backend: dummy: do not leak owned pixmaps

[absolutelynothelix]

fix a typo and an issue reported by xrescheck:

$ xrescheck.sh -p resource_leaked -r -t xcb_composite_named_windows_pixmaps,xcb_pixmaps ~/Work/picom/build/src/picom --backend=dummy
? xrescheck 0.0.1 is here!
[ 06/13/2023 00:05:55.378 session_init INFO ] Switching to log file: /home/helix/.local/state/picom.log
? checking for leaked resources...
! 0x3200027 allocated by xcb_composite_name_window_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/win.c:326
	/home/helix/Work/picom/build/../src/win.c:573
	/home/helix/Work/picom/build/../src/picom.c:1670 (discriminator 2)
! 0x320002b allocated by xcb_create_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/x.c:599
	/home/helix/Work/picom/build/../src/backend/backend_common.c:212
	/home/helix/Work/picom/build/../src/backend/backend_common.c:302
! 0x320002f allocated by xcb_composite_name_window_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/win.c:326
	/home/helix/Work/picom/build/../src/win.c:573
	/home/helix/Work/picom/build/../src/picom.c:1670 (discriminator 2)
! 0x3200033 allocated by xcb_create_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/x.c:599
	/home/helix/Work/picom/build/../src/backend/backend_common.c:212
	/home/helix/Work/picom/build/../src/backend/backend_common.c:302
! 0x3200037 allocated by xcb_composite_name_window_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/win.c:326
	/home/helix/Work/picom/build/../src/win.c:573
	/home/helix/Work/picom/build/../src/picom.c:1670 (discriminator 2)
! 0x320003b allocated by xcb_create_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/x.c:599
	/home/helix/Work/picom/build/../src/backend/backend_common.c:212
	/home/helix/Work/picom/build/../src/backend/backend_common.c:302
! 0x320003f allocated by xcb_composite_name_window_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/win.c:326
	/home/helix/Work/picom/build/../src/win.c:573
	/home/helix/Work/picom/build/../src/picom.c:1670 (discriminator 2)
! 0x3200043 allocated by xcb_create_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/x.c:599
	/home/helix/Work/picom/build/../src/backend/backend_common.c:212
	/home/helix/Work/picom/build/../src/backend/backend_common.c:302
! 0x3200047 allocated by xcb_composite_name_window_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/win.c:326
	/home/helix/Work/picom/build/../src/win.c:573
	/home/helix/Work/picom/build/../src/picom.c:1670 (discriminator 2)
! 0x320004b allocated by xcb_create_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/x.c:599
	/home/helix/Work/picom/build/../src/backend/backend_common.c:212
	/home/helix/Work/picom/build/../src/backend/backend_common.c:302
! 0x320004f allocated by xcb_composite_name_window_pixmap_checked wasn't freed, the allocation was made here:
	/home/helix/Work/picom/build/../src/win.c:326
	/home/helix/Work/picom/build/../src/win.c:573
	/home/helix/Work/picom/build/../src/picom.c:1670 (discriminator 2)

[codecov]

Codecov Report

Merging #1022 (223872b) into next (5b6f6ec) will increase coverage by 0.01%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##             next    #1022      +/-   ##
==========================================
+ Coverage   37.58%   37.59%   +0.01%     
==========================================
  Files          49       49              
  Lines       11155    11160       +5     
==========================================
+ Hits         4193     4196       +3     
- Misses       6962     6964       +2     

Impacted Files	Coverage Δ
src/backend/dummy/dummy.c	65.78% <60.00%> (-0.41%)	⬇️

[absolutelynothelix]

it works kinda weird with the root back pixmap and i can't figure out why 🤔

[yshui]

it works kinda weird with the root back pixmap

how weird?

[absolutelynothelix]

how weird?

iirc,

1. do watch -n1 xprop -root _XROOTPMAP_ID;
2. start and stop picom with backend other than dummy a few times and observe that the root back pixmap always binds successfully and it's id changes;
3. start picom with dummy backend once and observe that the root back pixmap binds successfully but it's id lefts unchanged;
4. start picom with dummy backend a few times and observe that the root back pixmap always fails to bind and it's id lefts unchanged;
5. go back to step 2.

do you have any ideas what could cause such behavior? i didn't have much time to investigate when i encountered this issue.

btw, i'm alive, just a bit short on time. i should be able to dedicate a lot of time to picom soon 🙂

[absolutelynothelix]

i have an idea! looks like it's about pixmap ownership controlled by the owned parameter when binding one.

[absolutelynothelix]

i have an idea! looks like it's about pixmap ownership controlled by the owned parameter when binding one.

exactly. now the fix is complete.