swapping ctrl and alt keys --- bug with alt-tabbing Topic is solved

[priestleylattice]

I have the following in a ahk script to switch ctrl and alt and map capslock to alt.

Code: Select all

SetCapsLockState, AlwaysOff

LCtrl::Alt
LAlt::Ctrl
CapsLock::Alt

If I press CapsLock+Tab (alt-tabbing) to switch from a window, say chrome (this doesn't matter; the bug is replicated for many choices here), to keepass, and press Alt (sending ctrl), for example as a combination Alt+C (to copy) or even by itself, the following sequence happens

• CapsLock+Tab (keepass pops up)
  Alt (sends ctrl; nothing happens)
  CapsLock+Tab (chrome pops up)
  CapsLock+Tab (keepass pops up)
  Alt (alt key is sent; the "file" menu is highlighted)
  CapsLock+Tab (chrome pops up)

If I repeat this sequence, the same exact behavior occurs.

The annoying thing about this is that in practice when I want to switch to keepass and copy a password by pressing Alt+C (sending Ctrl+C), the Alt grabs the "file" menu instead.

This bug also occurs when switching to Notepad++ with CapsLock+Tab (sending alt+tab).

[lexikos]

Fixed in v1.1.26.01.

There was a simpler way to reproduce it:

• Test with an Alt-blocking hotkey such as LAlt::return or LAlt::LCtrl.
• Open Notepad and alt-tab away using the other Alt key or a remapping such as LCtrl::LAlt.
• Reactivate Notepad.
• Press LAlt and the menus are activated once, even though LAlt is supposed to be blocked.

This is related to two Windows bugs/quirks:

1. Alt-tabbing away from a window (or holding Alt and clicking/activating a different window) usually leaves it in a confused state, where (after releasing Alt and reactivating the window):
   • The menu's keyboard accelerators are still visible, even if they're usually only visible while holding Alt.
   • Pressing a letter does not activate the menu (good).
   • Pressing and releasing Alt does not activate the menu, but instead just hides the keyboard accelerators (bad).
   • Releasing Alt (either the other physical Alt key, or by sending an Alt-up event) activates the menu, where normally it would do nothing.
2. Blocking an Alt key-down event does not prevent the system from processing menu activation hotkeys such as Alt+F (for File).

I can reproduce #1 with Notepad on Windows 10 (without any scripts running):

• Open Notepad: the keyboard accelerators are not visible.
• Deactivate Notepad.
• Hold Alt, reactivate Notepad and release Alt: nothing happens (normal behaviour).
• Alt-tab away from Notepad (slowly).
  OR: Hold Alt and click on another window to deactivate Notepad.
• ... release Alt, do other things, go make a coffee, etc. ...
• Hold Alt, reactivate Notepad and release Alt: the menu activates (abnormal).
• Press Alt to reset/deactivate the menus.
• Alt-tab away from Notepad (slowly).
• Reactivate Notepad: the keyboard accelerators are visible (abnormal).
• Press Alt: the keyboard accelerators hide and the menu does not activate (abnormal).

The workaround for #2 is to send an Alt-up event when an Alt-down event is being blocked, as commented in the source code:

Code: Select all

// Since this is a hotkey that fires on ALT-DOWN and it's a normal (suppressed) hotkey,
// send an up-event to "turn off" the OS's low-level handling for the alt key with
// respect to having it modify keypresses.  For example, the following hotkeys would
// fail to work properly without this workaround because the OS apparently sees that
// the ALT key is physically down even though it is not logically down:
// RAlt::Send f  ; Actually triggers !f, which activates the FILE menu if the active window has one.
// RAlt::Send {PgDn}  ; Fails to work because ALT-PgDn usually does nothing.

However, in v1.1.26.00 and earlier, the workaround triggered problem #1.

v1.1.26.01 fixes issues caused by the workaround in two ways:

• Send Alt-up but then block it via the keyboard hook, so the event never reaches the active window. This is apparently sufficient to counteract the previously blocked Alt key-down.
• #2 appears to have been fixed in Windows 10 (tested on 10.0.15063), so the workaround is applied only on Windows 8.1 and earlier.