Selection versus highlighting

Selection and highlighting are visual clues to identify and prepare nobs for a command to be applied to them.

Simple rule:
 * Highlight - Single nob
 * Selection - Multiple nobs

In detail: Highlighting and selections are as far as possible orthogonal. That means, they are independant of each other and can be combined, without influencing each other. For example, a selection can be moved as a whole, which is a typical application of selections. But in presence of a selection, single nobs can be moved individually by highlighting them. This holds true for member nobs of the selection as well as for nobs not belonging to the selection.
 * Only one nob can be highlighted at a time. Although it is possible to have only one knob selected, the purpose of a selection is to mark several knobs.
 * Highlighting happens automatically as soon as the mouse cursor is over a knob. Selection has to be explicitely caused by the user.
 * The highlighting of a nob automatically disappears if the mose cursor is no longer over the knob. A selection stays active until the user explicitely stops it.
 * Selections are visualized by orange interiors. Highlighted nobs have light green edges.