refactor(startup): improve overall startup time and remove first frames artifacts (#408)

Fixes #406

television-derive/src/lib.rs

@@ -272,6 +272,16 @@ fn impl_tv_channel(ast: &syn::DeriveInput) -> TokenStream {
                     )*
                 }
             }
+
+            fn supports_preview(&self) -> bool {
+                match self {
+                    #(
+                        #enum_name::#variant_names(ref channel) => {
+                            channel.supports_preview()
+                        }
+                    )*
+                }
+            }
         }
     };
 

television/channels/alias.rs

@@ -146,6 +146,10 @@ impl OnAir for Channel {
     }
 
     fn shutdown(&self) {}
+
+    fn supports_preview(&self) -> bool {
+        true
+    }
 }
 
 #[allow(clippy::unused_async)]

television/channels/cable.rs

@@ -213,6 +213,10 @@ impl OnAir for Channel {
     }
 
     fn shutdown(&self) {}
+
+    fn supports_preview(&self) -> bool {
+        self.preview_kind != PreviewKind::None
+    }
 }
 
 #[derive(Clone, Debug, serde::Deserialize, PartialEq)]

television/channels/dirs.rs

@@ -142,6 +142,10 @@ impl OnAir for Channel {
     fn shutdown(&self) {
         self.crawl_handle.abort();
     }
+
+    fn supports_preview(&self) -> bool {
+        true
+    }
 }
 
 #[allow(clippy::unused_async)]

television/channels/env.rs

@@ -131,4 +131,8 @@ impl OnAir for Channel {
     }
 
     fn shutdown(&self) {}
+
+    fn supports_preview(&self) -> bool {
+        true
+    }
 }

television/channels/files.rs

@@ -148,6 +148,10 @@ impl OnAir for Channel {
     fn shutdown(&self) {
         self.crawl_handle.abort();
     }
+
+    fn supports_preview(&self) -> bool {
+        true
+    }
 }
 
 #[allow(clippy::unused_async)]

television/channels/git_repos.rs

@@ -113,6 +113,10 @@ impl OnAir for Channel {
         debug!("Shutting down git repos channel");
         self.crawl_handle.abort();
     }
+
+    fn supports_preview(&self) -> bool {
+        true
+    }
 }
 
 fn get_ignored_paths() -> Vec<PathBuf> {

television/channels/mod.rs

@@ -84,6 +84,9 @@ pub trait OnAir: Send {
 
     /// Turn off
     fn shutdown(&self);
+
+    /// Whether this channel supports previewing entries.
+    fn supports_preview(&self) -> bool;
 }
 
 /// The available television channels.

television/channels/remote_control.rs

@@ -181,4 +181,8 @@ impl OnAir for RemoteControl {
     }
 
     fn shutdown(&self) {}
+
+    fn supports_preview(&self) -> bool {
+        false
+    }
 }

television/channels/stdin.rs

@@ -120,4 +120,8 @@ impl OnAir for Channel {
     }
 
     fn shutdown(&self) {}
+
+    fn supports_preview(&self) -> bool {
+        self.preview_type != PreviewType::None
+    }
 }

television/channels/text.rs

@@ -245,6 +245,10 @@ impl OnAir for Channel {
     fn shutdown(&self) {
         self.crawl_handle.abort();
     }
+
+    fn supports_preview(&self) -> bool {
+        true
+    }
 }
 
 /// The maximum file size we're willing to search in.

television/draw.rs

@@ -6,7 +6,7 @@ use rustc_hash::FxHashSet;
 
 use crate::{
     action::Action,
-    channels::entry::{Entry, PreviewType, ENTRY_PLACEHOLDER},
+    channels::entry::Entry,
     config::Config,
     picker::Picker,
     preview::PreviewState,
@@ -22,6 +22,9 @@ use crate::{
 };
 
