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Bug 4215

Summary: Key events can be buffered when compiling without Ibus support on an Ibus supported system
Product: SDL Reporter: Marc Di Luzio <marcdi>
Component: videoAssignee: Sam Lantinga <slouken>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2 CC: marcdi
Version: 2.0.8   
Hardware: x86_64   
OS: Linux   
Attachments: Simple reproduction file

Description Marc Di Luzio 2018-07-12 16:08:45 UTC 
Created attachment 3271 [details]
Simple reproduction file

Tested on latest tip of default (1a1133e9c7d4).

On Linux, if SDL is compiled without ibus or fcitx support, but the system does support either - ie. XMODIFIERS="@im=ibus", then X key events for held keys will be buffered at low FPS.

See the example file to repro.

Compile and link with a SDL configured with --disable-ibus and --disable-fcitx, and run on a system with either supported (Ubuntu 18.04 will do).

This was originally introduced with https://hg.libsdl.org/SDL/rev/c3874aa1f2d1, which wrapped the setting of new_xmods behind the HAVE_IBUS_IBUS_H or HAVE_FCITX_FRONTEND_H defines.

https://hg.libsdl.org/SDL/rev/b48d8a98e261 Fixed a related issue, but the bug still remained.

A possible patch fix will be attached i a subsequent comment, though I'm unsure if it's exactly the correct fix.
Comment 1 Marc Di Luzio 2018-07-12 16:10:14 UTC 
This patch fixes the issue locally. It simple ensures SDL still sets "@im=none" on systems that have ibus/fcitx support, regardless of whether SDL itself was configured with direct support.

# HG changeset patch
# User Marc Di Luzio <marcdi@unity3d.com>
# Date 1531410765 -3600
#      Thu Jul 12 16:52:45 2018 +0100
# Node ID 44ebedcfe8bf4b244d0cedb83019cc65985b6e83
# Parent  1a1133e9c7d40416af82e97711f91f5a857ffc54
Ensure we still clear the X locale modifiers even if not compiled with ibus or fcitx support

diff --git a/src/video/x11/SDL_x11keyboard.c b/src/video/x11/SDL_x11keyboard.c
--- a/src/video/x11/SDL_x11keyboard.c
+++ b/src/video/x11/SDL_x11keyboard.c
@@ -292,9 +292,7 @@
         char *prev_locale = setlocale(LC_ALL, NULL);
         char *prev_xmods  = X11_XSetLocaleModifiers(NULL);
         const char *new_xmods = "";
-#if defined(HAVE_IBUS_IBUS_H) || defined(HAVE_FCITX_FRONTEND_H)
         const char *env_xmods = SDL_getenv("XMODIFIERS");
-#endif
         SDL_bool has_dbus_ime_support = SDL_FALSE;
 
         if (prev_locale) {
@@ -309,16 +307,12 @@
            when it is used via XIM which causes issues. Prevent this by forcing
            @im=none if XMODIFIERS contains @im=ibus. IBus can still be used via 
            the DBus implementation, which also has support for pre-editing. */
-#ifdef HAVE_IBUS_IBUS_H
         if (env_xmods && SDL_strstr(env_xmods, "@im=ibus") != NULL) {
             has_dbus_ime_support = SDL_TRUE;
         }
-#endif
-#ifdef HAVE_FCITX_FRONTEND_H
         if (env_xmods && SDL_strstr(env_xmods, "@im=fcitx") != NULL) {
             has_dbus_ime_support = SDL_TRUE;
         }
-#endif
         if (has_dbus_ime_support || !xkb_repeat) {
             new_xmods = "@im=none";
         }
Comment 2 Marc Di Luzio 2018-07-13 10:51:02 UTC 
Just to add a little more info for the repro file - when running, hold a keyboard key for more than a second and see the output. Release the key, and see that the events keep repeating for an extended period of time. SDL_PollEvent should be returning true if it has events queued, but it doesn't, they're still buffered in X.
Comment 3 Sam Lantinga 2018-07-17 15:56:20 UTC 
Patch added, thanks!
https://hg.libsdl.org/SDL/rev/5b6f649b6488