fix(linux): Fix reordering of output

This change implements a commit queue which allows to control the
order of the output. This ensures that any backspace we generate
will be processed before the character we're adding.

Requires changes in ibus (surrounding text fix (see #7072) and
prefilter change)

Fixes #1489, #4028, #4029, #4030, #4505, #5510, #6639

linux/ibus-keyman/src/engine.c

@@ -51,34 +51,52 @@
 #define KEYMAN_LALT  56 // 0x38
 #define KEYMAN_RCTRL 97 // 0x61
 #define KEYMAN_RALT 100 // 0x64
+#define KEYMAN_F24_KEYCODE_OUTPUT_SENTINEL  202
+#define KEYMAN_NOCHAR_KEYSYM (0xffff | 0x1000000) // Unicode NOCHAR
 
 typedef struct _IBusKeymanEngine IBusKeymanEngine;
 typedef struct _IBusKeymanEngineClass IBusKeymanEngineClass;
 
+#define MAX_QUEUE_SIZE 100
+
+struct commit_queue_item {
+  gchar *char_buffer;
+  gboolean emitting_keystroke;
+  guint keyval;
+  guint keycode;
+  guint state;
+};
+
 struct _IBusKeymanEngine {
-	IBusEngine parent;
-
-    /* members */
-    km_kbp_keyboard *keyboard;
-    km_kbp_state    *state;
-    gchar           *ldmlfile;
-    gchar           *kb_name;
-    gchar           *char_buffer;
-    gunichar         firstsurrogate;
-    gboolean         lctrl_pressed;
-    gboolean         rctrl_pressed;
-    gboolean         lalt_pressed;
-    gboolean         ralt_pressed;
-    gboolean         emitting_keystroke;
-    IBusLookupTable *table;
-    IBusProperty    *status_prop;
-    IBusPropList    *prop_list;
+  IBusEngine parent;
+
+  /* members */
+  km_kbp_keyboard *keyboard;
+  km_kbp_state *state;
+  gchar *ldmlfile;
+  gchar *kb_name;
+  gchar *char_buffer;
+  gunichar firstsurrogate;
+  gboolean lctrl_pressed;
+  gboolean rctrl_pressed;
+  gboolean lalt_pressed;
+  gboolean ralt_pressed;
+  gboolean emitting_keystroke;
+  guint event_keyval;
+  guint event_keycode;
+  guint event_state;
+  IBusLookupTable *table;
+  IBusProperty *status_prop;
+  IBusPropList *prop_list;
 #ifdef GDK_WINDOWING_X11
-    Display         *xdisplay;
+  Display         *xdisplay;
 #endif
 #ifdef GDK_WINDOWING_WAYLAND
-    GdkWaylandDisplay *wldisplay;
+  GdkWaylandDisplay *wldisplay;
 #endif
+
+  struct commit_queue_item commit_queue[MAX_QUEUE_SIZE];
+  int queue_end;
 };
 
 struct _IBusKeymanEngineClass {
@@ -653,12 +671,8 @@ process_persist_action(
   return TRUE;
 }
 
-static gboolean process_emit_keystroke_action(IBusKeymanEngine *keyman) {
-  if (keyman->char_buffer != NULL) {
-    ibus_keyman_engine_commit_string(keyman, keyman->char_buffer);
-    g_free(keyman->char_buffer);
-    keyman->char_buffer = NULL;
-  }
+static gboolean
+process_emit_keystroke_action(IBusKeymanEngine *keyman) {
   keyman->emitting_keystroke = TRUE;
   return TRUE;
 }
@@ -692,18 +706,42 @@ process_capslock_action(
   return TRUE;
 }
 
