[Bug 2026228] Re: gnome-control-center crashed when switching to mirror mode and monitors don't have matched resolution

[Jeremy Bícha]

** Description changed:

  [Impact]
  gnome-control-center crashed when switching to mirror mode and monitors don't have matched resolution
  
  [Test case]
  Mirror mode is only an option if there are only 2 monitors connected even if one monitor is disabled. A laptop's internal screen counts as one of the monitors.
  
- 1. Connected monitors to system which don't have same resolution.
+ This particular bug requires two screens that have a screen resolution
+ that they don't both share. (See comment 12 for an example).
+ 
+ 1. Connect the monitors
  2. Open the GNOME Settings app (gnome-control-center)
  3. On the left sidebar, click Displays to switch to the Display panel
  4. Switch to mirror mode
  3. gnome-control-center won't crash
  
  [Where problems could occur]
- It only modified the code related to mirror mode in Displays panel. For KK and LL check variable (best_mode) before using it. For Jammy, modified the way to find cloning mode and check the variable (best_mode) . The second patch already included in gnome-42. The risk will be low.
+ This only modifies the code related to mirror mode in Displays panel.
+ 
+ For Lunar, check variable (best_mode) before using it. This patch is
+ backported from GNOME 45 Alpha.
+ 
+ For Jammy, include the Lunar patch and modify the way to find cloning
+ mode. This second patch is backported from gnome-control-center 42.
  
  [Other info]
  Two Merge Request are related
  1. Check best_mode exist before adding flag (https://gitlab.gnome.org/GNOME/gnome-control-center/-/merge_requests/1835)
  2. Use virtual clone modes when mirroring  (https://gitlab.gnome.org/GNOME/gnome-control-center/-/merge_requests/1376)

** Changed in: gnome-control-center (Ubuntu Lunar)
       Status: Confirmed => In Progress

** Changed in: gnome-control-center (Ubuntu Jammy)
       Status: New => In Progress

** Changed in: gnome-control-center (Ubuntu Jammy)
     Assignee: (unassigned) => Dirk Su (dirksu)

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https://bugs.launchpad.net/bugs/2026228

Title:
  gnome-control-center crashed when switching to mirror mode and
  monitors don't have matched resolution

Status in OEM Priority Project:
  Confirmed
Status in gnome-control-center package in Ubuntu:
  Fix Released
Status in gnome-control-center source package in Jammy:
  In Progress
Status in gnome-control-center source package in Kinetic:
  Won't Fix
Status in gnome-control-center source package in Lunar:
  In Progress

Bug description:
  [Impact]
  gnome-control-center crashed when switching to mirror mode and monitors don't have matched resolution

  [Test case]
  Mirror mode is only an option if there are only 2 monitors connected even if one monitor is disabled. A laptop's internal screen counts as one of the monitors.

  This particular bug requires two screens that have a screen resolution
  that they don't both share. (See comment 12 for an example).

  1. Connect the monitors
  2. Open the GNOME Settings app (gnome-control-center)
  3. On the left sidebar, click Displays to switch to the Display panel
  4. Switch to mirror mode
  3. gnome-control-center won't crash

  [Where problems could occur]
  This only modifies the code related to mirror mode in Displays panel.

  For Lunar, check variable (best_mode) before using it. This patch is
  backported from GNOME 45 Alpha.

  For Jammy, include the Lunar patch and modify the way to find cloning
  mode. This second patch is backported from gnome-control-center 42.

  [Other info]
  Two Merge Request are related
  1. Check best_mode exist before adding flag (https://gitlab.gnome.org/GNOME/gnome-control-center/-/merge_requests/1835)
  2. Use virtual clone modes when mirroring  (https://gitlab.gnome.org/GNOME/gnome-control-center/-/merge_requests/1376)

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