add default key maps for scrolling down/up by page

README.md

@@ -175,12 +175,14 @@ Default key mappings are as follows:
 | `Ctrl+N`, `↓`                                | Move cursor down by one line              |
 | `Alt+F`, `Ctrl+→`                            | Move cursor forward by word               |
 | `Atl+B`, `Ctrl+←`                            | Move cursor backward by word              |
-| `Alt+P`, `Ctrl+↑`                            | Move cursor up by paragraph               |
-| `Alt+N`, `Ctrl+↓`                            | Move cursor down by paragraph             |
+| `Alt+]`, `Alt+P`, `Ctrl+↑`                   | Move cursor up by paragraph               |
+| `Alt+[`, `Alt+N`, `Ctrl+↓`                   | Move cursor down by paragraph             |
 | `Ctrl+E`, `End`, `Ctrl+Alt+F`, `Ctrl+Alt+→`  | Move cursor to the end of line            |
 | `Ctrl+A`, `Home`, `Ctrl+Alt+B`, `Ctrl+Alt+←` | Move cursor to the head of line           |
 | `Alt+<`, `Ctrl+Alt+P`, `Ctrl+Alt+↑`          | Move cursor to top of lines               |
 | `Alt+>`, `Ctrl+Alt+N`, `Ctrl+Alt+↓`          | Move cursor to bottom of lines            |
+| `Ctrl+V`, `PageDown`                         | Scroll down by page                       |
+| `Alt+V`, `PageUp`                            | Scroll up by page                         |
 
 Deleting multiple characters at once saves the deleted text to yank buffer. It can be pasted with `Ctrl+Y` or `Ctrl+V`
 later.
@@ -387,7 +389,7 @@ All editor operations are defined as public methods of `TextArea`. To move curso
 notify how to move the cursor.
 
 | Method                                               | Operation                                       |
-|------------------------------------------------------|----------------------------------------------|
+|------------------------------------------------------|-------------------------------------------------|
 | `textarea.delete_char()`                             | Delete one character before cursor              |
 | `textarea.delete_next_char()`                        | Delete one character next to cursor             |
 | `textarea.insert_newline()`                          | Insert newline                                  |
@@ -415,7 +417,11 @@ notify how to move the cursor.
 | `textarea.set_search_pattern(pattern)`               | Set a pattern for text search                   |
 | `textarea.search_forward(match_cursor)`              | Move cursor to next match of text search        |
 | `textarea.search_back(match_cursor)`                 | Move cursor to previous match of text search    |
-| `textarea.scroll(scrolling)`                         | Scroll the viewport                          |
+| `textarea.scroll(Scrolling::PageDown)`               | Scroll down the viewport by page                |
+| `textarea.scroll(Scrolling::PageUp)`                 | Scroll up the viewport by page                  |
+| `textarea.scroll(Scrolling::HalfPageDown)`           | Scroll down the viewport by half-page           |
+| `textarea.scroll(Scrolling::HalfPageUp)`             | Scroll up the viewport by half-page             |
+| `textarea.scroll((row, col))`                        | Scroll down the viewport to (row, col) position |
 
 To define your own key mappings, simply call the above methods in your code instead of `TextArea::input()` method. The
 following example defines modal key mappings like Vim.

src/textarea.rs

@@ -399,6 +399,11 @@ impl<'a> TextArea<'a> {
                 false
             }
             Input {
+                key: Key::Char(']'),
+                ctrl: false,
+                alt: true,
+            }
+            | Input {
                 key: Key::Char('n'),
                 ctrl: false,
                 alt: true,
@@ -407,14 +412,16 @@ impl<'a> TextArea<'a> {
                 key: Key::Down,
                 ctrl: true,
                 alt: false,
-            }
-            | Input {
-                key: Key::PageDown, ..
             } => {
                 self.move_cursor(CursorMove::ParagraphForward);
                 false
             }
             Input {
+                key: Key::Char('['),
+                ctrl: false,
+                alt: true,
+            }
+            | Input {
                 key: Key::Char('p'),
                 ctrl: false,
                 alt: true,
@@ -423,9 +430,6 @@ impl<'a> TextArea<'a> {
                 key: Key::Up,
                 ctrl: true,
                 alt: false,
-            }
-            | Input {
-                key: Key::PageUp, ..
             } => {
                 self.move_cursor(CursorMove::ParagraphBack);
                 false
@@ -445,6 +449,28 @@ impl<'a> TextArea<'a> {
                 ctrl: true,
                 alt: false,
             } => self.paste(),
+            Input {
+                key: Key::Char('v'),
+                ctrl: true,
+                alt: false,
+            }
+            | Input {
+                key: Key::PageDown, ..
+            } => {
+                self.scroll(Scrolling::PageDown);
+                false
+            }
+            Input {
+                key: Key::Char('v'),
+                ctrl: false,
+                alt: true,
+            }
+            | Input {
+                key: Key::PageUp, ..
+            } => {
+                self.scroll(Scrolling::PageUp);
+                false
+            }
             Input {
                 key: Key::MouseScrollDown,
                 ..