Implement terminal resizing

The resize event is received from glutin on the update thread, but the
renderer needs to be informed as well for updating the viewport and
projection matrix. This is achieved with an mpsc::channel.

To support resizing, the grid now offers methods for growing and
shrinking, and there are several implementations available for
clear_region based on different Range* types.

Core resize logic is all in Term::resize. It attempts to keep as much
context as possible when shinking the window. When growing, it's
basically just adding rows.

4 files changed, 196 insertions, 11 deletions

diff --git a/src/grid.rs b/src/grid.rs
index 42dcf210..3ce0a036 100644
--- a/src/grid.rs
+++ b/src/grid.rs
@@ -1,6 +1,7 @@
 //! Functions for computing properties of the terminal grid
 
 use std::ops::{Index, IndexMut, Deref, DerefMut, Range, RangeTo, RangeFrom};
+use std::cmp::Ordering;
 use std::slice::{Iter, IterMut};
 
 use util::Rotate;
@@ -104,12 +105,55 @@ impl Grid {
         self.clear_region(region);
     }
 
-    pub fn clear_region(&mut self, region: Range<usize>) {
-        for row in self.raw[region].iter_mut() {
-            for cell in row.iter_mut() {
-                cell.reset();
-            }
+    pub fn resize(&mut self, rows: usize, cols: usize) {
+        // Check that there's actually work to do and return early if not
+        if rows == self.rows && cols == self.cols {
+            return;
+        }
+
+        match self.rows.cmp(&rows) {
+            Ordering::Less => self.grow_rows(rows),
+            Ordering::Greater => self.shrink_rows(rows),
+            Ordering::Equal => (),
+        }
+
+        match self.cols.cmp(&cols) {
+            Ordering::Less => self.grow_cols(cols),
+            Ordering::Greater => self.shrink_cols(cols),
+            Ordering::Equal => (),
+        }
+    }
+
+    fn grow_rows(&mut self, rows: usize) {
+        for _ in self.num_rows()..rows {
+            self.raw.push(Row::new(self.cols));
+        }
+
+        self.rows = rows;
+    }
+
+    fn shrink_rows(&mut self, rows: usize) {
+        while self.raw.len() != rows {
+            self.raw.pop();
         }
+
+        self.rows = rows;
+    }
+
+    fn grow_cols(&mut self, cols: usize) {
+        for row in self.rows_mut() {
+            row.grow(cols);
+        }
+
+        self.cols = cols;
+    }
+
+    fn shrink_cols(&mut self, cols: usize) {
+        for row in self.rows_mut() {
+            row.shrink(cols);
+        }
+
+        self.cols = cols;
     }
 }
 
@@ -154,6 +198,18 @@ impl Row {
         Row(vec![Cell::new(' '); columns])
     }
 
+    pub fn grow(&mut self, cols: usize) {
+        while self.len() != cols {
+            self.push(Cell::new(' '));
+        }
+    }
+
+    pub fn shrink(&mut self, cols: usize) {
+        while self.len() != cols {
+            self.pop();
+        }
+    }
+
     pub fn cells(&self) -> Iter<Cell> {
         self.0.iter()
     }
@@ -221,3 +277,25 @@ impl IndexMut<RangeTo<usize>> for Row {
         &mut self.0[index]
     }
 }
+
+pub trait ClearRegion<T> {
+    fn clear_region(&mut self, region: T);
+}
+
+macro_rules! clear_region_impl {
+    ($range:ty) => {
+        impl ClearRegion<$range> for Grid {
+            fn clear_region(&mut self, region: $range) {
+                for row in self.raw[region].iter_mut() {
+                    for cell in row.iter_mut() {
+                        cell.reset();
+                    }
+                }
+            }
+        }
+    }
+}
+
+clear_region_impl!(Range<usize>);
+clear_region_impl!(RangeTo<usize>);
+clear_region_impl!(RangeFrom<usize>);
diff --git a/src/main.rs b/src/main.rs
index 49f2655e..de0ea05e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -65,6 +65,7 @@ fn handle_event<W>(event: Event,
                    writer: &mut W,
                    terminal: &mut Term,
                    pty_parser: &mut ansi::Parser,
+                   render_tx: &mpsc::Sender<(u32, u32)>,
                    input_processor: &mut input::Processor) -> ShouldExit
     where W: Write
 {
@@ -78,6 +79,10 @@ fn handle_event<W>(event: Event,
                 let encoded = c.encode_utf8();
                 writer.write(encoded.as_slice()).unwrap();
             },
+            glutin::Event::Resized(w, h) => {
+                terminal.resize(w as f32, h as f32);
+                render_tx.send((w, h)).expect("render thread active");
+            },
             glutin::Event::KeyboardInput(state, _code, key) => {
                 input_processor.process(state, key, &mut WriteNotifier(writer), *terminal.mode())
             },
@@ -165,6 +170,8 @@ fn main() {
     let window = Arc::new(window);
     let window_ref = window.clone();
 
+    let (render_tx, render_rx) = mpsc::channel::<(u32, u32)>();
+
     let update_thread = thread::spawn_named("Update", move || {
         'main_loop: loop {
             let mut writer = BufWriter::new(&writer);
@@ -192,6 +199,7 @@ fn main() {
                                    &mut writer,
                                    &mut *terminal,
                                    &mut pty_parser,
+                                   &render_tx,
                                    &mut input_processor);
             if res == ShouldExit::Yes {
                 break;
@@ -205,6 +213,7 @@ fn main() {
                                                &mut writer,
                                                &mut *terminal,
                                                &mut pty_parser,
+                                               &render_tx,
                                                &mut input_processor);
 
