markdown: Add Support for HTML `img` tags in text (#38107)

Remco Smits created 2 months ago

Re-adds: https://github.com/zed-industries/zed/pull/37264

This PR re-adds basic support for showing HTML images, without touching
the display mode for images.
The initial PR changed the `div().flex().flex_col()` to
`h_flex().flex_wrap()` but this broke the text wrapping in almost all
cases.

**Note**: This does not add support for showing the images inline,
because we haven't figured out how they correctly do this.
I'm working on adding the CSS `inline` display feature support to taffy
that hopefully allows us to correctly show images/other elements inline
without breaking the text wrapping.

**Before (nightly) and after (dev) for the README file inside Zed.
(nothing has changed, which is good)**
<img width="3440" height="1380" alt="Screenshot 2025-09-13 at 12 49 08"
src="https://github.com/user-attachments/assets/9cbdcb07-dbe9-4236-9d20-e59acc0e955e"
/>

**Result**
<img width="1717" height="1314" alt="Screenshot 2025-09-13 at 12 51 54"
src="https://github.com/user-attachments/assets/1c0f8507-c63d-472e-8e82-a654a63f7153"
/>

cc @SomeoneToIgnore

Release Notes:

- markdown preview: Added support for HTML `img` tags inside paragraphs

Change summary

crates/markdown_preview/src/markdown_elements.rs |   2 
crates/markdown_preview/src/markdown_parser.rs   | 246 ++++++++++-------
2 files changed, 148 insertions(+), 100 deletions(-)

Detailed changes

crates/markdown_preview/src/markdown_elements.rs

@@ -155,7 +155,7 @@ pub struct ParsedMarkdownText {
     /// Where the text is located in the source Markdown document.
     pub source_range: Range<usize>,
     /// The text content stripped of any formatting symbols.
-    pub contents: String,
+    pub contents: SharedString,
     /// The list of highlights contained in the Markdown document.
     pub highlights: Vec<(Range<usize>, MarkdownHighlight)>,
     /// The regions of the various ranges in the Markdown document.

crates/markdown_preview/src/markdown_parser.rs

@@ -374,7 +374,7 @@ impl<'a> MarkdownParser<'a> {
                         if !text.is_empty() {
                             let parsed_regions = MarkdownParagraphChunk::Text(ParsedMarkdownText {
                                 source_range: source_range.clone(),
-                                contents: text.clone(),
+                                contents: text.into(),
                                 highlights: highlights.clone(),
                                 region_ranges: region_ranges.clone(),
                                 regions: regions.clone(),
@@ -429,7 +429,7 @@ impl<'a> MarkdownParser<'a> {
         if !text.is_empty() {
             markdown_text_like.push(MarkdownParagraphChunk::Text(ParsedMarkdownText {
                 source_range,
-                contents: text,
+                contents: text.into(),
                 highlights,
                 regions,
                 region_ranges,
@@ -835,15 +835,14 @@ impl<'a> MarkdownParser<'a> {
             markup5ever_rcdom::NodeData::Document => {
                 self.consume_children(source_range, node, elements);
             }
-            markup5ever_rcdom::NodeData::Doctype { .. } => {}
             markup5ever_rcdom::NodeData::Text { contents } => {
                 elements.push(ParsedMarkdownElement::Paragraph(vec![
                     MarkdownParagraphChunk::Text(ParsedMarkdownText {
                         source_range,
-                        contents: contents.borrow().to_string(),
-                        highlights: Vec::default(),
-                        region_ranges: Vec::default(),
                         regions: Vec::default(),
+                        region_ranges: Vec::default(),
+                        highlights: Vec::default(),
+                        contents: contents.borrow().to_string().into(),
                     }),
                 ]));
             }
@@ -853,6 +852,13 @@ impl<'a> MarkdownParser<'a> {
                     if let Some(image) = self.extract_image(source_range, attrs) {
                         elements.push(ParsedMarkdownElement::Image(image));
                     }
+                } else if local_name!("p") == name.local {
+                    let mut paragraph = MarkdownParagraph::new();
+                    self.parse_paragraph(source_range, node, &mut paragraph);
+
+                    if !paragraph.is_empty() {
+                        elements.push(ParsedMarkdownElement::Paragraph(paragraph));
+                    }
                 } else if matches!(
                     name.local,
                     local_name!("h1")
@@ -892,7 +898,7 @@ impl<'a> MarkdownParser<'a> {
                     self.consume_children(source_range, node, elements);
                 }
             }
-            markup5ever_rcdom::NodeData::ProcessingInstruction { .. } => {}
+            _ => {}
         }
     }
 
