keybindings: Split the resolved keybinding out from MetaKeyCombo

MetaKeyCombo is about the *unresolved* keybinding, which can either be a
"keysym" (<Ctrl>F) or a "keycode" (<Ctrl>0x21). When we resolved the
keysym to a keycode, we stuffed it back in the same MetaKeyCombo, which
confused about what the "keycode" field was for. Thus, we often stomped
on the user's explicit choice if they chose a keycode binding value.

To solve this, create a separate structure, the "devirtualized key combo"
or MetaKeyDevirtCombo, which contains a resolved keycode from the
keysym, and a devirtualized modifier mask. The MetaKeyCombo is now
always a "source" value, and the MetaKeyDevirtCombo is now always what
the user chose.

This also lets us significantly clean up the overlay and ISO key binding
paths.

src/core/keybindings-private.h

@@ -42,16 +42,10 @@ struct _MetaKeyHandler
   GDestroyNotify user_data_free_func;
 };
 
-struct _MetaKeyBinding
-{
-  const char *name;
-  KeySym keysym;
-  KeyCode keycode;
-  unsigned int mask;
-  MetaVirtualModifier modifiers;
-  gint flags;
-  MetaKeyHandler *handler;
-};
+typedef struct _MetaKeyDevirtCombo {
+  xkb_keycode_t keycode;
+  xkb_mod_mask_t mask;
+} MetaKeyDevirtCombo;
 
 /**
  * MetaKeyCombo:
@@ -67,6 +61,15 @@ struct _MetaKeyCombo
   MetaVirtualModifier modifiers;
 };
 
+struct _MetaKeyBinding
+{
+  const char *name;
+  MetaKeyCombo combo;
+  MetaKeyDevirtCombo devirt_combo;
+  gint flags;
+  MetaKeyHandler *handler;
+};
+
 typedef struct
 {
   char *name;
@@ -97,8 +100,9 @@ typedef struct
   xkb_mod_mask_t super_mask;
   xkb_mod_mask_t meta_mask;
   MetaKeyCombo overlay_key_combo;
+  MetaKeyDevirtCombo overlay_key_devirt_combo;
   gboolean overlay_key_only_pressed;
-  MetaKeyCombo *iso_next_group_combos;
+  MetaKeyDevirtCombo *iso_next_group_combos;
   int n_iso_next_group_combos;
 
   xkb_level_index_t keymap_num_levels;