Implement user actions for font resize (#625)

Adds support for font resizing at run-time. Three new actions are
introduced:

* IncreaseFontSize - Increases current font size by 1.0
* DecreaseFontSize - Decreases current font size by 1.0
* ResetFontSize - Resets font size to that specified in the
  configuration.

The stock config files have example configuration for each which should
match gnome-terminal. For convenience, the config entries are:

    - { key: Key0,     mods: Control, action: ResetFontSize    }
    - { key: Equals,   mods: Control, action: IncreaseFontSize }
    - { key: Subtract, mods: Control, action: DecreaseFontSize }

9 files changed, 149 insertions, 49 deletions

diff --git a/alacritty.yml b/alacritty.yml
index c5684397..f69640da 100644
--- a/alacritty.yml
+++ b/alacritty.yml
@@ -215,6 +215,9 @@ key_bindings:
   - { key: Q,        mods: Command, action: Quit                         }
   - { key: W,        mods: Command, action: Quit                         }
   - { key: Insert,   mods: Shift,   action: PasteSelection               }
+  - { key: Key0,     mods: Control, action: ResetFontSize                }
+  - { key: Equals,   mods: Control, action: IncreaseFontSize             }
+  - { key: Subtract, mods: Control, action: DecreaseFontSize             }
   - { key: Home,                    chars: "\x1bOH",   mode: AppCursor   }
   - { key: Home,                    chars: "\x1b[H",   mode: ~AppCursor  }
   - { key: End,                     chars: "\x1bOF",   mode: AppCursor   }
diff --git a/alacritty_macos.yml b/alacritty_macos.yml
index 1a16a8c9..61f53868 100644
--- a/alacritty_macos.yml
+++ b/alacritty_macos.yml
@@ -196,6 +196,9 @@ key_bindings:
   - { key: Home,                    chars: "\x1b[H",   mode: ~AppCursor  }
   - { key: End,                     chars: "\x1bOF",   mode: AppCursor   }
   - { key: End,                     chars: "\x1b[F",   mode: ~AppCursor  }
+  - { key: Key0,     mods: Control, action: ResetFontSize                }
+  - { key: Equals,   mods: Control, action: IncreaseFontSize             }
+  - { key: Subtract, mods: Control, action: DecreaseFontSize             }
   - { key: PageUp,   mods: Shift,   chars: "\x1b[5;2~"                   }
   - { key: PageUp,   mods: Control, chars: "\x1b[5;5~"                   }
   - { key: PageUp,                  chars: "\x1b[5~"                     }
diff --git a/src/config.rs b/src/config.rs
index 4dffa70a..a310ff81 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -409,6 +409,9 @@ impl<'a> de::Deserialize<'a> for ActionWrapper {
                     "Paste" => Action::Paste,
                     "Copy" => Action::Copy,
                     "PasteSelection" => Action::PasteSelection,
+                    "IncreaseFontSize" => Action::IncreaseFontSize,
+                    "DecreaseFontSize" => Action::DecreaseFontSize,
+                    "ResetFontSize" => Action::ResetFontSize,
                     "Quit" => Action::Quit,
                     _ => return Err(E::invalid_value(Unexpected::Str(value), &self)),
                 }))
@@ -1298,7 +1301,7 @@ impl DeserializeFromF32 for Size {
 /// field in this struct. It might be nice in the future to have defaults for
 /// each value independently. Alternatively, maybe erroring when the user
 /// doesn't provide complete config is Ok.
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, Clone)]
 pub struct Font {
     /// Font family
     pub normal: FontDescription,
@@ -1311,7 +1314,7 @@ pub struct Font {
 
     // Font size in points
     #[serde(deserialize_with="DeserializeFromF32::deserialize_from_f32")]
-    size: Size,
+    pub size: Size,
 
     /// Extra spacing per character
     offset: Delta,
@@ -1333,7 +1336,7 @@ fn default_italic_desc() -> FontDescription {
 }
 
 /// Description of a single font
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, Clone)]
 pub struct FontDescription {
     pub family: String,
     pub style: Option<String>,
@@ -1366,6 +1369,18 @@ impl Font {
     pub fn glyph_offset(&self) -> &Delta {
         &self.glyph_offset
     }
+
+    /// Get a font clone with a size modification
+    pub fn with_size_delta(self, delta: f32) -> Font {
+        let mut new_size = self.size.as_f32_pts() + delta;
+        if new_size < 1.0 {
+            new_size = 1.0;
+        }
+        Font {
+            size : Size::new(new_size),
+            .. self
+        }
+    }
 }
 
