Support empty ranges in replace-ranges highlighter

4 files changed, 78 insertions, 47 deletions

diff --git a/doc/pages/changelog.asciidoc b/doc/pages/changelog.asciidoc
index 4e706c89..a4ed429b 100644
--- a/doc/pages/changelog.asciidoc
+++ b/doc/pages/changelog.asciidoc
@@ -5,6 +5,8 @@ released versions.
 
 == Development version
 
+* replace-ranges highlighter now support empty ranges
+
 * `%var{...}` now expands to list of strings, `$kak_quoted_...` now work
   as expected with these.
 
diff --git a/doc/pages/options.asciidoc b/doc/pages/options.asciidoc
index d074accf..db070781 100644
--- a/doc/pages/options.asciidoc
+++ b/doc/pages/options.asciidoc
@@ -88,19 +88,37 @@ are exclusively available to built-in options.
 *range-specs*::
     a timestamp (like `%val{timestamp}`,
     see <<expansions#value-expansions,`:doc expansions value-expansions`>>)
-    followed by a list of range descriptors. Each range descriptor must use
-    the syntax `a.b,c.d|string` or `a.b+length|string`, where _a_ is the line
-    containing the first character, _b_ is the number of bytes from the start
-    of the line to the first byte of the first character, _c_ is the line
-    containing the last character, _d_ is the number of bytes from the start of
-    the line to the first byte of the last character, _length_ is the length of
-    the range in bytes and _string_ is an arbitrary string which is associated
-    with the range. All numeric fields are 1-based. When the `update-option` is
-    used on an option of this type, its ranges gets updated according to all the
-    buffer modifications that happened since its timestamp. See
-    <<highlighters#specs-highlighters,`:doc highlighters specs-highlighters`>>)
+    followed by a list of range descriptors.
+
+    Each range descriptor must use the syntax `a.b,c.d|string` or
+    `a.b+length|string`, with:
+
+        * _a_ is the line containing the first character
+
+        * _b_ is the number of bytes from the start of the line to the
+        first byte of the first character
+
+        * _c_ is the line containing the last character
+
+        * _d_ is the number of bytes from the start of the line to the
+          first byte of the last character
+
+        * _length_ is the length of the range in bytes, if 0 the range
+          is empty, but still valid.
+
+        * _string_ is an arbitrary string which is associated with
+          the range.
+
+    All numeric fields are 1-based.
+
+    When the `update-option` is used on an option of this type, its
+    ranges gets updated according to all the buffer modifications that
+    happened since its timestamp.
+
     `set -add` appends the new pair to the list
 
+    See <<highlighters#specs-highlighters,`:doc highlighters specs-highlighters`>>)
+
 *line-specs*::
     a list of a line number and a corresponding flag (`<line>|<flag
     text>`), except for the first element which is just the timestamp
diff --git a/src/changes.hh b/src/changes.hh
index 5b64cbec..5ebb3ded 100644
--- a/src/changes.hh
+++ b/src/changes.hh
@@ -28,6 +28,21 @@ struct ForwardChangesTracker
 const Buffer::Change* forward_sorted_until(const Buffer::Change* first, const Buffer::Change* last);
 const Buffer::Change* backward_sorted_until(const Buffer::Change* first, const Buffer::Change* last);
 
+template<typename Range, typename AdvanceFunc>
+auto update_range(ForwardChangesTracker& changes_tracker, Range& range, AdvanceFunc&& advance_while_relevant)
+{
+    auto& first = get_first(range);
+    auto& last = get_last(range);
+    advance_while_relevant(first);
+    first = changes_tracker.get_new_coord_tolerant(first);
+
+    if (last < BufferCoord{0,0})
+        return;
+
+    advance_while_relevant(last);
+    last = changes_tracker.get_new_coord_tolerant(last);
+}
+
 template<typename RangeContainer>
 void update_forward(ConstArrayView<Buffer::Change> changes, RangeContainer& ranges)
 {
@@ -39,15 +54,7 @@ void update_forward(ConstArrayView<Buffer::Change> changes, RangeContainer& rang
     };
 
     for (auto& range : ranges)
-    {
-        auto& first = get_first(range);
-        auto& last = get_last(range);
-        advance_while_relevant(first);
-        first = changes_tracker.get_new_coord_tolerant(first);
-
-        advance_while_relevant(last);
-        last = changes_tracker.get_new_coord_tolerant(last);
-    }
+        update_range(changes_tracker, range, advance_while_relevant);
 }
 
 template<typename RangeContainer>
@@ -69,15 +76,7 @@ void update_backward(ConstArrayView<Buffer::Change> changes, RangeContainer& ran
     };
 
     for (auto& range : ranges)
-    {
-        auto& first = get_first(range);
-        auto& last = get_last(range);
-        advance_while_relevant(first);
-        first = changes_tracker.get_new_coord_tolerant(first);
-
-        advance_while_relevant(last);
-        last = changes_tracker.get_new_coord_tolerant(last);
-    }
+        update_range(changes_tracker, range, advance_while_relevant);
 }
 
