent = 0);

    bool eventFilter(QObject *watched, QEvent *ev);

private:
    void setLabels(qreal step, const QList<QwtText> &labels, LabelScaleDraw &scaleDraw);

private slots:
    void setData();

private:
    QwtPlot *_plot;
    QwtPlotBarChart *_barChart;
    LabelScaleDraw *_scaleDraw;
};

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and

#include "widget.h"
 
#include "qwt_plot_barchart.h"
#include "qwt_plot_layout.h"
#include "qwt_scale_widget.h"
 
#include <QTimer>
#include <QResizeEvent>
#include <QVBoxLayout>
#include <QPushButton>
#include <QDebug>
 
class LabelScaleDraw: public QwtScaleDraw
{
public:
    LabelScaleDraw(){}
    QwtText label(double value) const
    {
        const int index = qRound(value);
        if (index % _sampleStep == 0)
            return _labelTexts.value(index);
        else
            return QwtText();
    }
    QList<QwtText> labelTexts() const
    {
        return _labelTexts;
    }
    void setLabelTexts(const QList<QwtText> &texts, int sampleStep = 1)
    {
        _labelTexts = texts;
        _sampleStep = sampleStep > 1 ? sampleStep : 1;
        invalidateCache();
    }
 
private:
    QList<QwtText> _labelTexts;
    int _sampleStep = 1;
};
 
Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
    _plot = new QwtPlot();
    _plot->axisWidget(QwtPlot::xBottom)->installEventFilter(this);
    _plot->setAutoReplot(false);
    _plot->plotLayout()->setAlignCanvasToScales(true);
 
    _scaleDraw = new LabelScaleDraw();
    _plot->setAxisScaleDraw(QwtPlot::xBottom, _scaleDraw);
 
    _barChart = new QwtPlotBarChart();
    _barChart->attach(_plot);
 
    QPushButton *button = new QPushButton("Push");
 
    QVBoxLayout *vLayout = new QVBoxLayout();
    vLayout->addWidget(_plot);
    vLayout->addWidget(button);
    setLayout(vLayout);
 
    QTimer::singleShot(300, this, SLOT(setData()));
//    setData();
//    connect(button, &QPushButton::clicked, this, &Widget::setData);
}
 
bool Widget::eventFilter(QObject *watched, QEvent *ev)
{
    if (watched == _plot->axisWidget(QwtPlot::xBottom) && ev->type() == QEvent::Resize)
    {
        QwtScaleMap xMap = _plot->canvasMap(QwtPlot::xBottom);
        qreal scaleMajorInterval = xMap.transform(1) - xMap.transform(0);
        setLabels(scaleMajorInterval, _scaleDraw->labelTexts(), *_scaleDraw);
        _plot->replot();
    }
    return QWidget::eventFilter(watched, ev);
}
 
void Widget::setLabels(qreal step, const QList<QwtText> &labels, LabelScaleDraw &scaleDraw)
{
    if (labels.isEmpty())
        return;
 
    qDebug() << "------------" << step;
 
    qreal maxLabelWidth = 0;
    for (const QwtText &text : labels)
    {
        QSizeF textSize = text.textSize();
        if (textSize.width() > maxLabelWidth)
            maxLabelWidth = textSize.width();
    }
 
    if (maxLabelWidth > step * 1.5)
    {
        scaleDraw.setLabelRotation(-90);
        scaleDraw.setLabelAlignment(Qt::AlignLeft);
    }
    else if (maxLabelWidth < step * 1.5 && maxLabelWidth > step * 0.9)
    {
        scaleDraw.setLabelRotation(-45);
        scaleDraw.setLabelAlignment(Qt::AlignLeft);
    }
    else
    {
        scaleDraw.setLabelRotation(0);
        scaleDraw.setLabelAlignment(Qt::AlignHCenter);
    }
    scaleDraw.setLabelTexts(labels);
}
 
void Widget::setData()
{
    const int numSamples = 10;
 
    QVector<double> series;
    QList<double> ticks;
    QList<QwtText> labels;
    for (int i = 0; i < numSamples; ++i)
    {
        series << 2 + i * 3;
        ticks << i;
        labels << QwtText("SteelBlue");
    }
    //setSample
    _barChart->setSamples(series);
 
    //setScaleDiv
    QwtScaleDiv xScaleDiv(- 0.5, numSamples - 0.5);
    xScaleDiv.setTicks(QwtScaleDiv::MajorTick, ticks);
    _plot->setAxisScaleDiv(QwtPlot::xBottom, xScaleDiv);
 
    //setLabels
    QwtScaleMap xMap = _plot->canvasMap(QwtPlot::xBottom);
    qreal scaleMajorInterval = xMap.transform(1) - xMap.transform(0);
    setLabels(scaleMajorInterval, labels, *_scaleDraw);
 