 #[cfg(target_os = "macos")]
diff --git a/src/display.rs b/src/display.rs
index cb5cf8c9..25318f0e 100644
--- a/src/display.rs
+++ b/src/display.rs
@@ -96,6 +96,7 @@ pub struct Display {
     rx: mpsc::Receiver<(u32, u32)>,
     tx: mpsc::Sender<(u32, u32)>,
     meter: Meter,
+    font_size_modifier: i8,
     size_info: SizeInfo,
     last_background_color: Rgb,
 }
@@ -133,7 +134,6 @@ impl Display {
         options: &cli::Options,
     ) -> Result<Display, Error> {
         // Extract some properties from config
-        let font = config.font();
         let render_timer = config.render_timer();
 
         // Create the window where Alacritty will be displayed
@@ -146,39 +146,17 @@ impl Display {
 
         info!("device_pixel_ratio: {}", dpr);
 
-        let rasterizer = font::Rasterizer::new(dpr, config.use_thin_strokes())?;
-
         // Create renderer
         let mut renderer = QuadRenderer::new(&config, size)?;
 
-        // Initialize glyph cache
-        let glyph_cache = {
-            info!("Initializing glyph cache");
-            let init_start = ::std::time::Instant::now();
-
-            let cache = renderer.with_loader(|mut api| {
-                GlyphCache::new(rasterizer, config, &mut api)
-            })?;
-
-            let stop = init_start.elapsed();
-            let stop_f = stop.as_secs() as f64 + stop.subsec_nanos() as f64 / 1_000_000_000f64;
-            info!("Finished initializing glyph cache in {}", stop_f);
-
-            cache
-        };
-
-        // Need font metrics to resize the window properly. This suggests to me the
-        // font metrics should be computed before creating the window in the first
-        // place so that a resize is not needed.
-        let metrics = glyph_cache.font_metrics();
-        let cell_width = (metrics.average_advance + font.offset().x as f64) as u32;
-        let cell_height = (metrics.line_height + font.offset().y as f64) as u32;
+        let (glyph_cache, cell_width, cell_height) =
+            Self::new_glyph_cache(&window, &mut renderer, config, 0)?;
 
         // Resize window to specified dimensions
         let dimensions = options.dimensions()
             .unwrap_or_else(|| config.dimensions());
-        let width = cell_width * dimensions.columns_u32();
-        let height = cell_height * dimensions.lines_u32();
+        let width = cell_width as u32 * dimensions.columns_u32();
+        let height = cell_height as u32 * dimensions.lines_u32();
         let size = Size { width: Pixels(width), height: Pixels(height) };
         info!("set_inner_size: {}", size);
 
@@ -222,11 +200,56 @@ impl Display {
             tx: tx,
             rx: rx,
             meter: Meter::new(),
+            font_size_modifier: 0,
             size_info: size_info,
             last_background_color: background_color,
         })
     }
 
