Fix #305387: Add spinner for controlling glissando line thickness in inspector

[sidharth-anand]

Resolves: https://musescore.org/en/node/305387

This patch allows the user to directly change the thickness of the glissando line from the inspector

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[cbjeukendrup]

I tested it and noticed two things:

• If you select a glissando that is already "wavy", the line thickness control is (erroneously) shown.
  However, if you select a glissando that is "straight" and then change it to "wavy", the line thickness control is correctly hidden (and comes back again if you change it back to "straight").
• The line thickness control shows no suffix / measurement unit. It would be nice if it would say 0.15sp instead of just 0.15. I believe this is supported out-of-the-box in Qt Creator, so you could just look at the properties of other spinboxes that do show sp.

[sidharth-anand]

I'll update the pr with these fixes

[cbjeukendrup]

Ah, for the first one, it looks like you need to add this:

void InspectorGlissando::setElement()
      {
      InspectorElementBase::setElement();
      if (!g.playGlissando->isChecked()) {
            g.labelGlissandoStyle->setEnabled(false);
            g.glissandoStyle->setEnabled(false);
            g.resetGlissandoStyle->setEnabled(false);
            }
      if (!g.showText->isChecked())
            g.textWidget->setVisible(false);
+     g.lineWidthWidget->setHidden(g.type->currentIndex() == 1);
      g.easeInSlider->setSliderPosition(g.easeInSpin->value());
      g.easeOutSlider->setSliderPosition(g.easeOutSpin->value());
      g.easeInOutCanvas->setEaseInOut(g.easeInSpin->value(), g.easeOutSpin->value());

      updateEvents();
      }

[sidharth-anand]

Updated with both the fixes

[Jojo-Schmitz]

Needs #7704

[Jojo-Schmitz]

I wonder whether this would need to get ported to master