How do I manually scroll a TextArea of ScrollView (Qt Quick)?

Question

If I have a TextArea or ScrollView, how can I manually set the scroll position, and ideally react to it too.

This is to create a log window - I want it so that if I append text and the view was previously scrolled to the bottom, it is scrolled there again.

Answer 1

Here is my solution for a log window based on Simon Warta's. It works pretty well and mostly behaves in the standard way - if you scroll to the bottom it will follow the output; if you scroll away from there it stops following. That's actually something that is apparently impossible to do in Java! (At least Eclipse and IntelliJ don't do it right.)

Unfortunately there is a weird bug in the TextEdit that makes it not update correctly if you remove text and then append some. If anyone has any idea about this it would be good to know. Otherwise I found selecting all the text and then immediately deselecting it works. Sadly that makes it impossible to copy text from the window.

Anyway here's my code.

import QtQuick 2.0
import QtQuick.Controls 1.2

ApplicationWindow {

    width: 500
    height: 300

    Timer {
        property int i: 0
        running: true
        interval: 250
        repeat: true
        onTriggered: {
            i += 1;
            root.appendLine(new Array(30).join(i + "_"));
            if (i === 100)
                root.clear();
        }
    }

    ScrollView {
        id: root
        anchors.fill: parent
        frameVisible: true

        property int maxLines: 50

        function appendLine(line)
        {
            // If we are scrolled near the end (up to 30 pixels away)
            // then scroll right to the end.
            var following = flickable.contentY > text.height - flickable.height - 30;

            line = String(line);
            text.lineLengths.push(line.length);
            if (text.lineLengths.length > maxLines)
                text.remove(0, text.lineLengths.shift()+1); // Plus 1 for new line.
            text.append(line);

            // These line work around a weird bug where it doesn't update the view.
            text.selectAll();
            text.deselect();

            if (following && text.height > flickable.height)
                flickable.contentY = text.height - flickable.height;
        }

        function clear()
        {
            text.text = "";
            text.lineLengths = [];
            flickable.contentY = 0;
        }

        Flickable {
            id: flickable
            anchors.fill: parent

            flickableDirection: Flickable.VerticalFlick
            contentHeight: text.height

            TextEdit {
                id: text

                // We have to store the length of each line because TextEdit
                // doesn't provide any *fast* ways to calculate it (accessing `text`
                // is extremely slow since it copies everything to/from javascript).
                property var lineLengths: []

                width: root.width - 30 // Space for scroll bar.
                wrapMode: TextEdit.Wrap

                text: ""
            }
        }
    }
}

Answer 2

Here you go:

import QtQuick 2.2
import QtQuick.Controls 1.1
import QtQuick.Window 2.0

ApplicationWindow {
    id: app
    title: qsTr("Hello World")
    width: 640
    height: 480

    function getTextLine(i) {
        var textLines = "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
        Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat.
        Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi.
        Nam liber tempor cum soluta nobis eleifend option congue nihil imperdiet doming id quod mazim placerat facer possim assum. Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat.
        Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis.
        At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, At accusam aliquyam diam diam dolore dolores duo eirmod eos erat, et nonumy sed tempor et et invidunt justo labore Stet clita ea et gubergren, kasd magna no rebum. sanctus sea sed takimata ut vero voluptua. est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat.
        Consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus.
        Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
        Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi. Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat.
        Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi.".split("\n");
        return textLines[i].trim();
    }

    Timer {
        property int i: 0
        running: true
        interval: 1000
        repeat: true
        onTriggered: {
            if (i < 10) {
                txt.text = txt.text.toString() + "\n\n" + getTextLine(i)
            }
            i += 1
        }
    }

    ScrollView {
        id: sv
        width: 600
        height: 300
        frameVisible: true

        Flickable {
            id: flickable
            anchors.fill: parent
            contentY: 50
            flickableDirection: Flickable.VerticalFlick
            contentHeight: txt.height
            Component.onCompleted: {
                console.log("Content height:", contentHeight)
                console.log("Height:", height)
                console.log("Implicit Height:", implicitHeight)
                console.log("Content Y:", contentY)
            }

            onContentYChanged: {
                console.log("Content Y:", contentY)
            }

            TextEdit {
                id: txt
                height: contentHeight
                width: 600-30
                wrapMode: TextEdit.Wrap
                onTextChanged: {
                    flickable.contentY = contentHeight - flickable.height
                }
                text: ""
            }
        }
    }
}