From 46deca4f3f711753c839d441f55ff6e2a0d52798 Mon Sep 17 00:00:00 2001
From: Maxime Coste <frrrwww@gmail.com>
Date: Fri, 12 Apr 2013 01:31:21 +0200
Subject: [PATCH] Add zj and zk command for scrolling the window

---
 README.asciidoc | 2 ++
 src/main.cc     | 6 ++++++
 src/window.cc   | 5 +++++
 src/window.hh   | 1 +
 4 files changed, 14 insertions(+)

diff --git a/README.asciidoc b/README.asciidoc
index 2e127dcb..8e8762f3 100644
--- a/README.asciidoc
+++ b/README.asciidoc
@@ -148,6 +148,8 @@ window.
  * _zz_ or _zc_: center the main selection in the window
  * _zt_: scroll to put the main selection on the top line of the window
  * _zb_: scroll to put the main selection on the bottom line of the window
+ * _zj_: scroll the window count line downward
+ * _zk_: scroll the window count line upward
 
 Multi Selection
 ---------------
diff --git a/src/main.cc b/src/main.cc
index 81cabb17..1d7d7c28 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -167,6 +167,12 @@ void do_disp_cmd(Context& context)
         case 'b':
             context.window().display_selection_at(window.dimensions().line-1);
             break;
+        case 'j':
+            context.window().scroll( std::max<LineCount>(1, context.numeric_param()));
+            break;
+        case 'k':
+            context.window().scroll(-std::max<LineCount>(1, context.numeric_param()));
+            break;
         }
     });
 }
diff --git a/src/window.cc b/src/window.cc
index 132c48fe..f77a200f 100644
--- a/src/window.cc
+++ b/src/window.cc
@@ -52,6 +52,11 @@ void Window::center_selection()
     display_selection_at(m_dimensions.line/2_line);
 }
 
+void Window::scroll(LineCount offset)
+{
+    m_position.line = std::max(0_line, m_position.line + offset);
+}
+
 void Window::update_display_buffer()
 {
     scroll_to_keep_cursor_visible_ifn();
diff --git a/src/window.hh b/src/window.hh
index b8cf0ddc..8f842f06 100644
--- a/src/window.hh
+++ b/src/window.hh
@@ -34,6 +34,7 @@ public:
 
     void center_selection();
     void display_selection_at(LineCount line);
+    void scroll(LineCount offset);
     void update_display_buffer();
 
     DisplayCoord display_position(const BufferIterator& it);