Support for highlighting all search matches (hlsearch) (#1762)

* Support for highlighting all search matches (hlsearch)

hlsearch is implemented efficiently using the buffer's line array,
somewhat similarly to the syntax highlighting.
Unlike the syntax highlighter which highlights the entire file,
hlsearch searches for matches for the displayed lines only.
Matches are searched when the given line is displayed first time
or after it was modified. Otherwise the previously found matches
are used.

* Add UnhighlightSearch action

and add it to the list of actions triggered by Esc key by default.

* Add comment explaining the purpose of search map

* Add hlsearch colors to colorschemes

Mostly just copied from the corresponding original (mostly vim) colorschemes.

* Highlight matches during/after replace as well

As a side effect it also changes the last search value, i.e. affects FindNext
and FindPrevious, but it's probably fine. In vim it works the same way.

* Improve hlsearch option description

internal/buffer/buffer.go

@@ -146,18 +146,20 @@ func (b *SharedBuffer) remove(start, end Loc) []byte {
 func (b *SharedBuffer) MarkModified(start, end int) {
 	b.ModifiedThisFrame = true
 
-	if !b.Settings["syntax"].(bool) || b.SyntaxDef == nil {
-		return
-	}
-
 	start = util.Clamp(start, 0, len(b.lines)-1)
 	end = util.Clamp(end, 0, len(b.lines)-1)
 
-	l := -1
-	for i := start; i <= end; i++ {
-		l = util.Max(b.Highlighter.ReHighlightStates(b, i), l)
+	if b.Settings["syntax"].(bool) && b.SyntaxDef != nil {
+		l := -1
+		for i := start; i <= end; i++ {
+			l = util.Max(b.Highlighter.ReHighlightStates(b, i), l)
+		}
+		b.Highlighter.HighlightMatches(b, start, l)
+	}
+
+	for i := start; i <= end; i++ {
+		b.LineArray.invalidateSearchMatches(i)
 	}
-	b.Highlighter.HighlightMatches(b, start, l)
 }
 
 // DisableReload disables future reloads of this sharedbuffer
@@ -181,6 +183,7 @@ type DiffStatus byte
 // The syntax highlighting info must be stored with the buffer because the syntax
 // highlighter attaches information to each line of the buffer for optimization
 // purposes so it doesn't have to rehighlight everything on every update.
+// Likewise for the search highlighting.
 type Buffer struct {
 	*EventHandler
 	*SharedBuffer
@@ -202,6 +205,12 @@ type Buffer struct {
 	// This is hacky. Maybe it would be better to move all the visual x logic
 	// from buffer to display, but it would require rewriting a lot of code.
 	GetVisualX func(loc Loc) int
+
+	// Last search stores the last successful search
+	LastSearch      string
+	LastSearchRegex bool
+	// HighlightSearch enables highlighting all instances of the last successful search
+	HighlightSearch bool
 }
 
 // NewBufferFromFileAtLoc opens a new buffer with a given cursor location
@@ -1199,6 +1208,12 @@ func (b *Buffer) DiffStatus(lineN int) DiffStatus {
 	return b.diff[lineN]
 }
 
+// SearchMatch returns true if the given location is within a match of the last search.
+// It is used for search highlighting
+func (b *Buffer) SearchMatch(pos Loc) bool {
+	return b.LineArray.SearchMatch(b, pos)
+}
+
 // WriteLog writes a string to the log buffer
 func WriteLog(s string) {
 	LogBuf.EventHandler.Insert(LogBuf.End(), s)