message: Use `mSlideBar.contains` to check range during thumb drag
  Inverting the nesting of the `if` check means we can use a single check
  for both `SliderType::Vertical` and `SliderType::Horizontal`.
diff: @@ -205,25 +205,18 @@ void Slider::onMouseMove(int x, int y, int /*dX*/, int /*dY*/)
  if (!enabled() || !visible()) { return; }
  if (!mThumbPressed) { return; }
  - if (mSliderType == SliderType::Vertical)
  + if (mSlideBar.contains({x, y}))
  {
  - if (y < mSlideBar.y || y > (mSlideBar.y + mSlideBar.height))
  + if (mSliderType == SliderType::Vertical)
  {
  - return;
  - }
  -
  value(mMax * (y - mSlideBar.y) / mSlideBar.height);
  }
  else
  {
  - if (x < mSlideBar.x || x > (mSlideBar.x + mSlideBar.width))
  - {
  - return;
  - }
  -
  value(mMax * (x - mSlideBar.x) / mSlideBar.width);
  }
  }
  +}
  void Slider::logic()
  