Method autoScroll

core/textfield.go:1452–1556

autoScroll scrolls the starting position to keep the cursor visible

()

// autoScroll scrolls the starting position to keep the cursor visible
func (tf *TextField) autoScroll() {
	sz := &tf.Geom.Size
	icsz := tf.iconsSize()
	availSz := sz.Actual.Content.Sub(icsz)
	tf.configTextSize(availSz)
	n := len(tf.editText)
	tf.cursorPos = math32.ClampInt(tf.cursorPos, 0, n)

	if tf.hasWordWrap() { // does not scroll
		tf.startPos = 0
		tf.endPos = n
		if len(tf.renderAll.Spans) != tf.numLines {
			tf.NeedsLayout()
		}
		return
	}
	st := &tf.Styles

	if n == 0 || tf.Geom.Size.Actual.Content.X <= 0 {
		tf.cursorPos = 0
		tf.endPos = 0
		tf.startPos = 0
		return
	}
	maxw := tf.effSize.X
	if maxw < 0 {
		return
	}
	tf.charWidth = int(maxw / st.UnitContext.Dots(units.UnitCh)) // rough guess in chars
	if tf.charWidth < 1 {
		tf.charWidth = 1
	}

	// first rationalize all the values
	if tf.endPos == 0 || tf.endPos > n { // not init
		tf.endPos = n
	}
	if tf.startPos >= tf.endPos {
		tf.startPos = max(0, tf.endPos-tf.charWidth)
	}

	inc := int(math32.Ceil(.1 * float32(tf.charWidth)))
	inc = max(4, inc)

	// keep cursor in view with buffer
	startIsAnchor := true
	if tf.cursorPos < (tf.startPos + inc) {
		tf.startPos -= inc
		tf.startPos = max(tf.startPos, 0)
		tf.endPos = tf.startPos + tf.charWidth
		tf.endPos = min(n, tf.endPos)
	} else if tf.cursorPos > (tf.endPos - inc) {
		tf.endPos += inc
		tf.endPos = min(tf.endPos, n)
		tf.startPos = tf.endPos - tf.charWidth
		tf.startPos = max(0, tf.startPos)
		startIsAnchor = false
	}