Scrolling in the editor by following the cursor now works.

src/buffer/mod.rs

@@ -61,6 +61,7 @@ impl TextBuffer {
     }
 
     
+    /// Creates an iterator at the first character
     pub fn root_iter<'a>(&'a self) -> TextBufferIter<'a> {
         let mut node_stack: Vec<&'a TextNode> = Vec::new();
         let mut cur_node = &self.root;
@@ -86,6 +87,49 @@ impl TextBuffer {
             }
         }
     }
+    
+    
+    /// Creates an iterator starting at the specified character index.
+    /// If the index is past the end of the text, then the iterator will
+    /// return None on next().
+    pub fn iter_at_char<'a>(&'a self, index: uint) -> TextBufferIter<'a> {
+        let mut node_stack: Vec<&'a TextNode> = Vec::new();
+        let mut cur_node = &self.root;
+        let mut char_i = index;
+        
+        loop {
+            match cur_node.data {
+                TextNodeData::Leaf(_) => {
+                    let mut char_iter = match cur_node.data {
+                        TextNodeData::Leaf(ref tb) => tb.as_str().chars(),
+                        _ => panic!("This should never happen.")
+                    };
+                    
+                    while char_i > 0 {
+                        char_iter.next();
+                        char_i -= 1;
+                    }
+                
+                    return TextBufferIter {
+                        node_stack: node_stack,
+                        cur_block: char_iter,
+                    };
+                },
+                
+                TextNodeData::Branch(ref left, ref right) => {
+                    if left.char_count > char_i {
+                        node_stack.push(&(**right));
+                        cur_node = &(**left);
+                    }
+                    else {
+                        cur_node = &(**right);
+                        char_i -= left.char_count;
+                    }
+                }
+            }
+        }
+    }
+
 }
 
 impl fmt::Show for TextBuffer {
@@ -129,6 +173,30 @@ impl<'a> TextBufferIter<'a> {
             }
         }
     }
+    
+    
+    // Skips the iterator n characters ahead, unless it hits a newline
+    // character.  If it hits a newline character, returns true, otherwise,
+    // false.
+    pub fn skip_non_newline_chars(&mut self, n: uint) -> bool {
+        // TODO: more efficient implementation, taking advantage of rope
+        // structure.
+        for _ in range(0, n) {
+            match self.next() {
+                Option::Some(c) => {
+                    if c == '\n' {
+                        return true;
+                    }
+                },
+                
+                Option::None => {
+                    break;
+                }
+            }
+        }
+        
+        return false;
+    }
 }
 
 

src/editor.rs

@@ -57,6 +57,26 @@ impl Editor {
         self.view_dim = (h, w);
     }
     
+    
+    /// Moves the editor's view the minimum amount to show the cursor
+    pub fn move_view_to_cursor(&mut self) {
+        // Horizontal
+        if self.cursor.1 < self.view_pos.1 {
+            self.view_pos.1 = self.cursor.1;
+        }
+        else if self.cursor.1 >= (self.view_pos.1 + self.view_dim.1) {
+            self.view_pos.1 = 1 + self.cursor.1 - self.view_dim.1;
+        }
+        
+        // Vertical
+        if self.cursor.0 < self.view_pos.0 {
+            self.view_pos.0 = self.cursor.0;
+        }
+        else if self.cursor.0 >= (self.view_pos.0 + self.view_dim.0) {
+            self.view_pos.0 = 1 + self.cursor.0 - self.view_dim.0;
+        }
+    }
+    
     pub fn insert_text_at_cursor(&mut self, text: &str) {
         let pos = self.buffer.pos_2d_to_closest_1d(self.cursor);
         let str_len = char_count(text);
@@ -68,6 +88,8 @@ impl Editor {
         
         // Move cursor
         self.cursor = self.buffer.pos_1d_to_closest_2d(p + str_len);
+        
+        self.move_view_to_cursor();
     }
     
     pub fn insert_text_at_char(&mut self, text: &str, pos: uint) {
@@ -87,6 +109,8 @@ impl Editor {
         self.buffer.remove_text(pos_a, pos_b);
         
         self.dirty = true;
+        
+        self.move_view_to_cursor();
     }
     
     pub fn cursor_left(&mut self) {
@@ -98,22 +122,30 @@ impl Editor {
         else {
             self.cursor = self.buffer.pos_1d_to_closest_2d(0);
         }
+        
+        self.move_view_to_cursor();
     }
     
     pub fn cursor_right(&mut self) {
         let p = self.buffer.pos_2d_to_closest_1d(self.cursor);
         self.cursor = self.buffer.pos_1d_to_closest_2d(p + 1);
+        
+        self.move_view_to_cursor();
     }
     
