Create `markdown` widget helpers in `iced_widget`

7 files changed, 277 insertions, 220 deletions

diff --git a/Cargo.toml b/Cargo.toml
index bc566bf6..d301b36d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -34,6 +34,8 @@ svg = ["iced_widget/svg"]
 canvas = ["iced_widget/canvas"]
 # Enables the `QRCode` widget
 qr_code = ["iced_widget/qr_code"]
+# Enables the `markdown` widget
+markdown = ["iced_widget/markdown"]
 # Enables lazy widgets
 lazy = ["iced_widget/lazy"]
 # Enables a debug view in native platforms (press F12)
@@ -51,7 +53,7 @@ web-colors = ["iced_renderer/web-colors"]
 # Enables the WebGL backend, replacing WebGPU
 webgl = ["iced_renderer/webgl"]
 # Enables the syntax `highlighter` module
-highlighter = ["iced_highlighter"]
+highlighter = ["iced_highlighter", "iced_widget/highlighter"]
 # Enables experimental multi-window support.
 multi-window = ["iced_winit/multi-window"]
 # Enables the advanced module
@@ -155,6 +157,7 @@ num-traits = "0.2"
 once_cell = "1.0"
 ouroboros = "0.18"
 palette = "0.7"
+pulldown-cmark = "0.11"
 qrcode = { version = "0.13", default-features = false }
 raw-window-handle = "0.6"
 resvg = "0.42"
diff --git a/examples/markdown/Cargo.toml b/examples/markdown/Cargo.toml
index 6875ee94..9404d5d2 100644
--- a/examples/markdown/Cargo.toml
+++ b/examples/markdown/Cargo.toml
@@ -7,6 +7,4 @@ publish = false
 
 [dependencies]
 iced.workspace = true
-iced.features = ["highlighter", "debug"]
-
-pulldown-cmark = "0.11"
+iced.features = ["markdown", "highlighter", "debug"]
diff --git a/examples/markdown/src/main.rs b/examples/markdown/src/main.rs
index 1e3769ff..28b5941f 100644
--- a/examples/markdown/src/main.rs
+++ b/examples/markdown/src/main.rs
@@ -1,7 +1,4 @@
-use iced::widget::{
-    self, column, container, rich_text, row, scrollable, span, text,
-    text_editor,
-};
+use iced::widget::{self, markdown, row, scrollable, text_editor};
 use iced::{Element, Fill, Font, Task, Theme};
 
 pub fn main() -> iced::Result {
@@ -12,7 +9,7 @@ pub fn main() -> iced::Result {
 
 struct Markdown {
     content: text_editor::Content,
-    items: Vec<Item>,
+    items: Vec<markdown::Item>,
     theme: Theme,
 }
 
@@ -30,7 +27,8 @@ impl Markdown {
         (
             Self {
                 content: text_editor::Content::with_text(INITIAL_CONTENT),
-                items: parse(INITIAL_CONTENT, &theme).collect(),
+                items: markdown::parse(INITIAL_CONTENT, theme.palette())
+                    .collect(),
                 theme,
             },
             widget::focus_next(),
@@ -44,8 +42,11 @@ impl Markdown {
                 self.content.perform(action);
 
