Use IBus semantic preedit hints API for Wayland support

Fix an issue where preedit decoration in ibus-mozc was missing under Wayland. This is because Wayland protocols do not support specifying arbitrary RGB colors for preedit styling.

Address this limitation by adopting new IBus semantic preedit hints API, which has been available since 1.5.33.

Fixes: #1484

Author: ftake

src/unix/ibus/preedit_handler.cc

@@ -52,8 +52,23 @@ IbusTextWrapper ComposePreeditText(const commands::Preedit& preedit) {
   int end = 0;
   for (int i = 0; i < preedit.segment_size(); ++i) {
     const commands::Preedit::Segment& segment = preedit.segment(i);
+#if IBUS_CHECK_VERSION(1, 5, 33)
+    // IBus's semantic pre-edit style name is since 1.5.33, which is necessary
+    // to use pre-edit style under Wayland session.
+    IBusAttrPreedit hint = IBUS_ATTR_PREEDIT_WHOLE;
+#else  // libibus (>=1.5.33)
     IBusAttrUnderline attr = IBUS_ATTR_UNDERLINE_ERROR;
+#endif  // !libibus (>=1.5.33)
     switch (segment.annotation()) {
+#if IBUS_CHECK_VERSION(1, 5, 33)
+      case commands::Preedit::Segment::NONE:
+      case commands::Preedit::Segment::UNDERLINE:
+        // Do nothing; use IBUS_ATTR_PREEDIT_WHOLE.
+        break;
+      case commands::Preedit::Segment::HIGHLIGHT:
+        hint = IBUS_ATTR_PREEDIT_SELECTION;
+        break;
+#else  // libibus (>=1.5.33)
       case commands::Preedit::Segment::NONE:
         attr = IBUS_ATTR_UNDERLINE_NONE;
         break;
@@ -63,11 +78,15 @@ IbusTextWrapper ComposePreeditText(const commands::Preedit& preedit) {
       case commands::Preedit::Segment::HIGHLIGHT:
         attr = IBUS_ATTR_UNDERLINE_DOUBLE;
         break;
+#endif  // !libibus (>=1.5.33)
       default:
         LOG(ERROR) << "unknown annotation:" << segment.annotation();
         break;
     }
     end += segment.value_length();
+#if IBUS_CHECK_VERSION(1, 5, 33)
+    text.AppendAttribute(IBUS_ATTR_TYPE_HINT, hint, start, end);
+#else  // libibus (>=1.5.33)
     text.AppendAttribute(IBUS_ATTR_TYPE_UNDERLINE, attr, start, end);
 
     // Many applications show a single underline regardless of using
@@ -84,6 +103,7 @@ IbusTextWrapper ComposePreeditText(const commands::Preedit& preedit) {
       text.AppendAttribute(IBUS_ATTR_TYPE_FOREGROUND, kForegroundColor, start,
                            end);
     }
+#endif  // !libibus (>=1.5.33)
     start = end;
   }