Rework highlighting management of cursor position

Move the whole responsibility of making the cursor visible to the
window, removing cursor_pos from the display setup and resolving
the cursor location by finding it in the display buffer afterwards.

This simplifies hightlighters' do_compute_display_setup as they do
not need to compute the cursor location. Highlighting may run on
more lines than necessary after this change but this should be a
minor performance hit.

3 files changed, 24 insertions, 139 deletions

diff --git a/src/highlighter.hh b/src/highlighter.hh
index 73520c53..8a60c0c1 100644
--- a/src/highlighter.hh
+++ b/src/highlighter.hh
@@ -43,11 +43,8 @@ struct DisplaySetup
     LineCount line_count;
     ColumnCount first_column;
     ColumnCount widget_columns;
-    // Position of the cursor in the window
-    DisplayCoord cursor_pos;
     // Offset of line and columns that must remain visible around cursor
     DisplayCoord scroll_offset;
-    bool ensure_cursor_visible;
 };
 
 using HighlighterIdList = ConstArrayView<StringView>;
diff --git a/src/highlighters.cc b/src/highlighters.cc
index 25f93245..2044ccd5 100644
--- a/src/highlighters.cc
+++ b/src/highlighters.cc
@@ -613,9 +613,7 @@ struct WrapHighlighter : Highlighter
             return;
 
         const Buffer& buffer = context.context.buffer();
-        const auto& cursor = context.context.selections().main().cursor();
         const int tabstop = context.context.options()["tabstop"].get<int>();
-        const LineCount win_height = context.context.window().dimensions().line;
         const ColumnCount marker_len = zero_if_greater(m_marker.column_length(), wrap_column);
         const Face face_marker = context.context.faces()["WrapMarker"];
         for (auto it = display_buffer.lines().begin();
@@ -658,19 +656,6 @@ struct WrapHighlighter : Highlighter
                     it->replace(String{' ', indent - marker_len});
                 }
 
-                if (it+1 - display_buffer.lines().begin() == win_height)
-                {
-                    if (cursor >= new_line.range().begin) // strip first lines if cursor is not visible
-                    {
-                        display_buffer.lines().erase(display_buffer.lines().begin(), display_buffer.lines().begin()+1);
-                        --it;
-                    }
-                    else
-                    {
-                        display_buffer.lines().erase(it+1, display_buffer.lines().end());
-                        return;
-                    }
-                }
                 it = display_buffer.lines().insert(it+1, new_line);
 
                 pos = next_split_pos(buffer, wrap_column - prefix_len, prefix_len, tabstop, buf_line, pos);
@@ -688,80 +673,9 @@ struct WrapHighlighter : Highlighter
         if (wrap_column <= 0)
             return;
 