                 if is_edit {
-                    self.items =
-                        parse(&self.content.text(), &self.theme).collect();
+                    self.items = markdown::parse(
+                        &self.content.text(),
+                        self.theme.palette(),
+                    )
+                    .collect();
                 }
             }
         }
@@ -70,210 +71,3 @@ impl Markdown {
         Theme::TokyoNight
     }
 }
-
-fn markdown<'a>(
-    items: impl IntoIterator<Item = &'a Item>,
-) -> Element<'a, Message> {
-    use iced::padding;
-
-    let blocks = items.into_iter().enumerate().map(|(i, item)| match item {
-        Item::Heading(heading) => container(rich_text(heading))
-            .padding(padding::top(if i > 0 { 8 } else { 0 }))
-            .into(),
-        Item::Paragraph(paragraph) => rich_text(paragraph).into(),
-        Item::List { start: None, items } => column(
-            items
-                .iter()
-                .map(|item| row!["•", rich_text(item)].spacing(10).into()),
-        )
-        .spacing(10)
-        .into(),
-        Item::List {
-            start: Some(start),
-            items,
-        } => column(items.iter().enumerate().map(|(i, item)| {
-            row![text!("{}.", i as u64 + *start), rich_text(item)]
-                .spacing(10)
-                .into()
-        }))
-        .spacing(10)
-        .into(),
-        Item::CodeBlock(code) => {
-            container(rich_text(code).font(Font::MONOSPACE).size(12))
-                .width(Fill)
-                .padding(10)
-                .style(container::rounded_box)
-                .into()
-        }
-    });
-
-    column(blocks).width(Fill).spacing(16).into()
-}
-
-#[derive(Debug, Clone)]
-enum Item {
-    Heading(Vec<text::Span<'static>>),
-    Paragraph(Vec<text::Span<'static>>),
-    CodeBlock(Vec<text::Span<'static>>),
-    List {
-        start: Option<u64>,
-        items: Vec<Vec<text::Span<'static>>>,
-    },
-}
-
-fn parse<'a>(
-    markdown: &'a str,
-    theme: &'a Theme,
-) -> impl Iterator<Item = Item> + 'a {
-    use iced::font;
-    use iced::highlighter::{self, Highlighter};
-    use text::Highlighter as _;
-
-    let mut spans = Vec::new();
-    let mut heading = None;
-    let mut strong = false;
-    let mut emphasis = false;
-    let mut link = false;
-    let mut list = Vec::new();
-    let mut list_start = None;
-    let mut highlighter = None;
-
-    let parser = pulldown_cmark::Parser::new(markdown);
-
-    // We want to keep the `spans` capacity
-    #[allow(clippy::drain_collect)]
-    parser.filter_map(move |event| match event {
-        pulldown_cmark::Event::Start(tag) => match tag {
-            pulldown_cmark::Tag::Heading { level, .. } => {
-                heading = Some(level);
-                None
-            }
-            pulldown_cmark::Tag::Strong => {
-                strong = true;
-                None
-            }
-            pulldown_cmark::Tag::Emphasis => {
-                emphasis = true;
-                None
-            }
-            pulldown_cmark::Tag::Link { .. } => {
-                link = true;
-                None
-            }
-            pulldown_cmark::Tag::List(first_item) => {
-                list_start = first_item;
-                None
-            }
-            pulldown_cmark::Tag::CodeBlock(
-                pulldown_cmark::CodeBlockKind::Fenced(language),
-            ) => {
-                highlighter = Some(Highlighter::new(&highlighter::Settings {
-                    theme: highlighter::Theme::Base16Ocean,
-                    token: language.to_string(),
-                }));
-
-                None
-            }
-            _ => None,
-        },
-        pulldown_cmark::Event::End(tag) => match tag {
-            pulldown_cmark::TagEnd::Heading(_) => {
-                heading = None;
-                Some(Item::Heading(spans.drain(..).collect()))
-            }
-            pulldown_cmark::TagEnd::Emphasis => {
-                emphasis = false;
-                None
-            }
-            pulldown_cmark::TagEnd::Strong => {
-                strong = false;
-                None
-            }
-            pulldown_cmark::TagEnd::Link => {
-                link = false;
-                None
-            }
-            pulldown_cmark::TagEnd::Paragraph => {
-                Some(Item::Paragraph(spans.drain(..).collect()))
-            }
-            pulldown_cmark::TagEnd::List(_) => Some(Item::List {
-                start: list_start,
-                items: list.drain(..).collect(),
-            }),
-            pulldown_cmark::TagEnd::Item => {
-                list.push(spans.drain(..).collect());
-                None
-            }
-            pulldown_cmark::TagEnd::CodeBlock => {
-                highlighter = None;
-                Some(Item::CodeBlock(spans.drain(..).collect()))
-            }
-            _ => None,
-        },
-        pulldown_cmark::Event::Text(text) => {
-            if let Some(highlighter) = &mut highlighter {
-                for (range, highlight) in
-                    highlighter.highlight_line(text.as_ref())
-                {
-                    let span = span(text[range].to_owned())
-                        .color_maybe(highlight.color())
-                        .font_maybe(highlight.font());
-
-                    spans.push(span);
-                }
-            } else {
-                let span = span(text.into_string());
-
-                let span = match heading {
-                    None => span,
-                    Some(heading) => span.size(match heading {
-                        pulldown_cmark::HeadingLevel::H1 => 32,
-                        pulldown_cmark::HeadingLevel::H2 => 28,
-                        pulldown_cmark::HeadingLevel::H3 => 24,
-                        pulldown_cmark::HeadingLevel::H4 => 20,
-                        pulldown_cmark::HeadingLevel::H5 => 16,
-                        pulldown_cmark::HeadingLevel::H6 => 16,
-                    }),
-                };
-
-                let span = if strong || emphasis {
-                    span.font(Font {
-                        weight: if strong {
-                            font::Weight::Bold
-                        } else {
-                            font::Weight::Normal
-                        },
-                        style: if emphasis {
-                            font::Style::Italic
-                        } else {
-                            font::Style::Normal
-                        },
-                        ..Font::default()
-                    })
-                } else {
-                    span
-                };
-
-                let span =
-                    span.color_maybe(link.then(|| theme.palette().primary));
-
-                spans.push(span);
-            }
-
-            None
-        }
-        pulldown_cmark::Event::Code(code) => {
-            spans.push(span(code.into_string()).font(Font::MONOSPACE));
-            None
-        }
-        pulldown_cmark::Event::SoftBreak => {
-            spans.push(span(" "));
-            None
-        }
-        pulldown_cmark::Event::HardBreak => {
-            spans.push(span("\n"));
-            None
-        }
-        _ => None,
-    })
-}
diff --git a/widget/Cargo.toml b/widget/Cargo.toml
index 498a768b..2f483b79 100644
--- a/widget/Cargo.toml
+++ b/widget/Cargo.toml
@@ -22,8 +22,10 @@ lazy = ["ouroboros"]
 image = ["iced_renderer/image"]
 svg = ["iced_renderer/svg"]
 canvas = ["iced_renderer/geometry"]
-qr_code = ["canvas", "qrcode"]
+qr_code = ["canvas", "dep:qrcode"]
 wgpu = ["iced_renderer/wgpu"]
+markdown = ["dep:pulldown-cmark"]
+highlighter = ["dep:iced_highlighter"]
 advanced = []
 
