sixel: Export $FZF_PREVIEW_TOP to the preview command (#2544)

So that it can determine if it should subtract 1 from $FZF_PREVIEW_LINES
to avoid scrolling issue of Sixel image that touches the bottom of the
screen.

bin/fzf-preview.sh

@@ -13,14 +13,14 @@ if [[ $# -ne 1 ]]; then
 fi
 
 file=${1/#\~\//$HOME/}
-type=$(file --mime-type "$file")
-
-dim=${FZF_PREVIEW_COLUMNS}x${FZF_PREVIEW_LINES}
-if [[ $dim = x ]]; then
-  dim=$(stty size | awk '{print $2 "x" $1}')
-fi
+type=$(file --dereference --mime -- "$file")
 
 if [[ ! $type =~ image/ ]]; then
+  if [[ $type =~ =binary ]]; then
+    file "$1"
+    exit
+  fi
+
   # Sometimes bat is installed as batcat.
   if command -v batcat > /dev/null; then
     batname="batcat"
@@ -32,7 +32,19 @@ if [[ ! $type =~ image/ ]]; then
   fi
 
   ${batname} --style="${BAT_STYLE:-numbers}" --color=always --pager=never -- "$file"
-elif [[ $KITTY_WINDOW_ID ]]; then
+  exit
+fi
+
+dim=${FZF_PREVIEW_COLUMNS}x${FZF_PREVIEW_LINES}
+if [[ $dim = x ]]; then
+  dim=$(stty size < /dev/tty | awk '{print $2 "x" $1}')
+elif ! [[ $KITTY_WINDOW_ID ]] && (( FZF_PREVIEW_TOP + FZF_PREVIEW_LINES == $(stty size < /dev/tty | awk '{print $1}') )); then
+  # Avoid scrolling issue when the Sixel image touches the bottom of the screen
+  # * https://github.com/junegunn/fzf/issues/2544
+  dim=${FZF_PREVIEW_COLUMNS}x$((FZF_PREVIEW_LINES - 1))
+fi
+
+if [[ $KITTY_WINDOW_ID ]]; then
   # 1. 'memory' is the fastest option but if you want the image to be scrollable,
   #    you have to use 'stream'.
   #
@@ -42,6 +54,7 @@ elif [[ $KITTY_WINDOW_ID ]]; then
   kitty icat --clear --transfer-mode=memory --stdin=no --place="$dim@0x0" "$file" | sed '$d' | sed $'$s/$/\e[m/'
 elif command -v chafa > /dev/null; then
   chafa -f sixel -s "$dim" "$file"
+  # Add a new line character so that fzf can display multiple images in the preview window
   echo
 else
   file "$file"

man/man1/fzf.1

@@ -548,6 +548,9 @@ they represent the exact size of the preview window. (It also overrides
 by the default shell, so prefer to refer to the ones with \fBFZF_PREVIEW_\fR
 prefix.)
 
+fzf also exports \fB$FZF_PREVIEW_TOP\fR and \fB$FZF_PREVIEW_LEFT\fR so that
+the preview command can determine the position of the preview window.
+
 A placeholder expression starting with \fB+\fR flag will be replaced to the
 space-separated list of the selected lines (or the current line if no selection
 was made) individually quoted.

src/terminal.go

@@ -2067,9 +2067,6 @@ Loop:
 
 				if requiredLines > 0 {
 					if y+requiredLines == height {
-						if t.tui.MaxY() == t.pwindow.Top()+height {
-							t.tui.PassThrough("\x1b[1T")
-						}
 						t.pwindow.Move(height-1, maxWidth-1)
 						t.previewed.filled = true
 						break Loop
@@ -2790,6 +2787,8 @@ func (t *Terminal) Loop() {
 						env = append(env, "FZF_PREVIEW_"+lines)
 						env = append(env, columns)
 						env = append(env, "FZF_PREVIEW_"+columns)
+						env = append(env, fmt.Sprintf("FZF_PREVIEW_TOP=%d", t.tui.Top()+t.pwindow.Top()))
+						env = append(env, fmt.Sprintf("FZF_PREVIEW_LEFT=%d", t.pwindow.Left()))
 					}
 					cmd.Env = env
 

src/tui/dummy.go

@@ -41,6 +41,7 @@ func (r *FullscreenRenderer) Close()                             {}
 func (r *FullscreenRenderer) Size() TermSize                     { return TermSize{} }
 
 func (r *FullscreenRenderer) GetChar() Event { return Event{} }
+func (r *FullscreenRenderer) Top() int       { return 0 }
 func (r *FullscreenRenderer) MaxX() int      { return 0 }
 func (r *FullscreenRenderer) MaxY() int      { return 0 }
 

src/tui/light.go

@@ -720,6 +720,10 @@ func (r *LightRenderer) Close() {
 	r.restoreTerminal()
 }
 
+func (r *LightRenderer) Top() int {
+	return r.yoffset
+}
+
 func (r *LightRenderer) MaxX() int {
 	return r.width
 }

src/tui/tcell.go

@@ -172,6 +172,10 @@ func (r *FullscreenRenderer) Init() {
 	initTheme(r.theme, r.defaultTheme(), r.forceBlack)
 }
 
+func (r *FullscreenRenderer) Top() int {
+	return 0
+}
+
 func (r *FullscreenRenderer) MaxX() int {
 	ncols, _ := _screen.Size()
 	return int(ncols)

src/tui/tui.go

@@ -494,6 +494,7 @@ type Renderer interface {
 
 	GetChar() Event
 
+	Top() int
 	MaxX() int
 	MaxY() int