 #[derive(Debug, Clone, PartialEq)]
+/// The state of the current television channel.
+///
+/// This struct is passed along to the UI thread as part of the `TvState` struct.
 pub struct ChannelState {
     pub current_channel_name: String,
     pub selected_entries: FxHashSet<Entry>,
@@ -57,6 +60,9 @@ impl Hash for ChannelState {
 }
 
 #[derive(Debug, Clone, PartialEq, Hash)]
+/// The state of the main thread `Television` struct.
+///
+/// This struct is passed along to the UI thread as part of the `Ctx` struct.
 pub struct TvState {
     pub mode: Mode,
     pub selected_entry: Option<Entry>,
@@ -91,6 +97,11 @@ impl TvState {
 }
 
 #[derive(Debug, Clone)]
+/// A drawing context that holds the current state of the application.
+///
+/// This is used as a message passing object between the main thread
+/// and the UI thread and should contain all the information needed to
+/// draw a frame.
 pub struct Ctx {
     pub tv_state: TvState,
     pub config: Config,
@@ -152,15 +163,24 @@ impl Ord for Ctx {
     }
 }
 
+/// Draw the current UI frame based on the given context.
+///
+/// This function is responsible for drawing the entire UI frame based on the given context by
+/// ultimately flushing buffers down to the underlying terminal.
+///
+/// This function is executed by the UI thread whenever it receives a render message from the main
+/// thread.
+///
+/// It will draw the help bar, the results list, the input box, the preview content block, and the
+/// remote control.
+///
+/// # Returns
+/// A `Result` containing the layout of the current frame if the drawing was successful.
+/// This layout can then be sent back to the main thread to serve for tasks where having that
+/// information can be useful or lead to optimizations.
 pub fn draw(ctx: &Ctx, f: &mut Frame<'_>, area: Rect) -> Result<Layout> {
-    let selected_entry = ctx
-        .tv_state
-        .selected_entry
-        .clone()
-        .unwrap_or(ENTRY_PLACEHOLDER);
-
-    let show_preview = ctx.config.ui.show_preview_panel
-        && !matches!(selected_entry.preview_type, PreviewType::None);
+    let show_preview =
+        ctx.config.ui.show_preview_panel && ctx.tv_state.preview_state.enabled;
     let show_remote = !matches!(ctx.tv_state.mode, Mode::Channel);
 
     let layout =
@@ -219,7 +239,7 @@ pub fn draw(ctx: &Ctx, f: &mut Frame<'_>, area: Rect) -> Result<Layout> {
         &ctx.colorscheme,
     )?;
 
-    if show_preview {
+    if layout.preview_window.is_some() {
         draw_preview_content_block(
             f,
             layout.preview_window.unwrap(),

television/preview/mod.rs

@@ -109,6 +109,7 @@ impl Preview {
 
 #[derive(Debug, Default, Clone, PartialEq, Hash)]
 pub struct PreviewState {
+    pub enabled: bool,
     pub preview: Arc<Preview>,
     pub scroll: u16,
     pub target_line: Option<u16>,
@@ -118,11 +119,13 @@ const PREVIEW_MIN_SCROLL_LINES: u16 = 3;
 
 impl PreviewState {
     pub fn new(
+        enabled: bool,
         preview: Arc<Preview>,
         scroll: u16,
         target_line: Option<u16>,
     ) -> Self {
         PreviewState {
+            enabled,
             preview,
             scroll,
             target_line,

television/render.rs

@@ -37,6 +37,11 @@ impl IoStream {
 }
 
 #[derive(Default)]
+/// The state of the UI after rendering.
+///
+/// This struct is returned by the UI thread to the main thread after each rendering cycle.
+/// It contains information that the main thread might be able to exploit to make certain
+/// decisions and optimizations.
 pub struct UiState {
     pub layout: Layout,
 }
@@ -47,6 +52,18 @@ impl UiState {
     }
 }
 
