Support different kinds of underline rendering

Adds four new  modifiers that can be used in themes:

- undercurled
- underdashed
- underdotted
- double-underline

3 files changed, 38 insertions, 12 deletions

diff --git a/helix-tui/src/backend/crossterm.rs b/helix-tui/src/backend/crossterm.rs
index eff098b3..252036f3 100644
--- a/helix-tui/src/backend/crossterm.rs
+++ b/helix-tui/src/backend/crossterm.rs
@@ -153,7 +153,7 @@ impl ModifierDiff {
         if removed.contains(Modifier::ITALIC) {
             map_error(queue!(w, SetAttribute(CAttribute::NoItalic)))?;
         }
-        if removed.contains(Modifier::UNDERLINED) {
+        if removed.intersects(Modifier::ANY_UNDERLINE) {
             map_error(queue!(w, SetAttribute(CAttribute::NoUnderline)))?;
         }
         if removed.contains(Modifier::DIM) {
@@ -179,6 +179,18 @@ impl ModifierDiff {
         if added.contains(Modifier::UNDERLINED) {
             map_error(queue!(w, SetAttribute(CAttribute::Underlined)))?;
         }
+        if added.contains(Modifier::UNDERCURLED) {
+            map_error(queue!(w, SetAttribute(CAttribute::Undercurled)))?;
+        }
+        if added.contains(Modifier::UNDERDOTTED) {
+            map_error(queue!(w, SetAttribute(CAttribute::Underdotted)))?;
+        }
+        if added.contains(Modifier::UNDERDASHED) {
+            map_error(queue!(w, SetAttribute(CAttribute::Underdashed)))?;
+        }
+        if added.contains(Modifier::DOUBLE_UNDERLINED) {
+            map_error(queue!(w, SetAttribute(CAttribute::DoubleUnderlined)))?;
+        }
         if added.contains(Modifier::DIM) {
             map_error(queue!(w, SetAttribute(CAttribute::Dim)))?;
         }
diff --git a/helix-view/src/graphics.rs b/helix-view/src/graphics.rs
index fb3c8b3f..15492119 100644
--- a/helix-view/src/graphics.rs
+++ b/helix-view/src/graphics.rs
@@ -327,17 +327,27 @@ bitflags! {
     ///
     /// let m = Modifier::BOLD | Modifier::ITALIC;
     /// ```
-    #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+    #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize), serde(rename_all = "kebab-case"))]
     pub struct Modifier: u16 {
-        const BOLD              = 0b0000_0000_0001;
-        const DIM               = 0b0000_0000_0010;
-        const ITALIC            = 0b0000_0000_0100;
-        const UNDERLINED        = 0b0000_0000_1000;
-        const SLOW_BLINK        = 0b0000_0001_0000;
-        const RAPID_BLINK       = 0b0000_0010_0000;
-        const REVERSED          = 0b0000_0100_0000;
-        const HIDDEN            = 0b0000_1000_0000;
-        const CROSSED_OUT       = 0b0001_0000_0000;
+        const BOLD              = 0b0000_0000_0000_0001;
+        const DIM               = 0b0000_0000_0000_0010;
+        const ITALIC            = 0b0000_0000_0000_0100;
+        const UNDERLINED        = 0b0000_0000_0000_1000;
+        const SLOW_BLINK        = 0b0000_0000_0001_0000;
+        const RAPID_BLINK       = 0b0000_0000_0010_0000;
+        const REVERSED          = 0b0000_0000_0100_0000;
+        const HIDDEN            = 0b0000_0000_1000_0000;
+        const CROSSED_OUT       = 0b0000_0001_0000_0000;
+        const UNDERCURLED       = 0b0000_0010_0000_0000;
+        const UNDERDOTTED       = 0b0000_0100_0000_0000;
+        const UNDERDASHED       = 0b0000_1000_0000_0000;
+        const DOUBLE_UNDERLINED = 0b0001_0000_0000_0000;
+
+        const ANY_UNDERLINE     = Self::UNDERLINED.bits
+                                    | Self::UNDERCURLED.bits
+                                    | Self::UNDERDOTTED.bits
+                                    | Self::UNDERDASHED.bits
+                                    | Self::DOUBLE_UNDERLINED.bits;
     }
 }
 
@@ -355,6 +365,10 @@ impl FromStr for Modifier {
             "reversed" => Ok(Self::REVERSED),
             "hidden" => Ok(Self::HIDDEN),
             "crossed_out" => Ok(Self::CROSSED_OUT),
+            "undercurled" => Ok(Self::UNDERCURLED),
+            "underdotted" => Ok(Self::UNDERDOTTED),
+            "underdashed" => Ok(Self::UNDERDASHED),
+            "double_underlined" => Ok(Self::DOUBLE_UNDERLINED),
             _ => Err("Invalid modifier"),
         }
     }
diff --git a/runtime/themes/onedark.toml b/runtime/themes/onedark.toml
index 1e7d9af1..a4cc12eb 100644
--- a/runtime/themes/onedark.toml
+++ b/runtime/themes/onedark.toml
@@ -39,7 +39,7 @@
 "diff.delta" = "gold"
 "diff.minus" = "red"
 
-diagnostic = { modifiers = ["underlined"] }
+diagnostic = { modifiers = ["undercurled"] }
 "info" = { fg = "blue", modifiers = ["bold"] }
 "hint" = { fg = "green", modifiers = ["bold"] }
 "warning" = { fg = "yellow", modifiers = ["bold"] }