qtile / qtile / 6686159547

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Build Type

push

github

Committed by web-flow

Commit Message

Add implicit pointer grabs in Wayland. (#4540)

* Add implicit pointer grabs in Wayland.

A Wayland client expects to receive pointer motion events from the time
a button is pressed until it is released, even if the pointer leaves the
client's surface while the button is held.  This is crucial for
scrollbar functionality: a scrollbar should continue to drag even if the
pointer leaves the window.  This does not currently work in qtile.  For
instance, in Chrome, if you drag the scrollbar, move the mouse off the
Chrome window, release the button, then move the pointer back onto the
Chrome window, Chrome will resume scrolling without any button press.

In X11, this functionality is implemented on the client side using
XGrabPointer or XIGrabDevice.  Wayland provides no such mechanism: this
behavior must be implemented in the compositor.  This does not seem to
be well documented.  However, if you look in gdk_wayland_device_grab in
the gtk source, you'll see that grabbing the pointer in GDK is basically
a no-op: it does some internal accounting and changes the cursor, then
simply assumes the pointer is already grabbed.

Implicit grabs are implemented in Sway (see
sway/sway/input/seatop_{default,down}.c), although that's not what
they're called.  In short, pressing a button on a client surface
switches the cursor handling code into "down" mode, which short-cuts
most of the WM pointer processing logic and sends events directly to the
client, until the button is released.  (This is part of a more general
mechanism in Sway: pointer events can be processed in several modes,
e.g. for moving floating windows.)

This commit implements basic implicit grabs in qtile Wayland, following
what Sway does (functionally, not structurally).  Pressing a button
creates an ImplicitGrab object in the Core; releasing the button
destroys it.  While the ImplicitGrab object is alive, all pointer
events (button, {absolute_,}motion, axis) are sent direct... (continued)

Run Details

12 of 52 new or added lines in 1 file covered. (23.08%)

1 existing line in 1 file now uncovered.

14580 of 19702 relevant lines covered (74.0%)

3.95 hits per line