Shade: Audio Latency meter fix

[daschuer]

This fixes an issue with the GLSL Shader when the widget has only on pixel height.
Simply by using two widgets.

I have moved a +1 to various places in our code, but I was not able to make it work. Only if the Widget itself has a height of two pixels, it works.

@m0dB do you have an idea how to fix it?
Can you confirm the issue with macOS?

[m0dB]

I confirm that on macOS the vumeter doesn't show either when the height is 1. The problem is not in the shader code, I tried by just simply making the window red with glClearColor and returning. With 2 pixels there is no problem (note btw that the size is determined by the background pixmap). Looks like a Qt bug to me.

I could implement a workaround: when the height is 1, make it two and set the glViewport to 1 pixel height.

Alternatively, I think it would be much better of the overload formed part of the vumeter, instead of using a separate statuslight for this. That would also solve the problem.

[daschuer]

Thank you for confirming that it is nothing wrong in your code. Maybe one with a more recent QT version can confirm if it has been fixed with QT 5.15.

A new widget that combined both indicators would be nice. However it affects the skins. Not suitable for a beta. It would be welcome for main though.

Is the glViewport workaround easy enough or should we just merge this workaround here?

[m0dB]

I think the glViewport workaround would be easy enough but still it would be a bit of a hack and it would make the code more dirty (it would not just be calling glViewport, but also conditionally clearing the background transparently I think), so I think your solution of using a 2 pixel high image in the skin is a better option. (I didn't check the png you provided, but if the bottom row is transparent, it should like exactly the same as before)

I would however add a check in the code so at least we show a warning when a 1-pixel height (or width I guess) is being created, so skin creators don't lose time figuring out why some widget is not being shown.

On a side note, when looking the skin xml, I noticed the tooltip of the audio latency vu meter is wrong.

[daschuer]

The tooltip is already fixed here: #11598

I had no luck with a transparent line in the background image, because black is shining through not gray.
I will verify it again and also add the skin warning.

[m0dB]

Hm, if the transparency shows black, this indicates that the background color is not determined correctly by

m_qBgColor = mixxx::widgethelper::findBaseColor(this);

If you confirm this is the case, I can debug that.

[daschuer]

With the border halve transparent and 200 % it looks like this:

[daschuer]

With QOPENGL=OFF

[daschuer]

And finally with --disable-vumetergl

[daschuer]

The issue is that in shade the background is a png, not a brush. The dark gray color is the backround color used before the background png is rendered. I don't think there is a big demand to fix that, we just need to look for another workaround here.

[daschuer]

Using the background color instead of transparent works:

[daschuer]

Now it looks exactly like before.
I have the fix for #11600 in my stash as well and added it here.

[daschuer]

Superseded by #11722

[daschuer]

I can confirm that this fixes the Shade issues on Ubuntu Jammy as well.
@m0dB should we merge this and carry on?

[m0dB]

LGTM! Merged. Thanks for taking care of this!