other: Speed up first draw and first data collection (#1100)

* other: add first draw immediately after initialization

Previously, I would only do the first draw after an event triggered, so
this just makes it so that I *always* draw once first. Some widgets look
a bit weird with no data, but this is fine I guess if we want to gain a
bit of responsiveness.

* other: potentially shorten first time to get data

* other: move event loop thread init earlier in app initialization

4 files changed, 39 insertions, 20 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f8a7dc92..0d63dbed 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,7 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - [#1016](https://github.com/ClementTsang/bottom/pull/1016): Add support for displaying process usernames on Windows.
 - [#1022](https://github.com/ClementTsang/bottom/pull/1022): Support three-character hex colour strings for styling.
 - [#1024](https://github.com/ClementTsang/bottom/pull/1024): Support FreeBSD temperature sensors based on `hw.temperature`.
-- [#1063](https://github.com/ClementTsang/bottom/pull/1063): Add buffer and cache memory tracking
+- [#1063](https://github.com/ClementTsang/bottom/pull/1063): Add buffer and cache memory tracking.
 
 ## Changes
 
@@ -35,6 +35,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Other
 
+- [#1100](https://github.com/ClementTsang/bottom/pull/1100): Speed up first draw and first data collection.
+
 ## [0.8.0] - 2023-01-22
 
 ## Bug Fixes
diff --git a/src/app/data_harvester.rs b/src/app/data_harvester.rs
index 67ff1e5b..362b7251 100644
--- a/src/app/data_harvester.rs
+++ b/src/app/data_harvester.rs
@@ -194,7 +194,20 @@ impl DataCollector {
 
         self.update_data();
 
-        std::thread::sleep(std::time::Duration::from_millis(250));
+        // Sleep a few seconds to avoid potentially weird data...
+        let sleep_duration = {
+            cfg_if::cfg_if! {
+                if #[cfg(target_os = "freebsd")] {
+                    // FreeBSD's min duration value is 1s, which is a bit too long for me so I'll accept the one-time
+                    // inaccuracy.
+                    std::time::Duration::from_millis(250)
+                } else {
+                    sysinfo::System::MINIMUM_CPU_UPDATE_INTERVAL + Duration::from_millis(1)
+                }
+            }
+        };
+
+        std::thread::sleep(sleep_duration);
         self.data.cleanup();
     }
 
diff --git a/src/app/layout_manager.rs b/src/app/layout_manager.rs
index 032ccf98..137a9b12 100644
--- a/src/app/layout_manager.rs
+++ b/src/app/layout_manager.rs
@@ -993,7 +993,7 @@ Supported widget names:
     }
 }
 
-#[derive(Clone, Default, Debug)]
+#[derive(Clone, Default, Debug, Copy)]
 pub struct UsedWidgets {
     pub use_cpu: bool,
     pub use_mem: bool,
diff --git a/src/bin/main.rs b/src/bin/main.rs
index b0596532..3ffaf234 100644
--- a/src/bin/main.rs
+++ b/src/bin/main.rs
@@ -42,7 +42,7 @@ fn main() -> Result<()> {
     // let _profiler = dhat::Profiler::new_heap();
 
     let matches = clap::get_matches();
-    #[cfg(all(feature = "fern", debug_assertions))]
+    #[cfg(all(feature = "fern"))]
     {
         utils::logging::init_logger(log::LevelFilter::Debug, std::ffi::OsStr::new("debug.log"))?;
     }
@@ -85,15 +85,28 @@ fn main() -> Result<()> {
     let thread_termination_lock = Arc::new(Mutex::new(false));
     let thread_termination_cvar = Arc::new(Condvar::new());
 
-    // Set up input handling
     let (sender, receiver) = mpsc::channel();
+
+    // Set up event loop thread; we set this up early to speed up first-time-to-data.
+    let (collection_thread_ctrl_sender, collection_thread_ctrl_receiver) = mpsc::channel();
+    let _collection_thread = create_collection_thread(
+        sender.clone(),
+        collection_thread_ctrl_receiver,
+        thread_termination_lock.clone(),
+        thread_termination_cvar.clone(),
+        &app.app_config_fields,
+        app.filters.clone(),
+        app.used_widgets,
+    );
+
+    // Set up input handling loop thread.
     let _input_thread = create_input_thread(sender.clone(), thread_termination_lock.clone());
 
-    // Cleaning loop
+    // Set up cleaning loop thread.
     let _cleaning_thread = {
         let lock = thread_termination_lock.clone();
         let cvar = thread_termination_cvar.clone();
-        let cleaning_sender = sender.clone();
+        let cleaning_sender = sender;
         let offset_wait_time = app.app_config_fields.retention_ms + 60000;
         thread::spawn(move || {
             loop {
@@ -114,19 +127,7 @@ fn main() -> Result<()> {
         })
     };
 
-    // Event loop
-    let (collection_thread_ctrl_sender, collection_thread_ctrl_receiver) = mpsc::channel();
-    let _collection_thread = create_collection_thread(
-        sender,
-        collection_thread_ctrl_receiver,
-        thread_termination_lock.clone(),
-        thread_termination_cvar.clone(),
-        &app.app_config_fields,
-        app.filters.clone(),
-        app.used_widgets.clone(),
-    );
-
-    // Set up up tui and crossterm
+    // Set up tui and crossterm
     let mut stdout_val = stdout();
     execute!(
         stdout_val,
@@ -162,6 +163,9 @@ fn main() -> Result<()> {
     })?;
     let mut first_run = true;
 
+    // Draw once first to initialize the canvas, so it doesn't feel like it's frozen.
+    try_drawing(&mut terminal, &mut app, &mut painter)?;
+
     while !is_terminated.load(Ordering::SeqCst) {
         // TODO: Would be good to instead use a mix of is_terminated check + recv. Probably use a termination event instead.
         if let Ok(recv) = receiver.recv_timeout(Duration::from_millis(TICK_RATE_IN_MILLISECONDS)) {