-        const Buffer& buffer = context.context.buffer();
-        const auto& cursor = context.context.selections().main().cursor();
-        const int tabstop = context.context.options()["tabstop"].get<int>();
-
-        auto line_wrap_count = [&](LineCount line, ColumnCount prefix_len) {
-            LineCount count = 0;
-            const ByteCount line_length = buffer[line].length();
-            SplitPos pos{0, 0};
-            while (true)
-            {
-                pos = next_split_pos(buffer, wrap_column - (pos.byte == 0 ? 0_col : prefix_len),
-                                     prefix_len, tabstop, line, pos);
-                if (pos.byte == line_length)
-                    break;
-                ++count;
-            }
-            return count;
-        };
-
-        const auto win_height = context.context.window().dimensions().line;
-
         // Disable horizontal scrolling when using a WrapHighlighter
         setup.first_column = 0;
-        setup.line_count = 0;
         setup.scroll_offset.column = 0;
-
-        const ColumnCount marker_len = zero_if_greater(m_marker.column_length(), wrap_column);
-
-        for (auto buf_line = setup.first_line, win_line = 0_line;
-             win_line < win_height or (setup.ensure_cursor_visible and buf_line <= cursor.line);
-             ++buf_line, ++setup.line_count)
-        {
-            if (buf_line >= buffer.line_count())
-                break;
-
-            const ColumnCount indent = m_preserve_indent ?
-                zero_if_greater(line_indent(buffer, tabstop, buf_line), wrap_column) : 0_col;
-            const ColumnCount prefix_len = std::max(marker_len, indent);
-
-            if (buf_line == cursor.line)
-            {
-                SplitPos pos{0, 0};
-                for (LineCount count = 0; true; ++count)
-                {
-                    auto next_pos = next_split_pos(buffer, wrap_column - (pos.byte != 0 ? prefix_len : 0_col),
-                                                   prefix_len, tabstop, buf_line, pos);
-                    if (next_pos.byte > cursor.column)
-                    {
-                        setup.cursor_pos = DisplayCoord{
-                            win_line + count,
-                            get_column(buffer, tabstop, cursor) -
-                            pos.column + (pos.byte != 0 ? indent : 0_col)
-                        };
-                        break;
-                    }
-                    pos = next_pos;
-                }
-            }
-            const auto wrap_count = line_wrap_count(buf_line, prefix_len);
-            win_line += wrap_count + 1;
-
-            // scroll window to keep cursor visible, and update range as lines gets removed
-            while (setup.ensure_cursor_visible and
-                   buf_line >= cursor.line and setup.first_line < cursor.line and
-                   setup.cursor_pos.line + setup.scroll_offset.line >= win_height)
-            {
-                auto remove_count = 1 + line_wrap_count(setup.first_line, indent);
-                ++setup.first_line;
-                --setup.line_count;
-                setup.cursor_pos.line -= std::min(win_height, remove_count);
-                win_line -= remove_count;
-                kak_assert(setup.cursor_pos.line >= 0);
-            }
-        }
     }
 
     void fill_unique_ids(Vector<StringView>& unique_ids) const override
@@ -947,7 +861,6 @@ struct TabulationHighlighter : Highlighter
         const ColumnCount offset = std::max(column + width - win_end, 0_col);
 
         setup.first_column += offset;
-        setup.cursor_pos.column -= offset;
     }
 };
 
@@ -1694,7 +1607,6 @@ private:
         auto& buffer = context.context.buffer();
         auto& sels = context.context.selections();
         auto& range_and_faces = get_option(context);
-        const int tabstop = context.context.options()["tabstop"].get<int>();
         update_ranges(buffer, range_and_faces.prefix, range_and_faces.list);
         range_and_faces.prefix = buffer.timestamp();
 
@@ -1707,19 +1619,7 @@ private:
             if (range.first.line < setup.first_line and last.line >= setup.first_line)
                 setup.first_line = range.first.line;
 
-            const auto& cursor = context.context.selections().main().cursor();
-            if (cursor.line == last.line and cursor.column >= last.column)
-            {
-                auto first_column = get_column(buffer, tabstop, range.first);
-                auto last_column = get_column(buffer, tabstop, last);
-                auto replacement = parse_display_line(spec, context.context.faces());
-                auto cursor_move = replacement.length() - ((range.first.line == last.line) ? last_column - first_column : last_column);
-                setup.cursor_pos.line -= last.line - range.first.line;
-                setup.cursor_pos.column += cursor_move;
-            }
-
-            if (setup.ensure_cursor_visible and
-                last.line >= setup.first_line and
+            if (last.line >= setup.first_line and
                 range.first.line <= setup.first_line + setup.line_count and
                 range.first.line != last.line)
             {
diff --git a/src/window.cc b/src/window.cc
index 520d77e1..2b8d4be9 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -132,7 +132,7 @@ const DisplayBuffer& Window::update_display_buffer(const Context& context)
         return m_display_buffer;
 
     kak_assert(&buffer() == &context.buffer());
-    const DisplaySetup setup = compute_display_setup(context);
+    DisplaySetup setup = compute_display_setup(context);
 
     for (LineCount line = 0; line < setup.line_count; ++line)
     {
@@ -147,6 +147,24 @@ const DisplayBuffer& Window::update_display_buffer(const Context& context)
     m_builtin_highlighters.highlight({context, setup, HighlightPass::Wrap, {}}, m_display_buffer, range);
     m_builtin_highlighters.highlight({context, setup, HighlightPass::Move, {}}, m_display_buffer, range);
 
