Only make cursor visible after buffer or selection change

Kakoune now does not touch cursors when scrolling. It checks
if either the buffer or selections has been modified since
last redraw.

Fixes #4124
Fixes #2844

1 files changed, 30 insertions, 27 deletions

diff --git a/src/window.cc b/src/window.cc
index 2a0469cf..b5d1db40 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -85,37 +85,34 @@ static uint32_t compute_faces_hash(const FaceRegistry& faces)
 
 Window::Setup Window::build_setup(const Context& context) const
 {
-    Vector<BufferRange, MemoryDomain::Display> selections;
-    for (auto& sel : context.selections())
-        selections.push_back({sel.cursor(), sel.anchor()});
-
-    return { m_position, m_dimensions,
-             context.buffer().timestamp(),
-             compute_faces_hash(context.faces()),
-             context.selections().main_index(),
-             std::move(selections) };
+    return {m_position, m_dimensions,
+            context.buffer().timestamp(),
+            compute_faces_hash(context.faces()),
+            context.selections().main_index(),
+            context.selections() | gather<Vector<BasicSelection, MemoryDomain::Display>>()};
 }
 
 bool Window::needs_redraw(const Context& context) const
 {
     auto& selections = context.selections();
-
-    if (m_position != m_last_setup.position or
+    return m_position != m_last_setup.position or
         m_dimensions != m_last_setup.dimensions or
         context.buffer().timestamp() != m_last_setup.timestamp or
         selections.main_index() != m_last_setup.main_selection or
         selections.size() != m_last_setup.selections.size() or
-        compute_faces_hash(context.faces()) != m_last_setup.faces_hash)
-        return true;
-
-    for (int i = 0; i < selections.size(); ++i)
-    {
-        if (selections[i].cursor() != m_last_setup.selections[i].begin or
-            selections[i].anchor() != m_last_setup.selections[i].end)
-            return true;
-    }
+        compute_faces_hash(context.faces()) != m_last_setup.faces_hash or
+        not std::equal(selections.begin(), selections.end(),
+                       m_last_setup.selections.begin(), m_last_setup.selections.end());
+}
 
-    return false;
+bool Window::should_make_cursor_visible(const Context& context) const
+{
+    auto& selections = context.selections();
+    return context.buffer().timestamp() != m_last_setup.timestamp or
+        selections.main_index() != m_last_setup.main_selection or
+        selections.size() != m_last_setup.selections.size() or
+        not std::equal(selections.begin(), selections.end(),
+                       m_last_setup.selections.begin(), m_last_setup.selections.end());
 }
 
 const DisplayBuffer& Window::update_display_buffer(const Context& context)
@@ -215,11 +212,15 @@ DisplaySetup Window::compute_display_setup(const Context& context) const
     const int tabstop = context.options()["tabstop"].get<int>();
     const auto& cursor = context.selections().main().cursor();
 
-    // Ensure cursor line is visible
-    if (cursor.line - offset.line < win_pos.line)
-        win_pos.line = std::max(0_line, cursor.line - offset.line);
-    if (cursor.line + offset.line >= win_pos.line + m_dimensions.line)
-        win_pos.line = std::min(buffer().line_count()-1, cursor.line + offset.line - m_dimensions.line + 1);
+    bool ensure_cursor_visible = should_make_cursor_visible(context);
+
+    if (ensure_cursor_visible)
+    {
+        if (cursor.line - offset.line < win_pos.line)
+            win_pos.line = std::max(0_line, cursor.line - offset.line);
+        if (cursor.line + offset.line >= win_pos.line + m_dimensions.line)
+            win_pos.line = std::min(buffer().line_count()-1, cursor.line + offset.line - m_dimensions.line + 1);
+    }
 
     DisplaySetup setup{
         win_pos.line,
@@ -228,13 +229,15 @@ DisplaySetup Window::compute_display_setup(const Context& context) const
         0_col,
         {cursor.line - win_pos.line,
          get_column(buffer(), tabstop, cursor) - win_pos.column},
-        offset
+        offset,
+        ensure_cursor_visible
     };
     for (auto pass : { HighlightPass::Move, HighlightPass::Wrap })
         m_builtin_highlighters.compute_display_setup({context, setup, pass, {}}, 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);