Fix stuck modifier issue in the non-xcb_xkb code path

Since updating the xkb_state throght core events is more
tricky (opposed to the xcb-xkb code path) where we have
to use xkb_state_update_key, we need to make sure that our
local state is in sync with the X server's state.

The local state was getting out of sync if key was pressed
down in a Qt application and released in other X client (by
changing the focus to another window with a mouse, for
example).

Task-number: QTBUG-32660
Change-Id: I662bf5aad3ab0e8591109994e746d85ff61ad6ef
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

1 files changed, 24 insertions, 19 deletions

diff --git a/src/plugins/platforms/xcb/qxcbkeyboard.cpp b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
index ae8bcb802b..14893d9acc 100644
--- a/src/plugins/platforms/xcb/qxcbkeyboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbkeyboard.cpp
@@ -716,14 +716,14 @@ void QXcbKeyboard::updateXKBState(xcb_xkb_state_notify_event_t *state)
 
     if (connection()->hasXKB()) {
 
-        xkb_state_component newState;
-        newState = xkb_state_update_mask(xkb_state,
-                              state->baseMods,
-                              state->latchedMods,
-                              state->lockedMods,
-                              state->baseGroup,
-                              state->latchedGroup,
-                              state->lockedGroup);
+        const xkb_state_component newState
+                = xkb_state_update_mask(xkb_state,
+                                  state->baseMods,
+                                  state->latchedMods,
+                                  state->lockedMods,
+                                  state->baseGroup,
+                                  state->latchedGroup,
+                                  state->lockedGroup);
 
         if ((newState & XKB_STATE_LAYOUT_EFFECTIVE) == XKB_STATE_LAYOUT_EFFECTIVE) {
             //qWarning("TODO: Support KeyboardLayoutChange on QPA (QTBUG-27681)");
@@ -737,17 +737,22 @@ void QXcbKeyboard::updateXKBStateFromCore(quint16 state)
     if (!m_config)
         return;
 
-    quint32 modsDepressed, modsLatched, modsLocked;
-    modsDepressed = xkb_state_serialize_mods(xkb_state, XKB_STATE_MODS_DEPRESSED);
-    modsLatched = xkb_state_serialize_mods(xkb_state, XKB_STATE_MODS_LATCHED);
-    modsLocked = xkb_state_serialize_mods(xkb_state, XKB_STATE_MODS_LOCKED);
-
-    quint32 xkbMask = xkbModMask(state);
-    xkb_state_component newState;
-    newState = xkb_state_update_mask(xkb_state,
-                          modsDepressed & xkbMask,
-                          modsLatched & xkbMask,
-                          modsLocked & xkbMask,
+    const quint32 modsDepressed = xkb_state_serialize_mods(xkb_state, XKB_STATE_MODS_DEPRESSED);
+    const quint32 modsLatched = xkb_state_serialize_mods(xkb_state, XKB_STATE_MODS_LATCHED);
+    const quint32 modsLocked = xkb_state_serialize_mods(xkb_state, XKB_STATE_MODS_LOCKED);
+    const quint32 xkbMask = xkbModMask(state);
+
+    const quint32 latched = modsLatched & xkbMask;
+    const quint32 locked = modsLocked & xkbMask;
+    quint32 depressed = modsDepressed & xkbMask;
+    // set modifiers in depressed if they don't appear in any of the final masks
+    depressed |= ~(depressed | latched | locked) & xkbMask;
+
+    const xkb_state_component newState
+            = xkb_state_update_mask(xkb_state,
+                          depressed,
+                          latched,
+                          locked,
                           0,
                           0,
                           (state >> 13) & 3); // bits 13 and 14 report the state keyboard group