+    fn new_glyph_cache(window : &Window, renderer : &mut QuadRenderer,
+                       config: &Config, font_size_delta: i8)
+        -> Result<(GlyphCache, f32, f32), Error>
+    {
+        let font = config.font().clone().with_size_delta(font_size_delta as f32);
+        let dpr = window.hidpi_factor();
+        let rasterizer = font::Rasterizer::new(dpr, config.use_thin_strokes())?;
+
+        // Initialize glyph cache
+        let glyph_cache = {
+            info!("Initializing glyph cache");
+            let init_start = ::std::time::Instant::now();
+
+            let cache = renderer.with_loader(|mut api| {
+                GlyphCache::new(rasterizer, &font, &mut api)
+            })?;
+
+            let stop = init_start.elapsed();
+            let stop_f = stop.as_secs() as f64 + stop.subsec_nanos() as f64 / 1_000_000_000f64;
+            info!("Finished initializing glyph cache in {}", stop_f);
+
+            cache
+        };
+
+        // Need font metrics to resize the window properly. This suggests to me the
+        // font metrics should be computed before creating the window in the first
+        // place so that a resize is not needed.
+        let metrics = glyph_cache.font_metrics();
+        let cell_width = (metrics.average_advance + font.offset().x as f64) as u32;
+        let cell_height = (metrics.line_height + font.offset().y as f64) as u32;
+
+        return Ok((glyph_cache, cell_width as f32, cell_height as f32));
+    }
+
+    pub fn update_glyph_cache(&mut self, config: &Config, font_size_delta: i8)
+    {
+        let (glyph_cache, cell_width, cell_height) =
+            Self::new_glyph_cache(&self.window,
+                        &mut self.renderer, config, font_size_delta).unwrap();
+        self.glyph_cache = glyph_cache;
+        self.size_info.cell_width = cell_width;
+        self.size_info.cell_height = cell_height;
+    }
+
     #[inline]
     pub fn resize_channel(&self) -> mpsc::Sender<(u32, u32)> {
         self.tx.clone()
@@ -240,6 +263,7 @@ impl Display {
     pub fn handle_resize(
         &mut self,
         terminal: &mut MutexGuard<Term>,
+        config: &Config,
         items: &mut [&mut OnResize]
     ) {
         // Resize events new_size and are handled outside the poll_events
@@ -252,11 +276,27 @@ impl Display {
             new_size = Some(sz);
         }
 
+        if terminal.font_size_modifier != self.font_size_modifier {
+            // Font size modification detected
+
+            self.font_size_modifier = terminal.font_size_modifier;
+            self.update_glyph_cache(config, terminal.font_size_modifier);
+
+            if new_size == None {
+                // Force a resize to refresh things
+                new_size = Some((self.size_info.width as u32,
+                                 self.size_info.height as u32));
+            }
+        }
+
         // Receive any resize events; only call gl::Viewport on last
         // available
         if let Some((w, h)) = new_size.take() {
-            terminal.resize(w as f32, h as f32);
-            let size = terminal.size_info();
+            self.size_info.width = w as f32;
+            self.size_info.height = h as f32;
+
+            let size = &self.size_info;
+            terminal.resize(size);
 
             for item in items {
                 item.on_resize(size)
diff --git a/src/event.rs b/src/event.rs
index 95685001..dda18652 100644
--- a/src/event.rs
+++ b/src/event.rs
@@ -107,6 +107,14 @@ impl<'a, N: Notify + 'a> input::ActionContext for ActionContext<'a, N> {
         self.terminal.pixels_to_coords(self.mouse.x as usize, self.mouse.y as usize)
     }
 
+    fn change_font_size(&mut self, delta: i8) {
+        self.terminal.change_font_size(delta);
+    }
+
+    fn reset_font_size(&mut self) {
+        self.terminal.reset_font_size();
+    }
+
     #[inline]
     fn mouse_mut(&mut self) -> &mut Mouse {
         self.mouse
diff --git a/src/input.rs b/src/input.rs
index 4be7dac5..7378e8dc 100644
--- a/src/input.rs
+++ b/src/input.rs
@@ -62,6 +62,8 @@ pub trait ActionContext {
     fn received_count(&mut self) -> &mut usize;
     fn suppress_chars(&mut self) -> &mut bool;
     fn last_modifiers(&mut self) -> &mut ModifiersState;
+    fn change_font_size(&mut self, delta: i8);
+    fn reset_font_size(&mut self);
 }
 
 /// Describes a state and action to take in that state
@@ -154,6 +156,15 @@ pub enum Action {
     /// Paste contents of selection buffer
     PasteSelection,
 
+    /// Increase font size
+    IncreaseFontSize,
+
+    /// Decrease font size
+    DecreaseFontSize,
+
+    /// Reset font size to the config value
+    ResetFontSize,
+
     /// Run given command
     Command(String, Vec<String>),
 
@@ -202,6 +213,15 @@ impl Action {
                 // FIXME should do a more graceful shutdown
                 ::std::process::exit(0);
             },
+            Action::IncreaseFontSize => {
+               ctx.change_font_size(1);
+            },
+            Action::DecreaseFontSize => {
+               ctx.change_font_size(-1);
+            }
+            Action::ResetFontSize => {
+               ctx.reset_font_size();
+            }
         }
     }
 
