Allow separate styles for markup headings (#1618)

* update markdown highlighting to use separate heading themes

* remove markdown theme scopes in ui

3 files changed, 40 insertions, 33 deletions

diff --git a/helix-term/src/commands/lsp.rs b/helix-term/src/commands/lsp.rs
index 255d545c..af11cd4e 100644
--- a/helix-term/src/commands/lsp.rs
+++ b/helix-term/src/commands/lsp.rs
@@ -632,8 +632,7 @@ pub fn hover(cx: &mut Context) {
 
                 // skip if contents empty
 
-                let contents =
-                    ui::Markdown::new(contents, editor.syn_loader.clone()).style_group("hover");
+                let contents = ui::Markdown::new(contents, editor.syn_loader.clone());
                 let popup = Popup::new("hover", contents);
                 compositor.replace_or_push("hover", Box::new(popup));
             }
diff --git a/helix-term/src/ui/completion.rs b/helix-term/src/ui/completion.rs
index 35afe81e..d3b618a9 100644
--- a/helix-term/src/ui/completion.rs
+++ b/helix-term/src/ui/completion.rs
@@ -305,8 +305,6 @@ impl Component for Completion {
             let coords = helix_core::visual_coords_at_pos(text, cursor_pos, doc.tab_width());
             let cursor_pos = (coords.row - view.offset.row) as u16;
 
-            let markdown_ui =
-                |content, syn_loader| Markdown::new(content, syn_loader).style_group("completion");
             let mut markdown_doc = match &option.documentation {
                 Some(lsp::Documentation::String(contents))
                 | Some(lsp::Documentation::MarkupContent(lsp::MarkupContent {
@@ -314,7 +312,7 @@ impl Component for Completion {
                     value: contents,
                 })) => {
                     // TODO: convert to wrapped text
-                    markdown_ui(
+                    Markdown::new(
                         format!(
                             "```{}\n{}\n```\n{}",
                             language,
@@ -329,7 +327,7 @@ impl Component for Completion {
                     value: contents,
                 })) => {
                     // TODO: set language based on doc scope
-                    markdown_ui(
+                    Markdown::new(
                         format!(
                             "```{}\n{}\n```\n{}",
                             language,
@@ -343,7 +341,7 @@ impl Component for Completion {
                     // TODO: copied from above
 
                     // TODO: set language based on doc scope
-                    markdown_ui(
+                    Markdown::new(
                         format!(
                             "```{}\n{}\n```",
                             language,
diff --git a/helix-term/src/ui/markdown.rs b/helix-term/src/ui/markdown.rs
index cfb5998c..bcb63c29 100644
--- a/helix-term/src/ui/markdown.rs
+++ b/helix-term/src/ui/markdown.rs
@@ -6,14 +6,14 @@ use tui::{
 
 use std::sync::Arc;
 
-use pulldown_cmark::{CodeBlockKind, CowStr, Event, Options, Parser, Tag};
+use pulldown_cmark::{CodeBlockKind, CowStr, Event, HeadingLevel, Options, Parser, Tag};
 
 use helix_core::{
     syntax::{self, HighlightEvent, Syntax},
     Rope,
 };
 use helix_view::{
-    graphics::{Margin, Rect},
+    graphics::{Margin, Rect, Style},
     Theme,
 };
 
@@ -21,30 +21,31 @@ pub struct Markdown {
     contents: String,
 
     config_loader: Arc<syntax::Loader>,
-
-    block_style: String,
-    heading_style: String,
 }
 
 // TODO: pre-render and self reference via Pin
 // better yet, just use Tendril + subtendril for references
 
 impl Markdown {
+    // theme keys, including fallbacks
+    const TEXT_STYLE: [&'static str; 2] = ["ui.text", "ui"];
+    const BLOCK_STYLE: [&'static str; 3] = ["markup.raw.inline", "markup.raw", "markup"];
+    const HEADING_STYLES: [[&'static str; 3]; 6] = [
+        ["markup.heading.1", "markup.heading", "markup"],
+        ["markup.heading.2", "markup.heading", "markup"],
+        ["markup.heading.3", "markup.heading", "markup"],
+        ["markup.heading.4", "markup.heading", "markup"],
+        ["markup.heading.5", "markup.heading", "markup"],
+        ["markup.heading.6", "markup.heading", "markup"],
+    ];
+
     pub fn new(contents: String, config_loader: Arc<syntax::Loader>) -> Self {
         Self {
             contents,
             config_loader,
-            block_style: "markup.raw.inline".into(),
-            heading_style: "markup.heading".into(),
         }
     }
 
