feat(wip): add markdown support

3 files changed, 261 insertions, 2 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 0576705..849c30e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,11 +14,13 @@ keywords = ["gui", "ui", "graphics", "interface", "widgets"]
 rust-version = "1.88"
 
 [dependencies]
-iced_widget = { git = "https://github.com/iced-rs/iced" }
+iced_widget = { git = "https://github.com/iced-rs/iced", features = [
+  "markdown",
+] }
 unicode-segmentation = "1.0"
 
 [dev-dependencies]
-iced = { git = "https://github.com/iced-rs/iced" }
+iced = { git = "https://github.com/iced-rs/iced", features = ["markdown"] }
 open = "5.3"
 
 [package.metadata.docs.rs]
diff --git a/src/lib.rs b/src/lib.rs
index ce5a124..a4c6a44 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,11 +2,13 @@
 //!
 //! [`Paragraph`]: https://docs.iced.rs/iced_graphics/text/paragraph/struct.Paragraph.html
 
+pub mod markdown;
 pub mod selection;
 pub mod text;
 
 use iced_widget::core;
 use iced_widget::graphics::text::Paragraph;
+pub use markdown::view as markdown;
 #[doc(no_inline)]
 pub use text::Text;
 
diff --git a/src/markdown.rs b/src/markdown.rs
new file mode 100644
index 0000000..c54271a
--- /dev/null
+++ b/src/markdown.rs
@@ -0,0 +1,255 @@
+//! A custom markdown viewer and its corresponding functions.
+//!
+//! To be used with [`view_with`]
+//!
+//! [`view_with`]: iced_widget::markdown::view_with
+use iced_widget::graphics::text::Paragraph;
+use iced_widget::markdown::{
+    Catalog, HeadingLevel, Item, Settings, Text, Url, Viewer, view_with,
+};
+use iced_widget::{column, container, row, scrollable};
+
+use crate::core::Font;
+use crate::core::alignment;
+use crate::core::padding;
+use crate::core::{self, Element, Length, Pixels};
+use crate::{rich_text, text};
+
+/// Display a bunch of markdown items.
+pub fn view<'a, Theme, Renderer>(
+    items: impl IntoIterator<Item = &'a Item>,
+    settings: impl Into<Settings>,
+) -> Element<'a, Url, Theme, Renderer>
+where
+    Theme: Catalog + text::Catalog + 'a,
+    Renderer: core::text::Renderer<Paragraph = Paragraph, Font = Font> + 'a,
+{
+    view_with(items, settings, &SelectableViewer)
+}
+/// Displays a heading using the default look.
+pub fn heading<'a, Message, Theme, Renderer>(
+    settings: Settings,
+    level: &'a HeadingLevel,
+    text: &'a Text,
+    index: usize,
+    on_link_click: impl Fn(Url) -> Message + 'a,
+) -> Element<'a, Message, Theme, Renderer>
+where
+    Message: 'a,
+    Theme: Catalog + text::Catalog + 'a,
+    Renderer: core::text::Renderer<Paragraph = Paragraph, Font = Font> + 'a,
+{
+    let Settings {
+        h1_size,
+        h2_size,
+        h3_size,
+        h4_size,
+        h5_size,
+        h6_size,
+        text_size,
+        ..
+    } = settings;
+
+    container(
+        rich_text(text.spans(settings.style))
+            .on_link_click(on_link_click)
+            .size(match level {
+                HeadingLevel::H1 => h1_size,
+                HeadingLevel::H2 => h2_size,
+                HeadingLevel::H3 => h3_size,
+                HeadingLevel::H4 => h4_size,
+                HeadingLevel::H5 => h5_size,
+                HeadingLevel::H6 => h6_size,
+            }),
+    )
+    .padding(padding::top(if index > 0 {
+        text_size / 2.0
+    } else {
+        Pixels::ZERO
+    }))
+    .into()
+}
+
+/// Displays a paragraph using the default look.
+pub fn paragraph<'a, Message, Theme, Renderer>(
+    settings: Settings,
+    text: &Text,
+    on_link_click: impl Fn(Url) -> Message + 'a,
+) -> Element<'a, Message, Theme, Renderer>
+where
+    Message: 'a,
+    Theme: Catalog + text::Catalog + 'a,
+    Renderer: core::text::Renderer<Paragraph = Paragraph, Font = Font> + 'a,
+{
+    rich_text(text.spans(settings.style))
+        .size(settings.text_size)
+        .on_link_click(on_link_click)
+        .into()
+}
+
+/// Displays an unordered list using the default look and
+/// calling the [`Viewer`] for each bullet point item.
+pub fn unordered_list<'a, Message, Theme, Renderer>(
+    viewer: &impl Viewer<'a, Message, Theme, Renderer>,
+    settings: Settings,
+    items: &'a [Vec<Item>],
+) -> Element<'a, Message, Theme, Renderer>
+where
+    Message: 'a,
+    Theme: Catalog + text::Catalog + 'a,
+    Renderer: core::text::Renderer<Paragraph = Paragraph, Font = Font> + 'a,
+{
+    column(items.iter().map(|items| {
