Support ANSI code for clearing the rest of the line (ESC[0K)

Some programs use it to set the background color for the whole line.

  fzf --preview "printf 'normal \x1b[42mgreen\x1b[0K \x1b[43myellow\x1b[m\nnormal again'"

  fzf --preview 'delta <(echo foo) <(echo bar) < /dev/tty'

Fix #2249

src/ansi.go

@@ -19,17 +19,18 @@ type ansiState struct {
 	fg   tui.Color
 	bg   tui.Color
 	attr tui.Attr
+	lbg  tui.Color
 }
 
 func (s *ansiState) colored() bool {
-	return s.fg != -1 || s.bg != -1 || s.attr > 0
+	return s.fg != -1 || s.bg != -1 || s.attr > 0 || s.lbg >= 0
 }
 
 func (s *ansiState) equals(t *ansiState) bool {
 	if t == nil {
 		return !s.colored()
 	}
-	return s.fg == t.fg && s.bg == t.bg && s.attr == t.attr
+	return s.fg == t.fg && s.bg == t.bg && s.attr == t.attr && s.lbg == t.lbg
 }
 
 func (s *ansiState) ToString() string {
@@ -195,11 +196,14 @@ func interpretCode(ansiCode string, prevState *ansiState) *ansiState {
 	// State
 	var state *ansiState
 	if prevState == nil {
-		state = &ansiState{-1, -1, 0}
+		state = &ansiState{-1, -1, 0, -1}
 	} else {
-		state = &ansiState{prevState.fg, prevState.bg, prevState.attr}
+		state = &ansiState{prevState.fg, prevState.bg, prevState.attr, prevState.lbg}
 	}
 	if ansiCode[0] != '\x1b' || ansiCode[1] != '[' || ansiCode[len(ansiCode)-1] != 'm' {
+		if strings.HasSuffix(ansiCode, "0K") {
+			state.lbg = prevState.bg
+		}
 		return state
 	}
 

src/terminal.go

@@ -525,7 +525,7 @@ func (t *Terminal) parsePrompt(prompt string) (func(), int) {
 	//             // unless the part has a non-default ANSI state
 	loc := whiteSuffix.FindStringIndex(trimmed)
 	if loc != nil {
-		blankState := ansiOffset{[2]int32{int32(loc[0]), int32(loc[1])}, ansiState{-1, -1, tui.AttrClear}}
+		blankState := ansiOffset{[2]int32{int32(loc[0]), int32(loc[1])}, ansiState{-1, -1, tui.AttrClear, -1}}
 		if item.colors != nil {
 			lastColor := (*item.colors)[len(*item.colors)-1]
 			if lastColor.offset[1] < int32(loc[1]) {
@@ -1277,6 +1277,10 @@ func (t *Terminal) renderPreviewText(unchanged bool) {
 	}
 	var ansi *ansiState
 	for _, line := range t.previewer.lines {
+		var lbg tui.Color = -1
+		if ansi != nil {
+			ansi.lbg = -1
+		}
 		line = strings.TrimSuffix(line, "\n")
 		if lineNo >= height || t.pwindow.Y() == height-1 && t.pwindow.X() > 0 {
 			t.previewed.filled = true
@@ -1292,6 +1296,7 @@ func (t *Terminal) renderPreviewText(unchanged bool) {
 				str, width := t.processTabs(trimmed, prefixWidth)
 				prefixWidth += width
 				if t.theme.Colored && ansi != nil && ansi.colored() {
+					lbg = ansi.lbg
 					fillRet = t.pwindow.CFill(ansi.fg, ansi.bg, ansi.attr, str)
 				} else {
 					fillRet = t.pwindow.CFill(tui.ColPreview.Fg(), tui.ColPreview.Bg(), tui.AttrRegular, str)
@@ -1308,7 +1313,12 @@ func (t *Terminal) renderPreviewText(unchanged bool) {
 			if unchanged && lineNo == 0 {
 				break
 			}
-			t.pwindow.Fill("\n")
+			if lbg >= 0 {
+				t.pwindow.CFill(-1, lbg, tui.AttrRegular,
+					strings.Repeat(" ", t.pwindow.Width()-t.pwindow.X())+"\n")
+			} else {
+				t.pwindow.Fill("\n")
+			}
 		}
 		lineNo++
 	}

src/tui/dummy.go

@@ -4,7 +4,7 @@
 
 package tui
 
-type Attr int
+type Attr int32
 
 func HasFullscreenRenderer() bool {
 	return false