 [dependencies]
@@ -41,3 +43,9 @@ ouroboros.optional = true
 
 qrcode.workspace = true
 qrcode.optional = true
+
+pulldown-cmark.workspace = true
+pulldown-cmark.optional = true
+
+iced_highlighter.workspace = true
+iced_highlighter.optional = true
diff --git a/widget/src/helpers.rs b/widget/src/helpers.rs
index 0390079f..43fee845 100644
--- a/widget/src/helpers.rs
+++ b/widget/src/helpers.rs
@@ -7,6 +7,7 @@ use crate::core;
 use crate::core::widget::operation;
 use crate::core::{Element, Length, Pixels, Widget};
 use crate::keyed;
+use crate::markdown::{self};
 use crate::overlay;
 use crate::pick_list::{self, PickList};
 use crate::progress_bar::{self, ProgressBar};
@@ -702,6 +703,10 @@ pub fn span<'a, Font>(
     text::Span::new(text)
 }
 
+#[cfg(feature = "markdown")]
+#[doc(inline)]
+pub use markdown::view as markdown;
+
 /// Creates a new [`Checkbox`].
 ///
 /// [`Checkbox`]: crate::Checkbox
diff --git a/widget/src/lib.rs b/widget/src/lib.rs
index 00e9aaa4..115a29e5 100644
--- a/widget/src/lib.rs
+++ b/widget/src/lib.rs
@@ -130,5 +130,8 @@ pub mod qr_code;
 #[doc(no_inline)]
 pub use qr_code::QRCode;
 
