Fix rendering of decomposed Hangul

When looking backwards to combine into a character, it didn't take into
account characters with two column width. It also assumed that all
characters that needed to be combined were in the Mn unicode character
category, while the Hangul starting consonants are in the Lo category.

src/Screen.cpp

@@ -634,34 +634,34 @@ void Screen::displayCharacter(unsigned short c)
     // putting the cursor one right to the last column of the screen.
 
     int w = konsole_wcwidth(c);
-    if (w < 0)
+
+    if (w < 0) {
+        // Non-printable character
         return;
-    else if (w == 0) {
-        if (QChar(c).category() != QChar::Mark_NonSpacing)
+    } else if (w == 0) {
+        const QChar::Category category = QChar(c).category();
+        if (category != QChar::Mark_NonSpacing && category != QChar::Letter_Other) {
             return;
-        int charToCombineWithX = -1;
-        int charToCombineWithY = -1;
-        if (_cuX == 0) {
-            // We are at the beginning of a line, check
-            // if previous line has a character at the end we can combine with
-            if (_cuY > 0 && _columns == _screenLines[_cuY - 1].size()) {
-                charToCombineWithX = _columns - 1;
-                charToCombineWithY = _cuY - 1;
+        }
+        // Find previous "real character" to try to combine with
+        int charToCombineWithX = _cuX;
+        int charToCombineWithY = _cuY;
+        do {
+            if (charToCombineWithX > 0) {
+                charToCombineWithX--;
+            } else if (charToCombineWithY > 0) { // Try previous line
+                charToCombineWithY--;
+                charToCombineWithX = _screenLines[charToCombineWithY].length() - 1;
             } else {
-                // There is nothing to combine with
-                // TODO Seems gnome-terminal shows the characters alone
-                // might be worth investigating how to do that
+                // Give up
                 return;
             }
-        } else {
-            charToCombineWithX = _cuX - 1;
-            charToCombineWithY = _cuY;
-        }
 
-        // Prevent "cat"ing binary files from causing crashes.
-        if (charToCombineWithX >= _screenLines[charToCombineWithY].size()) {
-            return;
-        }
+            // Failsafe
+            if (charToCombineWithX < 0) {
+                return;
+            }
+        } while(!_screenLines[charToCombineWithY][charToCombineWithX].isRealCharacter);
 
         Character& currentChar = _screenLines[charToCombineWithY][charToCombineWithX];
         if ((currentChar.rendition & RE_EXTENDED_CHAR) == 0) {