Priority: P3: Somewhat important
Affects Version/s: 4.8.5
Fix Version/s: None
Component/s: GUI: Basic Input System (keyboard, mouse, touch)
Environment:Microsoft Windows 7 SP1 x64.
System locale: Japanese.
The patch from https://bugreports.qt-project.org/secure/attachment/30642/0001-Fixed-dead-keys-on-Windows-QTBUG-8764-QTBUG-10032.patch introduces issues with Cyrillic layouts that support dead keys. An example would be the layout from http://ilyabirman.net/projects/typography-layout/ which is often used by translators, editors, correctors and the likes.
1. Install a layout with Cyrillic and dead keys support
2. Open a Qt application that uses Qt version 184.108.40.206 or later
3. Switch to Cyrillic input (Russian in the case of aforementioned layout) and type relatively fast
This results in garbled input as illustrated in the attached screenshot (of Blizzard's Battle.net client). Same results can be produced in Psi+ (an XMPP client) messaging windows.