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Thread: using one signal to update multiple multiple controls

  1. #1
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    Default using one signal to update multiple multiple controls

    I have multiple QDoubleSpinBox in a dialog as follows:

    QDoubleSpinBox *qsb_fov_min_x;
    QDoubleSpinBox *qsb_fov_max_x;
    QDoubleSpinBox *qsb_fov_min_y;
    QDoubleSpinBox *qsb_fov_max_y;
    QDoubleSpinBox *qsb_fov_min_z;
    QDoubleSpinBox *qsb_fov_max_z;
    QDoubleSpinBox *qsb_fov_step_x;
    QDoubleSpinBox *qsb_fov_step_y;
    QDoubleSpinBox *qsb_fov_step_z;

    When the value in each QDoubleSpinBox is changed, I do some updates in update(). This works fine for me. Now I add one QPushButton as a "reset" button. When I click this reset button, I need to reset values of all QDoubleSpinBox to their own default values. So I connect button's click() signal to my own slot resetFOVDIM(). When I run this program and click the "reset" button, I found that not all QDoubleSpinBox values are set to their default values at the same time, but only one QDoubleSpinBox value is set on each clicking. I need to click the "reset" button nine times to reset all nine QDoubleSpinBox values.

    Could anyone show me what the problem is in my code and how to reset all values one time when I click the "reset" button? Many thanks!


    Here are code snippets:

    Setup_Dialog::void Setup_Dialog()
    {
    // other initializations
    ......

    // signal / slot connection
    connect(qsb_fov_min_x, SIGNAL(valueChanged(double)), this, SLOT(update()));
    connect(qsb_fov_max_x, SIGNAL(valueChanged(double)), this, SLOT(update()));
    connect(qsb_fov_min_y, SIGNAL(valueChanged(double)), this, SLOT(update()));
    connect(qsb_fov_max_y, SIGNAL(valueChanged(double)), this, SLOT(update()));
    connect(qsb_fov_min_z, SIGNAL(valueChanged(double)), this, SLOT(update()));
    connect(qsb_fov_max_z, SIGNAL(valueChanged(double)), this, SLOT(update()));

    connect(qsb_fov_step_x, SIGNAL(valueChanged(double)), this, SLOT(update()));
    connect(qsb_fov_step_y, SIGNAL(valueChanged(double)), this, SLOT(update()));
    connect(qsb_fov_step_z, SIGNAL(valueChanged(double)), this, SLOT(update()));

    connect(reset, SIGNAL(clicked()), this, SLOT(resetFOV()));
    }

    void Setup_Dialog::resetFOV()
    {
    fov_min_x = -150.0;
    fov_max_x = 150.0;
    fov_step_x = 1.0;

    fov_min_y = -150.0;
    fov_max_y = 150.0;
    fov_step_y = 1.0;

    fov_min_z = 50.0;
    fov_max_z = 60.0;
    fov_step_z = 1.0;


    // set values
    qsb_fov_min_x->setValue(fov_min_x);
    qsb_fov_max_x->setValue(fov_max_x);
    qsb_fov_step_x->setValue(fov_step_x);

    qsb_fov_min_y->setValue(fov_min_y);
    qsb_fov_max_y->setValue(fov_max_y);
    qsb_fov_step_y->setValue(fov_step_y);

    qsb_fov_min_z->setValue(fov_min_z);
    qsb_fov_max_z->setValue(fov_max_z);
    qsb_fov_step_z->setValue(fov_step_z);

    }

    void Setup_Dialog::update()
    {
    // do other updates
    }

  2. #2
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    Default Re: using one signal to update multiple multiple controls

    When you call
    Qt Code:
    1. qsb_fov_min_x->setValue(fov_min_x)
    To copy to clipboard, switch view to plain text mode 
    in resetFOV() you will cause update() to run via the valueChanged() signal. If update() changes any of fov_* members variables, for example reading all the slider values into the variables, then the next call to setValue() may not be using the value you think it is.
    "We can't solve problems by using the same kind of thinking we used when we created them." -- Einstein
    If you are posting code then please use [code] [/code] tags around it - makes addressing the problem easier.