-static gboolean process_end_action(IBusKeymanEngine *keyman) {
-  keyman->firstsurrogate = 0;
-  if (keyman->char_buffer != NULL) {
-    ibus_keyman_engine_commit_string(keyman, keyman->char_buffer);
-    g_free(keyman->char_buffer);
-    keyman->char_buffer = NULL;
-  }
-  if (keyman->emitting_keystroke) {
-    keyman->emitting_keystroke = FALSE;
-    return FALSE;
+static void
+commit_text(IBusKeymanEngine *keyman) {
+  if (keyman->queue_end > 0) {
+    keyman->firstsurrogate = 0;
+    if (keyman->commit_queue[0].char_buffer != NULL) {
+      ibus_keyman_engine_commit_string(keyman, keyman->commit_queue[0].char_buffer);
+      g_free(keyman->commit_queue[0].char_buffer);
+    }
+    if (keyman->commit_queue[0].emitting_keystroke) {
+      ibus_engine_forward_key_event(keyman, keyman->commit_queue[0].keyval, keyman->commit_queue[0].keycode, keyman->commit_queue[0].state);
+    }
+    keyman->queue_end--;
+    memmove(keyman->commit_queue, &keyman->commit_queue[1], sizeof(struct commit_queue_item) * keyman->queue_end);
   }
+}
 
+static gboolean
+process_end_action(IBusKeymanEngine *keyman) {
+  keyman->commit_queue[keyman->queue_end].char_buffer        = keyman->char_buffer;
+  keyman->commit_queue[keyman->queue_end].emitting_keystroke = keyman->emitting_keystroke;
+  keyman->commit_queue[keyman->queue_end].keyval             = keyman->event_keyval;
+  keyman->commit_queue[keyman->queue_end].keycode            = keyman->event_keycode;
+  keyman->commit_queue[keyman->queue_end].state              = keyman->event_state;
+  keyman->queue_end++;
+  if (keyman->queue_end >= MAX_QUEUE_SIZE) {
+    g_error("Overflow of keyman commit_queue!");
+    keyman->queue_end = MAX_QUEUE_SIZE - 1;
+  }
+  keyman->char_buffer = NULL;
+  keyman->emitting_keystroke = FALSE;
+
+  // Forward a fake key event to get the correct order of events so that any backspace key we
+  // generated will be processed before the character we're adding. We need to send a
+  // valid keyval/keycode combination so that it doesn't get swallowed by GTK but which
+  // isn't very likely used in real keyboards. F24 seems to work for that.
+  ibus_engine_forward_key_event(keyman, KEYMAN_NOCHAR_KEYSYM, KEYMAN_F24_KEYCODE_OUTPUT_SENTINEL, IBUS_PREFILTER_MASK);
   return TRUE;
 }
 
@@ -769,6 +807,9 @@ ibus_keyman_engine_process_key_event(
   guint state
 ) {
   IBusKeymanEngine *keyman = (IBusKeymanEngine *)engine;
+  keyman->event_keyval     = keyval;
+  keyman->event_keycode    = keycode;
+  keyman->event_state      = state;
 
   gboolean isKeyDown = !(state & IBUS_RELEASE_MASK);
 
@@ -777,6 +818,11 @@ ibus_keyman_engine_process_key_event(
       "DAR: ibus_keyman_engine_process_key_event - keyval=0x%02x keycode=0x%02x, state=0x%02x, isKeyDown=%d", keyval, keycode,
       state, isKeyDown);
 
+  if (keycode == KEYMAN_F24_KEYCODE_OUTPUT_SENTINEL && (state & IBUS_PREFILTER_MASK)) {
+    commit_text(keyman);
+    return TRUE;
+  }
+
   // REVIEW: why don't we handle these keys?
   switch (keycode) {
   case KEYMAN_LCTRL:
@@ -850,7 +896,7 @@ ibus_keyman_engine_process_key_event(
   const km_kbp_action_item *action_items = km_kbp_state_action_items(keyman->state, &num_action_items);
 
   if (!process_actions(engine, action_items, num_action_items))
-    return FALSE;
+    return TRUE;
 
   context = km_kbp_state_context(keyman->state);
   g_message("after processing all actions");