[bonninr]

The right-click part of #474. On a phone or tablet a finger held still for half a second opens what a right-click opens: a stop's or piston's MIDI menu on the drawn console, a shoe's mapping, the page's own menu on the background, and an element's MIDI window on a generated panel. Android reports every press as the left button, a mouse's too, so a right-click never arrived there.

• A stop or switch changes as the finger lifts, so a finger held on it opens the menu and leaves it as it was. A finger that slides off leaves it alone.
• A piston fires on the press as before; a long press lets it go and opens its menu.
• Keys play on the press and hold their note however long the finger stays.
• On a generated panel, a fader's name takes the long press; its track moves with the finger as before.
• With a mouse, everything works as before: a click draws a stop on the press.

MASTERPIECE_TOUCH=1 turns the same handling on with a mouse on a desktop, which is how it was checked.

Checked in the program on Windows, GrandOrgue demo, MASTERPIECE_TOUCH=1:

Action	Result
Press on Montre 8	stays in while the button is down
Release	Montre 8 drawn
Hold on Prestant 4 for 0.9 s	its MIDI menu opens: "Prestant 4'", "Not mapped", "MIDI window...", "Learn"
Release after the menu	Prestant 4 still in
Same hold without the variable	Prestant 4 drawn on the press, no menu

New test functional.ui.touch-long-press: a tap, a long press, a slide off and a small tremble, on the drawn console and on a generated panel's cell, and a mouse click unchanged. mp_tests --no-perf: 301 run, 0 failed.

Still to check on an Android device: the long press with a finger and with a mouse. The combination window's pistons and the expression bar's shoes keep the right-click only for now.