NCurses: When mode line is too long, trim it rather hiding it

src/display_buffer.cc

@@ -169,11 +169,11 @@ CharCount DisplayLine::length() const
     return len;
 }
 
-void DisplayLine::trim(CharCount first_char, CharCount char_count)
+void DisplayLine::trim(CharCount first_char, CharCount char_count, bool only_buffer)
 {
     for (auto it = begin(); first_char > 0 and it != end(); )
     {
-        if (not it->has_buffer_range())
+        if (only_buffer and not it->has_buffer_range())
         {
             ++it;
             continue;

src/display_buffer.hh

@@ -114,7 +114,7 @@ public:
 
     // remove first_char from the begining of the line, and make sure
     // the line is less that char_count character
-    void trim(CharCount first_char, CharCount char_count);
+    void trim(CharCount first_char, CharCount char_count, bool only_buffer);
 
     void     optimize();
 private:

src/ncurses_ui.cc

@@ -388,14 +388,25 @@ void NCursesUI::draw(const DisplayBuffer& display_buffer,
     wmove(m_window, status_line_pos, 0);
     wclrtoeol(m_window);
     draw_line(status_line, 0);
-    CharCount status_len = mode_line.length();
-    // only draw mode_line if it does not overlap one status line
-    if (m_dimensions.column - status_line.length() > status_len + 1)
+    const auto mode_len = mode_line.length();
+    const auto remaining = m_dimensions.column - status_line.length();
+    if (mode_len < remaining)
     {
-        CharCount col = m_dimensions.column - status_len;
+        CharCount col = m_dimensions.column - mode_len;
         wmove(m_window, status_line_pos, (int)col);
         draw_line(mode_line, col);
     }
+    else if (remaining > 2)
+    {
+        DisplayLine trimmed_mode_line = mode_line;
+        trimmed_mode_line.trim(mode_len + 2 - remaining, remaining - 2, false);
+        trimmed_mode_line.insert(trimmed_mode_line.begin(), { "<" });
+        kak_assert(trimmed_mode_line.length() == remaining - 1);
+
+        CharCount col = m_dimensions.column - remaining + 1;
+        wmove(m_window, status_line_pos, (int)col);
+        draw_line(trimmed_mode_line, col);
+    }
 
     const char* tsl = tigetstr((char*)"tsl");
     const char* fsl = tigetstr((char*)"fsl");

src/window.cc

@@ -83,7 +83,7 @@ void Window::update_display_buffer(const Context& context)
 
     // cut the start of the line before m_position.column
     for (auto& line : lines)
-        line.trim(m_position.column, m_dimensions.column);
+        line.trim(m_position.column, m_dimensions.column, true);
     m_display_buffer.optimize();
 
     m_timestamp = buffer().timestamp();