Knobs with arcs

[zezic]

This PR makes it possible to draw the knob arcs programmatically.

XML example:

<KnobComposed>
  <Size>40f,40f</Size>
  <Knob>handle.svg</Knob>
  <BackPath>bg.svg</BackPath>
  <MinAngle>-135</MinAngle>
  <MaxAngle>135</MaxAngle>
  <ArcThickness>2</ArcThickness>
  <ArcColor>#ffffff</ArcColor>
  <ArcUnipolar>true</ArcUnipolar>
  <Connection>
    <ConfigKey>[Master],gain</ConfigKey>
  </Connection>
</KnobComposed>

where new nodes are:
ArcThickness, ArcColor and ArcUnipolar

Demo:

[ronso0]

nice one!
did you test it with color schemes?

[zezic]

It works well with variable-based theming, but it does not work with filters. Should I make it work with filters too?

[ronso0]

It would just be nice-to-have feature if the entire scheming could be done in one place... I don't mind, and i can't estimate the effort to make it work with filters.
Right now it's only Shade (and future skins ;) that would benefit from this change, and Shade's color schemes work mostly with filters.

Besides, we recently discovered a SVG filter issue in #2130

[zezic]

It was pretty easy to add (d3b4abf).

I will look into that issue later, maybe I will be able to track it down but at least, I think, it should not affect this particular PR.

[daschuer]

Thank you and welcome back. The changes are looking good to me.
Is this ready for merge?

[zezic]

Hi, @daschuer! Nice to see you.
Yes, it's ready for merge.

[daschuer]

I have just noticed that there is no KnobComposed section here:
https://www.mixxx.org/wiki/doku.php/creating_skins
If you like you can create one, including your new fetaue.

[ferranlala]

I opened a similar PR time ago. It might be worth checking for future directions on this topic.
For example how to handle knobs which should be unipolar sometimes but should not be other times, like the effect knobs.

#645

[ronso0]

While doing a quick test how to make the arcs fit LateNight in #2342 I found they transform (stretch) with the knob's background path rectangle, and <KnobCenterYOffset> is not respected, thus they're elliptical and displaced in LateNight which has knobs with 34 x 40px:

@zezic Do you have time to fix this?

[ronso0]

And, for the knob arc wishlist:

• It would be nice do draw a a background arc illustrating the span of the knob (like a groove), with width and color configurable separate from the 'position arc'.
• @Be-ing also mentioned a configurable center gap / highlight as hint for the default position. Right now this would only make sense for EQs, QuickEffect and Master/Headphone knobs where we have static default positions.

[zezic]

Hi, @ronso0
I'm able to implement all the things you mentioned above but I'm a bit busy at the moment.
What's a deadline for this?

[ronso0]

Nice. Aahhm, no deadline as this is no company ;)
It's just that several users asked for this to be included in the LateNight redesign #2342

My guess is that we can merge #2342 before the beta release, any minor skin changes can be added during beta period. Actually beta = feature freeze, and afaict this will be after #2345 is merged. I'm not sure if that rule can be bent for innocuous changes to the knob widget. Otoh that would unleash quite some potential for skin designers.

[Holzhaus]

@zezic Hey zezic, have you made any progress yet? The 2.3 release is finally getting closer 😉

[ronso0]

Hej @zezic !
I'm working on a daylight theme for LateNight and arcs would be a huge win for that.
So before I start wrapping my head around all that math going on for painting the arcs, I first want to check if you made any progress and if you might be able to tweak this for 2.3?

[zezic]

Hi, @ronso0!
Thank you for bumping that another time, as the issue has started to fade out in my TODO memory. I'm going to fix that today. Will link the corresponding PR here.

[ronso0]

Aahhm nevermind @zezic
I also started working on that because I was curious and wanted to add other features like

• optional, customizable background arc (width, color, cap shape)
• customizable cap shape for foreground arc?

Then I reworked the WKnobComposed a bit and moved some math from drawArc() to the setup(), maybe it needs a resizeEvent now.

I'll publish my branch maybe tomorrow I think.
Looks useable already:

[zezic]

Okay! I will not touch it then. Mixxx is on its way to the complete vector UI!

[Be-ing]

Mixxx has used all vectors since 2.1.