@@ -907,13 +913,19 @@ impl<'a> MarkdownParser<'a> {
                 paragraph.push(MarkdownParagraphChunk::Text(ParsedMarkdownText {
                     source_range,
                     regions: Vec::default(),
-                    contents: contents.borrow().to_string(),
                     region_ranges: Vec::default(),
                     highlights: Vec::default(),
+                    contents: contents.borrow().to_string().into(),
                 }));
             }
-            markup5ever_rcdom::NodeData::Element { .. } => {
-                self.consume_paragraph(source_range, node, paragraph);
+            markup5ever_rcdom::NodeData::Element { name, attrs, .. } => {
+                if local_name!("img") == name.local {
+                    if let Some(image) = self.extract_image(source_range, attrs) {
+                        paragraph.push(MarkdownParagraphChunk::Image(image));
+                    }
+                } else {
+                    self.consume_paragraph(source_range, node, paragraph);
+                }
             }
             _ => {}
         }
@@ -991,14 +1003,14 @@ impl<'a> MarkdownParser<'a> {
 
         if let Some(width) = Self::attr_value(attrs, local_name!("width"))
             .or_else(|| styles.get("width").cloned())
-            .and_then(|width| Self::parse_length(&width))
+            .and_then(|width| Self::parse_html_element_dimension(&width))
         {
             image.set_width(width);
         }
 
         if let Some(height) = Self::attr_value(attrs, local_name!("height"))
             .or_else(|| styles.get("height").cloned())
-            .and_then(|height| Self::parse_length(&height))
+            .and_then(|height| Self::parse_html_element_dimension(&height))
         {
             image.set_height(height);
         }
@@ -1006,6 +1018,22 @@ impl<'a> MarkdownParser<'a> {
         Some(image)
     }
 
+    fn parse_html_element_dimension(value: &str) -> Option<DefiniteLength> {
+        if value.ends_with("%") {
+            value
+                .trim_end_matches("%")
+                .parse::<f32>()
+                .ok()
+                .map(|value| relative(value / 100.))
+        } else {
+            value
+                .trim_end_matches("px")
+                .parse()
+                .ok()
+                .map(|value| px(value).into())
+        }
+    }
+
     fn extract_html_blockquote(
         &self,
         node: &Rc<markup5ever_rcdom::Node>,
@@ -1072,23 +1100,6 @@ impl<'a> MarkdownParser<'a> {
             None
         }
     }
-
-    /// Parses the width/height attribute value of an html element (e.g. img element)
-    fn parse_length(value: &str) -> Option<DefiniteLength> {
-        if value.ends_with("%") {
-            value
-                .trim_end_matches("%")
-                .parse::<f32>()
-                .ok()
-                .map(|value| relative(value / 100.))
-        } else {
-            value
-                .trim_end_matches("px")
-                .parse()
-                .ok()
-                .map(|value| px(value).into())
-        }
-    }
 }
 
 #[cfg(test)]
@@ -1173,7 +1184,7 @@ mod tests {
             ParsedMarkdownElement::Paragraph(vec![MarkdownParagraphChunk::Text(
                 ParsedMarkdownText {
                     source_range: 0..35,
-                    contents: "Some bostrikethroughld text".to_string(),
+                    contents: "Some bostrikethroughld text".into(),
                     highlights: Vec::new(),
                     region_ranges: Vec::new(),
                     regions: Vec::new(),
@@ -1347,7 +1358,7 @@ mod tests {
                 }),
                 MarkdownParagraphChunk::Text(ParsedMarkdownText {
                     source_range: 0..81,
-                    contents: " Lorem Ipsum ".to_string(),
+                    contents: " Lorem Ipsum ".into(),
                     highlights: Vec::new(),
                     region_ranges: Vec::new(),
                     regions: Vec::new(),
@@ -1366,72 +1377,113 @@ mod tests {
     }
 
