Enabling mouse-wheel-mode binds two different mouse events, depending
on the operating system. The correct way to check for those events is
by checking mouse-wheel-up-event, as explained in the ELisp manual.
* test/lisp/mwheel-tests.el (mwheel-test-enable/disable): Check
mouse-wheel-up-event instead of mouse-4 to make the test work
irrespective of the platform it's running.
* lisp/mwheel.el (mouse-wheel--remove-bindings): Update call
signature to take no arguments. Doc fix.
(mouse-wheel--add-binding): Break out from...
(mouse-wheel-mode): ...here. Simplify by using above functions.
(mouse-wheel--installed-bindings-alist): New variable.
(mwheel-installed-bindings): Make obsolete.
(mwheel-installed-text-scale-bindings): Make obsolete.
* test/lisp/mwheel-tests.el (mwheel-test-enable/disable):
New test.
* test/lisp/mwheel-tests.el (mwheel-test--create-scroll-keys): Fix
binding mouse wheel with modifiers in buffer area, while ignoring them
for fringes, margins, etc. My previous change mistakenly ignored all
modifiers in `mouse-wheel-scroll-amount'.
* lisp/mwheel.el (mouse-wheel--create-scroll-keys): Fix test to
reflect the above.
* lisp/mwheel.el (mouse-wheel-mode): Bind unmodified 'mwheel-scroll'
on scroll bars, fringes, margins, header and mode line. (Bug#5557)
(mouse-wheel--create-scroll-keys): New helper function for
'mouse-wheel-mode'.
* test/lisp/mwheel-tests.el: New file.
