Could you describe in more detail what changed?

Also, is it the F11 type of full screen, or the click-the-button-on-the-video kind of full screen?

in Version 54 after going in full screen mode by pressing F11 Key, then minimize the window by pressing (Windows key + Down Arrow ), then restoring the window by clicking on the taskbar icon the window restore in the same full screen state as it was before minimizing.

in version 55 and above after going in full screen mode and minimizing the window by pressing (Windows key + Down Arrow ) the window exit full screen mode insted of minimizing, although its work fine by clicking on the minimize button on the title bar, and then by clicking on the task bar icon it restore in full screen mode.

Thanks. I can't quite figure it out.

I seem to get this:

Start with a resizable window:

• F11 => Full screen
• Win + Down => minimized
• Use toolbar button to restore => Full screen

Start with a maximized window:

• F11 => Full screen
• Win + Down => maximized

I can't think of a reason for Win + Down to cancel full screen for a full-screened maximized window, but minimize a full-screened resizable window.

I am not aware of any Firefox setting to change it.

Maybe another volunteer will have an idea.

Nothing mentioned about full screen changes in Firefox Version 65 Release Notes. Maybe the best way to find out what have been changed is taking a look at the source code wich is beyond my scope, maybe if the source code available on github its easier for me to see the changes, i'm aware of the compressed source code file download on the ftp.mozilla.org but is the source code available on github ?

thank you for taking the time to help me and others, you already helped me alot over the past 5 year by solving other peaple problems, your answers always the best.

Thank you for your kind comments. If you have a fast, high-bandwidth internet connection, you could explore further using a tool called mozregression. It loads temporary copies of the nightly version of Firefox from different points in time to triangulate the exact day with the change, and then possibly to the specific patch. Since you need to test the feature on each version, the time can add up; maybe 20-30 minutes?

https://mozilla.github.io/mozregression/

Using mozregression, testing 29 different build (1.81 GB) (60 Minutes) finally it ends with good results.

Mozregression Build selection: Last Known good build: 64 (release) First known bad build: 65 (release)

Mozregression Log: DEBUG : Found commit message: Bug 1482920: Force fullscreen window position. r=jmathies Differential Revision: https://phabricator.services.mozilla.com/D13042

Comment from the differential revision page above that explains the new added code wich is the cause of the new full screen behavior: Force fullscreen. This works around a bug in Windows 10 1809 where using fullscreen when a window is "snapped" causes a spurious resize smaller than the full screen, see bug 1482920.

Thank you so much for your help.

Wow, great work. Are you going to file a bug? Maybe you already did.

thanks.

hmmm.. reporting a bug about a bug workaround for microsoft bug! :)

as its hard for me to write in english since its not my language, also i'm currently using temporary mozilla account, reporting a bug better to be done by someone else with more experience and also it might helps to build their account reputation or as i know for some its just makes them feels good that they have find or reporting a bug.

there is another problem that the newly added code for the "microsoft bug workaround" is causing, i use a script that moves and resize the full screend window to the secondary monitor wich is higher resolution and the window need to be resized, the problem now is the window won't resize.

if this need to be reported, please take the time to do so, thank you.

i'm sure reporting a bug requires following certain rules and a good explanation of the problem and being active to reply which i can't do right now, currently doing backup getting ready for a new clean OS setup, which is a mess right now so i had to use a temporary email service to create this mozilla account, with all my respact sir, you are one of the reasons that i dont have a mozilla account, never had to ask anything you already answerd all the questions and solved all the problems, maybe i need to create one just to hit the yes button of "Was this helpful to you?" of your answers! :)

I didn't like using two monitors, so my experience with that configuration was only for a few days a couple years ago. Hopefully someone else who can test on a multi-monitor setup can pursue it.