[PATCH] ephyr: don't allow a shift+ctrl keygrab if mod1 was enabled

[Peter Hutterer]

Xephyr wants ctrl+shift to grab the window, but that conflicts with
ctrl+alt+shift key combos. Remember the modifier state on key presses and
releases, if mod1 is pressed, we need ctrl, shift and mod1 released
before we allow a shift-ctrl grab activation.

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
This is a bit hackish, but rooting around in the xkb mappings to find the
right key code for Mod1 is, well, unappealing.

 hw/kdrive/ephyr/ephyr.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/hw/kdrive/ephyr/ephyr.c b/hw/kdrive/ephyr/ephyr.c
index b2a7985..94b9397 100644
--- a/hw/kdrive/ephyr/ephyr.c
+++ b/hw/kdrive/ephyr/ephyr.c
@@ -1008,6 +1008,29 @@ ephyrProcessButtonRelease(xcb_generic_event_t *xev)
     KdEnqueuePointerEvent(ephyrMouse, mouseState | KD_MOUSE_DELTA, 0, 0, 0);
 }
 
+/* Xephyr wants ctrl+shift to grab the window, but that conflicts with
+   ctrl+alt+shift key combos. Remember the modifier state on key presses and
+   releases, if mod1 is pressed, we need ctrl, shift and mod1 released
+   before we allow a shift-ctrl grab activation.
+
+   note: a key event contains the mask _before_ the current key takes
+   effect, so mod1_was_down will be reset on the first key press after all
+   three were released, not on the last release. That'd require some more
+   effort.
+ */
+static int
+ephyrUpdateGrabModifierState(int state)
+{
+    static int mod1_was_down = 0;
+
+    if ((state & (XCB_MOD_MASK_CONTROL|XCB_MOD_MASK_SHIFT|XCB_MOD_MASK_1)) == 0)
+        mod1_was_down = 0;
+    else if (state & XCB_MOD_MASK_1)
+        mod1_was_down = 1;
+
+    return mod1_was_down;
+}
+
 static void
 ephyrProcessKeyPress(xcb_generic_event_t *xev)
 {
@@ -1018,6 +1041,7 @@ ephyrProcessKeyPress(xcb_generic_event_t *xev)
         return;
     }
 
+    ephyrUpdateGrabModifierState(key->state);
     ephyrUpdateModifierState(key->state);
     KdEnqueueKeyboardEvent(ephyrKbd, key->detail, FALSE);
 }
@@ -1029,6 +1053,7 @@ ephyrProcessKeyRelease(xcb_generic_event_t *xev)
     xcb_key_release_event_t *key = (xcb_key_release_event_t *)xev;
     static xcb_key_symbols_t *keysyms;
     static int grabbed_screen = -1;
+    int mod1_down = ephyrUpdateGrabModifierState(key->state);
 
     if (!keysyms)
         keysyms = xcb_key_symbols_alloc(conn);
@@ -1049,7 +1074,7 @@ ephyrProcessKeyRelease(xcb_generic_event_t *xev)
             hostx_set_win_title(screen,
                                 "(ctrl+shift grabs mouse and keyboard)");
         }
-        else {
+        else if (!mod1_down) {
             /* Attempt grab */
             xcb_grab_keyboard_cookie_t kbgrabc =
                 xcb_grab_keyboard(conn,
-- 
1.8.4.2