     #[test]
-    fn test_parse_length() {
+    fn test_parse_html_element_dimension() {
         // Test percentage values
         assert_eq!(
-            MarkdownParser::parse_length("50%"),
+            MarkdownParser::parse_html_element_dimension("50%"),
             Some(DefiniteLength::Fraction(0.5))
         );
         assert_eq!(
-            MarkdownParser::parse_length("100%"),
+            MarkdownParser::parse_html_element_dimension("100%"),
             Some(DefiniteLength::Fraction(1.0))
         );
         assert_eq!(
-            MarkdownParser::parse_length("25%"),
+            MarkdownParser::parse_html_element_dimension("25%"),
             Some(DefiniteLength::Fraction(0.25))
         );
         assert_eq!(
-            MarkdownParser::parse_length("0%"),
+            MarkdownParser::parse_html_element_dimension("0%"),
             Some(DefiniteLength::Fraction(0.0))
         );
 
         // Test pixel values
         assert_eq!(
-            MarkdownParser::parse_length("100px"),
+            MarkdownParser::parse_html_element_dimension("100px"),
             Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(100.0))))
         );
         assert_eq!(
-            MarkdownParser::parse_length("50px"),
+            MarkdownParser::parse_html_element_dimension("50px"),
             Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(50.0))))
         );
         assert_eq!(
-            MarkdownParser::parse_length("0px"),
+            MarkdownParser::parse_html_element_dimension("0px"),
             Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(0.0))))
         );
 
         // Test values without units (should be treated as pixels)
         assert_eq!(
-            MarkdownParser::parse_length("100"),
+            MarkdownParser::parse_html_element_dimension("100"),
             Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(100.0))))
         );
         assert_eq!(
-            MarkdownParser::parse_length("42"),
+            MarkdownParser::parse_html_element_dimension("42"),
             Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(42.0))))
         );
 
         // Test invalid values
-        assert_eq!(MarkdownParser::parse_length("invalid"), None);
-        assert_eq!(MarkdownParser::parse_length("px"), None);
-        assert_eq!(MarkdownParser::parse_length("%"), None);
-        assert_eq!(MarkdownParser::parse_length(""), None);
-        assert_eq!(MarkdownParser::parse_length("abc%"), None);
-        assert_eq!(MarkdownParser::parse_length("abcpx"), None);
+        assert_eq!(
+            MarkdownParser::parse_html_element_dimension("invalid"),
+            None
+        );
+        assert_eq!(MarkdownParser::parse_html_element_dimension("px"), None);
+        assert_eq!(MarkdownParser::parse_html_element_dimension("%"), None);
+        assert_eq!(MarkdownParser::parse_html_element_dimension(""), None);
+        assert_eq!(MarkdownParser::parse_html_element_dimension("abc%"), None);
+        assert_eq!(MarkdownParser::parse_html_element_dimension("abcpx"), None);
 
         // Test decimal values
         assert_eq!(
-            MarkdownParser::parse_length("50.5%"),
+            MarkdownParser::parse_html_element_dimension("50.5%"),
             Some(DefiniteLength::Fraction(0.505))
         );
         assert_eq!(
-            MarkdownParser::parse_length("100.25px"),
+            MarkdownParser::parse_html_element_dimension("100.25px"),
             Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(100.25))))
         );
         assert_eq!(
-            MarkdownParser::parse_length("42.0"),
+            MarkdownParser::parse_html_element_dimension("42.0"),
             Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(42.0))))
         );
     }
 
+    #[gpui::test]
+    async fn test_inline_html_image_tag() {
+        let parsed =
+            parse("<p>Some text<img src=\"http://example.com/foo.png\" /> some more text</p>")
+                .await;
+
+        assert_eq!(
+            ParsedMarkdown {
+                children: vec![ParsedMarkdownElement::Paragraph(vec![
+                    MarkdownParagraphChunk::Text(ParsedMarkdownText {
+                        source_range: 0..71,
+                        contents: "Some text".into(),
+                        highlights: Default::default(),
+                        region_ranges: Default::default(),
+                        regions: Default::default()
+                    }),
+                    MarkdownParagraphChunk::Image(Image {
+                        source_range: 0..71,
+                        link: Link::Web {
+                            url: "http://example.com/foo.png".to_string(),
+                        },
+                        alt_text: None,
+                        height: None,
+                        width: None,
+                    }),
+                    MarkdownParagraphChunk::Text(ParsedMarkdownText {
+                        source_range: 0..71,
+                        contents: " some more text".into(),
+                        highlights: Default::default(),
+                        region_ranges: Default::default(),
+                        regions: Default::default()
+                    }),
+                ])]
+            },
+            parsed
+        );
+    }
+
     #[gpui::test]
     async fn test_html_block_quote() {
         let parsed = parse(
@@ -1668,20 +1720,19 @@ mod tests {
     async fn test_html_image_tag() {
         let parsed = parse("<img src=\"http://example.com/foo.png\" />").await;
 
