Reduce the initial delay when --tac is not given

fzf defers the initial rendering of the screen up to 100ms if the input
stream is ongoing to prevent unnecessary redraw during the initial
phase. However, 100ms delay is quite noticeable and might give the
impression that fzf is not snappy enough. This commit reduces the
maximum delay down to 20ms when --tac is not specified, in which case
the input list quickly fills the entire screen.

src/constants.go

@@ -18,7 +18,8 @@ const (
 	defaultCommand = `find . -path '*/\.*' -prune -o -type f -print -o -type l -print 2> /dev/null | sed s/^..//`
 
 	// Terminal
-	initialDelay    = 100 * time.Millisecond
+	initialDelay    = 20 * time.Millisecond
+	initialDelayTac = 100 * time.Millisecond
 	spinnerDuration = 200 * time.Millisecond
 
 	// Matcher

src/terminal.go

@@ -22,6 +22,7 @@ import (
 
 // Terminal represents terminal input/output
 type Terminal struct {
+	initDelay  time.Duration
 	inlineInfo bool
 	prompt     string
 	reverse    bool
@@ -198,7 +199,14 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		header = reverseStringArray(opts.Header)
 	}
 	_tabStop = opts.Tabstop
+	var delay time.Duration
+	if opts.Tac {
+		delay = initialDelayTac
+	} else {
+		delay = initialDelay
+	}
 	return &Terminal{
+		initDelay:  delay,
 		inlineInfo: opts.InlineInfo,
 		prompt:     opts.Prompt,
 		reverse:    opts.Reverse,
@@ -751,7 +759,7 @@ func (t *Terminal) Loop() {
 		t.printHeader()
 		t.mutex.Unlock()
 		go func() {
-			timer := time.NewTimer(initialDelay)
+			timer := time.NewTimer(t.initDelay)
 			<-timer.C
 			t.reqBox.Set(reqRefresh, nil)
 		}()