 template<typename RangeContainer>
diff --git a/src/highlighters.cc b/src/highlighters.cc
index 464f78cd..d3fe1164 100644
--- a/src/highlighters.cc
+++ b/src/highlighters.cc
@@ -89,8 +89,8 @@ void replace_range(DisplayBuffer& display_buffer,
                    BufferCoord begin, BufferCoord end, T func)
 {
     // tolerate begin > end as that can be triggered by wrong encodings
-    if (begin >= end or end <= display_buffer.range().begin
-                     or begin >= display_buffer.range().end)
+    if (begin > end or end <= display_buffer.range().begin
+                    or begin >= display_buffer.range().end)
         return;
 
     for (auto& line : display_buffer.lines())
@@ -112,7 +112,9 @@ void replace_range(DisplayBuffer& display_buffer,
                     atom_it = ++line.split(atom_it, begin);
                 beg_idx = atom_it - line.begin();
             }
-            if (end <= atom_it->end())
+            if (end == atom_it->begin())
+                end_idx = atom_it - line.begin();
+            else if (end <= atom_it->end())
             {
                 if (end < atom_it->end())
                     atom_it = line.split(atom_it, end);
@@ -1448,8 +1450,15 @@ private:
     String m_default_face;
 };
 
+bool is_empty(const InclusiveBufferRange& range)
+{
+    return range.last < BufferCoord{0,0};
+}
+
 String option_to_string(InclusiveBufferRange range)
 {
+    if (is_empty(range))
+        return format("{}.{}+0", range.first.line+1, range.first.column+1);
     return format("{}.{},{}.{}",
                   range.first.line+1, range.first.column+1,
                   range.last.line+1, range.last.column+1);
@@ -1468,12 +1477,17 @@ InclusiveBufferRange option_from_string(Meta::Type<InclusiveBufferRange>, String
     const BufferCoord first{str_to_int({str.begin(), dot_beg}) - 1,
                             str_to_int({dot_beg+1, sep}) - 1};
 
-    const bool len = (*sep == '+');
-    const BufferCoord last{len ? first.line : str_to_int({sep+1, dot_end}) - 1,
-                           len ? first.column + str_to_int({sep+1, str.end()}) - 1
-                               : str_to_int({dot_end+1, str.end()}) - 1 };
+    if (first.line < 0 or first.column < 0)
+        throw runtime_error("coordinates elements should be >= 1");
+
+    if (*sep == '+')
+    {
+        auto len = str_to_int({sep+1, str.end()});
+        return {first, len == 0 ? BufferCoord{-1,-1} : BufferCoord{first.line, first.column + len}};
+    }
 
-    if (first.line < 0 or first.column < 0 or last.line < 0 or last.column < 0)
+    const BufferCoord last{str_to_int({sep+1, dot_end}) - 1, str_to_int({dot_end+1, str.end()}) - 1};
+    if (last.line < 0 or last.column < 0)
         throw runtime_error("coordinates elements should be >= 1");
 
     return { std::min(first, last), std::max(first, last) };
@@ -1522,14 +1536,13 @@ private:
         auto& range_and_faces = context.context.options()[m_option_name].get_mutable<RangeAndStringList>();
         update_ranges(buffer, range_and_faces.prefix, range_and_faces.list);
 
-        for (auto& range : range_and_faces.list)
+        for (auto& [range, face] : range_and_faces.list)
         {
             try
             {
-                auto& r = std::get<0>(range);
-                if (buffer.is_valid(r.first) and (buffer.is_valid(r.last) and not buffer.is_end(r.last)))
-                    highlight_range(display_buffer, r.first, buffer.char_next(r.last), false,
-                                    apply_face(context.context.faces()[std::get<1>(range)]));
+                if (buffer.is_valid(range.first) and (buffer.is_valid(range.last) and not buffer.is_end(range.last)))
+                    highlight_range(display_buffer, range.first, buffer.char_next(range.last), false,
+                                    apply_face(context.context.faces()[face]));
             }
             catch (runtime_error&)
             {}
@@ -1564,15 +1577,14 @@ private:
         auto& range_and_faces = context.context.options()[m_option_name].get_mutable<RangeAndStringList>();
         update_ranges(buffer, range_and_faces.prefix, range_and_faces.list);
 
-        for (auto& range : range_and_faces.list)
+        for (auto& [range, spec] : range_and_faces.list)
         {
             try
             {
-                auto& r = std::get<0>(range);
-                if (buffer.is_valid(r.first) and buffer.is_valid(r.last))
+                if (buffer.is_valid(range.first) and (buffer.is_valid(range.last) or is_empty(range)))
                 {
-                    auto replacement = parse_display_line(std::get<1>(range), context.context.faces());
-                    replace_range(display_buffer, r.first, buffer.char_next(r.last),
+                    auto replacement = parse_display_line(spec, context.context.faces());
+                    replace_range(display_buffer, range.first, is_empty(range) ? range.first : buffer.char_next(range.last),
                                   [&](DisplayLine& line, int beg_idx, int end_idx){
                                       auto it = line.erase(line.begin() + beg_idx, line.begin() + end_idx);
                                       for (auto& atom : replacement)