From 60dde3a40928e010e518b225b948c413f995a383 Mon Sep 17 00:00:00 2001
From: Stephen Broadley <stephen.broadley@locimi.com>
Date: Fri, 2 Aug 2024 18:53:23 +0100
Subject: [PATCH] added 'nullspace' option

---
 helix-term/src/ui/editor.rs | 56 ++++++++++++++++++++++++++++++++++---
 helix-view/src/editor.rs    | 19 +++++++++++++
 helix-view/src/view.rs      | 20 ++++++++++++-
 3 files changed, 90 insertions(+), 5 deletions(-)

diff --git a/helix-term/src/ui/editor.rs b/helix-term/src/ui/editor.rs
index f7541fe25..61a8f392f 100644
--- a/helix-term/src/ui/editor.rs
+++ b/helix-term/src/ui/editor.rs
@@ -93,7 +93,51 @@ impl EditorView {
         let theme = &editor.theme;
         let config = editor.config();
 
-        let view_offset = doc.view_offset(view.id);
+        if config.nullspace.enable {
+            let gutter_width = view.gutter_offset(doc);
+            let text_width = config.text_width as u16;
+
+            let view_width = text_width + gutter_width;
+
+            if view_width < view.area.width {
+                let null_width = (area.width - view_width) / 2;
+
+                let null_l = area.with_width(null_width).clip_bottom(1);
+                let null_r = Rect::new(
+                    area.x + view_width + null_width,
+                    area.y,
+                    area.width - view_width - null_width,
+                    area.height,
+                )
+                .clip_bottom(1);
+
+                let null_style = theme
+                    .try_get("ui.null")
+                    .or_else(|| Some(theme.get("ui.linenr")))
+                    .unwrap();
+
+                fn fill_area(s: &mut Surface, r: Rect, c: char) {
+                    for y in r.top()..r.bottom() {
+                        for x in r.left()..r.right() {
+                            let cell = s.get_mut(x, y).unwrap();
+                            cell.symbol.clear();
+                            cell.symbol.push(c);
+                        }
+                    }
+                }
+
+                // We currently on use the first char in the 'pattern'
+                // but in future I would like to use the whole string
+                // to render nicer patterns.
+                let c = config.nullspace.pattern.chars().nth(0).unwrap();
+
+                fill_area(surface, null_l, c);
+                fill_area(surface, null_r, c);
+
+                surface.set_style(null_l, null_style);
+                surface.set_style(null_r, null_style);
+            }
+        }
 
         let text_annotations = view.text_annotations(doc, Some(theme));
         let mut decorations = DecorationManager::default();
@@ -165,13 +209,16 @@ impl EditorView {
             }
         }
 
-        let gutter_overflow = view.gutter_offset(doc) == 0;
-        if !gutter_overflow {
+        let gutter_width = view.gutter_offset(doc);
+        if gutter_width > 0 {
+            let mut gutter_area = inner.with_width(gutter_width);
+            gutter_area.x -= gutter_width;
+
             Self::render_gutter(
                 editor,
                 doc,
                 view,
-                view.area,
+                gutter_area,
                 theme,
                 is_focused & self.terminal_focused,
                 &mut decorations,
@@ -201,6 +248,7 @@ impl EditorView {
             inline_diagnostic_config,
             config.end_of_line_diagnostics,
         ));
+
         render_document(
             surface,
             inner,
diff --git a/helix-view/src/editor.rs b/helix-view/src/editor.rs
index 1708b3b4e..5054e79d5 100644
--- a/helix-view/src/editor.rs
+++ b/helix-view/src/editor.rs
@@ -315,6 +315,8 @@ pub struct Config {
     /// Column numbers at which to draw the rulers. Defaults to `[]`, meaning no rulers.
     pub rulers: Vec<u16>,
     #[serde(default)]
+    pub nullspace: NullspaceConfig,
+    #[serde(default)]
     pub whitespace: WhitespaceConfig,
     /// Persistently display open buffers along the top
     pub bufferline: BufferLine,
@@ -698,6 +700,22 @@ impl std::str::FromStr for GutterType {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(default)]
+pub struct NullspaceConfig {
+    pub enable: bool,
+    pub pattern: String,
+}
+
+impl Default for NullspaceConfig {
+    fn default() -> Self {
+        Self {
+            enable: true,
+            pattern: String::from("╲"),
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(default)]
 pub struct WhitespaceConfig {
@@ -960,6 +978,7 @@ impl Default for Config {
             lsp: LspConfig::default(),
             terminal: get_terminal_provider(),
             rulers: Vec::new(),
+            nullspace: NullspaceConfig::default(),
             whitespace: WhitespaceConfig::default(),
             bufferline: BufferLine::default(),
             indent_guides: IndentGuidesConfig::default(),
diff --git a/helix-view/src/view.rs b/helix-view/src/view.rs
index a229f01ea..2c3130c22 100644
--- a/helix-view/src/view.rs
+++ b/helix-view/src/view.rs
@@ -191,7 +191,25 @@ impl View {
     }
 
     pub fn inner_area(&self, doc: &Document) -> Rect {
-        self.area.clip_left(self.gutter_offset(doc)).clip_bottom(1) // -1 for statusline
+        let config = doc.config.load();
+        let gutter_width = self.gutter_offset(doc);
+
+        if config.nullspace.enable {
+            let text_width = config.text_width as u16;
+            let view_width = gutter_width + text_width;
+
+            if self.area.width > view_width {
+                let null_width = (self.area.width - view_width) / 2;
+
+                return self
+                    .area
+                    .clip_left(gutter_width + null_width)
+                    .clip_bottom(1)
+                    .with_width(text_width.min(self.area.width));
+            }
+        }
+
+        self.area.clip_left(gutter_width).clip_bottom(1) // -1 for statusline
     }
 
     pub fn inner_height(&self) -> usize {