>>> - Horizontal scroll by wheel is supported.
>>> - Moving text using mouse is supported.
>
>> Please explain how horizontal scroll by wheel is supported.
>> Also please explain how moving text using mouse is supported.
>
> Try something like this.
>
> (setq mouse-wheel-tilt-scroll t)
I tried this, but still it doesn't scroll horizontally
with the mouse wheel. It seems this feature expects the
mouse events mouse-6 and mouse-7, but scrolling the mouse wheel
produces mouse-4 and mouse-5.
FWIW, emacs uses the "original" (I think they started with XFree86?) bindings that treat up/down mouse wheel as mouse buttons 4/5, while left/right are 6&7, so this is working as (at least at one point in the past) intended. There might be a communication issue around "by wheel" here: are you using a mouse with a wheel that tilts to the left/right? I believe that's what the OP had in mind.
(There is some added complication here, in that windows and macos seem to use mouse-up/down/left/right, whereas the x11 code uses mouse-4/5/6/7. My current environment is a little odd, but it seems like gtk (ala emacs-pgtk) ise still using the numbers rather than the names.)
Poking around the internet suggests that the "standard" for horizontal roll-the-wheel-scrolling is to add shift to rolling the wheel (and this works in the couple apps that I tried). Emacs' mwheel.el doesn't currently do this, but it looks like it wouldn't be hard to add.
~Chad