implement eraser using PorterDuff Xfer mode

[bizzguy]

This requires a bump for minimum SDK from 9 to 11 because of the View setLayer method. This commit also has a bunch of changes to the layouts that occurred just because of reformatting.

Erases get added to undo/redo stack properly.

Also tested with screen rotation.

[RiccardoMoro]

Thanks (again) for the pull request!
I'm reviewing this in a few days, this weekend max

[RiccardoMoro]

I'm having a problem on KitKat and below, the eraser seems to be painting black instead of actually canceling the previous paint

[RiccardoMoro]

But when I take the "screenshot" of the draw, the erased content is rendered correctly even on KitKat-

[RiccardoMoro]

Also, if you add just a dot, it's rendered with the paint, instead of erasing

[bizzguy]

I was having a similar problem (painting in black) until I added the "setLayer" command which solved it for API 21 and above. I'll try to do some more testing on KitKat and see what I can find. This is turning out to be harder than I thought. There is another approach - specify a background color and then paint in the background color for erase. This might be more robust than the Xfer mode approach. I'll try again. Thanks Jim

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On Tue, Apr 18, 2017 at 4:54 AM, Riccardo Moro ***@***.***> wrote: Also, if you add just a dot, it's rendered with the paint, instead of erasing — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#12 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAUn0u9uqFX_O6wfVOSIaSHfjqmwZQrtks5rxIhlgaJpZM4M8dgp> .

[rajajawahar]

If we add a background for the image, the above trick won't work..

[RiccardoMoro]

@rajajawahar correct..

[rajajawahar]

Is there a way we can remove the HistoryPath when user in EraserMode..
Something like that.. I was trying to acheive it.. But it din't worked at all..
Can you help me out for eraser.. If I add Image to the view from Gallery or Camera..