W32: Fix for commit 1f74f12d9, re-enabling decimal separator key

1f74f12d9 rendered entry of keypad decimal mark unuseable for
several national keyboard layouts, this commit amends that, at
least for W32, and makes GTK+ behave more or less the same way
W32 behaves.

The patch works like this:
- When typing the first character at the keyboard or when switching
  keyboard layouts, the decimal mark character will be cached in the
  static variable "decimal_mark" within gdkkeys-win32.c

- in case of WIN32, gdk_keyval_to_unicode() asks gdkkeys-win32.c for the
  current decimal_mark when converting GDK_KEY_KP_Decimal.

https://bugzilla.gnome.org/show_bug.cgi?id=756751

gdk/gdkkeyuni.c

@@ -27,6 +27,10 @@
 #include "gdkkeys.h"
 #include "gdktypes.h"
 
+#ifdef GDK_WINDOWING_WIN32
+#include "win32/gdkwin32.h"
+#include "win32/gdkprivate-win32.h"
+#endif
 
 /* Thanks to Markus G. Kuhn <mkuhn@acm.org> for the ksysym<->Unicode
  * mapping functions, from the xterm sources.
@@ -899,6 +903,14 @@ gdk_keyval_to_unicode (guint keyval)
   if ((keyval & 0xff000000) == 0x01000000)
     return keyval & 0x00ffffff;
 
+#if defined(GDK_WINDOWING_WIN32)
+  if (GDK_IS_WIN32_DISPLAY (gdk_display_get_default ()))
+    {
+      if (keyval == 0xffae)
+        return (guint32) _gdk_win32_keymap_get_decimal_mark ();
+    }
+#endif
+
   /* binary search in table */
   while (max >= min) {
     mid = (min + max) / 2;

gdk/win32/gdkkeys-win32.c

@@ -64,6 +64,7 @@ static GdkModifierType gdk_shift_modifiers = GDK_SHIFT_MASK;
 static GdkKeymap *default_keymap = NULL;
 
 static guint *keysym_tab = NULL;
+static wchar_t decimal_mark = 0;
 
 #define KEY_STATE_SIZE 256
 
@@ -348,6 +349,18 @@ handle_dead (guint  keysym,
     }
 }
 
+/* keypad decimal mark depends on active keyboard layout
+ * return current decimal mark as unicode character
+ */
+guint32
+_gdk_win32_keymap_get_decimal_mark (void)
+{
+  if (decimal_mark)
+    return (decimal_mark);
+
+  return ((guint32) '.');
+}
+
 static void
 update_keymap (void)
 {
@@ -401,7 +414,7 @@ update_keymap (void)
 	       */
 	      handle_special (vk, ksymp, shift);
 
-	      if (*ksymp == 0)
+	      if ((*ksymp == 0) || ((vk == VK_DECIMAL) && (shift == 0)))
 		{
 		  wchar_t wcs[10];
 		  gint k;
@@ -415,7 +428,12 @@ update_keymap (void)
 			   vk, scancode, shift, k,
 			   wcs[0], wcs[1]);
 #endif
-		  if (k == 1)
+		  if ((vk == VK_DECIMAL) && (shift == 0))
+		    {
+		      if (k == 1)
+		        decimal_mark = wcs[0];
+		    }
+		  else if (k == 1)
 		    *ksymp = gdk_unicode_to_keyval (wcs[0]);
 		  else if (k == -1)
 		    {

gdk/win32/gdkprivate-win32.h

@@ -533,6 +533,8 @@ gchar *_gdk_win32_display_manager_get_atom_name (GdkDisplayManager *manager,
 void _gdk_win32_append_event (GdkEvent *event);
 void _gdk_win32_emit_configure_event (GdkWindow *window);
 
+guint32 _gdk_win32_keymap_get_decimal_mark (void);
+
 /* Initialization */
 void _gdk_win32_windowing_init (void);
 void _gdk_screen_init_root_window (GdkWin32Screen *screen_win32);