From 6783a7b68cbe7f9844666df7da1e343b7d87b82f Mon Sep 17 00:00:00 2001
From: FelisDiligens <47528453+FelisDiligens@users.noreply.github.com>
Date: Tue, 1 Aug 2023 15:51:50 +0200
Subject: [PATCH] Add relative line numbers (issue #2)

---
 src/cmoptions.ts | 15 +++++++++++++++
 src/settings.ts  | 10 ++++++++++
 2 files changed, 25 insertions(+)

diff --git a/src/cmoptions.ts b/src/cmoptions.ts
index 52259f4..911383f 100644
--- a/src/cmoptions.ts
+++ b/src/cmoptions.ts
@@ -4,6 +4,17 @@
 
 import { PluginSettings } from "./settings";
 
+function showRelativeLines(cm) {
+    // Source: https://github.com/codemirror/codemirror5/issues/4116
+    const lineNum = cm.getCursor().line + 1;
+    if (cm.state.curLineNum === lineNum) {
+        return;
+    }
+    cm.state.curLineNum = lineNum;
+    cm.setOption('lineNumberFormatter', l =>
+        l === lineNum ? lineNum : Math.abs(lineNum - l));
+}
+
 module.exports = {
     default: function (context) {
         return {
@@ -30,6 +41,10 @@ module.exports = {
                             cm.setOption(key, value);
                         }
                     }
+
+                    // Apply relative line numbers:
+                    if (settings.relativeLineNumbers)
+                        cm.on('cursorActivity', showRelativeLines);
                 });
             },
 
diff --git a/src/settings.ts b/src/settings.ts
index eb486ac..8bc8f7d 100644
--- a/src/settings.ts
+++ b/src/settings.ts
@@ -7,6 +7,7 @@ export interface PluginSettings {
     showCursorWhenSelecting: boolean;
     cursorBlinkRate: number;
     resetSelectionOnContextMenu: boolean;
+    relativeLineNumbers: boolean;
     fixLineNumbersCSS: boolean;
 }
 
@@ -20,6 +21,7 @@ export async function getPluginSettings(): Promise<PluginSettings> {
         "showCursorWhenSelecting": await joplin.settings.value('cmoptions_showCursorWhenSelecting'),
         "cursorBlinkRate": await joplin.settings.value('cmoptions_cursorBlinkRate'),
         "resetSelectionOnContextMenu": await joplin.settings.value('cmoptions_resetSelectionOnContextMenu'),
+        "relativeLineNumbers": await joplin.settings.value('cmoptions_relativeLineNumbers'),
         "fixLineNumbersCSS": await joplin.settings.value('cmoptions_fixLineNumbersCSS'),
     }
 }
@@ -77,6 +79,14 @@ export async function registerAllSettings() {
             label: 'Reset selection on context menu',
             description: 'Controls whether, when the context menu is opened with a click outside of the current selection, the cursor is moved to the point of the click. Defaults to true.',
         },
+        ['cmoptions_relativeLineNumbers']: {
+            public: true,
+            section: section,
+            type: SettingItemType.Bool,
+            value: false,
+            label: 'Relative line numbers',
+            description: 'Enable vim-like relative line numbers',
+        },
         ['cmoptions_fixLineNumbersCSS']: {
             public: true,
             section: section,