print glutin events if --print-events is passed

When debugging many issues, it's often very helpful to have the raw
glutin events printed out to stderr as they come in. This does that.

Note that since `glutin::Event` doesn't implement `Display`, we just use
rust's debugging output for now via `{:?}`.

src/cli.rs

@@ -16,6 +16,7 @@ use index::{Line, Column};
 
 /// Options specified on the command line
 pub struct Options {
+    pub print_events: bool,
     pub ref_test: bool,
     pub columns: Column,
     pub lines: Line,
@@ -25,6 +26,7 @@ pub struct Options {
 impl Default for Options {
     fn default() -> Options {
         Options {
+            print_events: false,
             ref_test: false,
             columns: Column(80),
             lines: Line(24),
@@ -43,6 +45,7 @@ impl Options {
             match &arg[..] {
                 // Generate ref test
                 "--ref-test" => options.ref_test = true,
+                "--print-events" => options.print_events = true,
                 // Set dimensions
                 "-d" | "--dimensions" => {
                     args_iter.next()

src/event.rs

@@ -9,6 +9,7 @@ use parking_lot::MutexGuard;
 use glutin::{self, ElementState};
 
 use config::Config;
+use cli::Options;
 use display::OnResize;
 use index::{Line, Column, Side};
 use input::{self, ActionContext, MouseBinding, KeyBinding};
@@ -58,6 +59,7 @@ impl Default for Mouse {
 pub struct Processor<N> {
     key_bindings: Vec<KeyBinding>,
     mouse_bindings: Vec<MouseBinding>,
+    print_events: bool,
     notifier: N,
     mouse: Mouse,
     resize_tx: mpsc::Sender<(u32, u32)>,
@@ -83,6 +85,7 @@ impl<N: Notify> Processor<N> {
     pub fn new(
         notifier: N,
         resize_tx: mpsc::Sender<(u32, u32)>,
+        options: &Options,
         config: &Config,
         ref_test: bool,
         size_info: SizeInfo,
@@ -90,6 +93,7 @@ impl<N: Notify> Processor<N> {
         Processor {
             key_bindings: config.key_bindings().to_vec(),
             mouse_bindings: config.mouse_bindings().to_vec(),
+            print_events: options.print_events,
             notifier: notifier,
             resize_tx: resize_tx,
             ref_test: ref_test,
@@ -184,6 +188,9 @@ impl<N: Notify> Processor<N> {
             // Convenience macro which curries most arguments to handle_event.
             macro_rules! process {
                 ($event:expr) => {
+                    if self.print_events {
+                        err_println!("glutin event: {:?}", $event);
+                    }
                     Processor::handle_event(
                         &mut processor,
                         $event,

src/main.rs

@@ -118,6 +118,7 @@ fn run(mut config: Config, options: cli::Options) -> Result<(), Box<Error>> {
     let mut processor = event::Processor::new(
         event_loop::Notifier(loop_tx),
         display.resize_channel(),
+        &options,
         &config,
         options.ref_test,
         display.size().to_owned(),