+#[cfg(feature = "markdown")]
+pub mod markdown;
+
 pub use crate::core::theme::{self, Theme};
 pub use renderer::Renderer;
diff --git a/widget/src/markdown.rs b/widget/src/markdown.rs
new file mode 100644
index 00000000..bbb5b463
--- /dev/null
+++ b/widget/src/markdown.rs
@@ -0,0 +1,246 @@
+//! Parse and display Markdown.
+//!
+//! You can enable the `highlighter` feature for syntax highligting
+//! in code blocks.
+//!
+//! Only the variants of [`Item`] are currently supported.
+use crate::core::font::{self, Font};
+use crate::core::padding;
+use crate::core::theme::{self, Theme};
+use crate::core::{self, Element, Length};
+use crate::{column, container, rich_text, row, span, text};
+
+/// A Markdown item.
+#[derive(Debug, Clone)]
+pub enum Item {
+    /// A heading.
+    Heading(Vec<text::Span<'static>>),
+    /// A paragraph.
+    Paragraph(Vec<text::Span<'static>>),
+    /// A code block.
+    ///
+    /// You can enable the `highlighter` feature for syntax highligting.
+    CodeBlock(Vec<text::Span<'static>>),
+    /// A list.
+    List {
+        /// The first number of the list, if it is ordered.
+        start: Option<u64>,
+        /// The items of the list.
+        items: Vec<Vec<text::Span<'static>>>,
+    },
+}
+
+/// Parse the given Markdown content.
+pub fn parse(
+    markdown: &str,
+    palette: theme::Palette,
+) -> impl Iterator<Item = Item> + '_ {
+    let mut spans = Vec::new();
+    let mut heading = None;
+    let mut strong = false;
+    let mut emphasis = false;
+    let mut link = false;
+    let mut list = Vec::new();
+    let mut list_start = None;
+
+    #[cfg(feature = "highlighter")]
+    let mut highlighter = None;
+
+    let parser = pulldown_cmark::Parser::new(markdown);
+
+    // We want to keep the `spans` capacity
+    #[allow(clippy::drain_collect)]
+    parser.filter_map(move |event| match event {
+        pulldown_cmark::Event::Start(tag) => match tag {
+            pulldown_cmark::Tag::Heading { level, .. } => {
+                heading = Some(level);
+                None
+            }
+            pulldown_cmark::Tag::Strong => {
+                strong = true;
+                None
+            }
+            pulldown_cmark::Tag::Emphasis => {
+                emphasis = true;
+                None
+            }
+            pulldown_cmark::Tag::Link { .. } => {
+                link = true;
+                None
+            }
+            pulldown_cmark::Tag::List(first_item) => {
+                list_start = first_item;
+                None
+            }
+            pulldown_cmark::Tag::CodeBlock(
+                pulldown_cmark::CodeBlockKind::Fenced(_language),
+            ) => {
+                #[cfg(feature = "highlighter")]
+                {
+                    use iced_highlighter::{self, Highlighter};
+                    use text::Highlighter as _;
+
+                    highlighter =
+                        Some(Highlighter::new(&iced_highlighter::Settings {
+                            theme: iced_highlighter::Theme::Base16Ocean,
+                            token: _language.to_string(),
+                        }));
+                }
+
+                None
+            }
+            _ => None,
+        },
+        pulldown_cmark::Event::End(tag) => match tag {
+            pulldown_cmark::TagEnd::Heading(_) => {
+                heading = None;
+                Some(Item::Heading(spans.drain(..).collect()))
+            }
+            pulldown_cmark::TagEnd::Emphasis => {
+                emphasis = false;
+                None
+            }
+            pulldown_cmark::TagEnd::Strong => {
+                strong = false;
+                None
+            }
+            pulldown_cmark::TagEnd::Link => {
+                link = false;
+                None
+            }
+            pulldown_cmark::TagEnd::Paragraph => {
+                Some(Item::Paragraph(spans.drain(..).collect()))
+            }
+            pulldown_cmark::TagEnd::List(_) => Some(Item::List {
+                start: list_start,
+                items: list.drain(..).collect(),
+            }),
+            pulldown_cmark::TagEnd::Item => {
