Hi Anders, what about using an easier hotkey combo. Personally I use alt-z to toggle zoom (just set it as a hotkey for gnome's inbuilt desktop zoom found in the keyboard hotkey section). Alternatively, in the extension you're writing, you can use Alt-z/Super-z for zoom in/out. The keys are right next to each other, making them alot easier to press than shift-alt-a.
On 5 January 2018 at 07:00, <gnome-shell-list-requ...@gnome.org> wrote: > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 4 Jan 2018 15:14:33 +0100 > From: Anders Rillbert <anders.rillb...@kutso.se> > To: gnome-shell-list@gnome.org > Subject: Globally grab mousewheel scroll events > Message-ID: > <CAB2t-4x8jBxodbpsO3QCVrc0XiQ1ORtMGcUFL0R= > vk_5zp_...@mail.gmail.com> > Content-Type: text/plain; charset="utf-8" > > Hi. > > Being a visually impaired coder, a 'killer feature' for me is the ability > to zoom the desktop in/out using the mouse wheel together with a modifier > key such as <shift>, <ctrl> or similar. This functionality is supported by > the 'Enhanced Desktop Zoom' feature in compiz-based desktops and by OSX > out-of-the box (not in Windows however...). > > Currently this is not supported in a gnome-shell/wayland environment such > as Ubuntu 17.10 so I thought I might take a stab at implementing this. I am > however completely new to the whole gnome ecosystem so I have spent a > couple of days trying to read-up on relevant concepts such as Wayland, > Clutter, Mutter, Gjs, gnome-shell, etc. > > The main technical problem seems to be how to globally grab the > Clutter.EventType.SCROLL events when a modifier key is pressed and I would > be thankful for all help and pointers to the best way to accomplish this > (if possible). > > My research so far seems to indicate the following: > > 1. There is a gnome-shell extension written in Vala by Tobias Quinn ( > https://github.com/tobiasquinn/gnome-shell-mousewheel-zoom) that > accomplishes what I want but as I understand it, it requires gnome-shell to > run under X and not Wayland. > 2. It is possible to globally grab key combinations from within a > gnome-shell extension using the 'accelerator-activated' signal like this: > global.display.connect('accelerator-activated',... > (see > https://stackoverflow.com/questions/12325405/gnome- > shell-extension-key-binding#42466781 > for the source of this) > 3. I have not succeeded in receiving scroll events when connecting to the > 'scroll-event' or 'captured-event' signals on 'high-level' actors such as > global.stage or Main.layoutManager.uiGroup. My guess is that the scroll > events are routed directly to the actor under the mouse cursor and > swallowed by them, thus not propagated upwards in the scene graph. > 4. The Magnifier included in the gnome-shell uses a number of 'special' > techniques to accomplish its task > - to follow the mouse it gets hold of a 'CursorTracker' that Mutter > provides. (in src/meta/meta-cursor-tracker.h) but the CursorTracker only > seems to care about pointer position and not about scroll events. > - to register global listeners for 'focus change' and 'caret change' it > uses the Atspi library but I haven't had the time to try to see if this > library also supports a global listener for scroll events. > > The best hypothesis I have come up with so far is to emulate the behaviour > of the SwitcherPopup and write a gnome-shell extension that: > - globally captures a key combination > - implement an invisible actor that covers the whole screen and 'pops up' > when the key combination above is captured (and destroyed when the keys are > released). > - use the scroll-events that are received by the invisible actor to change > the magnification factor for the magnifier in 'real time'. > > If the above would work, a draw-back would be that I can't just press > <shift> and scroll but have to press a valid accelerator combo (e.g. > <ctrl>+<shift>+'a' or similar) which would make it less ergonomical and > swift. > > So, any ideas about how to accomplish a global grab of mousewheel scroll > together with a single modifier key? > > Regards > /Anders > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <https://mail.gnome.org/archives/gnome-shell-list/ > attachments/20180104/ed50b7c9/attachment.html> > > ------------------------------ > >
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