majaha

Awesome, thanks! This bug has kept me awake at night for four years, looking forward to getting some much needed shut-eye tonight 👍

Yes, it's too late to try to fix old maps, but the mapping is still doubled up. The directions 0-3 are visually identical to directions 4-7, but are technically different e.g. comparators give different values (MC45892). This can still be fixed, e.g. by coercing the direction values to a set half the size.

I guess it's too late to prevent conversion problems, but the underlying bug can still be fixed.

Still affects 1.8
By the way, I filed my related bug as MC-68941.

Affects 1.8-pre3

Affects 1.8-pre2

Still affects 1.8-pre1

This still affects 14w34d.
Also, should we add some of the information from my earlier comment to this bug report? Or maybe split it into it's own report? It seems Mojang is getting ready to release 1.8 soon and this bug is going to break maps-in-item-frames in existing worlds.

This still affects 14w34c

I think the point is that there's a mismatch between what you think you've done to the inventory, and what has actually happened to it, rather than an exploit you could use in survival to cheat.

A very closely related problem: when upgrading from 1.7 to 1.8, Maps in Item Frames are rotated wrong. I believe this all has to do with the 1.8 feature of being able to rotate items in item frames by 45 degrees rather than 90. When 1.8 loads an item frame from 1.7, it multiplies the ItemRotation value by 2, thereby keeping most items at the same rotation angle. However, because maps still rotate by 90 degrees for every ItemRotation, maps come out rotated twice as much as they should be.
Ways to fix this: 1. When loading 1.7 item frames in 1.8, check if the item is a map and decide whether to multiply the ItemRotation by 2 accordingly. And keep ItemRotation in the range 0-3 for item frames with maps in them.
2. Redefine ItemRotation for item frames with maps in, so they are always in (0, 2, 4, 6).

P.S. This bug still affects 14w29b

Definitely related to mipmapping being turned off. You can see it only effects blocks a certain distance away, just like mipmapping. I took a closer look at a screenshot I took and it seems textures are mipmapped anyway even when the setting is turned off. Also, when I turn mipmapping up from off in the settings all the buttons turn white.

Actually, you can use pick block (bound by default to middle click) on an item to duplicate it, enchantments and all.

This is still a bug,I just checked in 14w18a. You have to jump whilst sprinting to see this. This is hardly a game breaking bug, but it's a bug non the less. I just updated this report to make it a bit clearer.

This still seems to effect 1.7.9, it's a pretty big bug. Renders the server exe useless, but running the server jar with java or javaw (see below) seems to work. This makes server setup on windows a bit less intuitive.
I wonder if this is related to MC-33041, which occurs when the server jar is run with javaw.

Still affecting 1.7.9 it seems!
Edit: I wonder if this is related to MC-38758

I'm no longer using the computer on which I found this bug, but on my laptop I cannot notice any such distortion in 14w08a or in 1.7 for which this bug was reported. As such I can't really comment at the moment on whether this is a concern for some computers/graphics in 14w08a.

This seems too deliberate to be a bug. Also, Jens commented about a fix in the future. With the new way transparency rendering is handled, is it time to revisit this?

Still effects 1.7 prerelease

I discovered this with "/give @p 0" which crashes the game. However, as they are replacing this functionality, is it really worth fixing?