QDial pointer start position(value - 0) at top

sayan275

Hello All,

I want a qdial pointer with the start value(0 or 360) at the top. By default it appears at the bottom.

So the pointer of the dial with value 0 should be at the green mark .
Is there any flag to do so, or-else, I have do manual calculation with +/- 180 .

Any suggestion is appreciated.

Regards,
Sayan

J.Hilk

@sayan275
here ya go:

//.h
#ifndef JHDIAL_H
#define JHDIAL_H

#include <QDial>

class JhDial : public QDial
{
    Q_OBJECT
    Q_PROPERTY(int adjustedValue READ adjustedValue WRITE setAdjustedValue NOTIFY adjustedValueChanged)
public:
    explicit JhDial(QWidget *parent = nullptr);

    inline int adjustedValue() const { return m_adjustedValue; }

signals:
    void adjustedValueChanged(int adjustedValue);

public slots:
    void setAdjustedValue(int adjustedValue);

private:
    int mapValueToRange(int y, int y_min, int y_max, int x_min, int x_max);
    void adjustValue(int value);
    int m_adjustedValue = -1;
};

#endif // JHDIAL_H

//.cpp
#include "jhdial.h"

JhDial::JhDial(QWidget *parent) : QDial(parent)
{
    connect(this, &QDial::valueChanged, this, &JhDial::adjustValue);

    setWrapping(true);
    setRange(0,360);
    setAdjustedValue(0);
}

void JhDial::setAdjustedValue(int adjustedValue)
{
    if (m_adjustedValue == adjustedValue)
        return;

    if(adjustedValue < 180)
        setValue(mapValueToRange(adjustedValue,0,179,180,360));
    else
        setValue(mapValueToRange(adjustedValue,180,360, 0, 180));

}

int JhDial::mapValueToRange(int y, int y_min, int y_max, int x_min, int x_max)
{
    return qRound((y-y_min)/static_cast<double>(y_max-y_min)*(x_max-x_min)+x_min);
}

void JhDial::adjustValue(int value)
{
    if(value < 180)
        m_adjustedValue = mapValueToRange(value,0, 179, 180, 360);
    else
        m_adjustedValue = mapValueToRange(value,180, 360, 0, 180);

    emit adjustedValueChanged(m_adjustedValue);
}

~~You may have to adjust the borders for the mapping, so that they don't overlap, I mad this in a rush ;)~~
you had to, cleaned it up a bit.

mrjj

Hi
Did you try with
alt text

If that is not working with Dial then you have to do it manually.

sayan275

This post is deleted!

mrjj

@sayan275
Hi
Ok you must have something that block images then.
Anyway, it show the property
"inverted appearance "
that normally flips a slider to be reversed.
But sadly it didn't work with 0-360 as the zero is still in the bottom.

http://imagizer.imageshack.com/img922/2451/awXZvi.png

sayan275

@mrjj sorry I got your posted image..its the property.

Yes it didn't work...I tried all possible combinations with the flags available.
Can we rotated a widget? .. can't remember any api.
Meanwhile I got the expected output by calculating with +/- 180

//    if(value > 180)
//        value -= 180;
//    else if(value <= 180)
//        value += 180;

I didn't want to update the value in this manner.

@mrjj Anyways thanks for your reply.

mrjj

@sayan275
well we cant rotate a widget as such
but we could subclass it and then flip the painter.
If that works in terms of navigation, im not sure.

void QDial::paintEvent(QPaintEvent *)
{
    QStylePainter p(this);
    QStyleOptionSlider option;
    initStyleOption(&option);
    p.drawComplexControl(QStyle::CC_Dial, option);
}

use p and
https://doc.qt.io/qt-5/qtwidgets-painting-transformations-example.html
to flip it and see :)

sayan275

@mrjj Thanks for the suggestion.
I'll try out the overriding the paintEvent()

Pablo J. Rogina

@sayan275 just in case, do you really need the dial to wrap?

mrjj

Hi
Just as a note.

void MyDial::paintEvent(QPaintEvent *event)
{
    QStylePainter p(this);
    QStyleOptionSlider option;
    initStyleOption(&option);
    p.translate(0, height());
    p.scale(1.0, -1.0);
    p.drawComplexControl(QStyle::CC_Dial, option);
}

Did draw as we wanted and using keys (left , right ) moves it ok
but click and drag with the mouse it jumps back to the old zero.

So sadly was not a solution as navigation did went banans.

sayan275

@Pablo-J-Rogina yes...we need to wrap...so that the starting and endpoints are similar.

J.Hilk

@sayan275
here ya go:

//.h
#ifndef JHDIAL_H
#define JHDIAL_H

#include <QDial>

class JhDial : public QDial
{
    Q_OBJECT
    Q_PROPERTY(int adjustedValue READ adjustedValue WRITE setAdjustedValue NOTIFY adjustedValueChanged)
public:
    explicit JhDial(QWidget *parent = nullptr);

    inline int adjustedValue() const { return m_adjustedValue; }

signals:
    void adjustedValueChanged(int adjustedValue);

public slots:
    void setAdjustedValue(int adjustedValue);

private:
    int mapValueToRange(int y, int y_min, int y_max, int x_min, int x_max);
    void adjustValue(int value);
    int m_adjustedValue = -1;
};

#endif // JHDIAL_H

//.cpp
#include "jhdial.h"

JhDial::JhDial(QWidget *parent) : QDial(parent)
{
    connect(this, &QDial::valueChanged, this, &JhDial::adjustValue);

    setWrapping(true);
    setRange(0,360);
    setAdjustedValue(0);
}

void JhDial::setAdjustedValue(int adjustedValue)
{
    if (m_adjustedValue == adjustedValue)
        return;

    if(adjustedValue < 180)
        setValue(mapValueToRange(adjustedValue,0,179,180,360));
    else
        setValue(mapValueToRange(adjustedValue,180,360, 0, 180));

}

int JhDial::mapValueToRange(int y, int y_min, int y_max, int x_min, int x_max)
{
    return qRound((y-y_min)/static_cast<double>(y_max-y_min)*(x_max-x_min)+x_min);
}

void JhDial::adjustValue(int value)
{
    if(value < 180)
        m_adjustedValue = mapValueToRange(value,0, 179, 180, 360);
    else
        m_adjustedValue = mapValueToRange(value,180, 360, 0, 180);

    emit adjustedValueChanged(m_adjustedValue);
}

~~You may have to adjust the borders for the mapping, so that they don't overlap, I mad this in a rush ;)~~
you had to, cleaned it up a bit.

sayan275

@J-Hilk Thanks ...I tried this.