                         if res == ShouldExit::Yes {
@@ -249,6 +258,15 @@ fn main() {
                 gl::Clear(gl::COLOR_BUFFER_BIT);
             }
 
+            // Receive any resize events; only call gl::Viewport on last available
+            let mut new_size = None;
+            while let Ok(val) = render_rx.try_recv() {
+                new_size = Some(val);
+            }
+            if let Some((w, h)) = new_size.take() {
+                renderer.resize(w as i32, h as i32);
+            }
+
             // Need scope so lock is released when swap_buffers is called
             {
                 // Flag that it's time for render
diff --git a/src/renderer/mod.rs b/src/renderer/mod.rs
index 9df4052d..8e548dd3 100644
--- a/src/renderer/mod.rs
+++ b/src/renderer/mod.rs
@@ -478,6 +478,18 @@ impl QuadRenderer {
         self.active_tex = 0;
         self.program = program;
     }
+
+    pub fn resize(&mut self, width: i32, height: i32) {
+        // viewport
+        unsafe {
+            gl::Viewport(0, 0, width, height);
+        }
+
+        // update projection
+        self.program.activate();
+        self.program.update_projection(width as f32, height as f32);
+        self.program.deactivate();
+    }
 }
 
 impl<'a> RenderApi<'a> {
@@ -665,20 +677,25 @@ impl ShaderProgram {
             u_background: background,
         };
 
+        shader.update_projection(width as f32, height as f32);
+
+        shader.deactivate();
+
+        Ok(shader)
+    }
+
+    fn update_projection(&self, width: f32, height: f32) {
         // set projection uniform
-        let ortho = cgmath::ortho(0., width as f32, 0., height as f32, -1., 1.);
+        let ortho = cgmath::ortho(0., width, 0., height, -1., 1.);
         let projection: [[f32; 4]; 4] = ortho.into();
 
         println!("width: {}, height: {}", width, height);
 
         unsafe {
-            gl::UniformMatrix4fv(shader.u_projection,
+            gl::UniformMatrix4fv(self.u_projection,
                                  1, gl::FALSE, projection.as_ptr() as *const _);
         }
 
-        shader.deactivate();
-
-        Ok(shader)
     }
 
     fn set_term_uniforms(&self, props: &term::SizeInfo) {
diff --git a/src/term.rs b/src/term.rs
index c11a0d08..d4168ead 100644
--- a/src/term.rs
+++ b/src/term.rs
@@ -2,10 +2,21 @@
 use std::ops::Range;
 
 use ansi::{self, Attr};
-use grid::{self, Grid, CellFlags};
+use grid::{self, Grid, CellFlags, ClearRegion};
 use tty;
 use ::Rgb;
 
+/// coerce val to be between min and max
+fn limit<T: PartialOrd>(val: T, min: T, max: T) -> T {
+    if val < min {
+        min
+    } else if val > max {
+        max
+    } else {
+        val
+    }
+}
+
 /// tomorrow night bright
 ///
 /// because contrast
@@ -190,6 +201,67 @@ impl Term {
         }
     }
 
+    /// Resize terminal to new dimensions
+    pub fn resize(&mut self, width: f32, height: f32) {
+        let size = SizeInfo {
+            width: width,
+            height: height,
+            cell_width: self.size_info.cell_width,
+            cell_height: self.size_info.cell_height,
+        };
+
+        let old_cols = self.size_info.cols();
+        let old_rows = self.size_info.rows();
+        let num_cols = size.cols();
+        let num_rows = size.rows();
+
+        self.size_info = size;
+
+        if old_cols == num_cols && old_rows == num_rows {
+            return;
+        }
+
+        // Scroll up to keep cursor and as much context as possible in grid. This only runs when the
+        // rows decreases.
+        self.scroll_region = 0..self.grid.num_rows();
+        // XXX why is +1 required?
+        let row_diff = (self.cursor_y() as isize - num_rows as isize) + 1;
+        if row_diff > 0 {
+            self.scroll(row_diff);
+            self.cursor.advance(-row_diff as i64, 0);
+        }
+
+        println!("num_cols, num_rows = {}, {}", num_cols, num_rows);
+
+        // Resize grids to new size
+        self.grid.resize(num_rows, num_cols);
+        self.alt_grid.resize(num_rows, num_cols);
+
+        // Ensure cursor is in-bounds
+        self.cursor.y = limit(self.cursor.y, 0, num_rows as u16);
+        self.cursor.x = limit(self.cursor.x, 0, num_cols as u16);
+
+        // Recreate tabs list
+        self.tabs = (0..self.grid.num_cols()).map(|i| i % TAB_SPACES == 0)
+                                             .collect::<Vec<bool>>();
+
+        // Make sure bottom of terminal is clear
+        if row_diff > 0 {
+            self.grid.clear_region((self.cursor.y as usize)..);
+            self.alt_grid.clear_region((self.cursor.y as usize)..);
+        }
+
+        // Reset scrolling region to new size
+        self.scroll_region = 0..self.grid.num_rows();
+
+        // Inform tty of new dimensions
+        self.tty.resize(num_rows,
+                        num_cols,
+                        self.size_info.width as usize,
+                        self.size_info.height as usize);
+
+    }
+
     #[inline]
     pub fn tty(&self) -> &tty::Tty {
         &self.tty