mouse events in black border around desktop area

[mviereck]

xpra v2.2-r17160 on debian 9

If running xpra --start-desktop and maximizing the client window, there can be a black area around the shown desktop if the vfb X server does not provide a matching resolution.

Mouse events (moving and clicks) in the black area should not do anything, but they happen to the outer border of the desktop.

Example: mouse click in black area above clock in xfce4-panel shows calendar, but this should only happen if I click directly on the clock.

Mouse movements in black area above the panel causes highlighting of nearest panel objects.

Not really a problem so far, just different from what I would expect.

[Antoine Martin]

Originally reported in #1656, see ticket:1656#comment:24.

If we swallow pointer motion events, there are some potential problems with seamless mode when the window size does not match its contents exactly: the virtual pointer could linger on the edge of the server side window - which could trigger unwanted behaviour.

[Antoine Martin]

example of black border around the window contents

[Antoine Martin]

there can be a black area around the shown desktop if the vfb X server does not provide a matching resolution.

This is less of a problem nowadays since you can:

• use Xvfb and have perfect match for any resolutions
• Xdummy now has a large set of pre-defined resolutions which should match all possible configurations with a maximum gap of 128 pixels

(converted link to an attachment so it doesn't bitrot)

[mviereck]

This happens rather with Xwayland than with Xvfb or Xdummy as it unfortunately does not support resolution changes with xrandr.

In seamless mode for single applications I do not expect an issue as they are always scaled up to the client screen resolution. In that case I am not able to move the mouse outside of the virtual desktop.

[Antoine Martin]

This happens rather with Xwayland than with Xvfb or Xdummy as it unfortunately does not support resolution changes with xrandr.

Then this is an unsupported configuration, we rely on randr to make things match. Use Xvfb instead.

[mviereck]

Use Xvfb instead.

For most things I use Xvfb or Xdummy. Xwayland has the advantage of supporting hardware acceleration, but the disadvantage of bad xrandr support.

Aside from this minor issue of mouse events at the edge in desktop mode, xpra works quite well with Xwayland. Also, xpra clients sets the window size right, the issue only appears if I maximize the window.

So far, it is fine for me, xpra handles Xwayland quite well.

[Antoine Martin]

Testing as per ticket:1656#comment:12

• I can only reproduce this bug by maximizing the window, so r19613 detects wayland / that randr doesn't work and the window is now made non-resizable, non-maximizable
• the non-opengl backends have problems rendering correctly with the offsets, new ticket: #1874
• r19615 fixes the pointer events issue: shadow and desktop servers discard events that land outside the vfb rather than clipping them (seamless servers are unchanged: the events may be outside the window but they will still land on the vfb so we still want them) - easier to test by patching check_randr_sizes to return True (just like #1874)

Still TODO:

• check win32 and macos shadow servers with multi-window mode (#1805) and check for regressions
• maybe handle the transition from discarded to not-discarded and back by sending cursor updates so that the client doesn't show the cursor that would apply if the pointer was still in the active region of the window? (ie: the edge of the window may have a resize handle, which is no longer relevant when hovering over the padding area since both motion and button events will be ignored there)

[Antoine Martin]

The cursor handling is "fixed" in r19621, though it does break the neat dependency separation from #1838.

Only one item left: re-test all the desktop and shadow servers with multi-window mode by hand. (#1805) Maybe use fullscreen to trigger more easily?

[Antoine Martin]

Was worth re-testing (I temporarily disabled size-hints to get black borders without using fullscreen or maximize): r19615 was buggy for the multi-monitor multi-window case (#1805), fixed in r20162.

I have not re-tested on macos shadow servers since that involves lugging too many things around. Those are similar to mswindows shadow servers anyway.

@mviereck: please close if this works for you. beta builds with these changes can be found here: https://xpra.org/beta

[Antoine Martin]

Not heard back, closing.

[Antoine Martin]

Related bug: #2249