Once in a while (maybe once every second or third day of heavy minecraft use across the whole family), the keyboard gets stuck in some mode so that when typing in the text window of the creative inventory or the cheat command prompt, the keys 'a', 'c', (and a few 2 or 3 others) do not input the requested letters, but rather highlight the existing inputted text blue and underline it, and subsequent keystrokes (any letter) clear all inputted text and start anew. This makes it impossible to type any word containing these letters. See these screenshots:
It only affects a few keys (a,c, ...?), so some words can be typed correctly, but many important ones cannot, eg "bars" or "/say". In game-play mode, the 'a' key does cause player to strafe left as expected; only text input is affected. Quitting the world and reloading it does not resolve the problem (and quitting the world and loading different world, the problem persists), but quitting the world and quitting minecraft and relaunching it does cause the keys to input text correctly. I cannot reproduce the behavior reliably, though it occurs fairly often. It feels like some kind of "shift lock", or modifier lock, but repeatedly hitting shift or toggling CAPS LOCK does not resolve the issue. Alt-tabbing to a text editor, all keys work normally (so it seems to be confined to the minecraft application). And even exiting a minecraft world and typing the name of a "create new world", the keys work correctly. But upon entering a new world, the 'a', 'c' keys in creative inventory or command line will still produce highlighted underlines instead of the letters 'a' or 'c', unless I completely exit Minecraft and relaunch.
I have seen this issue occur on three different computers. All three were 64bit Macs (so this may be a mac specific issue?) running Mac OS X 10.10.1 or 10.10.2, running Apple Java 1.6 or Oracle Java 1.8 64bit, using internal laptop keyboards or external third party PC keyboards. All were running Minecraft 1.8.1 with launcher 1.6.11.
Hopefully I'm being dumb, and this is a supported keyboard mode that I can escape out of with a simple keystroke. Clue me in?
The full list of keys which seem to fail when the keyboard is stuck is: a, x, c, and v. Pressing x and c appear to do nothing, pressing a changes text to underlined and blue, while pressing v sometimes seems to do nothing, other times seems to put a bunch of junk after your entered text.
At this point, it is perfectly clear what is going on: the modifier key is locked in the on state, so instead of typing a, x, c, v, I'm selecting all text, cutting, copying, and pasting text, respectively. The Minecraft keyboard gets in this state when I alt-tab to another application, and then alt-tab back to minecraft. Since Minecraft doesn't have keyboard focus, it never gets updated that the modifier key was released.
This problem would only occur on a Mac, I guess, since the modifier key on a Mac for alt-tabbing is the same as for copy/paste. On a Mac alt-tab is actually command-tab, and copy/paste/cut/select-all hotkeys are cmd-c/cmd-v/cmd-x/cmd-a. On a Windows PC the modifier key for those is control, not alt, so this issue would not occur (might trick Minecraft into getting alt-locked, but I guess the alt key is not used in Minecraft so no effect).
Anyway, the issue is easily fixed on a Mac whenever it occurs by just pressing command again one time in the Minecraft application.
Mojang's bugtracker has a bug open for a related issue, MC-3643, which is about the keyboard getting stuck in some mode where a single keystroke of backspace deletes an entire word instead of a single char, and another mode where a single keystroke of backspace deletes an entire line. And apparently yet another symptom of being stuck in this keyboard mode is that the Q key throws an entire stack of items instead of a single stack. And This comment mentions the issue of the copy/paste keys on a Mac.
http://i.imgur.com/WA6AtKS.png
http://i.imgur.com/42ucyo3.png
It only affects a few keys (a,c, ...?), so some words can be typed correctly, but many important ones cannot, eg "bars" or "/say". In game-play mode, the 'a' key does cause player to strafe left as expected; only text input is affected. Quitting the world and reloading it does not resolve the problem (and quitting the world and loading different world, the problem persists), but quitting the world and quitting minecraft and relaunching it does cause the keys to input text correctly. I cannot reproduce the behavior reliably, though it occurs fairly often. It feels like some kind of "shift lock", or modifier lock, but repeatedly hitting shift or toggling CAPS LOCK does not resolve the issue. Alt-tabbing to a text editor, all keys work normally (so it seems to be confined to the minecraft application). And even exiting a minecraft world and typing the name of a "create new world", the keys work correctly. But upon entering a new world, the 'a', 'c' keys in creative inventory or command line will still produce highlighted underlines instead of the letters 'a' or 'c', unless I completely exit Minecraft and relaunch.
I have seen this issue occur on three different computers. All three were 64bit Macs (so this may be a mac specific issue?) running Mac OS X 10.10.1 or 10.10.2, running Apple Java 1.6 or Oracle Java 1.8 64bit, using internal laptop keyboards or external third party PC keyboards. All were running Minecraft 1.8.1 with launcher 1.6.11.
Hopefully I'm being dumb, and this is a supported keyboard mode that I can escape out of with a simple keystroke. Clue me in?
At this point, it is perfectly clear what is going on: the modifier key is locked in the on state, so instead of typing a, x, c, v, I'm selecting all text, cutting, copying, and pasting text, respectively. The Minecraft keyboard gets in this state when I alt-tab to another application, and then alt-tab back to minecraft. Since Minecraft doesn't have keyboard focus, it never gets updated that the modifier key was released.
This problem would only occur on a Mac, I guess, since the modifier key on a Mac for alt-tabbing is the same as for copy/paste. On a Mac alt-tab is actually command-tab, and copy/paste/cut/select-all hotkeys are cmd-c/cmd-v/cmd-x/cmd-a. On a Windows PC the modifier key for those is control, not alt, so this issue would not occur (might trick Minecraft into getting alt-locked, but I guess the alt key is not used in Minecraft so no effect).
Anyway, the issue is easily fixed on a Mac whenever it occurs by just pressing command again one time in the Minecraft application.
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It is quite annoying, I admit
Mojang's bugtracker has a bug open for a related issue, MC-3643, which is about the keyboard getting stuck in some mode where a single keystroke of backspace deletes an entire word instead of a single char, and another mode where a single keystroke of backspace deletes an entire line. And apparently yet another symptom of being stuck in this keyboard mode is that the Q key throws an entire stack of items instead of a single stack. And This comment mentions the issue of the copy/paste keys on a Mac.