Experimental Sixel support (#2544)

9 files changed, 117 insertions, 11 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3cdd6c82..8fa95437 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,26 @@
 CHANGELOG
 =========
 
+0.43.1
+------
+- (Experimental) Added support for Sixel graphics in the preview window
+  ```sh
+  # 1. $FZF_PREVIEW_WIDTH and $FZF_PREVIEW_HEIGHT will be set to the pixel width
+  #    and height of the preview window
+  # 2. Special preview window flag 'clear' is added to always completely
+  #    erase the preview window. This is similar to https://github.com/vifm/vifm/issues/588.
+  fzf --preview='
+    if file --mime-type {} | grep -qvF image/; then
+      bat --color=always {}
+    elif [[ -n $FZF_PREVIEW_WIDTH ]]; then
+      convert {} -resize ${FZF_PREVIEW_WIDTH}x${FZF_PREVIEW_HEIGHT} sixel:-
+    else
+      echo "Cannot display image data (unsupported platform)"
+    fi
+  ' --preview-window clear
+  ```
+- Bug fixes
+
 0.43.0
 ------
 - (Experimental) Added support for Kitty image protocol in the preview window
diff --git a/man/man1/fzf.1 b/man/man1/fzf.1
index 27d687b8..735fa7f6 100644
--- a/man/man1/fzf.1
+++ b/man/man1/fzf.1
@@ -21,7 +21,7 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ..
-.TH fzf 1 "Oct 2023" "fzf 0.43.0" "fzf - a command-line fuzzy finder"
+.TH fzf 1 "Oct 2023" "fzf 0.43.1" "fzf - a command-line fuzzy finder"
 
 .SH NAME
 fzf - a command-line fuzzy finder
@@ -603,6 +603,24 @@ e.g.
           bat --color=always {}
         fi
       '\fR
+
+fzf also has experimental support for Sixel graphics.
+
+e.g.
+      \fB# 1. $FZF_PREVIEW_WIDTH and $FZF_PREVIEW_HEIGHT will be set to
+      #    the pixel width and height of the preview window
+      # 2. Special preview window flag 'clear' is needed to always completely
+      #    erase the preview window
+      fzf --preview='
+        if file --mime-type {} | grep -qvF image/; then
+          bat --color=always {}
+        elif [[ -n $FZF_PREVIEW_WIDTH ]]; then
+          convert {} -resize ${FZF_PREVIEW_WIDTH}x${FZF_PREVIEW_HEIGHT} sixel:-
+        else
+          echo "Cannot display image data (unsupported platform)"
+        fi
+      ' --preview-window clear\fR
+
 .RE
 
 .TP
diff --git a/src/options.go b/src/options.go
index b4f74e95..83258820 100644
--- a/src/options.go
+++ b/src/options.go
@@ -219,6 +219,7 @@ type previewOpts struct {
 	scroll      string
 	hidden      bool
 	wrap        bool
+	clear       bool
 	cycle       bool
 	follow      bool
 	border      tui.BorderShape
@@ -340,7 +341,7 @@ type Options struct {
 }
 
 func defaultPreviewOpts(command string) previewOpts {
-	return previewOpts{command, posRight, sizeSpec{50, true}, "", false, false, false, false, tui.DefaultBorderShape, 0, 0, nil}
+	return previewOpts{command, posRight, sizeSpec{50, true}, "", false, false, false, false, false, tui.DefaultBorderShape, 0, 0, nil}
 }
 
 func defaultOptions() *Options {
@@ -1454,6 +1455,10 @@ func parsePreviewWindowImpl(opts *previewOpts, input string, exit func(string))
 			opts.wrap = true
 		case "nowrap":
 			opts.wrap = false
+		case "clear":
+			opts.clear = true
+		case "noclear":
+			opts.clear = false
 		case "cycle":
 			opts.cycle = true
 		case "nocycle":
@@ -1788,7 +1793,7 @@ func parseOptions(opts *Options, allArgs []string) {
 			opts.Preview.command = ""
 		case "--preview-window":
 			parsePreviewWindow(&opts.Preview,
-				nextString(allArgs, &i, "preview window layout required: [up|down|left|right][,SIZE[%]][,border-BORDER_OPT][,wrap][,cycle][,hidden][,+SCROLL[OFFSETS][/DENOM]][,~HEADER_LINES][,default]"))
+				nextString(allArgs, &i, "preview window layout required: [up|down|left|right][,SIZE[%]][,border-BORDER_OPT][,wrap][,clear][,cycle][,hidden][,+SCROLL[OFFSETS][/DENOM]][,~HEADER_LINES][,default]"))
 		case "--height":
 			opts.Height = parseHeight(nextString(allArgs, &i, "height required: [~]HEIGHT[%]"))
 		case "--min-height":
diff --git a/src/terminal.go b/src/terminal.go
index 9fac9779..ab385e2d 100644
--- a/src/terminal.go
+++ b/src/terminal.go
@@ -65,7 +65,8 @@ func init() {
 	// Parts of the preview output that should be passed through to the terminal
 	// * https://github.com/tmux/tmux/wiki/FAQ#what-is-the-passthrough-escape-sequence-and-how-do-i-use-it
 	// * https://sw.kovidgoyal.net/kitty/graphics-protocol
-	passThroughRegex = regexp.MustCompile(`\x1bPtmux;\x1b\x1b.*?[^\x1b]\x1b\\|\x1b_G.*?\x1b\\`)
+	// * https://en.wikipedia.org/wiki/Sixel
+	passThroughRegex = regexp.MustCompile(`\x1bPtmux;\x1b\x1b.*?[^\x1b]\x1b\\|\x1b(_G|P[0-9;]*q).*?\x1b\\`)
 }
 
