Merge pull request #2776 from iced-rs/fix/markdown

Incremental `markdown` parsing and various fixes

2 files changed, 100 insertions, 13 deletions

diff --git a/examples/markdown/Cargo.toml b/examples/markdown/Cargo.toml
index cb74b954..fa6ced74 100644
--- a/examples/markdown/Cargo.toml
+++ b/examples/markdown/Cargo.toml
@@ -7,6 +7,6 @@ publish = false
 
 [dependencies]
 iced.workspace = true
-iced.features = ["markdown", "highlighter", "debug"]
+iced.features = ["markdown", "highlighter", "tokio", "debug"]
 
 open = "5.3"
diff --git a/examples/markdown/src/main.rs b/examples/markdown/src/main.rs
index 5605478f..5b9a3b4a 100644
--- a/examples/markdown/src/main.rs
+++ b/examples/markdown/src/main.rs
@@ -1,23 +1,37 @@
 use iced::highlighter;
-use iced::widget::{self, markdown, row, scrollable, text_editor};
-use iced::{Element, Fill, Font, Task, Theme};
+use iced::time::{self, milliseconds};
+use iced::widget::{
+    self, hover, markdown, right, row, scrollable, text_editor, toggler,
+};
+use iced::{Element, Fill, Font, Subscription, Task, Theme};
 
 pub fn main() -> iced::Result {
     iced::application("Markdown - Iced", Markdown::update, Markdown::view)
+        .subscription(Markdown::subscription)
         .theme(Markdown::theme)
         .run_with(Markdown::new)
 }
 
 struct Markdown {
     content: text_editor::Content,
-    items: Vec<markdown::Item>,
+    mode: Mode,
     theme: Theme,
 }
 
+enum Mode {
+    Preview(Vec<markdown::Item>),
+    Stream {
+        pending: String,
+        parsed: markdown::Content,
+    },
+}
+
 #[derive(Debug, Clone)]
 enum Message {
     Edit(text_editor::Action),
     LinkClicked(markdown::Url),
+    ToggleStream(bool),
+    NextToken,
 }
 
 impl Markdown {
@@ -29,14 +43,14 @@ impl Markdown {
         (
             Self {
                 content: text_editor::Content::with_text(INITIAL_CONTENT),
-                items: markdown::parse(INITIAL_CONTENT).collect(),
+                mode: Mode::Preview(markdown::parse(INITIAL_CONTENT).collect()),
                 theme,
             },
             widget::focus_next(),
         )
     }
 
-    fn update(&mut self, message: Message) {
+    fn update(&mut self, message: Message) -> Task<Message> {
         match message {
             Message::Edit(action) => {
                 let is_edit = action.is_edit();
@@ -44,12 +58,56 @@ impl Markdown {
                 self.content.perform(action);
 
                 if is_edit {
-                    self.items =
-                        markdown::parse(&self.content.text()).collect();
+                    self.mode = Mode::Preview(
+                        markdown::parse(&self.content.text()).collect(),
+                    );
                 }
+
+                Task::none()
             }
             Message::LinkClicked(link) => {
                 let _ = open::that_in_background(link.to_string());
+
+                Task::none()
+            }
+            Message::ToggleStream(enable_stream) => {
+                if enable_stream {
+                    self.mode = Mode::Stream {
+                        pending: self.content.text(),
+                        parsed: markdown::Content::new(),
+                    };
+
+                    scrollable::snap_to(
+                        "preview",
+                        scrollable::RelativeOffset::END,
+                    )
+                } else {
+                    self.mode = Mode::Preview(
+                        markdown::parse(&self.content.text()).collect(),
+                    );
+
+                    Task::none()
+                }
+            }
+            Message::NextToken => {
+                match &mut self.mode {
+                    Mode::Preview(_) => {}
+                    Mode::Stream { pending, parsed } => {
+                        if pending.is_empty() {
+                            self.mode = Mode::Preview(parsed.items().to_vec());
+                        } else {
+                            let mut tokens = pending.split(' ');
+
+                            if let Some(token) = tokens.next() {
+                                parsed.push_str(&format!("{token} "));
+                            }
+
+                            *pending = tokens.collect::<Vec<_>>().join(" ");
+                        }
+                    }
+                }
+
+                Task::none()
             }
         }
     }
@@ -63,20 +121,49 @@ impl Markdown {
             .font(Font::MONOSPACE)
             .highlight("markdown", highlighter::Theme::Base16Ocean);
 
+        let items = match &self.mode {
+            Mode::Preview(items) => items.as_slice(),
+            Mode::Stream { parsed, .. } => parsed.items(),
+        };
+
         let preview = markdown(
-            &self.items,
+            items,
             markdown::Settings::default(),
             markdown::Style::from_palette(self.theme.palette()),
         )
         .map(Message::LinkClicked);
 
-        row![editor, scrollable(preview).spacing(10).height(Fill)]
-            .spacing(10)
-            .padding(10)
-            .into()
+        row![
+            editor,
+            hover(
+                scrollable(preview)
+                    .spacing(10)
+                    .width(Fill)
+                    .height(Fill)
+                    .id("preview"),
+                right(
+                    toggler(matches!(self.mode, Mode::Stream { .. }))
+                        .label("Stream")
+                        .on_toggle(Message::ToggleStream)
+                )
+                .padding([0, 20])
+            )
+        ]
+        .spacing(10)
+        .padding(10)
+        .into()
     }
 
     fn theme(&self) -> Theme {
         self.theme.clone()
     }
+
+    fn subscription(&self) -> Subscription<Message> {
+        match self.mode {
+            Mode::Preview(_) => Subscription::none(),
+            Mode::Stream { .. } => {
+                time::every(milliseconds(20)).map(|_| Message::NextToken)
+            }
+        }
+    }
 }