-    pub fn style_group(mut self, suffix: &str) -> Self {
-        self.block_style = format!("markup.raw.inline.{}", suffix);
-        self.heading_style = format!("markup.heading.{}", suffix);
-        self
-    }
-
     fn parse(&self, theme: Option<&Theme>) -> tui::text::Text<'_> {
         // // also 2021-03-04T16:33:58.553 helix_lsp::transport [INFO] <- {"contents":{"kind":"markdown","value":"\n```rust\ncore::num\n```\n\n```rust\npub const fn saturating_sub(self, rhs:Self) ->Self\n```\n\n---\n\n```rust\n```"},"range":{"end":{"character":61,"line":101},"start":{"character":47,"line":101}}}
         // let text = "\n```rust\ncore::iter::traits::iterator::Iterator\n```\n\n```rust\nfn collect<B: FromIterator<Self::Item>>(self) -> B\nwhere\n        Self: Sized,\n```\n\n---\n\nTransforms an iterator into a collection.\n\n`collect()` can take anything iterable, and turn it into a relevant\ncollection. This is one of the more powerful methods in the standard\nlibrary, used in a variety of contexts.\n\nThe most basic pattern in which `collect()` is used is to turn one\ncollection into another. You take a collection, call [`iter`](https://doc.rust-lang.org/nightly/core/iter/traits/iterator/trait.Iterator.html) on it,\ndo a bunch of transformations, and then `collect()` at the end.\n\n`collect()` can also create instances of types that are not typical\ncollections. For example, a [`String`](https://doc.rust-lang.org/nightly/core/iter/std/string/struct.String.html) can be built from [`char`](type@char)s,\nand an iterator of [`Result<T, E>`](https://doc.rust-lang.org/nightly/core/result/enum.Result.html) items can be collected\ninto `Result<Collection<T>, E>`. See the examples below for more.\n\nBecause `collect()` is so general, it can cause problems with type\ninference. As such, `collect()` is one of the few times you'll see\nthe syntax affectionately known as the 'turbofish': `::<>`. This\nhelps the inference algorithm understand specifically which collection\nyou're trying to collect into.\n\n# Examples\n\nBasic usage:\n\n```rust\nlet a = [1, 2, 3];\n\nlet doubled: Vec<i32> = a.iter()\n                         .map(|&x| x * 2)\n                         .collect();\n\nassert_eq!(vec![2, 4, 6], doubled);\n```\n\nNote that we needed the `: Vec<i32>` on the left-hand side. This is because\nwe could collect into, for example, a [`VecDeque<T>`](https://doc.rust-lang.org/nightly/core/iter/std/collections/struct.VecDeque.html) instead:\n\n```rust\nuse std::collections::VecDeque;\n\nlet a = [1, 2, 3];\n\nlet doubled: VecDeque<i32> = a.iter().map(|&x| x * 2).collect();\n\nassert_eq!(2, doubled[0]);\nassert_eq!(4, doubled[1]);\nassert_eq!(6, doubled[2]);\n```\n\nUsing the 'turbofish' instead of annotating `doubled`:\n\n```rust\nlet a = [1, 2, 3];\n\nlet doubled = a.iter().map(|x| x * 2).collect::<Vec<i32>>();\n\nassert_eq!(vec![2, 4, 6], doubled);\n```\n\nBecause `collect()` only cares about what you're collecting into, you can\nstill use a partial type hint, `_`, with the turbofish:\n\n```rust\nlet a = [1, 2, 3];\n\nlet doubled = a.iter().map(|x| x * 2).collect::<Vec<_>>();\n\nassert_eq!(vec![2, 4, 6], doubled);\n```\n\nUsing `collect()` to make a [`String`](https://doc.rust-lang.org/nightly/core/iter/std/string/struct.String.html):\n\n```rust\nlet chars = ['g', 'd', 'k', 'k', 'n'];\n\nlet hello: String = chars.iter()\n    .map(|&x| x as u8)\n    .map(|x| (x + 1) as char)\n    .collect();\n\nassert_eq!(\"hello\", hello);\n```\n\nIf you have a list of [`Result<T, E>`](https://doc.rust-lang.org/nightly/core/result/enum.Result.html)s, you can use `collect()` to\nsee if any of them failed:\n\n```rust\nlet results = [Ok(1), Err(\"nope\"), Ok(3), Err(\"bad\")];\n\nlet result: Result<Vec<_>, &str> = results.iter().cloned().collect();\n\n// gives us the first error\nassert_eq!(Err(\"nope\"), result);\n\nlet results = [Ok(1), Ok(3)];\n\nlet result: Result<Vec<_>, &str> = results.iter().cloned().collect();\n\n// gives us the list of answers\nassert_eq!(Ok(vec![1, 3]), result);\n```";
@@ -67,17 +68,19 @@ impl Markdown {
             })
         }
 
-        macro_rules! get_theme {
-            ($s1: expr) => {
-                theme
-                    .map(|theme| theme.try_get($s1.as_str()))
-                    .flatten()
-                    .unwrap_or_default()
-            };
-        }
-        let text_style = theme.map(|theme| theme.get("ui.text")).unwrap_or_default();
-        let code_style = get_theme!(self.block_style);
-        let heading_style = get_theme!(self.heading_style);
+        let get_theme = |keys: &[&str]| match theme {
+            Some(theme) => keys
+                .iter()
+                .find_map(|key| theme.try_get(key))
+                .unwrap_or_default(),
+            None => Default::default(),
+        };
+        let text_style = get_theme(&Self::TEXT_STYLE);
+        let code_style = get_theme(&Self::BLOCK_STYLE);
+        let heading_styles: Vec<Style> = Self::HEADING_STYLES
+            .iter()
+            .map(|key| get_theme(key))
+            .collect();
 
         for event in parser {
             match event {
@@ -172,9 +175,16 @@ impl Markdown {
                                 lines.push(Spans::from(span));
                             }
                         }
-                    } else if let Some(Tag::Heading(_, _, _)) = tags.last() {
+                    } else if let Some(Tag::Heading(level, _, _)) = tags.last() {
                         let mut span = to_span(text);
-                        span.style = heading_style;
+                        span.style = match level {
+                            HeadingLevel::H1 => heading_styles[0],
+                            HeadingLevel::H2 => heading_styles[1],
+                            HeadingLevel::H3 => heading_styles[2],
+                            HeadingLevel::H4 => heading_styles[3],
+                            HeadingLevel::H5 => heading_styles[4],
+                            HeadingLevel::H6 => heading_styles[5],
+                        };
                         spans.push(span);
                     } else {
                         let mut span = to_span(text);