+/// The main UI rendering task loop.
+///
+/// This function is responsible for rendering the UI based on the rendering tasks it receives from
+/// the main thread via `render_rx`.
+///
+/// This has a handle to the main action queue `action_tx` (for things like self-triggering
+/// subsequent rendering instructions) and the UI state queue `ui_state_tx` to send back the layout
+/// of the UI after each rendering cycle to the main thread to help make decisions and
+/// optimizations.
+///
+/// When starting the rendering loop, a choice is made to either render to stdout or stderr based
+/// on if the output is believed to be a TTY or not.
 pub async fn render(
     mut render_rx: mpsc::UnboundedReceiver<RenderingTask>,
     action_tx: mpsc::UnboundedSender<Action>,

television/television.rs

@@ -1,6 +1,6 @@
 use crate::action::Action;
 use crate::cable::load_cable_channels;
-use crate::channels::entry::{Entry, PreviewType, ENTRY_PLACEHOLDER};
+use crate::channels::entry::{Entry, ENTRY_PLACEHOLDER};
 use crate::channels::{
     remote_control::{load_builtin_channels, RemoteControl},
     OnAir, TelevisionChannel, UnitChannel,
@@ -9,7 +9,7 @@ use crate::config::{Config, Theme};
 use crate::draw::{ChannelState, Ctx, TvState};
 use crate::input::convert_action_to_input_request;
 use crate::picker::Picker;
-use crate::preview::{PreviewState, Previewer};
+use crate::preview::{Preview, PreviewState, Previewer};
 use crate::render::UiState;
 use crate::screen::colors::Colorscheme;
 use crate::screen::layout::InputPosition;
@@ -21,6 +21,7 @@ use anyhow::Result;
 use rustc_hash::{FxBuildHasher, FxHashSet};
 use serde::{Deserialize, Serialize};
 use std::collections::HashSet;
+use std::sync::Arc;
 use tokio::sync::mpsc::UnboundedSender;
 
 #[derive(PartialEq, Copy, Clone, Hash, Eq, Debug, Serialize, Deserialize)]
@@ -79,6 +80,13 @@ impl Television {
         channel.find(&input.unwrap_or(EMPTY_STRING.to_string()));
         let spinner = Spinner::default();
 
+        let preview_state = PreviewState::new(
+            channel.supports_preview(),
+            Arc::new(Preview::default()),
+            0,
+            None,
+        );
+
         Self {
             action_tx,
             config,
@@ -91,7 +99,7 @@ impl Television {
             results_picker,
             rc_picker: Picker::default(),
             previewer,
-            preview_state: PreviewState::default(),
+            preview_state,
             spinner,
             spinner_state: SpinnerState::from(&spinner),
             app_metadata,
@@ -261,11 +269,13 @@ impl Television {
     }
 }
 
+const RENDER_FIRST_N_TICKS: u64 = 20;
 const RENDER_EVERY_N_TICKS: u64 = 10;
 
 impl Television {
     fn should_render(&self, action: &Action) -> bool {
-        self.ticks == RENDER_EVERY_N_TICKS
+        self.ticks < RENDER_FIRST_N_TICKS
+            || self.ticks % RENDER_EVERY_N_TICKS == 0
             || matches!(
                 action,
                 Action::AddInputChar(_)
@@ -300,8 +310,7 @@ impl Television {
         &mut self,
         selected_entry: &Entry,
     ) -> Result<()> {
-        if self.config.ui.show_preview_panel
-            && !matches!(selected_entry.preview_type, PreviewType::None)
+        if self.config.ui.show_preview_panel && self.channel.supports_preview()
         {
             // preview content
             if let Some(preview) = self
@@ -591,7 +600,6 @@ impl Television {
             if self.channel.running() {
                 self.spinner.tick();
             }
-            self.ticks = 0;
 
             Some(Action::Render)
         } else {

television/utils/metadata.rs

@@ -1,4 +1,5 @@
 #[derive(Debug, Clone, PartialEq, Hash, Eq)]
+/// Global application metadata like version and current directory.
 pub struct AppMetadata {
     pub version: String,
     pub current_directory: String,