[gtk+] gdk-win32: Send fake release key event for shift key

[Fabiano Fidêncio <ffidencio src gnome org>]

commit 44608dadc67749df15525b8386f95ad39e48c5ef
Author: Pavel Grunt <pgrunt redhat com>
Date:   Wed Jul 1 15:12:23 2015 +0200

    gdk-win32: Send fake release key event for shift key
    
    Windows does not send any release key event for one of the shift keys
    when both shift keys were pressed together. This commit solves
    the problem by sending the extra release key event for the shift key
    which was released as first, when the other shift key is released.
    
    Other modifiers (e.g. Ctrl, Alt) do not have this problem.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=751721

 gdk/win32/gdkevents-win32.c |   34 ++++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)
---
diff --git a/gdk/win32/gdkevents-win32.c b/gdk/win32/gdkevents-win32.c
index eed1bc6..82e9368 100644
--- a/gdk/win32/gdkevents-win32.c
+++ b/gdk/win32/gdkevents-win32.c
@@ -136,6 +136,8 @@ static UINT     sync_timer = 0;
 
 static int debug_indent = 0;
 
+static int both_shift_pressed[2]; /* to store keycodes for shift keys */
+
 static void
 assign_object (gpointer lhsp,
               gpointer rhs)
@@ -2110,6 +2112,38 @@ gdk_event_translate (MSG  *msg,
 
       fill_key_event_string (event);
 
+  /* Only one release key event is fired when both shift keys are pressed together
+     and then released. In order to send the missing event, press events for shift
+     keys are recorded and sent together when the release event occurs.
+     Other modifiers (e.g. ctrl, alt) don't have this problem. */
+  if (msg->message == WM_KEYDOWN && msg->wParam == VK_SHIFT)
+    {
+      int pressed_shift = msg->lParam & 0xffffff; /* mask shift modifier */
+      if (both_shift_pressed[0] == 0)
+        both_shift_pressed[0] = pressed_shift;
+      else if (both_shift_pressed[0] != pressed_shift)
+        both_shift_pressed[1] = pressed_shift;
+    }
+
+  if (msg->message == WM_KEYUP && msg->wParam == VK_SHIFT)
+    {
+      if (both_shift_pressed[0] != 0 && both_shift_pressed[1] != 0)
+        {
+          gint tmp_retval;
+          MSG fake_release = *msg;
+          int pressed_shift = msg->lParam & 0xffffff;
+
+          if (both_shift_pressed[0] == pressed_shift)
+            fake_release.lParam = both_shift_pressed[1];
+          else
+            fake_release.lParam = both_shift_pressed[0];
+
+          both_shift_pressed[0] = both_shift_pressed[1] = 0;
+          gdk_event_translate (&fake_release, &tmp_retval);
+        }
+      both_shift_pressed[0] = both_shift_pressed[1] = 0;
+    }
+
       /* Reset MOD1_MASK if it is the Alt key itself */
       if (msg->wParam == VK_MENU)
        event->key.state &= ~GDK_MOD1_MASK;