From a5ddd9e5215ede7ef66d7ed8d09c592df4e45c0e Mon Sep 17 00:00:00 2001
From: Zachary Yedidia <zyedidia@gmail.com>
Date: Sat, 19 Mar 2016 09:12:03 -0400
Subject: [PATCH] Add pagedown, pageup, halfpagedown, halfpageup

---
 todolist.md  | 32 ++++++++++++++++++++++++++++++++
 todolist.txt | 27 ---------------------------
 view.go      | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 80 insertions(+), 27 deletions(-)
 create mode 100644 todolist.md
 delete mode 100644 todolist.txt

diff --git a/todolist.md b/todolist.md
new file mode 100644
index 00000000..bee544f7
--- /dev/null
+++ b/todolist.md
@@ -0,0 +1,32 @@
+- [ ] Line numbers
+
+- [ ] Optimization
+
+- [ ] Better selection
+    - [ ] Double click selects current word
+    - [ ] Triple click enables line selection
+
+- [ ] More keybindings
+    - [x] Use pageup and pagedown keys
+    - [ ] Much more (copy sublime text or standard system applications)
+
+- [ ] Syntax highlighting
+    - [ ] Use nano-like syntax files (https://github.com/scopatz/nanorc)
+    - [ ] Allow additional colors and colorschemes
+        - [ ] Support for 256 color and true color
+
+- [ ] Help screen
+    - [ ] Help screen which lists keybindings and commands
+    - [ ] Opened with Ctrl-h
+
+- [ ] Undo/redo
+    - [ ] Undo/redo stack
+    - [ ] Functionality similar to nano
+
+- [ ] Command execution
+    - [ ] Allow executing simple commands at the bottom of the editor 
+      (like vim or emacs)
+
+- [ ] Options
+    - [ ] Add options such as tab size, use tabs or use spaces, etc...
+
diff --git a/todolist.txt b/todolist.txt
deleted file mode 100644
index 8859a098..00000000
--- a/todolist.txt
+++ /dev/null
@@ -1,27 +0,0 @@
-- Better selection
-    - Double click selects current word
-    - Triple click enables line selection
-
-- More keybindings
-    - Use pageup and pagedown keys
-
-- Syntax highlighting
-    - Use nano-like syntax files (https://github.com/scopatz/nanorc)
-    - Allow additional colors and colorschemes
-        - Support for 256 color and true color
-
-- Help screen
-    - Help screen which lists keybindings and commands
-    - Opened with Ctrl-h
-
-- Undo/redo
-    - Undo/redo stack
-    - Functionality similar to nano
-
-- Command execution
-    - Allow executing simple commands at the bottom of the editor 
-      (like vim or emacs)
-
-- Options
-    - Add options such as tab size, use tabs or use spaces, etc...
-
diff --git a/view.go b/view.go
index 21c1d215..364d6edc 100644
--- a/view.go
+++ b/view.go
@@ -71,6 +71,42 @@ func (v *View) ScrollDown(n int) {
 	}
 }
 
+// PageUp scrolls the view up a page
+func (v *View) PageUp() {
+	if v.topline > v.height {
+		v.ScrollUp(v.height)
+	} else {
+		v.topline = 0
+	}
+}
+
+// PageDown scrolls the view down a page
+func (v *View) PageDown() {
+	if len(v.buf.lines)-(v.topline+v.height) > v.height {
+		v.ScrollDown(v.height)
+	} else {
+		v.topline = len(v.buf.lines) - v.height
+	}
+}
+
+// HalfPageUp scrolls the view up half a page
+func (v *View) HalfPageUp() {
+	if v.topline > v.height/2 {
+		v.ScrollUp(v.height / 2)
+	} else {
+		v.topline = 0
+	}
+}
+
+// HalfPageDown scrolls the view down half a page
+func (v *View) HalfPageDown() {
+	if len(v.buf.lines)-(v.topline+v.height) > v.height/2 {
+		v.ScrollDown(v.height / 2)
+	} else {
+		v.topline = len(v.buf.lines) - v.height
+	}
+}
+
 // HandleEvent handles an event passed by the main loop
 // It returns an int describing how the screen needs to be redrawn
 // 0: Screen does not need to be redrawn
@@ -122,6 +158,18 @@ func (v *View) HandleEvent(event tcell.Event) int {
 			}
 			// Need to redraw the status line
 			ret = 1
+		case tcell.KeyPgUp:
+			v.PageUp()
+			return 2
+		case tcell.KeyPgDn:
+			v.PageDown()
+			return 2
+		case tcell.KeyCtrlU:
+			v.HalfPageUp()
+			return 2
+		case tcell.KeyCtrlD:
+			v.HalfPageDown()
+			return 2
 		case tcell.KeyRune:
 			if v.cursor.HasSelection() {
 				v.cursor.DeleteSelected()