Add visual error/warning message

Whenever a warning or an error has been written to the log file/stdout,
a message is now displayed in Alacritty which indicates where the error
came from.

The message is cleared whenever the screen is cleared using either the
`clear` command or the `Ctrl+L` key binding.

6 files changed, 93 insertions, 29 deletions

diff --git a/Cargo.lock b/Cargo.lock
index b1aadb3c..1c48899d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2123,6 +2123,19 @@ dependencies = [
 ]
 
 [[package]]
+name = "tempfile"
+version = "3.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.43 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "redox_syscall 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",
+ "remove_dir_all 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "termcolor"
 version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -2996,6 +3009,7 @@ dependencies = [
 "checksum syn 0.15.18 (registry+https://github.com/rust-lang/crates.io-index)" = "90c39a061e2f412a9f869540471ab679e85e50c6b05604daf28bc3060f75c430"
 "checksum synstructure 0.10.1 (registry+https://github.com/rust-lang/crates.io-index)" = "73687139bf99285483c96ac0add482c3776528beac1d97d444f6e91f203a2015"
 "checksum tempdir 0.3.7 (registry+https://github.com/rust-lang/crates.io-index)" = "15f2b5fb00ccdf689e0149d1b1b3c03fead81c2b37735d812fa8bddbbf41b6d8"
+"checksum tempfile 3.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "55c1195ef8513f3273d55ff59fe5da6940287a0d7a98331254397f464833675b"
 "checksum termcolor 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "4096add70612622289f2fdcdbd5086dc81c1e2675e6ae58d6c4f62a16c6d7f2f"
 "checksum terminfo 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "8e51065bafd2abe106b6036483b69d1741f4a1ec56ce8a2378de341637de689e"
 "checksum termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "689a3bdfaab439fd92bc87df5c4c78417d3cbe537487274e9b0b2dce76e92096"
diff --git a/src/display.rs b/src/display.rs
index 6ab622f2..b185b6be 100644
--- a/src/display.rs
+++ b/src/display.rs
@@ -28,6 +28,7 @@ use renderer::{self, GlyphCache, QuadRenderer};
 use term::{Term, SizeInfo, RenderableCell};
 use sync::FairMutex;
 use window::{self, Window};
+use logging;
 use Rgb;
 
 #[derive(Debug)]
@@ -396,10 +397,32 @@ impl Display {
                     g: 0x4e,
                     b: 0x53,
                 };
-                self.renderer
-                    .with_api(config, &size_info, visual_bell_intensity, |mut api| {
-                        api.render_string(&timing[..], glyph_cache, color);
-                    });
+                self.renderer.with_api(config, &size_info, visual_bell_intensity, |mut api| {
+                    api.render_string(&timing[..], size_info.lines() - 2, glyph_cache, color);
+                });
+            }
+
+            // Display errors and warnings
+            if logging::errors() {
+                let msg = " ERROR: Full log at /tmp/alacritty-todo.log ";
+                let color = Rgb {
+                    r: 0xff,
+                    g: 0x00,
+                    b: 0x00
+                };
+                self.renderer.with_api(config, &size_info, visual_bell_intensity, |mut api| {
+                    api.render_string(&msg, size_info.lines() - 1, glyph_cache, color);
+                });
+            } else if logging::warnings() {
+                let msg = " WARNING: Full log at /tmp/alacritty-todo.log ";
+                let color = Rgb {
+                    r: 0xff,
+                    g: 0xff,
+                    b: 0x00
+                };
+                self.renderer.with_api(config, &size_info, visual_bell_intensity, |mut api| {
+                    api.render_string(&msg, size_info.lines() - 1, glyph_cache, color);
+                });
             }
         }
 
diff --git a/src/logging.rs b/src/logging.rs
index 3fb768e9..6b43c2a7 100644
--- a/src/logging.rs
+++ b/src/logging.rs
@@ -18,13 +18,43 @@
 //! startup. All logging messages are written to stdout, given that their
 //! log-level is sufficient for the level configured in `cli::Options`.
 use cli;
-use log;
+use log::{self, Level};
 use tempfile;
 
 use std::fs::File;
 use std::io::{self, LineWriter, Stdout, Write};
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::Mutex;
 