@@ -593,6 +613,10 @@ mod tests {
         fn last_modifiers(&mut self) -> &mut ModifiersState {
             &mut self.last_modifiers
         }
+        fn change_font_size(&mut self, _delta: i8) {
+        }
+        fn reset_font_size(&mut self) {
+        }
     }
 
     macro_rules! test_clickstate {
diff --git a/src/main.rs b/src/main.rs
index ec327009..ca7a40c6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -188,7 +188,7 @@ fn run(mut config: Config, options: cli::Options) -> Result<(), Box<Error>> {
             //
             // The second argument is a list of types that want to be notified
             // of display size changes.
-            display.handle_resize(&mut terminal, &mut [&mut pty, &mut processor]);
+            display.handle_resize(&mut terminal, &config, &mut [&mut pty, &mut processor]);
 
             // Draw the current state of the terminal
             display.draw(terminal, &config, processor.selection.as_ref());
diff --git a/src/renderer/mod.rs b/src/renderer/mod.rs
index 9ce690ca..9e6036d4 100644
--- a/src/renderer/mod.rs
+++ b/src/renderer/mod.rs
@@ -29,7 +29,7 @@ use gl;
 use index::{Line, Column, RangeInclusive};
 use notify::{Watcher, watcher, RecursiveMode, DebouncedEvent};
 
-use config::{self, Config, Delta};
+use config::{self, Config, Font, Delta};
 use term::{self, cell, RenderableCell};
 use window::{Size, Pixels};
 
@@ -170,12 +170,11 @@ pub struct GlyphCache {
 impl GlyphCache {
     pub fn new<L>(
         mut rasterizer: Rasterizer,
-        config: &Config,
+        font: &Font,
         loader: &mut L
     ) -> Result<GlyphCache, font::Error>
         where L: LoadGlyph
     {
-        let font = config.font();
         let size = font.size();
         let glyph_offset = *font.glyph_offset();
 
diff --git a/src/term/mod.rs b/src/term/mod.rs
index f9bd5541..a16971b5 100644
--- a/src/term/mod.rs
+++ b/src/term/mod.rs
@@ -655,6 +655,9 @@ pub struct Term {
     /// Scroll region
     scroll_region: Range<Line>,
 
+    /// Font size modifier
+    pub font_size_modifier: i8,
+
     /// Size
     size_info: SizeInfo,
 
@@ -767,6 +770,7 @@ impl Term {
             grid: grid,
             alt_grid: alt,
             alt: false,
+            font_size_modifier: 0,
             active_charset: Default::default(),
             cursor: Default::default(),
             cursor_save: Default::default(),
@@ -783,6 +787,18 @@ impl Term {
         }
     }
 
+    pub fn change_font_size(&mut self, delta: i8) {
+        if let Some(sum) = self.font_size_modifier.checked_add(delta) {
+            self.font_size_modifier = sum;
+            self.dirty = true;
+        }
+    }
+
+    pub fn reset_font_size(&mut self) {
+        self.font_size_modifier = 0;
+        self.dirty = true;
+    }
+
     pub fn update_config(&mut self, config: &Config) {
         self.semantic_escape_chars = config.selection().semantic_escape_chars.clone();
         self.original_colors.fill_named(config.colors());
@@ -965,30 +981,22 @@ impl Term {
     }
 
     /// Resize terminal to new dimensions
-    pub fn resize(&mut self, width: f32, height: f32) {
+    pub fn resize(&mut self, size : &SizeInfo) {
         debug!("Term::resize");
+
         // Bounds check; lots of math assumes width and height are > 0
-        if width as usize <= 2 * self.size_info.padding_x as usize ||
-            height as usize <= 2 * self.size_info.padding_y as usize
+        if size.width as usize <= 2 * self.size_info.padding_x as usize ||
+            size.height as usize <= 2 * self.size_info.padding_y as usize
         {
             return;
         }
 
-        let size = SizeInfo {
-            width: width,
-            height: height,
-            cell_width: self.size_info.cell_width,
-            cell_height: self.size_info.cell_height,
-            padding_x: self.size_info.padding_x,
-            padding_y: self.size_info.padding_y,
-        };
-
         let old_cols = self.grid.num_cols();
         let old_lines = self.grid.num_lines();
         let mut num_cols = size.cols();
         let mut num_lines = size.lines();
 
-        self.size_info = size;
+        self.size_info = *size;
 
         if old_cols == num_cols && old_lines == num_lines {
             debug!("Term::resize dimensions unchanged");