Desktop Zoom passes through scrolling (5-year-old issue)

Distribution

Linux Mint 22 Cinnamon 6.2.9 6.8.0-51-generic

Package version

Cinnamon 6.2.9

Graphics hardware in use

AMD Ryzen 9 7940HS w/ Radeon 780M Graphics × 8 / Advanced Micro Devices, Inc. [AMD/ATI] Navi 33 [Radeon RX 7700S/7600/7600S/7600M XT/PRO W7600]

Frequency

Always

Bug description

Desktop Zoom enabled in Accessibility > Enable zoom.

Mouse wheel modifier -> Any of the options (try Super, then Shift).

Hold modifier and scroll with either a mouse or the touchpad. Zoom works.

Actual Behavior:
The application under the mouse pointer scrolls vertically (when modifier is Super).
The application under the mouse pointer scrolls horizontally (when modifier is Shift), if such application supports horizontal scrolling.

Ideal fix:
Capture the scroll events when the Zoom's "Mouse wheel modifier" is pressed, so that they only zoom the screen and not scroll the underlying application.

Alternative fix:
Give us a way to disable Shift-scroll to scroll horizontally (I've looked and cannot find one), then we could use Shift as the modifier.

Impact:
This is hard on low vision users because we use zoom constantly. When the underlying application scrolls while zooming, this makes it very difficult to use.

Steps to reproduce

1. Enable Desktop Zoom.
2. Set a "Mouse wheel modifier" to any of the modifiers.
3. Zoom in and out using the modifier and either the mouse wheel or the touchpad scroll gesture. The zoom itself does work.
4. Do the zoom in / out gesture while the pointer is over an application window that supports scrolling. It does not matter what application it is; if it supports scrolling, it will scroll:

• horizontally, if the modifier is Shift
• vertically, if the modifier is Super
• zoom in and out in the application in addition to the screen, if the modifier is Control and the application is a browser or possibly Electron-based app
• possibly do something else, if the modifier is Alt

Expected behavior

The application under the mouse pointer does not scroll vertically (when modifier is Super).
The application under the mouse pointer does not scroll horizontally (when modifier is Shift).

Additional information

Please try to capture the zoom action. I did find another issue on this, but it is 5 years old and still has not been addressed, hence I feel it's been forgotten and hence I'm opening a new issue. Hoping the new bug issue template might help it get into the backlog more easily.

Start by locating Cinnamon's Desktop Zoom implementation and the handling of mouse-wheel and touchpad scroll events. Reproduce the issue with each configured modifier over a scrollable application, then verify that zooming no longer passes scrolling through to the application.