From 3b0c86e4013abb66f36108aedad4ef81fe2a06e2 Mon Sep 17 00:00:00 2001
From: Junegunn Choi <junegunn.c@gmail.com>
Date: Fri, 29 Nov 2024 00:26:12 +0900
Subject: [PATCH] Much faster image processing

Fix #3984
---
 CHANGELOG.md         |  1 +
 src/terminal.go      | 79 ++++++++++++++++++++++++++++++++++++++++----
 src/terminal_test.go | 28 ++++++++++++++++
 3 files changed, 102 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0312b93..f385666 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@ CHANGELOG
 - Built-in walker improvements
     - `--walker-root` can take multiple directory arguments. e.g. `--walker-root include src lib`
     - `--walker-skip` can handle multi-component patterns. e.g. `--walker-skip target/build`
+- Removed long processing delay when displaying images in the preview window
 - `FZF_PREVIEW_*` environment variables are exported to all child processes (#4098)
 - Bug fixes in fish scripts
 
diff --git a/src/terminal.go b/src/terminal.go
index b456e12..58c244e 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -51,7 +51,8 @@ var placeholder *regexp.Regexp
 var whiteSuffix *regexp.Regexp
 var offsetComponentRegex *regexp.Regexp
 var offsetTrimCharsRegex *regexp.Regexp
-var passThroughRegex *regexp.Regexp
+var passThroughBeginRegex *regexp.Regexp
+var passThroughEndTmuxRegex *regexp.Regexp
 var ttyin *os.File
 
 const clearCode string = "\x1b[2J"
@@ -74,7 +75,15 @@ func init() {
 	// * https://sw.kovidgoyal.net/kitty/graphics-protocol
 	// * https://en.wikipedia.org/wiki/Sixel
 	// * https://iterm2.com/documentation-images.html
-	passThroughRegex = regexp.MustCompile(`\x1bPtmux;\x1b\x1b.*?[^\x1b]\x1b\\|\x1b(_G|P[0-9;]*q).*?\x1b\\\r?|\x1b]1337;.*?(\a|\x1b\\)`)
+	/*
+		passThroughRegex = regexp.MustCompile(`
+			  \x1bPtmux;\x1b\x1b  .*?  [^\x1b]\x1b\\
+			| \x1b(_G|P[0-9;]*q)  .*?  \x1b\\\r?
+			| \x1b]1337;          .*?  (\a|\x1b\\)
+		`)
+	*/
+	passThroughBeginRegex = regexp.MustCompile(`\x1bPtmux;\x1b\x1b|\x1b(_G|P[0-9;]*q)|\x1b]1337;`)
+	passThroughEndTmuxRegex = regexp.MustCompile(`[^\x1b]\x1b\\`)
 }
 
 type jumpMode int
@@ -2622,6 +2631,67 @@ func (t *Terminal) makeImageBorder(width int, top bool) string {
 	return v + strings.Repeat(" ", repeat) + v
 }
 
+func findPassThrough(line string) []int {
+	loc := passThroughBeginRegex.FindStringIndex(line)
+	if loc == nil {
+		return nil
+	}
+
+	rest := line[loc[0]:]
+	after := line[loc[1]:]
+	if strings.HasPrefix(rest, "\x1bPtmux") { // Tmux
+		eloc := passThroughEndTmuxRegex.FindStringIndex(after)
+		if eloc == nil {
+			return nil
+		}
+		return []int{loc[0], loc[1] + eloc[1]}
+	} else if strings.HasPrefix(rest, "\x1b]1337;") { // iTerm2
+		index := loc[1]
+		for {
+			after := line[index:]
+			pos := strings.IndexAny(after, "\x1b\a")
+			if pos < 0 {
+				return nil
+			}
+			if after[pos] == '\a' {
+				return []int{loc[0], index + pos + 1}
+			}
+			if pos < len(after)-1 && after[pos+1] == '\\' {
+				return []int{loc[0], index + pos + 2}
+			}
+			index += pos + 1
+		}
+	}
+	// Kitty
+	pos := strings.Index(after, "\x1b\\")
+	if pos < 0 {
+		return nil
+	}
+	if pos < len(after)-2 && after[pos+2] == '\r' {
+		return []int{loc[0], loc[1] + pos + 3}
+	}
+	return []int{loc[0], loc[1] + pos + 2}
+}
+
+func extractPassThroughs(line string) ([]string, string) {
+	passThroughs := []string{}
+	transformed := ""
+	index := 0
+	for {
+		rest := line[index:]
+		loc := findPassThrough(rest)
+		if loc == nil {
+			transformed += rest
+			break
+		}
+		passThroughs = append(passThroughs, rest[loc[0]:loc[1]])
+		transformed += line[index : index+loc[0]]
+		index += loc[1]
+	}
+
+	return passThroughs, transformed
+}
+
 func (t *Terminal) renderPreviewText(height int, lines []string, lineNo int, unchanged bool) {
 	maxWidth := t.pwindow.Width()
 	var ansi *ansiState
@@ -2636,10 +2706,7 @@ Loop:
 			ansi.lbg = -1
 		}
 
-		passThroughs := passThroughRegex.FindAllString(line, -1)
-		if passThroughs != nil {
-			line = passThroughRegex.ReplaceAllString(line, "")
-		}
+		passThroughs, line := extractPassThroughs(line)
 		line = strings.TrimLeft(strings.TrimRight(line, "\r\n"), "\r")
 
 		if lineNo >= height || t.pwindow.Y() == height-1 && t.pwindow.X() > 0 {
diff --git a/src/terminal_test.go b/src/terminal_test.go
index 317cd5f..44da2bc 100644
--- a/src/terminal_test.go
+++ b/src/terminal_test.go
@@ -507,6 +507,34 @@ func TestParsePlaceholder(t *testing.T) {
 	}
 }
 
+func TestExtractPassthroughs(t *testing.T) {
+	for _, middle := range []string{
+		"\x1bPtmux;\x1b\x1bbar\x1b\\",
+		"\x1bPtmux;\x1b\x1bbar\x1bbar\x1b\\",
+		"\x1b]1337;bar\x1b\\",
+		"\x1b]1337;bar\x1bbar\x1b\\",
+		"\x1b]1337;bar\a",
+		"\x1b_Ga=T,f=32,s=1258,v=1295,c=74,r=35,m=1\x1b\\",
+		"\x1b_Ga=T,f=32,s=1258,v=1295,c=74,r=35,m=1\x1b\\\r",
+		"\x1b_Ga=T,f=32,s=1258,v=1295,c=74,r=35,m=1\x1bbar\x1b\\\r",
+		"\x1b_Gm=1;AAAAAAAAA=\x1b\\",
+		"\x1b_Gm=1;AAAAAAAAA=\x1b\\\r",
+		"\x1b_Gm=1;\x1bAAAAAAAAA=\x1b\\\r",
+	} {
+		line := "foo" + middle + "baz"
+		loc := findPassThrough(line)
+		if loc == nil || line[0:loc[0]] != "foo" || line[loc[1]:] != "baz" {
+			t.Error("failed to find passthrough")
+		}
+		garbage := "\x1bPtmux;\x1b]1337;\x1b_Ga=\x1b]1337;bar\x1b."
+		line = strings.Repeat("foo"+middle+middle+"baz", 3) + garbage
+		passthroughs, result := extractPassThroughs(line)
+		if result != "foobazfoobazfoobaz"+garbage || len(passthroughs) != 6 {
+			t.Error("failed to extract passthroughs")
+		}
+	}
+}
+
 /* utilities section */
 
 // Item represents one line in fzf UI. Usually it is relative path to files and folders.