  3. #3
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    Default Re: using one signal to update multiple multiple controls

    Quote Originally Posted by ChrisW67 View Post
    When you call
    Qt Code:
    1. qsb_fov_min_x->setValue(fov_min_x)
    To copy to clipboard, switch view to plain text mode 
    in resetFOV() you will cause update() to run via the valueChanged() signal. If update() changes any of fov_* members variables, for example reading all the slider values into the variables, then the next call to setValue() may not be using the value you think it is.
    Many thanks! yes, you are right. update() changes some fov_* variables. in this case, could you mind to show me any cues on how to solve this problem? Thank you very much!

  4. #4
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    Default Re: using one signal to update multiple multiple controls

    Two approaches come to mind:
    • In resetFOV() set the slider widgets with the default values (as literals) and allow the update() function to propagate the change into the member variables.
    • Dispense with the member variables altogether and use the widgets as the only storage of the values... no need to maintain sync.

  5. #5
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    Default Re: using one signal to update multiple multiple controls

    Quote Originally Posted by ChrisW67 View Post
    Two approaches come to mind:
    • In resetFOV() set the slider widgets with the default values (as literals) and allow the update() function to propagate the change into the member variables.
    • Dispense with the member variables altogether and use the widgets as the only storage of the values... no need to maintain sync.
    Many thanks! I may re-interprete your solutions:
    o The first one: I do not completely understand this solution. It seems that my current version is like that.
    o The second one: this means that each widget has a separate slot function for the corresponding signal, but not use one slot for all widgets. Am i right?
    Thank you!

  6. #6
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    Default Re: using one signal to update multiple multiple controls

    Or simply add a Boolean "resetInProgress" member variable to Setup_Dialog that gets set to true on entry into resetFOV() and set to false on exit. In update(), check to see if resetInProgress == true, and ignore the signal from the spin box if it is.

  7. #7
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    Default Re: using one signal to update multiple multiple controls

    Quote Originally Posted by henryjoye View Post
    Many thanks! I may re-interprete your solutions:
    o The first one: I do not completely understand this solution. It seems that my current version is like that.
    You would remove the lines from resetPOV() that set the member variables and change the setValue() lines.
    Qt Code:
    1. void Setup_Dialog::resetFOV()
    2. {
    3. // set values
    4. qsb_fov_min_x->setValue(-150.0);
    5. qsb_fov_max_x->setValue(50.0);
    6. qsb_fov_step_x->setValue(1.0);
    7.  
    8. qsb_fov_min_y->setValue(-150.0);
    9. qsb_fov_max_y->setValue(150.0);
    10. qsb_fov_step_y->setValue(1.0);
    11.  
    12. qsb_fov_min_z->setValue(50.0);
    13. qsb_fov_max_z->setValue(60.0);
    14. qsb_fov_step_z->setValue(1.0);
    15. }
    To copy to clipboard, switch view to plain text mode 
    o The second one: this means that each widget has a separate slot function for the corresponding signal, but not use one slot for all widgets. Am i right?
    Thank you!
    Your current arrangement doesn't know or care which slider changed; update() reads/works with the current state of all of them anyway. This need not change except that you don't need to read each slider and stash it into a variable... everywhere you previously used the variable you would directly use the slider value. It really depends on how the current member variables are used as to whether this is feasible.

  8. #8
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    Default Re: using one signal to update multiple multiple controls

    Quote Originally Posted by ChrisW67 View Post
    You would remove the lines from resetPOV() that set the member variables and change the setValue() lines.
    Qt Code:
    1. void Setup_Dialog::resetFOV()
    2. {
    3. // set values
    4. qsb_fov_min_x->setValue(-150.0);
    5. qsb_fov_max_x->setValue(50.0);
    6. qsb_fov_step_x->setValue(1.0);
    7.  
    8. qsb_fov_min_y->setValue(-150.0);
    9. qsb_fov_max_y->setValue(150.0);
    10. qsb_fov_step_y->setValue(1.0);
    11.  
    12. qsb_fov_min_z->setValue(50.0);
    13. qsb_fov_max_z->setValue(60.0);
    14. qsb_fov_step_z->setValue(1.0);
    15. }
    To copy to clipboard, switch view to plain text mode 

    Your current arrangement doesn't know or care which slider changed; update() reads/works with the current state of all of them anyway. This need not change except that you don't need to read each slider and stash it into a variable... everywhere you previously used the variable you would directly use the slider value. It really depends on how the current member variables are used as to whether this is feasible.
    Thank you very much! Both ChrisW67's solution and d_stranz's solution work. Many thanks!

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