+    if (context.ensure_cursor_visible)
+    {
+        auto cursor_pos = display_coord(context.selections().main().cursor());
+        kak_assert(cursor_pos);
+
+        if (auto line_overflow = cursor_pos->line - m_dimensions.line + setup.scroll_offset.line + 1; line_overflow > 0)
+        {
+            lines.erase(lines.begin(), lines.begin() + (size_t)line_overflow);
+            setup.first_line = lines.begin()->range().begin.line;
+        }
+
+        auto max_first_column = cursor_pos->column - (setup.widget_columns + setup.scroll_offset.column);
+        setup.first_column = std::min(setup.first_column, max_first_column);
+
+        auto min_first_column = cursor_pos->column - (m_dimensions.column - setup.scroll_offset.column) + 1;
+        setup.first_column = std::max(setup.first_column, min_first_column);
+    }
+
     for (auto& line : m_display_buffer.lines())
         line.trim_from(setup.widget_columns, setup.first_column, m_dimensions.column);
     if (m_display_buffer.lines().size() > m_dimensions.line)
@@ -203,11 +221,9 @@ DisplaySetup Window::compute_display_setup(const Context& context) const
     offset.line = std::min(offset.line, (m_dimensions.line + 1) / 2);
     offset.column = std::min(offset.column, (m_dimensions.column + 1) / 2);
 
-    const int tabstop = context.options()["tabstop"].get<int>();
     const auto& cursor = context.selections().main().cursor();
 
-    bool ensure_cursor_visible = context.ensure_cursor_visible;
-    if (ensure_cursor_visible)
+    if (context.ensure_cursor_visible)
     {
         if (cursor.line - offset.line < win_pos.line)
             win_pos.line = std::max(0_line, cursor.line - offset.line);
@@ -216,39 +232,11 @@ DisplaySetup Window::compute_display_setup(const Context& context) const
     }
     win_pos.line = std::min(win_pos.line, buffer().line_count()-1);
 
-    DisplaySetup setup{
-        win_pos.line,
-        m_dimensions.line,
-        win_pos.column,
-        0_col,
-        {cursor.line - win_pos.line,
-         get_column(buffer(), tabstop, cursor) - win_pos.column},
-        offset,
-        ensure_cursor_visible
-    };
-    for (auto pass : { HighlightPass::Move, HighlightPass::Wrap })
-        m_builtin_highlighters.compute_display_setup({context, setup, pass, {}}, setup);
+    DisplaySetup setup{win_pos.line, m_dimensions.line, win_pos.column, 0_col, offset};
+    m_builtin_highlighters.compute_display_setup({context, setup, HighlightPass::Move, {}}, setup);
+    m_builtin_highlighters.compute_display_setup({context, setup, HighlightPass::Wrap, {}}, setup);
     check_display_setup(setup, *this);
 
-    // now ensure the cursor column is visible
-    if (ensure_cursor_visible)
-    {
-        auto underflow = std::max(-setup.first_column,
-                                  setup.cursor_pos.column - setup.scroll_offset.column);
-        if (underflow < 0)
-        {
-            setup.first_column += underflow;
-            setup.cursor_pos.column -= underflow;
-        }
-        auto overflow = setup.cursor_pos.column + setup.scroll_offset.column - (m_dimensions.column - setup.widget_columns)  + 1;
-        if (overflow > 0)
-        {
-            setup.first_column += overflow;
-            setup.cursor_pos.column -= overflow;
-        }
-        check_display_setup(setup, *this);
-    }
-
     return setup;
 }