D8388: Do not hardcode unhovered windows brightness on present windows effect

Zren added inline comments.

INLINE COMMENTS

> presentwindows.cpp:317
>          else if (!isInMotion && w->isDesktop())
> -            winData->highlight = 0.3;
> +            winData->highlight = m_unhoverBright;
>          else

There's code in `PresentWindowsEffect::postPaintScreen()` that fires if it's using the magic number `0.3`.

  if (i.value().highlight != 0.3)

`winData->highlight` is used to tell us how far into a "scale + brightness" tween we're in.

  data.multiplyBrightness(interpolate(0.4, 1.0, winData->highlight));

  const qreal scale = interpolate(1.0, tScale, winData->highlight);
  tx = qRound((tx-rect.x())*winData->highlight);
  ty = qRound((ty-rect.y())*winData->highlight);
  rect.setWidth(rect.width()*scale);
  rect.setHeight(rect.height()*scale);

So it controls more than just the brightness.

We could change the code to:

  data.multiplyBrightness(interpolate(m_unhoverBright, 1.0, winData->highlight));

Which I know works: https://www.youtube.com/watch?v=QEHC43zMIMc#t=6m00

REPOSITORY
  R108 KWin

REVISION DETAIL
  https://phabricator.kde.org/D8388

To: salvacorts, #kwin, #vdg, #plasma
Cc: Zren, muratcileli, zzag, graesslin, ngraham, kwin, #kwin, mkulinski, ragreen, jackyalcine, Pitel, iodelay, bwowk, ZrenBot, lesliezhai, ali-mohamed, hardening, jensreuterberg, abetts, sebas, apol, mart