Synchronize an QOpengl line with audio file

[HW-Developer]

I want to create an app that can play an audio and synchronize it with a QOpenglWidget that include a divided ruler instead of a qslider like this:

but i can't figure out how to create positionchanged method in my QOpenglWidget class, so any one has a simple example or an idea, i really appreciate it. Thank you.

[mrjj]

Hi
you mean some method or signal to move the red line ?

[HW-Developer]

@mrjj Yes that's right

[mrjj]

@HW-Developer
well did u subclass QOpenglWidget ?
If yes, you can just add a slot to it like
public slots:
void PositionChanged( int pos) ;

and in cpp
void yourclassname:: PositionChanged( int pos) {
change the variable that controls the red line.
}

[HW-Developer]

@mrjj for example if we have this code to draw the red line

glColor3f(1.0, 0.0, 0.0);
glBegin(GL_LINES);
glVertex3f(-1 + (redLine*scaleFactor), 1 + -(0 * 0.016), -1.0);
glVertex3f(-1 + (redLine*scaleFactor), 1 + -(130 * 0.016), -1.0);
glEnd();

//scaleFactor is a float variable which determines the space before the red line
//redline is a float variable = 320 + 160;

and i create the positionChanged(int position) methode, what should i change using the position variable?

[mrjj]

@HW-Developer
I would assume redLine variable ?

[HW-Developer]

@mrjj When i use redLine =0, it gives me this result:

so 160 is the space between the small grey lines
and 320 is just a number that i added so the red line will be in the same line with my slider

[mrjj]

@HW-Developer
so the redline default offset is 320+160.
so if you add to that, it will move the redline.
Do you mean to hook up the slider so it moves the redline or what is task?

[HW-Developer]

@mrjj The slider was my first test so to have the same result i did have with my slider i initialize the red line on the same line with that slider so when the audio is playing, they will be moving in the same time

[mrjj]

@HW-Developer
ok.
so now you want a method in QOpenglWidget that also moves the redLine ?

[HW-Developer]

@mrjj Yes that's right

[mrjj]

@HW-Developer
Ok, i assumed you subclassed it ?
like
class MyGLWidget : public QOpenGLWidget ...

so you can just add a new method to it to alter the redLine variable.

[HW-Developer]

@mrjj Yes of course i already did what is necessary to have the drawing ruler that i upload it above

[mrjj]

@HW-Developer
ok but you question was
" how to create positionchanged method in my QOpenglWidget class,"
so i must be missing something you ask about ?
(if you already did make such method)

[HW-Developer]

@mrjj I already draw the qopenglwidget but I did not synchronize it with the audio file using positionchanged method that I did ask you about

[mrjj]

hi
well you can hook up the AUDIO positionchanged
signal to your own method (slot)
using connect.
http://doc.qt.io//qt-5/signalsandslots.html

so it will directly call your method when it changes.