Add html callback function

Closes #73

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Added
 
 - Callback function `render_math_fn` for custom math rendering
+- Callback function `render_html_fn` for custom html rendering
 
 ### Fixed
 

egui_commonmark/examples/html.rs

@@ -0,0 +1,81 @@
+//! Add `light` or `dark` to the end of the command to specify theme. Default
+//! is light. `cargo r --example html -- dark`
+
+use eframe::egui;
+use egui_commonmark::*;
+use std::cell::RefCell;
+use std::rc::Rc;
+
+struct App {
+    cache: CommonMarkCache,
+    /// To avoid id collisions
+    counter: Rc<RefCell<usize>>,
+}
+
+impl eframe::App for App {
+    fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
+        *self.counter.as_ref().borrow_mut() = 0;
+
+        egui::CentralPanel::default().show(ctx, |ui| {
+            egui::ScrollArea::vertical().show(ui, |ui| {
+                CommonMarkViewer::new()
+                    .render_html_fn({
+                        let counter = Rc::clone(&self.counter);
+                        Some(&move |ui, html| {
+                            // For simplicity lets just hide the content regardless of what kind of
+                            // node it is.
+                            ui.collapsing(
+                                format!("Collapsed {}", counter.as_ref().borrow()),
+                                |ui| {
+                                    ui.label(html);
+                                },
+                            );
+
+                            *counter.as_ref().borrow_mut() += 1;
+                        })
+                    })
+                    .show(ui, &mut self.cache, EXAMPLE_TEXT);
+            });
+        });
+    }
+}
+
+fn main() -> eframe::Result {
+    let mut args = std::env::args();
+    args.next();
+
+    eframe::run_native(
+        "Markdown viewer",
+        eframe::NativeOptions::default(),
+        Box::new(move |cc| {
+            if let Some(theme) = args.next() {
+                if theme == "light" {
+                    cc.egui_ctx.set_theme(egui::Theme::Light);
+                } else if theme == "dark" {
+                    cc.egui_ctx.set_theme(egui::Theme::Dark);
+                }
+            }
+
+            cc.egui_ctx.style_mut(|style| {
+                // Show the url of a hyperlink on hover
+                style.url_in_tooltip = true;
+            });
+
+            Ok(Box::new(App {
+                cache: CommonMarkCache::default(),
+                counter: Rc::new(RefCell::new(0)),
+            }))
+        }),
+    )
+}
+
+const EXAMPLE_TEXT: &str = r#"
+# Customized rendering using html
+<p>
+some text
+</p>
+
+<p>
+some text 2
+</p>
+"#;

egui_commonmark/src/lib.rs

@@ -209,8 +209,15 @@ impl<'f> CommonMarkViewer<'f> {
     ///     );
     ///     }));
     /// ```
-    pub fn render_math_fn(mut self, math_fn: Option<&'f RenderMathFn>) -> Self {
-        self.options.math_fn = math_fn;
+    pub fn render_math_fn(mut self, func: Option<&'f RenderMathFn>) -> Self {
+        self.options.math_fn = func;
+        self
+    }
+
+    /// Allows custom handling of html. Enabling this will disable plain text rendering
+    /// of html blocks. Nodes are included in the provided text
+    pub fn render_html_fn(mut self, func: Option<&'f RenderHtmlFn>) -> Self {
+        self.options.html_fn = func;
         self
     }
 

egui_commonmark/src/parsers/pulldown.rs

@@ -72,6 +72,9 @@ pub struct CommonMarkViewerInternal {
     image: Option<Image>,
     line: Newline,
     code_block: Option<CodeBlock>,
+
+    /// Only populated if the html_fn option has been set
+    html_block: String,
     is_list_item: bool,
     def_list: DefinitionList,
     is_table: bool,
@@ -96,6 +99,7 @@ impl CommonMarkViewerInternal {
             is_list_item: false,
             def_list: Default::default(),
             code_block: None,
+            html_block: String::new(),
             is_table: false,
             is_blockquote: false,
             checkbox_events: Vec::new(),
@@ -520,8 +524,13 @@ impl CommonMarkViewerInternal {
             pulldown_cmark::Event::InlineHtml(text) => {
                 self.event_text(text, ui);
             }
-            pulldown_cmark::Event::Html(node) => {
-                self.event_text(node, ui);
+
+            pulldown_cmark::Event::Html(text) => {
+                if options.html_fn.is_some() {
+                    self.html_block.push_str(&text);
+                } else {
+                    self.event_text(text, ui);
+                }
             }
             pulldown_cmark::Event::FootnoteReference(footnote) => {
                 footnote_start(ui, &footnote);
@@ -755,7 +764,13 @@ impl CommonMarkViewerInternal {
                     image.end(ui, options);
                 }
             }
-            pulldown_cmark::TagEnd::HtmlBlock => {}
+            pulldown_cmark::TagEnd::HtmlBlock => {
+                if let Some(html_fn) = options.html_fn {
+                    html_fn(ui, &self.html_block);
+                    self.html_block.clear();
+                }
+            }
+
             pulldown_cmark::TagEnd::MetadataBlock(_) => {}
 
             pulldown_cmark::TagEnd::DefinitionList => self.line.try_insert_end(ui),

egui_commonmark_backend/src/lib.rs

@@ -28,3 +28,5 @@ pub use misc::CommonMarkCache;
 
 /// Takes [`egui::Ui`], the math text to be rendered and whether it is inline
 pub type RenderMathFn = dyn Fn(&mut egui::Ui, &str, bool);
+/// Takes [`egui::Ui`] and the html text to be rendered/used
+pub type RenderHtmlFn = dyn Fn(&mut egui::Ui, &str);

egui_commonmark_backend/src/misc.rs

@@ -32,6 +32,7 @@ pub struct CommonMarkOptions<'f> {
     /// Whether to present a mutable ui for things like checkboxes
     pub mutable: bool,
     pub math_fn: Option<&'f crate::RenderMathFn>,
+    pub html_fn: Option<&'f crate::RenderHtmlFn>,
 }
 
 impl<'f> std::fmt::Debug for CommonMarkOptions<'f> {
@@ -74,6 +75,7 @@ impl Default for CommonMarkOptions<'_> {
             alerts: AlertBundle::gfm(),
             mutable: false,
             math_fn: None,
+            html_fn: None,
         }
     }
 }