Greeter wallpaper glitch before login

[Sean Haugh]

Setting the wallpaper to an image with dimensions different from my screen resolution causes pantheon-greeter to create extra white space around the image briefly before logging in. The image is correctly displayed before and after logging in, with the bug only occurring in between.

[Vishal Rao (vishalrao)]

I experience similar issue with HiDPI enabled, wallpaper scaling issue, it shows a 2x2 grid of scaled down wallpaper.

I tried fiddling with the code and attaching diffs for scaling wallpaper if anyone wants to review test.

[Vishal Rao (vishalrao)]

Adding other diff , sorry for the multiples.

[Vishal Rao (vishalrao)]

Pastebins:

https://paste.ubuntu.com/23953995/

and

https://paste.ubuntu.com/23953996/

(although i dont know how long these will be preserved)

[Vishal Rao (vishalrao)]

Proposed a merge here: https://code.launchpad.net/~vishalrao/pantheon-greeter/fix-login-wallpaper-glitch/+merge/316812

Although, my patch addresses my hidpi scenario (scale factor > 1) and my wallpaper aspect is same as my monitor aspect of 16:9

This bug is occurring likely due to aspect ratio mismatch between wallpaper and monitor and/or mismatch in greeter scaling (fit to screen) versus gala desktop wallpaper scaling method (fit, zoom, scale, stretch).