Make scrolling around work more correctly with wrapping

src/highlighter.hh

@@ -39,7 +39,8 @@ struct DisplaySetup
     DisplayCoord window_pos;
     // Range of lines and columns from the buffer that will get displayed
     DisplayCoord window_range;
-
+    // Offset of line and columns that must remain visible around cursor
+    DisplayCoord scroll_offset;
     // Position of the cursor in the window
     DisplayCoord cursor_pos;
 };
@@ -50,7 +51,7 @@ struct Highlighter
     virtual void highlight(const Context& context, HighlightPass pass, DisplayBuffer& display_buffer, BufferRange range) = 0;
 
     virtual void compute_display_setup(const Context& context, HighlightPass pass,
-                                       DisplayCoord scroll_offset, DisplaySetup& setup) {}
+                                       DisplaySetup& setup) {}
 
     virtual bool has_children() const { return false; }
     virtual Highlighter& get_child(StringView path) { throw runtime_error("this highlighter do not hold children"); }

src/highlighter_group.cc

@@ -13,10 +13,10 @@ void HighlighterGroup::highlight(const Context& context, HighlightPass pass,
 }
 
 void HighlighterGroup::compute_display_setup(const Context& context, HighlightPass pass,
-                                             DisplayCoord scroll_offset, DisplaySetup& setup)
+                                             DisplaySetup& setup)
 {
     for (auto& hl : m_highlighters)
-       hl.value->compute_display_setup(context, pass, scroll_offset, setup);
+       hl.value->compute_display_setup(context, pass, setup);
 }
 
 void HighlighterGroup::add_child(HighlighterAndId&& hl)

src/highlighter_group.hh

@@ -20,7 +20,7 @@ public:
     void highlight(const Context& context, HighlightPass pass, DisplayBuffer& display_buffer, BufferRange range) override;
 
     void compute_display_setup(const Context& context, HighlightPass pass,
-                               DisplayCoord scroll_offset, DisplaySetup& setup) override;
+                               DisplaySetup& setup) override;
 
     bool has_children() const override { return true; }
     void add_child(HighlighterAndId&& hl) override;

src/highlighters.cc

@@ -719,12 +719,12 @@ struct WrapHighlighter : Highlighter
     }
 
     void compute_display_setup(const Context& context, HighlightPass pass,
-                               DisplayCoord scroll_offset, DisplaySetup& setup) override
+                               DisplaySetup& setup) override
     {
         if (pass != HighlightPass::Wrap)
             return;
 
-        ColumnCount column = context.window().display_setup().window_range.column;
+        ColumnCount column = setup.window_range.column;
         if (column < 0)
             return;
 
@@ -752,9 +752,11 @@ struct WrapHighlighter : Highlighter
                 setup.cursor_pos.line += (int)(cursor_buffer_column / column);
                 auto new_cursor_buffer_column = (cursor_buffer_column % column);
 
-                if (new_cursor_buffer_column < setup.window_pos.column + scroll_offset.column)
+                if (new_cursor_buffer_column < setup.window_pos.column + setup.scroll_offset.column)
-                    setup.window_pos.column = new_cursor_buffer_column - scroll_offset.column;
+                    setup.window_pos.column = new_cursor_buffer_column - setup.scroll_offset.column;
                 setup.cursor_pos.column = new_cursor_buffer_column - setup.window_pos.column;
+
+                kak_assert(setup.cursor_pos.column >= 0 and setup.cursor_pos.column < setup.window_range.column);
             }
 
             const auto wrap_count = line_wrap_count(buf_line);
@@ -775,8 +777,10 @@ struct WrapHighlighter : Highlighter
                 setup.window_range.line += removed_lines - 1;
             }
 
-            if (setup.window_range.line < buf_line - setup.window_pos.line + 1)
+            if (setup.window_range.line <= buf_line - setup.window_pos.line)
                 setup.window_range.line = buf_line - setup.window_pos.line + 1;
+
+            kak_assert(setup.cursor_pos.line >= 0 and setup.cursor_pos.line < win_height);
         }
     }
 
@@ -941,18 +945,13 @@ struct LineNumbersHighlighter : Highlighter
     }
 
     void compute_display_setup(const Context& context, HighlightPass pass,
-                               DisplayCoord scroll_offset, DisplaySetup& setup) override
+                               DisplaySetup& setup) override
     {
         if (pass != HighlightPass::Move)
             return;
 