+                list.push(spans.drain(..).collect());
+                None
+            }
+            pulldown_cmark::TagEnd::CodeBlock => {
+                #[cfg(feature = "highlighter")]
+                {
+                    highlighter = None;
+                }
+
+                Some(Item::CodeBlock(spans.drain(..).collect()))
+            }
+            _ => None,
+        },
+        pulldown_cmark::Event::Text(text) => {
+            #[cfg(feature = "highlighter")]
+            if let Some(highlighter) = &mut highlighter {
+                use text::Highlighter as _;
+
+                for (range, highlight) in
+                    highlighter.highlight_line(text.as_ref())
+                {
+                    let span = span(text[range].to_owned())
+                        .color_maybe(highlight.color())
+                        .font_maybe(highlight.font());
+
+                    spans.push(span);
+                }
+
+                return None;
+            }
+
+            let span = span(text.into_string());
+
+            let span = match heading {
+                None => span,
+                Some(heading) => span.size(match heading {
+                    pulldown_cmark::HeadingLevel::H1 => 32,
+                    pulldown_cmark::HeadingLevel::H2 => 28,
+                    pulldown_cmark::HeadingLevel::H3 => 24,
+                    pulldown_cmark::HeadingLevel::H4 => 20,
+                    pulldown_cmark::HeadingLevel::H5 => 16,
+                    pulldown_cmark::HeadingLevel::H6 => 16,
+                }),
+            };
+
+            let span = if strong || emphasis {
+                span.font(Font {
+                    weight: if strong {
+                        font::Weight::Bold
+                    } else {
+                        font::Weight::Normal
+                    },
+                    style: if emphasis {
+                        font::Style::Italic
+                    } else {
+                        font::Style::Normal
+                    },
+                    ..Font::default()
+                })
+            } else {
+                span
+            };
+
+            let span = span.color_maybe(link.then_some(palette.primary));
+
+            spans.push(span);
+
+            None
+        }
+        pulldown_cmark::Event::Code(code) => {
+            spans.push(span(code.into_string()).font(Font::MONOSPACE));
+            None
+        }
+        pulldown_cmark::Event::SoftBreak => {
+            spans.push(span(" "));
+            None
+        }
+        pulldown_cmark::Event::HardBreak => {
+            spans.push(span("\n"));
+            None
+        }
+        _ => None,
+    })
+}
+
+/// Display a bunch of Markdown items.
+///
+/// You can obtain the items with [`parse`].
+pub fn view<'a, Message, Renderer>(
+    items: impl IntoIterator<Item = &'a Item>,
+) -> Element<'a, Message, Theme, Renderer>
+where
+    Message: 'a,
+    Renderer: core::text::Renderer<Font = Font> + 'a,
+{
+    let blocks = items.into_iter().enumerate().map(|(i, item)| match item {
+        Item::Heading(heading) => container(rich_text(heading))
+            .padding(padding::top(if i > 0 { 8 } else { 0 }))
+            .into(),
+        Item::Paragraph(paragraph) => rich_text(paragraph).into(),
+        Item::List { start: None, items } => column(
+            items
+                .iter()
+                .map(|item| row!["•", rich_text(item)].spacing(10).into()),
+        )
+        .spacing(10)
+        .into(),
+        Item::List {
+            start: Some(start),
+            items,
+        } => column(items.iter().enumerate().map(|(i, item)| {
+            row![text!("{}.", i as u64 + *start), rich_text(item)]
+                .spacing(10)
+                .into()
+        }))
+        .spacing(10)
+        .into(),
+        Item::CodeBlock(code) => {
+            container(rich_text(code).font(Font::MONOSPACE).size(12))
+                .width(Length::Fill)
+                .padding(10)
+                .style(container::rounded_box)
+                .into()
+        }
+    });
+
+    Element::new(column(blocks).width(Length::Fill).spacing(16))
+}