From 92d9597f2e425f789334ae9e33140d5f53d90459 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Sun, 1 Jan 2017 23:00:44 -0500
Subject: [PATCH] BufferPane: add functions to move cursor up/down by screen
 row

---
 src/gui/BufferPane.cc | 71 +++++++++++++++++++++++++++++++++++++++++++
 src/gui/BufferPane.h  |  2 ++
 src/gui/Window.h      |  2 ++
 3 files changed, 75 insertions(+)

diff --git a/src/gui/BufferPane.cc b/src/gui/BufferPane.cc
index 7928533..fef6ca1 100644
--- a/src/gui/BufferPane.cc
+++ b/src/gui/BufferPane.cc
@@ -163,6 +163,71 @@ void BufferPane::update_cursor_row(std::list<std::pair<int, Buffer::Iterator>> &
     m_cursor_screen_row = std::min(rows_above, m_cursor_screen_row);
 }
 
+bool BufferPane::move_cursor_screen_row_up()
+{
+    size_t previous_iterator_offset = m_iterator->offset();
+    if (m_cursor_row_offset > 0)
+    {
+        Buffer::Iterator start_of_line = *m_iterator;
+        start_of_line.go_start_of_line();
+        walk_line(start_of_line, [this](int row_offset, int screen_column, int virtual_column, int character_width, const Buffer::Iterator & i) {
+            if (((*i != '\n') || insert_mode()) &&
+                (screen_column <= m_cursor_screen_column) &&
+                (row_offset < m_cursor_row_offset))
+            {
+                *m_iterator = i;
+            }
+        });
+    }
+    else
+    {
+        if (!m_iterator->go_previous_line())
+        {
+            return false;
+        }
+        walk_line(*m_iterator, [this](int row_offset, int screen_column, int virtual_column, int character_width, const Buffer::Iterator & i) {
+            if (((*i != '\n') || insert_mode()) &&
+                (screen_column <= m_cursor_screen_column))
+            {
+                *m_iterator = i;
+            }
+        });
+    }
+    return m_iterator->offset() != previous_iterator_offset;
+}
+
+bool BufferPane::move_cursor_screen_row_down()
+{
+    size_t previous_iterator_offset = m_iterator->offset();
+    Buffer::Iterator start_of_line = *m_iterator;
+    start_of_line.go_start_of_line();
+    walk_line(start_of_line, [this](int row_offset, int screen_column, int virtual_column, int character_width, const Buffer::Iterator & i) {
+        if (((*i != '\n') || insert_mode()) &&
+            (screen_column <= m_cursor_screen_column) &&
+            (row_offset > m_cursor_row_offset))
+        {
+            *m_iterator = i;
+        }
+    });
+    if (m_iterator->offset() != previous_iterator_offset)
+    {
+        return true;
+    }
+    if (!m_iterator->go_next_line())
+    {
+        return false;
+    }
+    walk_line(*m_iterator, [this](int row_offset, int screen_column, int virtual_column, int character_width, const Buffer::Iterator & i) {
+        if (((*i != '\n') || insert_mode()) &&
+            (screen_column <= m_cursor_screen_column) &&
+            (row_offset == 0))
+        {
+            *m_iterator = i;
+        }
+    });
+    return m_iterator->offset() != previous_iterator_offset;
+}
+
 int BufferPane::determine_new_cursor_screen_row()
 {
     if (m_screen_lines.size() > 0)
@@ -456,6 +521,12 @@ void BufferPane::cursor_move(Window::CursorMovement which)
             }
         }
         break;
+    case Window::CursorMovement::SCREEN_ROW_UP:
+        moved = move_cursor_screen_row_up();
+        break;
+    case Window::CursorMovement::SCREEN_ROW_DOWN:
+        moved = move_cursor_screen_row_down();
+        break;
     }
     if (moved)
     {
diff --git a/src/gui/BufferPane.h b/src/gui/BufferPane.h
index 81cd5d8..782e1ce 100644
--- a/src/gui/BufferPane.h
+++ b/src/gui/BufferPane.h
@@ -38,6 +38,8 @@ protected:
     int screen_rows_below_line(const Buffer::Iterator & line);
     int screen_rows_above_line(const Buffer::Iterator & line, std::list<std::pair<int, Buffer::Iterator>> & backward_lines);
     void update_cursor_row(std::list<std::pair<int, Buffer::Iterator>> & backward_lines);
+    bool move_cursor_screen_row_up();
+    bool move_cursor_screen_row_down();
     void walk_line(const Buffer::Iterator & start_of_line, std::function<void(int, int, int, int, const Buffer::Iterator &)> callback);
     int determine_new_cursor_screen_row();
     int col_x(int col)
diff --git a/src/gui/Window.h b/src/gui/Window.h
index d69c71a..cee712f 100644
--- a/src/gui/Window.h
+++ b/src/gui/Window.h
@@ -35,6 +35,8 @@ public:
         EOL,
         FIRST_LINE,
         LAST_LINE,
+        SCREEN_ROW_UP,
+        SCREEN_ROW_DOWN,
     };
 
     enum class EnterInsertModeMode : uint8_t