+static ERRORS: AtomicBool = AtomicBool::new(false);
+static WARNINGS: AtomicBool = AtomicBool::new(false);
+
+pub fn initialize(options: &cli::Options) -> Result<(), log::SetLoggerError> {
+    // Use env_logger if RUST_LOG environment variable is defined. Otherwise,
+    // use the alacritty-only logger.
+    if ::std::env::var("RUST_LOG").is_ok() {
+        ::env_logger::try_init()
+    } else {
+        log::set_boxed_logger(Box::new(Logger::new(options.log_level)))
+    }
+}
+
+pub fn warnings() -> bool {
+    WARNINGS.load(Ordering::Relaxed)
+}
+
+pub fn errors() -> bool {
+    ERRORS.load(Ordering::Relaxed)
+}
+
+pub fn clear_errors() {
+    ERRORS.store(false, Ordering::Relaxed);
+}
+
+pub fn clear_warnings() {
+    WARNINGS.store(false, Ordering::Relaxed);
+}
+
 pub struct Logger {
     level: log::LevelFilter,
     logfile: Mutex<OnDemandTempFile>,
@@ -63,6 +93,12 @@ impl log::Log for Logger {
             if let Ok(ref mut stdout) = self.stdout.lock() {
                 let _ = stdout.write_all(format!("{}\n", record.args()).as_ref());
             }
+
+            match record.level() {
+                Level::Error => ERRORS.store(true, Ordering::Relaxed),
+                Level::Warn => WARNINGS.store(true, Ordering::Relaxed),
+                _ => (),
+            }
         }
     }
 
@@ -108,13 +144,3 @@ impl Write for OnDemandTempFile {
         self.file()?.flush()
     }
 }
-
-pub fn initialize(options: &cli::Options) -> Result<(), log::SetLoggerError> {
-    // Use env_logger if RUST_LOG environment variable is defined. Otherwise,
-    // use the alacritty-only logger.
-    if ::std::env::var("RUST_LOG").is_ok() {
-        ::env_logger::try_init()
-    } else {
-        log::set_boxed_logger(Box::new(Logger::new(options.log_level)))
-    }
-}
diff --git a/src/macros.rs b/src/macros.rs
index f3327083..519f8b6a 100644
--- a/src/macros.rs
+++ b/src/macros.rs
@@ -19,13 +19,3 @@ macro_rules! die {
         ::std::process::exit(1);
     }}
 }
-
-#[macro_export]
-macro_rules! maybe {
-    ($option:expr) => {
-        match $option {
-            Some(value) => value,
-            None => return None,
-        }
-    }
-}
diff --git a/src/renderer/mod.rs b/src/renderer/mod.rs
index df219cf5..8c013e48 100644
--- a/src/renderer/mod.rs
+++ b/src/renderer/mod.rs
@@ -819,10 +819,16 @@ impl<'a> RenderApi<'a> {
 
         self.batch.clear();
     }
-    /// Render a string in a predefined location. Used for printing render time for profiling and
-    /// optimization.
-    pub fn render_string(&mut self, string: &str, glyph_cache: &mut GlyphCache, color: Rgb) {
-        let line = Line(23);
+
+    /// Render a string in a variable location. Used for printing the render timer, warnings and
+    /// errors.
+    pub fn render_string(
+        &mut self,
+        string: &str,
+        line: Line,
+        glyph_cache: &mut GlyphCache,
+        color: Rgb
+    ) {
         let col = Column(0);
 
         let cells = string
diff --git a/src/term/mod.rs b/src/term/mod.rs
index 39213ee2..8663a073 100644
--- a/src/term/mod.rs
+++ b/src/term/mod.rs
@@ -31,6 +31,7 @@ use config::{Config, VisualBellAnimation};
 use {MouseCursor, Rgb};
 use copypasta::{Clipboard, Load, Store};
 use input::FONT_SIZE_STEP;
+use logging;
 
 pub mod cell;
 pub mod color;
@@ -1822,6 +1823,10 @@ impl ansi::Handler for Term {
                 }
             },
             ansi::ClearMode::All => {
+                // Clear errors and warnings
+                logging::clear_errors();
+                logging::clear_warnings();
+
                 self.grid.region_mut(..).each(|c| c.reset(&template));
             },
             ansi::ClearMode::Above => {