scroll through file with J/K keys

src/core/Buffer.h

@@ -23,6 +23,8 @@ public:
     auto crbegin() const { return m_lines.crbegin(); }
     auto crend() const { return m_lines.crend(); }
 
+    int get_num_lines() { return m_lines.size(); }
+
 protected:
     LinesType m_lines;
     /* TODO: delete this */

src/gui/Window.cc

@@ -111,6 +111,7 @@ bool Window::create(std::shared_ptr<Buffer> buffer)
     m_programs.text->set_color(1.0, 1.0, 1.0, 1.0);
 
     m_buffer = buffer;
+    m_line = 0;
 
     resize();
 
@@ -149,6 +150,20 @@ void Window::handle_event(SDL_Event & event)
         case SDLK_ESCAPE:
             m_exit_requested = true;
             break;
+        case SDLK_j:
+            if (m_line < m_buffer->get_num_lines() - 1)
+            {
+                m_line++;
+                redraw();
+            }
+            break;
+        case SDLK_k:
+            if (m_line > 0)
+            {
+                m_line--;
+                redraw();
+            }
+            break;
         }
         break;
 
@@ -185,8 +200,13 @@ void Window::redraw()
     int advance = m_font.get_advance();
     int line_height = m_font.get_line_height();
     int y = m_height - line_height;
+    int line_number = 0;
     for (auto line = m_buffer->cbegin(); line != m_buffer->cend(); line++)
     {
+        if (line_number++ < m_line)
+        {
+            continue;
+        }
         int x = 0;
         for (int i = 0, len = (*line)->size(); i < len; i++)
         {

src/gui/Window.h

@@ -29,6 +29,8 @@ protected:
     Font m_font;
 
     std::shared_ptr<Buffer> m_buffer;
+
+    int m_line;
 };
 
 #endif