+        row![
+            text("•").size(settings.text_size),
+            view_with(
+                items,
+                Settings {
+                    spacing: settings.spacing * 0.6,
+                    ..settings
+                },
+                viewer,
+            )
+        ]
+        .spacing(settings.spacing)
+        .into()
+    }))
+    .spacing(settings.spacing * 0.75)
+    .padding([0.0, settings.spacing.0])
+    .into()
+}
+
+/// Displays an ordered list using the default look and
+/// calling the [`Viewer`] for each numbered item.
+pub fn ordered_list<'a, Message, Theme, Renderer>(
+    viewer: &impl Viewer<'a, Message, Theme, Renderer>,
+    settings: Settings,
+    start: u64,
+    items: &'a [Vec<Item>],
+) -> Element<'a, Message, Theme, Renderer>
+where
+    Message: 'a,
+    Theme: Catalog + text::Catalog + 'a,
+    Renderer: core::text::Renderer<Paragraph = Paragraph, Font = Font> + 'a,
+{
+    let digits = ((start + items.len() as u64).max(1) as f32).log10().ceil();
+
+    column(items.iter().enumerate().map(|(i, items)| {
+        row![
+            text!("{}.", i as u64 + start)
+                .size(settings.text_size)
+                .align_x(alignment::Horizontal::Right)
+                .width(settings.text_size * ((digits / 2.0).ceil() + 1.0)),
+            view_with(
+                items,
+                Settings {
+                    spacing: settings.spacing * 0.6,
+                    ..settings
+                },
+                viewer,
+            )
+        ]
+        .spacing(settings.spacing)
+        .into()
+    }))
+    .spacing(settings.spacing * 0.75)
+    .into()
+}
+
+/// Displays a code block using the default look.
+pub fn code_block<'a, Message, Theme, Renderer>(
+    settings: Settings,
+    lines: &'a [Text],
+    on_link_click: impl Fn(Url) -> Message + Clone + 'a,
+) -> Element<'a, Message, Theme, Renderer>
+where
+    Message: 'a,
+    Theme: Catalog + text::Catalog + 'a,
+    Renderer: core::text::Renderer<Paragraph = Paragraph, Font = Font> + 'a,
+{
+    container(
+        scrollable(
+            container(column(lines.iter().map(|line| {
+                rich_text(line.spans(settings.style))
+                    .on_link_click(on_link_click.clone())
+                    .font(Font::MONOSPACE)
+                    .size(settings.code_size)
+                    .into()
+            })))
+            .padding(settings.code_size),
+        )
+        .direction(scrollable::Direction::Horizontal(
+            scrollable::Scrollbar::default()
+                .width(settings.code_size / 2)
+                .scroller_width(settings.code_size / 2),
+        )),
+    )
+    .width(Length::Fill)
+    .padding(settings.code_size / 4)
+    .class(Theme::code_block())
+    .into()
+}
+
+#[derive(Debug, Clone, Copy)]
+struct SelectableViewer;
+
+impl<'a, Theme, Renderer> Viewer<'a, Url, Theme, Renderer> for SelectableViewer
+where
+    Theme: Catalog + text::Catalog + 'a,
+    Renderer: core::text::Renderer<Paragraph = Paragraph, Font = Font> + 'a,
+{
+    fn on_link_click(url: Url) -> Url {
+        url
+    }
+
+    fn heading(
+        &self,
+        settings: Settings,
+        level: &'a HeadingLevel,
+        text: &'a Text,
+        index: usize,
+    ) -> Element<'a, Url, Theme, Renderer> {
+        heading::<'a, Url, Theme, Renderer>(
+            settings,
+            level,
+            text,
+            index,
+            Self::on_link_click,
+        )
+    }
+
+    fn paragraph(
+        &self,
+        settings: Settings,
+        text: &Text,
+    ) -> Element<'a, Url, Theme, Renderer> {
+        paragraph(settings, text, Self::on_link_click)
+    }
+
+    fn unordered_list(
+        &self,
+        settings: Settings,
+        items: &'a [Vec<Item>],
+    ) -> Element<'a, Url, Theme, Renderer> {
+        unordered_list(self, settings, items)
+    }
+
+    fn ordered_list(
+        &self,
+        settings: Settings,
+        start: u64,
+        items: &'a [Vec<Item>],
+    ) -> Element<'a, Url, Theme, Renderer> {
+        ordered_list(self, settings, start, items)
+    }
+
+    fn code_block(
+        &self,
+        settings: Settings,
+        _language: Option<&'a str>,
+        _code: &'a str,
+        lines: &'a [Text],
+    ) -> Element<'a, Url, Theme, Renderer> {
+        code_block(settings, lines, Self::on_link_click)
+    }
+}