 type jumpMode int
@@ -1929,11 +1930,15 @@ func (t *Terminal) renderPreviewSpinner() {
 }
 
 func (t *Terminal) renderPreviewArea(unchanged bool) {
-	if unchanged {
+	if t.previewOpts.clear {
+		t.pwindow.Erase()
+	} else if unchanged {
 		t.pwindow.MoveAndClear(0, 0) // Clear scroll offset display
 	} else {
 		t.previewed.filled = false
-		t.pwindow.Erase()
+		// We don't erase the window here to avoid flickering during scroll
+		t.pwindow.DrawBorder()
+		t.pwindow.Move(0, 0)
 	}
 
 	height := t.pwindow.Height()
@@ -1946,11 +1951,15 @@ func (t *Terminal) renderPreviewArea(unchanged bool) {
 		body = t.previewer.lines[headerLines:]
 		// Always redraw header
 		t.renderPreviewText(height, header, 0, false)
-		t.pwindow.MoveAndClear(t.pwindow.Y(), 0)
+		if t.previewOpts.clear {
+			t.pwindow.Move(t.pwindow.Y(), 0)
+		} else {
+			t.pwindow.MoveAndClear(t.pwindow.Y(), 0)
+		}
 	}
 	t.renderPreviewText(height, body, -t.previewer.offset+headerLines, unchanged)
 
-	if !unchanged {
+	if !unchanged && !t.previewOpts.clear {
 		t.pwindow.FinishFill()
 	}
 
@@ -1994,6 +2003,10 @@ func (t *Terminal) renderPreviewText(height int, lines []string, lineNo int, unc
 			for _, passThrough := range passThroughs {
 				t.tui.PassThrough(passThrough)
 			}
+			if len(passThroughs) > 0 && len(line) == 0 {
+				continue
+			}
+
 			var fillRet tui.FillReturn
 			prefixWidth := 0
 			_, _, ansi = extractColor(line, ansi, func(str string, ansi *ansiState) bool {
@@ -2686,6 +2699,11 @@ func (t *Terminal) Loop() {
 						env = append(env, "FZF_PREVIEW_"+lines)
 						env = append(env, columns)
 						env = append(env, "FZF_PREVIEW_"+columns)
+						size, err := t.tui.Size()
+						if err == nil {
+							env = append(env, fmt.Sprintf("FZF_PREVIEW_WIDTH=%d", pwindow.Width()*size.Width/size.Columns))
+							env = append(env, fmt.Sprintf("FZF_PREVIEW_HEIGHT=%d", height*size.Height/size.Lines))
+						}
 					}
 					cmd.Env = env
 
diff --git a/src/tui/dummy.go b/src/tui/dummy.go
index 352e2b09..d893a747 100644
--- a/src/tui/dummy.go
+++ b/src/tui/dummy.go
@@ -38,6 +38,9 @@ func (r *FullscreenRenderer) Clear()                             {}
 func (r *FullscreenRenderer) NeedScrollbarRedraw() bool          { return false }
 func (r *FullscreenRenderer) Refresh()                           {}
 func (r *FullscreenRenderer) Close()                             {}
+func (r *FullscreenRenderer) Size() (termSize, error) {
+	return termSize{}, nil
+}
 
 func (r *FullscreenRenderer) GetChar() Event { return Event{} }
 func (r *FullscreenRenderer) MaxX() int      { return 0 }
diff --git a/src/tui/light.go b/src/tui/light.go
index cc828fa9..6b7eaaf4 100644
--- a/src/tui/light.go
+++ b/src/tui/light.go
@@ -32,7 +32,7 @@ var offsetRegexp *regexp.Regexp = regexp.MustCompile("(.*)\x1b\\[([0-9]+);([0-9]
 var offsetRegexpBegin *regexp.Regexp = regexp.MustCompile("^\x1b\\[[0-9]+;[0-9]+R")
 
 func (r *LightRenderer) PassThrough(str string) {
-	r.queued.WriteString(str)
+	r.queued.WriteString("\x1b7" + str + "\x1b8")
 	r.flush()
 }
 
