Merge remote-tracking branch 'enricozb/enricozb/column-ruler'

Author: mawww

doc/pages/highlighters.asciidoc

@@ -111,8 +111,13 @@ highlighter is replaced with the new one.
 *fill* <face>::
     fill using the given *face*, mostly useful with regions highlighters
 
-*column* <number> <face>::
-    highlight column *number* with face *face*
+*column* <number> <face> [options]::
+    highlight column *number* with face *face*, with the following *options*:
+
+    *-ruler* <character>:::
+        a single character to display instead of empty or whitespace cells at
+        column *number*. If this option is provided, *face* will also not
+        apply to non-empty cells, and will only apply to *character*.
 
 *line* <number> <face>::
     highlight line *number* with face *face*

src/highlighters.cc

@@ -19,6 +19,7 @@
 #include "utf8.hh"
 #include "utf8_iterator.hh"
 #include "window.hh"
+#include "unicode.hh"
 
 #include <cstdio>
 #include <limits>
@@ -519,16 +520,26 @@ UniquePtr<Highlighter> create_line_highlighter(HighlighterParameters params, Hig
 }
 
 const HighlighterDesc column_desc = {
-    "Parameters: <value string> <face>\n"
-    "Highlight the column given by evaluating <value string> with <face>",
-    {}
+    "Parameters: [-ruler <character>] <column> <face>\n"
+    "Highlight the column <column> with <face>",
+    {
+        { { "ruler", { ArgCompleter{}, "replace empty or whitespace cells with the given character. When provided, <face> is not applied to non-empty cells" } } },
+        ParameterDesc::Flags::None, 2, 2
+    },
 };
 UniquePtr<Highlighter> create_column_highlighter(HighlighterParameters params, Highlighter*)
 {
-    if (params.size() != 2)
-        throw runtime_error("wrong parameter count");
+    ParametersParser parser{params, column_desc.params};
+
+    auto positionals = parser.positionals_from(0);
 
-    auto func = [col_expr=params[0], facespec=parse_face(params[1])]
+    auto ruler = parser.get_switch("ruler");
+    bool highlight_non_blank = not (bool)ruler;
+    auto col_char = ruler.value_or(" ").str();
+    if (col_char.char_length() > 1)
+        throw runtime_error("-ruler expects a single character");
+
+    auto func = [col_expr=positionals[0], facespec=parse_face(positionals[1]), highlight_non_blank, col_char]
                 (HighlightContext context, DisplayBuffer& display_buffer, BufferRange)
     {
         ColumnCount column = -1;
@@ -563,7 +574,13 @@ UniquePtr<Highlighter> create_column_highlighter(HighlighterParameters params, H
                         atom_it = ++line.split(atom_it, remaining_col);
                     if (atom_it->length() > 1)
                         atom_it = line.split(atom_it, 1_col);
-                    atom_it->face = merge_faces(atom_it->face, face);
+                    if (highlight_non_blank)
+                        atom_it->face = merge_faces(atom_it->face, face);
+                    else if (is_blank(atom_it->content()[0]))
+                    {
+                        atom_it->replace(col_char);
+                        atom_it->face = merge_faces(atom_it->face, face);
+                    }
                     found = true;
                     break;
                 }
@@ -574,7 +591,7 @@ UniquePtr<Highlighter> create_column_highlighter(HighlighterParameters params, H
 
             if (remaining_col > 0)
                 line.push_back({String{' ', remaining_col}, Face{}});
-            line.push_back({" ", face});
+            line.push_back({col_char, face});
         }
     };