Improve column highlighter to cooperate better with other highlighters

Fixes #268

src/display_buffer.cc

@@ -94,6 +94,19 @@ DisplayLine::iterator DisplayLine::split(iterator it, ByteCoord pos)
     return m_atoms.insert(it, std::move(atom));
 }
 
+DisplayLine::iterator DisplayLine::split(iterator it, CharCount pos)
+{
+    kak_assert(it->type() == DisplayAtom::Text);
+    kak_assert(pos > 0);
+    kak_assert(pos < it->length());
+
+    DisplayAtom atom(it->m_text.substr(0, pos).str());
+    it->m_text = it->m_text.substr(pos).str();
+    atom.check_invariant();
+    it->check_invariant();
+    return m_atoms.insert(it, std::move(atom));
+}
+
 DisplayLine::iterator DisplayLine::insert(iterator it, DisplayAtom atom)
 {
     if (atom.has_buffer_range())

src/display_buffer.hh

@@ -117,9 +117,14 @@ public:
     CharCount length() const;
     const BufferRange& range() const { return m_range; }
 
-    // Split atom pointed by it at pos, returns an iterator to the first atom
+    // Split atom pointed by it at buffer coord pos,
+    // returns an iterator to the first atom
     iterator split(iterator it, ByteCoord pos);
 
+    // Split atom pointed by it at its pos character,
+    // returns an iterator to the first atom
+    iterator split(iterator it, CharCount pos);
+
     iterator insert(iterator it, DisplayAtom atom);
     iterator erase(iterator beg, iterator end);
     void     push_back(DisplayAtom atom);

src/highlighters.cc

@@ -577,12 +577,54 @@ HighlighterAndId create_column_highlighter(HighlighterParameters params)
             }
             if (not found)
             {
-                CharCount col = get_column(buffer, tabstop, buffer.prev(line.range().end));
+                CharCount first_buffer_col = -1;
-                if (col < column)
+                CharCount first_display_col = 0;
+                for (auto& atom : line)
                 {
-                    line.push_back({String{' ', column - col - 1}});
+                    if (atom.has_buffer_range())
+                    {
+                        first_buffer_col = get_column(buffer, tabstop, atom.begin());
+                        break;
+                    }
+                    first_display_col += atom.length();
+                }
+
+                if (first_buffer_col == -1)
+                    continue;
+
+                CharCount eol_col = line.length();
+                CharCount count = column + first_display_col - first_buffer_col - eol_col;
+                if (count >= 0)
+                {
+                    if (count > 0)
+                        line.push_back({String{' ',  count}});
                     line.push_back({String{" "}, face});
                 }
+                else
+                {
+                    for (auto atom_it = line.end(); atom_it != line.begin() and count < 0; --atom_it)
+                    {
+                        DisplayAtom& atom = *(atom_it-1);
+
+                        const CharCount len = atom.length();
+                        if (atom.type() == DisplayAtom::Text and -count <= len)
+                        {
+                            auto it = atom_it - 1;
+                            CharCount pos = len + count;
+                            if (pos > 0)
+                            {
+                                it = ++line.split(it, pos);
+                                pos = 0;
+                            }
+                            if (pos+1 != it->length())
+                                it = line.split(it, pos+1);
+
+                            apply_face(face)(*it);
+                            break;
+                        }
+                        count += len;
+                    }
+                }
             }
         }
     };