Add theme key for selected line number

Adds `ui.linenr.selected` which controls highlight of linu numbes which
have cursors on.

- Fallback to linenr if linenr.selected is missing

- Update docs and themes

- Add TODOs for themes with temporary linenr.selected

7 files changed, 56 insertions, 38 deletions

diff --git a/book/src/configuration.md b/book/src/configuration.md
index 363279f2..649aa21f 100644
--- a/book/src/configuration.md
+++ b/book/src/configuration.md
@@ -70,6 +70,7 @@ Possible keys:
 | `module`                |                                     |
 | `ui.background`         |                                     |
 | `ui.linenr`             |                                     |
+| `ui.linenr.selected`    | For lines with cursors              |
 | `ui.statusline`         |                                     |
 | `ui.popup`              |                                     |
 | `ui.window`             |                                     |
diff --git a/contrib/themes/bogster.toml b/contrib/themes/bogster.toml
index 0fbafd23..205e464c 100644
--- a/contrib/themes/bogster.toml
+++ b/contrib/themes/bogster.toml
@@ -30,6 +30,7 @@
 
 "ui.background" = { bg = "#161c23" }
 "ui.linenr" = { fg = "#415367" }
+"ui.linenr.selected" = { fg = "#e5ded6" }  # TODO
 "ui.statusline" = { bg = "#232d38" }
 "ui.popup" = { bg = "#232d38" }
 "ui.window" = { bg = "#232d38" }
diff --git a/contrib/themes/ingrid.toml b/contrib/themes/ingrid.toml
index 0dd53164..da333fb8 100644
--- a/contrib/themes/ingrid.toml
+++ b/contrib/themes/ingrid.toml
@@ -30,6 +30,7 @@
 
 "ui.background" = { bg = "#FFFCFD" }
 "ui.linenr" = { fg = "#bbbbbb" }
+"ui.linenr.selected" = { fg = "#F3EAE9" }  # TODO
 "ui.statusline" = { bg = "#F3EAE9" }
 "ui.popup" = { bg = "#F3EAE9" }
 "ui.window" = { bg = "#D8B8B3" }
diff --git a/contrib/themes/onedark.toml b/contrib/themes/onedark.toml
index ccf6a2cc..4c13a217 100644
--- a/contrib/themes/onedark.toml
+++ b/contrib/themes/onedark.toml
@@ -33,6 +33,7 @@
 "ui.background" = { fg = "#ABB2BF", bg = "#282C34" }
 "ui.help" = { bg = "#3E4452" }
 "ui.linenr" = { fg = "#4B5263", modifiers = ['dim'] }
+"ui.linenr.selected" = { fg = "#ABB2BF" }
 "ui.popup" = { bg = "#3E4452" }
 "ui.statusline" = { fg = "#ABB2BF", bg = "#2C323C" }
 "ui.selection" = { bg = "#3E4452" }
diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index 95587b4c..63b3e277 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -232,7 +232,45 @@ impl EditorView {
             }
         }
 
-        // render selections
+        // render gutters
+
+        let linenr: Style = theme.get("ui.linenr");
+        let warning: Style = theme.get("warning");
+        let error: Style = theme.get("error");
+        let info: Style = theme.get("info");
+        let hint: Style = theme.get("hint");
+
+        for (i, line) in (view.first_line..last_line).enumerate() {
+            use helix_core::diagnostic::Severity;
+            if let Some(diagnostic) = doc.diagnostics().iter().find(|d| d.line == line) {
+                surface.set_stringn(
+                    viewport.x - OFFSET,
+                    viewport.y + i as u16,
+                    "●",
+                    1,
+                    match diagnostic.severity {
+                        Some(Severity::Error) => error,
+                        Some(Severity::Warning) | None => warning,
+                        Some(Severity::Info) => info,
+                        Some(Severity::Hint) => hint,
+                    },
+                );
+            }
+
+            // line numbers having selections are rendered differently
+            surface.set_stringn(
+                viewport.x + 1 - OFFSET,
+                viewport.y + i as u16,
+                format!("{:>5}", line + 1),
+                5,
+                linenr,
+            );
+        }
+
+        // render selections and selected linenr(s)
+        let linenr_select: Style = theme
+            .try_get("ui.linenr.selected")
+            .unwrap_or_else(|| theme.get("ui.linenr"));
 
         if is_focused {
             let screen = {
@@ -329,6 +367,13 @@ impl EditorView {
                         ),
                         cursor_style,
                     );
+                    surface.set_stringn(
+                        viewport.x + 1 - OFFSET,
+                        viewport.y + head.row as u16,
+                        format!("{:>5}", view.first_line + head.row + 1),
+                        5,
+                        linenr_select,
+                    );
                     // TODO: set cursor position for IME
                     if let Some(syntax) = doc.syntax() {
                         use helix_core::match_brackets;
@@ -357,40 +402,6 @@ impl EditorView {
                 }
             }
         }
-
-        // render gutters
-
-        let style: Style = theme.get("ui.linenr");
-        let warning: Style = theme.get("warning");
-        let error: Style = theme.get("error");
-        let info: Style = theme.get("info");
-        let hint: Style = theme.get("hint");
-
-        for (i, line) in (view.first_line..last_line).enumerate() {
-            use helix_core::diagnostic::Severity;
-            if let Some(diagnostic) = doc.diagnostics().iter().find(|d| d.line == line) {
-                surface.set_stringn(
-                    viewport.x - OFFSET,
-                    viewport.y + i as u16,
-                    "●",
-                    1,
-                    match diagnostic.severity {
-                        Some(Severity::Error) => error,
-                        Some(Severity::Warning) | None => warning,
-                        Some(Severity::Info) => info,
-                        Some(Severity::Hint) => hint,
-                    },
-                );
-            }
-
-            surface.set_stringn(
-                viewport.x + 1 - OFFSET,
-                viewport.y + i as u16,
-                format!("{:>5}", line + 1),
-                5,
-                style,
-            );
-        }
     }
 
     pub fn render_diagnostics(
diff --git a/helix-view/src/theme.rs b/helix-view/src/theme.rs
index efb6a1af..51a21421 100644
--- a/helix-view/src/theme.rs
+++ b/helix-view/src/theme.rs
@@ -200,12 +200,14 @@ fn parse_modifier(value: &Value) -> Option<Modifier> {
 
 impl Theme {
     pub fn get(&self, scope: &str) -> Style {
-        self.styles
-            .get(scope)
-            .copied()
+        self.try_get(scope)
             .unwrap_or_else(|| Style::default().fg(Color::Rgb(0, 0, 255)))
     }
 
+    pub fn try_get(&self, scope: &str) -> Option<Style> {
+        self.styles.get(scope).copied()
+    }
+
     #[inline]
     pub fn scopes(&self) -> &[String] {
         &self.scopes
diff --git a/theme.toml b/theme.toml
index fd5572a6..903a5e26 100644
--- a/theme.toml
+++ b/theme.toml
@@ -40,6 +40,7 @@
 
 "ui.background" = { bg = "#3b224c" } # midnight
 "ui.linenr" = { fg = "#5a5977" } # comet
+"ui.linenr.selected" = { fg = "#dbbfef" } # lilac
 "ui.statusline" = { bg = "#281733" } # revolver
 "ui.popup" = { bg = "#281733" } # revolver
 "ui.window" = { bg = "#452859" } # bossa nova