Allow search query longer than the screen width

By implementing horizontal scrolling of the prompt line.
Maximum length is hard-coded to 300-chars.

Close #1312
Fix #1225

src/constants.go

@@ -22,9 +22,10 @@ const (
 	readerPollIntervalMax  = 50 * time.Millisecond
 
 	// Terminal
-	initialDelay    = 20 * time.Millisecond
-	initialDelayTac = 100 * time.Millisecond
-	spinnerDuration = 200 * time.Millisecond
+	initialDelay     = 20 * time.Millisecond
+	initialDelayTac  = 100 * time.Millisecond
+	spinnerDuration  = 200 * time.Millisecond
+	maxPatternLength = 300
 
 	// Matcher
 	numPartitionsMultiplier = 8

src/terminal.go

@@ -59,6 +59,7 @@ type Terminal struct {
 	inlineInfo bool
 	prompt     string
 	promptLen  int
+	queryLen   [2]int
 	layout     layoutType
 	fullscreen bool
 	hscroll    bool
@@ -68,6 +69,7 @@ type Terminal struct {
 	cx         int
 	cy         int
 	offset     int
+	xoffset    int
 	yanked     []rune
 	input      []rune
 	multi      bool
@@ -364,6 +366,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 	t := Terminal{
 		initDelay:  delay,
 		inlineInfo: opts.InlineInfo,
+		queryLen:   [2]int{0, 0},
 		layout:     opts.Layout,
 		fullscreen: fullscreen,
 		hscroll:    opts.Hscroll,
@@ -373,6 +376,7 @@ func NewTerminal(opts *Options, eventBox *util.EventBox) *Terminal {
 		cx:         len(input),
 		cy:         0,
 		offset:     0,
+		xoffset:    0,
 		yanked:     []rune{},
 		input:      input,
 		multi:      opts.Multi,
@@ -640,7 +644,6 @@ func (t *Terminal) resizeWindows() {
 	for i := 0; i < t.window.Height(); i++ {
 		t.window.MoveAndClear(i, 0)
 	}
-	t.truncateQuery()
 }
 
 func (t *Terminal) move(y int, x int, clear bool) {
@@ -668,20 +671,44 @@ func (t *Terminal) move(y int, x int, clear bool) {
 	}
 }
 
+func (t *Terminal) truncateQuery() {
+	t.input, _ = t.trimRight(t.input, maxPatternLength)
+	t.cx = util.Constrain(t.cx, 0, len(t.input))
+}
+
+func (t *Terminal) updatePromptOffset() ([]rune, []rune) {
+	maxWidth := util.Max(1, t.window.Width()-t.promptLen-1)
+
+	_, overflow := t.trimLeft(t.input[:t.cx], maxWidth)
+	minOffset := int(overflow)
+	maxOffset := util.Min(util.Min(len(t.input), minOffset+maxWidth), t.cx)
+
+	t.xoffset = util.Constrain(t.xoffset, minOffset, maxOffset)
+	before, _ := t.trimLeft(t.input[t.xoffset:t.cx], maxWidth)
+	beforeLen := t.displayWidth(before)
+	after, _ := t.trimRight(t.input[t.cx:], maxWidth-beforeLen)
+	afterLen := t.displayWidth(after)
+	t.queryLen = [2]int{beforeLen, afterLen}
+	return before, after
+}
+
 func (t *Terminal) placeCursor() {
-	t.move(0, t.promptLen+t.displayWidth(t.input[:t.cx]), false)
+	t.move(0, t.promptLen+t.queryLen[0], false)
 }
 
 func (t *Terminal) printPrompt() {
 	t.move(0, 0, true)
 	t.window.CPrint(tui.ColPrompt, t.strong, t.prompt)
-	t.window.CPrint(tui.ColNormal, t.strong, string(t.input))
+
+	before, after := t.updatePromptOffset()
+	t.window.CPrint(tui.ColNormal, t.strong, string(before))
+	t.window.CPrint(tui.ColNormal, t.strong, string(after))
 }
 
 func (t *Terminal) printInfo() {
 	pos := 0
 	if t.inlineInfo {
-		pos = t.promptLen + t.displayWidth(t.input) + 1
+		pos = t.promptLen + t.queryLen[0] + t.queryLen[1] + 1
 		if pos+len(" < ") > t.window.Width() {
 			return
 		}
@@ -1334,12 +1361,6 @@ func (t *Terminal) buildPlusList(template string, forcePlus bool) (bool, []*Item
 	return true, sels
 }
 
-func (t *Terminal) truncateQuery() {
-	maxPatternLength := util.Max(1, t.window.Width()-t.promptLen-1)
-	t.input, _ = t.trimRight(t.input, maxPatternLength)
-	t.cx = util.Constrain(t.cx, 0, len(t.input))
-}
-
 func (t *Terminal) selectItem(item *Item) {
 	t.selected[item.Index()] = selectedItem{time.Now(), item}
 	t.version++
@@ -1392,10 +1413,10 @@ func (t *Terminal) Loop() {
 		t.initFunc()
 		t.resizeWindows()
 		t.printPrompt()
-		t.placeCursor()
-		t.refresh()
 		t.printInfo()
 		t.printHeader()
+		t.placeCursor()
+		t.refresh()
 		t.mutex.Unlock()
 		go func() {
 			timer := time.NewTimer(t.initDelay)
@@ -1529,9 +1550,9 @@ func (t *Terminal) Loop() {
 					}
 				}
 				t.placeCursor()
+				t.refresh()
 				t.mutex.Unlock()
 			})
-			t.refresh()
 		}
 	}()
 
@@ -1852,7 +1873,7 @@ func (t *Terminal) Loop() {
 					} else if me.Down {
 						if my == 0 && mx >= 0 {
 							// Prompt
-							t.cx = mx
+							t.cx = mx + t.xoffset
 						} else if my >= min {
 							// List
 							if t.vset(t.offset+my-min) && t.multi && me.Mod {