Cursor line as percentage

doc/pages/expansions.asciidoc

@@ -288,6 +288,11 @@ The following expansions are supported (with required context _in italics_):
     _in window scope_ +
     line of the main cursor, the third component of `%val{selection_desc}`
 
+*%val{cursor_line_percent}*::
+    _in window scope_ +
+    line of the main cursor expressed as percentage of the number of lines
+    in the current buffer
+
 *%val{error}*::
     _in `try` command's <on_error_commands> parameter_ +
     the text of the error that cancelled execution of the <commands> parameter

src/main.cc

@@ -226,6 +226,11 @@ static const EnvVarDesc builtin_env_vars[] = { {
         "cursor_line", false,
         [](StringView name, const Context& context) -> Vector<String>
         { return {to_string(context.selections().main().cursor().line + 1)}; }
+    }, {
+        "cursor_line_percent", false,
+        [](StringView name, const Context& context) -> Vector<String>
+        { auto cursor_line = context.selections().main().cursor().line + 1;
+          return {to_string(100 * cursor_line / context.buffer().line_count())}; }
     }, {
         "cursor_column", false,
         [](StringView name, const Context& context) -> Vector<String>

test/display/cursor-line-percent/cmd

@@ -0,0 +1,2 @@
+:set-option global modelinefmt '%val{cursor_line_percent}'
+6g

test/display/cursor-line-percent/in

@@ -0,0 +1,10 @@
+1
+2
+3
+4
+5
+6
+7
+8
+9
+10

test/display/cursor-line-percent/script

@@ -0,0 +1 @@
+ui_out -until '{ "jsonrpc": "2.0", "method": "draw_status", "params": [[], [{ "face": { "fg": "default", "bg": "default", "underline": "default", "attributes": [] }, "contents": "60" }], { "fg": "cyan", "bg": "default", "underline": "default", "attributes": [] }] }'