Well, I thought it would be neat to have a transparent screen on my WP7 phone so I went and created a fully transparent 480x800 image and saved it as a PNG. Of course Zune software didn’t allow me to sync it with the phone (doesn’t support PNGs) so I renamed the image to JPG, which synced perfectly (shown as black image in the photo list).
I set the image as my lock screen image.
I now have a black lock screen on my phone, but whenever I touch the screen, the black fades away and reveals what’s beneath the lock screen (that’s when the lock screen is supposed to slide up a bit to hint the gesture to unlock).
Furthermore, it appears that this tap that hints the gesture also causes the reactivation of the app that was running (and deactivated) when the phone got locked. You can play a little game too… if you tap your finger fast enough to not let the lock screen fully reappear again, you can cause the app to fully reactivate (and continue to run)! I’ve got plenty of practice with this from my ZX Spectrum days so I managed to fully reactivate the official twitter app to load and refresh my timeline :) So what’s going on is the device is launching (and obviously terminating) the deactivated app each time you touch the lock screen?
I also noticed that sometimes the application bar from the deactivated app is displayed on my “transparent” locked screen even without touching it… I couldn’t figure out when this happens though.
Anyway, I’m enclosing my test transparent image here in case you’d want to give it a try.