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.

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