@@ -756,6 +756,10 @@ func (r *LightRenderer) NewWindow(top int, left int, width int, height int, prev
 	return w
 }
 
+func (w *LightWindow) DrawBorder() {
+	w.drawBorder(false)
+}
+
 func (w *LightWindow) DrawHBorder() {
 	w.drawBorder(true)
 }
@@ -1095,7 +1099,8 @@ func (w *LightWindow) FinishFill() {
 }
 
 func (w *LightWindow) Erase() {
-	w.drawBorder(false)
-	// We don't erase the window here to avoid flickering during scroll
+	w.DrawBorder()
+	w.Move(0, 0)
+	w.FinishFill()
 	w.Move(0, 0)
 }
diff --git a/src/tui/light_unix.go b/src/tui/light_unix.go
index 6dc058c8..b9e433cc 100644
--- a/src/tui/light_unix.go
+++ b/src/tui/light_unix.go
@@ -8,6 +8,7 @@ import (
 	"os/exec"
 	"strings"
 	"syscall"
+	"unsafe"
 
 	"github.com/junegunn/fzf/src/util"
 	"golang.org/x/term"
@@ -108,3 +109,19 @@ func (r *LightRenderer) getch(nonblock bool) (int, bool) {
 	}
 	return int(b[0]), true
 }
+
+type window struct {
+	lines   uint16
+	columns uint16
+	width   uint16
+	height  uint16
+}
+
+func (r *LightRenderer) Size() (termSize, error) {
+	w := new(window)
+	_, _, err := syscall.Syscall(syscall.SYS_IOCTL, r.ttyin.Fd(), syscall.TIOCGWINSZ, uintptr(unsafe.Pointer(w)))
+	if err != 0 {
+		return termSize{}, err
+	}
+	return termSize{int(w.lines), int(w.columns), int(w.width), int(w.height)}, nil
+}
diff --git a/src/tui/tcell.go b/src/tui/tcell.go
index 0c3d4694..54feaf16 100644
--- a/src/tui/tcell.go
+++ b/src/tui/tcell.go
@@ -203,6 +203,11 @@ func (r *FullscreenRenderer) Refresh() {
 	// noop
 }
 
+func (r *FullscreenRenderer) Size() (termSize, error) {
+	cols, lines := _screen.Size()
+	return termSize{lines, cols, 0, 0}, error("Not implemented")
+}
+
 func (r *FullscreenRenderer) GetChar() Event {
 	ev := _screen.PollEvent()
 	switch ev := ev.(type) {
@@ -541,6 +546,7 @@ func fill(x, y, w, h int, n ColorPair, r rune) {
 }
 
 func (w *TcellWindow) Erase() {
+	w.drawBorder(false)
 	fill(w.left-1, w.top, w.width+1, w.height-1, w.normal, ' ')
 }
 
@@ -692,6 +698,10 @@ func (w *TcellWindow) CFill(fg Color, bg Color, a Attr, str string) FillReturn {
 	return w.fillString(str, NewColorPair(fg, bg, a))
 }
 
+func (w *TcellWindow) DrawBorder() {
+	w.drawBorder(false)
+}
+
 func (w *TcellWindow) DrawHBorder() {
 	w.drawBorder(true)
 }
diff --git a/src/tui/tui.go b/src/tui/tui.go
index 4625e9b5..69ae8a1a 100644
--- a/src/tui/tui.go
+++ b/src/tui/tui.go
@@ -473,6 +473,13 @@ func MakeTransparentBorder() BorderStyle {
 		bottomRight: ' '}
 }
 
+type termSize struct {
+	Lines   int
+	Columns int
+	Width   int
+	Height  int
+}
+
 type Renderer interface {
 	Init()
 	Resize(maxHeightFunc func(int) int)
@@ -490,6 +497,8 @@ type Renderer interface {
 	MaxX() int
 	MaxY() int
 
+	Size() (termSize, error)
+
 	NewWindow(top int, left int, width int, height int, preview bool, borderStyle BorderStyle) Window
 }
 
@@ -499,6 +508,7 @@ type Window interface {
 	Width() int
 	Height() int
 
+	DrawBorder()
 	DrawHBorder()
 	Refresh()
 	FinishFill()