    _plot->replot();
}

#include "widget.h"

#include "qwt_plot_barchart.h"
#include "qwt_plot_layout.h"
#include "qwt_scale_widget.h"

#include <QTimer>
#include <QResizeEvent>
#include <QVBoxLayout>
#include <QPushButton>
#include <QDebug>

class LabelScaleDraw: public QwtScaleDraw
{
public:
    LabelScaleDraw(){}
    QwtText label(double value) const
    {
        const int index = qRound(value);
        if (index % _sampleStep == 0)
            return _labelTexts.value(index);
        else
            return QwtText();
    }
    QList<QwtText> labelTexts() const
    {
        return _labelTexts;
    }
    void setLabelTexts(const QList<QwtText> &texts, int sampleStep = 1)
    {
        _labelTexts = texts;
        _sampleStep = sampleStep > 1 ? sampleStep : 1;
        invalidateCache();
    }

private:
    QList<QwtText> _labelTexts;
    int _sampleStep = 1;
};

Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
    _plot = new QwtPlot();
    _plot->axisWidget(QwtPlot::xBottom)->installEventFilter(this);
    _plot->setAutoReplot(false);
    _plot->plotLayout()->setAlignCanvasToScales(true);

    _scaleDraw = new LabelScaleDraw();
    _plot->setAxisScaleDraw(QwtPlot::xBottom, _scaleDraw);

    _barChart = new QwtPlotBarChart();
    _barChart->attach(_plot);

    QPushButton *button = new QPushButton("Push");

    QVBoxLayout *vLayout = new QVBoxLayout();
    vLayout->addWidget(_plot);
    vLayout->addWidget(button);
    setLayout(vLayout);

    QTimer::singleShot(300, this, SLOT(setData()));
//    setData();
//    connect(button, &QPushButton::clicked, this, &Widget::setData);
}

bool Widget::eventFilter(QObject *watched, QEvent *ev)
{
    if (watched == _plot->axisWidget(QwtPlot::xBottom) && ev->type() == QEvent::Resize)
    {
        QwtScaleMap xMap = _plot->canvasMap(QwtPlot::xBottom);
        qreal scaleMajorInterval = xMap.transform(1) - xMap.transform(0);
        setLabels(scaleMajorInterval, _scaleDraw->labelTexts(), *_scaleDraw);
        _plot->replot();
    }
    return QWidget::eventFilter(watched, ev);
}

void Widget::setLabels(qreal step, const QList<QwtText> &labels, LabelScaleDraw &scaleDraw)
{
    if (labels.isEmpty())
        return;

    qDebug() << "------------" << step;

    qreal maxLabelWidth = 0;
    for (const QwtText &text : labels)
    {
        QSizeF textSize = text.textSize();
        if (textSize.width() > maxLabelWidth)
            maxLabelWidth = textSize.width();
    }

    if (maxLabelWidth > step * 1.5)
    {
        scaleDraw.setLabelRotation(-90);
        scaleDraw.setLabelAlignment(Qt::AlignLeft);
    }
    else if (maxLabelWidth < step * 1.5 && maxLabelWidth > step * 0.9)
    {
        scaleDraw.setLabelRotation(-45);
        scaleDraw.setLabelAlignment(Qt::AlignLeft);
    }
    else
    {
        scaleDraw.setLabelRotation(0);
        scaleDraw.setLabelAlignment(Qt::AlignHCenter);
    }
    scaleDraw.setLabelTexts(labels);
}

void Widget::setData()
{
    const int numSamples = 10;

    QVector<double> series;
    QList<double> ticks;
    QList<QwtText> labels;
    for (int i = 0; i < numSamples; ++i)
    {
        series << 2 + i * 3;
        ticks << i;
        labels << QwtText("SteelBlue");
    }
    //setSample
    _barChart->setSamples(series);

    //setScaleDiv
    QwtScaleDiv xScaleDiv(- 0.5, numSamples - 0.5);
    xScaleDiv.setTicks(QwtScaleDiv::MajorTick, ticks);
    _plot->setAxisScaleDiv(QwtPlot::xBottom, xScaleDiv);

    //setLabels
    QwtScaleMap xMap = _plot->canvasMap(QwtPlot::xBottom);
    qreal scaleMajorInterval = xMap.transform(1) - xMap.transform(0);
    setLabels(scaleMajorInterval, labels, *_scaleDraw);

    _plot->replot();
}

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What it doesn't work before is I set auto plot to true, without the explicit

_plot->replot()

_plot->replot()

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in the resize eventFilter; But I don't know why it wasn't work. Shouldn't it auto replot itself as the explicit one?
Thanks.