     pub fn cursor_up(&mut self) {
         if self.cursor.0 > 0 {
             self.cursor.0 -= 1;
         }
+        
+        self.move_view_to_cursor();
     }
     
     pub fn cursor_down(&mut self) {
         if self.cursor.0 < self.buffer.newline_count() {
             self.cursor.0 += 1;
         }
+        
+        self.move_view_to_cursor();
     }
 }

src/term_ui.rs

@@ -48,6 +48,7 @@ impl TermUI {
     
         let mut width = self.rb.width();
         let mut height = self.rb.height();
+        self.editor.update_dim(height, width);
     
         loop {
             // Draw the editor to screen
@@ -121,6 +122,7 @@ impl TermUI {
                     Ok(rustbox::Event::ResizeEvent(w, h)) => {
                         width = w as uint;
                         height = h as uint;
+                        self.editor.update_dim(height, width);
                     }
                     
                     _ => {
@@ -140,12 +142,14 @@ impl TermUI {
     }
 
     pub fn draw_editor(&self, editor: &Editor, c1: (uint, uint), c2: (uint, uint)) {
-        let mut tb_iter = editor.buffer.root_iter();
+        let mut tb_iter = editor.buffer.iter_at_char(editor.buffer.pos_2d_to_closest_1d(editor.view_pos));
-        let mut line: uint = 0;
+        let mut pline = c1.0;
-        let mut column: uint = 0;
+        let mut pcol = c1.1;
-        let mut pos: uint = 0;
+        let mut line = editor.view_pos.0;
-        let height = c2.0 - c1.0;
+        let mut column = editor.view_pos.1;
-        let width = c2.1 - c1.1;
+        let mut pos = editor.buffer.pos_2d_to_closest_1d(editor.view_pos);
+        let max_line = line + (c2.0 - c1.0);
+        let max_col = column + (c2.1 - c1.1);
         
         let cursor_pos = editor.buffer.pos_2d_to_closest_1d(editor.cursor);
         
@@ -153,20 +157,23 @@ impl TermUI {
             if let Option::Some(c) = tb_iter.next() {
                 if c == '\n' {
                     if pos == cursor_pos {
-                        self.rb.print(column, line, rustbox::RB_NORMAL, Color::Black, Color::White, " ".to_string().as_slice());
+                        self.rb.print(pcol, pline, rustbox::RB_NORMAL, Color::Black, Color::White, " ".to_string().as_slice());
                     }
                     
+                    pline += 1;
+                    pcol = c1.1;
                     line += 1;
                     column = 0;
                 }
                 else {
                     if pos == cursor_pos  {
-                        self.rb.print(column, line, rustbox::RB_NORMAL, Color::Black, Color::White, c.to_string().as_slice());
+                        self.rb.print(pcol, pline, rustbox::RB_NORMAL, Color::Black, Color::White, c.to_string().as_slice());
                     }
                     else {
-                        self.rb.print(column, line, rustbox::RB_NORMAL, Color::White, Color::Black, c.to_string().as_slice());
+                        self.rb.print(pcol, pline, rustbox::RB_NORMAL, Color::White, Color::Black, c.to_string().as_slice());
                     }
                     
+                    pcol += 1;
                     column += 1;
                 }
             }
@@ -174,24 +181,57 @@ impl TermUI {
                 // Show cursor at end of document if it's past the end of
                 // the document
                 if cursor_pos >= pos {
-                    self.rb.print(column, line, rustbox::RB_NORMAL, Color::Black, Color::White, " ");
+                    self.rb.print(pcol, pline, rustbox::RB_NORMAL, Color::Black, Color::White, " ");
                 }
                 
-                break;
+                return;
             }
 
-            pos += 1;
+            if line > max_line {
-
+                return;
-            if line > height {
-                break;
             }
             
-            if column > width {
+            // If we're past the edge of the display, go to the next line
+            if column > max_col {
                 tb_iter.next_line();
+                
+                pline += 1;
+                pcol = c1.1;
                 line += 1;
                 column = 0;
+                
+                if line > max_line {
+                    return;
+                }
+            }
+            
+            // If we're before the edge of the display, move forward to get
+            // to it.
+            loop {
+                if column < editor.view_pos.1 {
+                    let nl = tb_iter.skip_non_newline_chars(editor.view_pos.1);
+                    if !nl {
+                        column = editor.view_pos.1;
+                        break;
+                    }
+                    else {
+                        pline += 1;
+                        line += 1;
+                    }
+                    
+                    if line > max_line {
+                        return;
+                    }
+                }
+                else {
+                    break;
+                }
+            }
+            
+            // Get the 1d position of the char to be printed next
             pos = editor.buffer.pos_2d_to_closest_1d((line, column));
         }
     }
-    }
+    
+    
 }