         ColumnCount width = compute_digit_count(context) + m_separator.column_length();
         setup.window_range.column -= width;
-
-        auto cursor_overflow = setup.cursor_pos.column + scroll_offset.column -
-                               setup.window_range.column + 1;
-        if (cursor_overflow > 0)
-            setup.window_pos.column += cursor_overflow;
     }
 
     static HighlighterAndId create(HighlighterParameters params)
@@ -1171,7 +1170,7 @@ struct FlagLinesHighlighter : Highlighter
     }
 
     void compute_display_setup(const Context& context, HighlightPass pass,
-                               DisplayCoord scroll_offset, DisplaySetup& setup) override
+                               DisplaySetup& setup) override
     {
         if (pass != HighlightPass::Move)
             return;
@@ -1185,11 +1184,6 @@ struct FlagLinesHighlighter : Highlighter
             width = std::max(parse_display_line(std::get<1>(line)).length(), width);
 
         setup.window_range.column -= width;
-
-        auto cursor_overflow = setup.cursor_pos.column + scroll_offset.column -
-                               setup.window_range.column + 1;
-        if (cursor_overflow > 0)
-            setup.window_pos.column += cursor_overflow;
     }
 
     static HighlighterAndId create(HighlighterParameters params)

src/window.cc

@@ -122,8 +122,7 @@ const DisplayBuffer& Window::update_display_buffer(const Context& context)
         return m_display_buffer;
 
     kak_assert(&buffer() == &context.buffer());
-    m_display_setup = compute_display_setup(context);
+    compute_display_setup(context);
-    m_position = m_display_setup.window_pos;
 
     for (LineCount line = 0; line < m_display_setup.window_range.line; ++line)
     {
@@ -174,18 +173,7 @@ void Window::set_dimensions(DisplayCoord dimensions)
     }
 }
 
-template<typename Unit>
+void Window::compute_display_setup(const Context& context)
-static Unit adapt_view_pos(Unit pos, Unit offset,
-                           Unit view_pos, Unit view_size)
-{
-    if (pos - offset < view_pos)
-        return std::max(Unit{0}, pos - offset);
-    else if (pos + offset >= view_pos + view_size)
-        return std::max(Unit{0}, pos + offset - view_size + 1);
-    return view_pos;
-}
-
-DisplaySetup Window::compute_display_setup(const Context& context)
 {
     DisplayCoord offset = options()["scrolloff"].get<DisplayCoord>();
     offset.line = std::min(offset.line, (m_dimensions.line + 1) / 2);
@@ -193,25 +181,42 @@ DisplaySetup Window::compute_display_setup(const Context& context)
 
     const auto& cursor = context.selections().main().cursor();
 
-    m_position.line = adapt_view_pos(cursor.line, offset.line,
+    // Ensure cursor line is visible
-                                     m_position.line, m_dimensions.line);
+    if (cursor.line - offset.line < m_position.line)
+        m_position.line = cursor.line - offset.line;
+    if (cursor.line + offset.line >= m_position.line + m_dimensions.line)
+        m_position.line = cursor.line + offset.line - m_dimensions.line + 1;
 
     const int tabstop = context.options()["tabstop"].get<int>();
     auto cursor_col = get_column(buffer(), tabstop, cursor);
-    m_position.column = adapt_view_pos(cursor_col, offset.column,
-                                       m_position.column, m_dimensions.column);
 
-    DisplaySetup setup{
+    m_display_setup = DisplaySetup{
         m_position,
         m_dimensions,
+        offset,
         DisplayCoord{cursor.line - m_position.line, cursor_col - m_position.column}
     };
     for (auto pass : { HighlightPass::Move, HighlightPass::Wrap })
-        m_highlighters.compute_display_setup(context, pass, offset, setup);
+        m_highlighters.compute_display_setup(context, pass, m_display_setup);
     for (auto pass : { HighlightPass::Move, HighlightPass::Wrap })
-        m_builtin_highlighters.compute_display_setup(context, pass, offset, setup);
+        m_builtin_highlighters.compute_display_setup(context, pass, m_display_setup);
 
-    return setup;
+    // now ensure the cursor column is visible
+    {
+        auto underflow = m_display_setup.cursor_pos.column - m_display_setup.scroll_offset.column;
+        if (underflow < 0)
+        {
+            m_display_setup.window_pos.column += underflow;
+            m_display_setup.cursor_pos.column -= underflow;
+        }
+        auto overflow = m_display_setup.cursor_pos.column + m_display_setup.scroll_offset.column - m_display_setup.window_range.column + 1;
+        if (overflow > 0)
+        {
+            m_display_setup.window_pos.column += overflow;
+            m_display_setup.cursor_pos.column -= overflow;
+        }
+    }
+    m_position = m_display_setup.window_pos;
 }
 
 namespace

src/window.hh

@@ -53,7 +53,7 @@ private:
     Window(const Window&) = delete;
 
     void on_option_changed(const Option& option) override;
-    DisplaySetup compute_display_setup(const Context& context);
+    void compute_display_setup(const Context& context);
 
     void run_hook_in_own_context(StringView hook_name, StringView param,
                                  String client_name = "");
@@ -63,8 +63,8 @@ private:
 
     DisplayCoord m_position;
     DisplayCoord m_dimensions;
-    DisplayBuffer m_display_buffer;
     DisplaySetup m_display_setup;
+    DisplayBuffer m_display_buffer;
 
     HighlighterGroup m_highlighters;
     HighlighterGroup m_builtin_highlighters;