From b3eb6dd38b5390f3d5a5bd00b66cec1bdb56e49d Mon Sep 17 00:00:00 2001
From: Denis Bernard <db047h@gmail.com>
Date: Thu, 30 May 2019 00:37:26 +0200
Subject: [PATCH] X11: Query and keep track of Xkb group index

For users with multiple keyboard layouts configured, glfwGetKeyName
works fine only with the primary layout.  Switching layouts results in
changing the group index.  This commit querries the current group index
when initializing keyboard input and keeps track of any change to it.

As a result the scancode -> keyname mapping may change while the program
is running (needs to be documented).

Fixes #1462.
Closes #1528.

(cherry picked from commit 36f90800d8d490b27d4dc2109c07a95a12007327)
---
 src/x11_init.c     | 12 ++++++++++--
 src/x11_platform.h | 15 ++++++++-------
 src/x11_window.c   | 11 ++++++++++-
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/src/x11_init.c b/src/x11_init.c
index 77f543cb6e..f00080d644 100644
--- a/src/x11_init.c
+++ b/src/x11_init.c
@@ -54,7 +54,7 @@ static int translateKeyCode(int scancode)
         // Note: This way we always force "NumLock = ON", which is intentional
         // since the returned key code should correspond to a physical
         // location.
-        keySym = XkbKeycodeToKeysym(_glfw.x11.display, scancode, 0, 1);
+        keySym = XkbKeycodeToKeysym(_glfw.x11.display, scancode, _glfw.x11.xkb.group, 1);
         switch (keySym)
         {
             case XK_KP_0:           return GLFW_KEY_KP_0;
@@ -76,7 +76,7 @@ static int translateKeyCode(int scancode)
 
         // Now try primary keysym for function keys (non-printable keys)
         // These should not depend on the current keyboard layout
-        keySym = XkbKeycodeToKeysym(_glfw.x11.display, scancode, 0, 0);
+        keySym = XkbKeycodeToKeysym(_glfw.x11.display, scancode, _glfw.x11.xkb.group, 0);
     }
     else
     {
@@ -659,6 +659,14 @@ static GLFWbool initExtensions(void)
             if (supported)
                 _glfw.x11.xkb.detectable = GLFW_TRUE;
         }
+
+        _glfw.x11.xkb.group = 0;
+        XkbStateRec state;
+        if (XkbGetState(_glfw.x11.display, XkbUseCoreKbd, &state) == Success)
+        {
+            XkbSelectEventDetails(_glfw.x11.display, XkbUseCoreKbd, XkbStateNotify, XkbAllStateComponentsMask, XkbGroupStateMask);
+            _glfw.x11.xkb.group = (unsigned int)state.group;
+        }
     }
 
 #if defined(__CYGWIN__)
diff --git a/src/x11_platform.h b/src/x11_platform.h
index 9fffa78ea0..5b3652419a 100644
--- a/src/x11_platform.h
+++ b/src/x11_platform.h
@@ -323,13 +323,14 @@ typedef struct _GLFWlibraryX11
     } randr;
 
     struct {
-        GLFWbool    available;
-        GLFWbool    detectable;
-        int         majorOpcode;
-        int         eventBase;
-        int         errorBase;
-        int         major;
-        int         minor;
+        GLFWbool     available;
+        GLFWbool     detectable;
+        int          majorOpcode;
+        int          eventBase;
+        int          errorBase;
+        int          major;
+        int          minor;
+        unsigned int group;
     } xkb;
 
     struct {
diff --git a/src/x11_window.c b/src/x11_window.c
index 2eeaf572b1..47e7a40e54 100644
--- a/src/x11_window.c
+++ b/src/x11_window.c
@@ -1180,6 +1180,15 @@ static void processEvent(XEvent *event)
         }
     }
 
+    if (_glfw.x11.xkb.available && event->type == _glfw.x11.xkb.eventBase)
+    {
+        if (((XkbEvent *)event)->any.xkb_type == XkbStateNotify &&
+            ((XkbEvent *)event)->state.changed & XkbGroupStateMask)
+        {
+            _glfw.x11.xkb.group = ((XkbEvent *)event)->state.group;
+        }
+    }
+
     if (event->type == GenericEvent)
     {
         if (_glfw.x11.xi.available)
@@ -2780,7 +2789,7 @@ const char* _glfwPlatformGetScancodeName(int scancode)
     if (!_glfw.x11.xkb.available)
         return NULL;
 
-    const KeySym keysym = XkbKeycodeToKeysym(_glfw.x11.display, scancode, 0, 0);
+    const KeySym keysym = XkbKeycodeToKeysym(_glfw.x11.display, scancode, _glfw.x11.xkb.group, 0);
     if (keysym == NoSymbol)
         return NULL;