-        let ParsedMarkdownElement::Image(image) = &parsed.children[0] else {
-            panic!("Expected a image element");
-        };
         assert_eq!(
-            image.clone(),
-            Image {
-                source_range: 0..40,
-                link: Link::Web {
-                    url: "http://example.com/foo.png".to_string(),
-                },
-                alt_text: None,
-                height: None,
-                width: None,
+            ParsedMarkdown {
+                children: vec![ParsedMarkdownElement::Image(Image {
+                    source_range: 0..40,
+                    link: Link::Web {
+                        url: "http://example.com/foo.png".to_string(),
+                    },
+                    alt_text: None,
+                    height: None,
+                    width: None,
+                })]
             },
+            parsed
         );
     }
 
@@ -1689,20 +1740,19 @@ mod tests {
     async fn test_html_image_tag_with_alt_text() {
         let parsed = parse("<img src=\"http://example.com/foo.png\" alt=\"Foo\" />").await;
 
-        let ParsedMarkdownElement::Image(image) = &parsed.children[0] else {
-            panic!("Expected a image element");
-        };
         assert_eq!(
-            image.clone(),
-            Image {
-                source_range: 0..50,
-                link: Link::Web {
-                    url: "http://example.com/foo.png".to_string(),
-                },
-                alt_text: Some("Foo".into()),
-                height: None,
-                width: None,
+            ParsedMarkdown {
+                children: vec![ParsedMarkdownElement::Image(Image {
+                    source_range: 0..50,
+                    link: Link::Web {
+                        url: "http://example.com/foo.png".to_string(),
+                    },
+                    alt_text: Some("Foo".into()),
+                    height: None,
+                    width: None,
+                })]
             },
+            parsed
         );
     }
 
@@ -1711,20 +1761,19 @@ mod tests {
         let parsed =
             parse("<img src=\"http://example.com/foo.png\" height=\"100\" width=\"200\" />").await;
 
-        let ParsedMarkdownElement::Image(image) = &parsed.children[0] else {
-            panic!("Expected a image element");
-        };
         assert_eq!(
-            image.clone(),
-            Image {
-                source_range: 0..65,
-                link: Link::Web {
-                    url: "http://example.com/foo.png".to_string(),
-                },
-                alt_text: None,
-                height: Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(100.)))),
-                width: Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(200.)))),
+            ParsedMarkdown {
+                children: vec![ParsedMarkdownElement::Image(Image {
+                    source_range: 0..65,
+                    link: Link::Web {
+                        url: "http://example.com/foo.png".to_string(),
+                    },
+                    alt_text: None,
+                    height: Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(100.)))),
+                    width: Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(200.)))),
+                })]
             },
+            parsed
         );
     }
 
@@ -1735,20 +1784,19 @@ mod tests {
         )
         .await;
 
-        let ParsedMarkdownElement::Image(image) = &parsed.children[0] else {
-            panic!("Expected a image element");
-        };
         assert_eq!(
-            image.clone(),
-            Image {
-                source_range: 0..75,
-                link: Link::Web {
-                    url: "http://example.com/foo.png".to_string(),
-                },
-                alt_text: None,
-                height: Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(100.)))),
-                width: Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(200.)))),
+            ParsedMarkdown {
+                children: vec![ParsedMarkdownElement::Image(Image {
+                    source_range: 0..75,
+                    link: Link::Web {
+                        url: "http://example.com/foo.png".to_string(),
+                    },
+                    alt_text: None,
+                    height: Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(100.)))),
+                    width: Some(DefiniteLength::Absolute(AbsoluteLength::Pixels(px(200.)))),
+                })]
             },
+            parsed
         );
     }
 
@@ -2199,7 +2247,7 @@ fn main() {
             region_ranges: Vec::new(),
             regions: Vec::new(),
             source_range,
-            contents: contents.to_string(),
+            contents: contents.to_string().into(),
         })]
     }