Squares in text where carriage returns should be

Can this bve reproduced with simple QML TextEdit component instead of TextArea?

I suspect yes, which brings us to Qt5.2 text rendering being screwed.

A small test qml file which reproduces the error would also be appreciated.

Even Text shows that issue, so it's not a UITK but Qt 5.2 issue:

import QtQuick 2.0

Text {
    width: 50
    height: 50
    maximumLineCount: 2
    text: "foo\nfoo"
}

Checked on Mac OSX with Qt5.2.1, with Ubuntu font installed. Rendering is all fine, font is also fine.

Issue reported upstream: https://bugreports.qt-project.org/browse/QTBUG-37475

Seeing this with in-line HTML as well. Both in Ubuntu.Components Label and QtQuick Text.

Example:

import QtQuick 2.0
import Ubuntu.Components 0.1

Rectangle {
    width: units.gu(40)
    height: units.gu(30)

    Text{
        anchors.fill: parent
        text: "<h1>Bug</h1><br><p>Line breaks are shown.</p>"
    }
}

I think it is the Ubuntu font that causes the problem.

This works fine:
import QtQuick 2.0

Text {
    font.family: "Helvetica"
    width: 200
    height: 200
    maximumLineCount: 2
    text: "foo\nfoo"
}

This gives the problem:

import QtQuick 2.0
Text {
    font.family: "Ubuntu"
    width: 200
    height: 200
    maximumLineCount: 2
    text: "foo\nfoo"
}

Without specifying font.family, the problem is there because Ubuntu font is chosen by default (I don't know why, probably a system setting). When I uninstalled the ttf-ubuntu-font-family package, the app ran without the problem when not specifying font.family.

The problem persists with both renderType: Text.QtRendering and renderType: Text.NativeRendering

No problem with a Qt Widgets application that uses the Ubuntu font.

I modified availableFonts.qml (from qt 5.2.1 souces) to show a newline for each font, and it exposes this problem for many fonts (but not all).

Run this program with qmlscene and you'll see: http://pastebin.ubuntu.com/7108737/plain/

Status changed to 'Confirmed' because the bug affects multiple users.

I tried the same with QtQuick1 (and qmlviewer), and the bug is not present in qtquick1

I can confirm that it also happens in Debian, so if the bug isn't upstream it is something about our environment that we share with them.

It seems not an ubuntu-only bug:

00:06:56 < special> t1mp: reproduces for Cantarell and Arial in fedora 20

QT_HARFBUZZ=old qmlscene texttest.qml
and the bug is gone

I don't know what's the reason for using HarfBuzz (text shaping) that's still marked as experimental in Qt (I guess there's a good one), but the bug comes from qtbase when built with HarfBuzz support. QT_HARFBUZZ=old disables the use of HarfBuzz, as if not built in, so we can force that environment variable, we can switch back to a non-HarfBuzz build or we can backport that patch from trunk : https://codereview.qt-project.org/#change,78991

The Qt font engine maintainer has just proposed to backport the patch too : https://codereview.qt-project.org/#change,81150

It seems it builds on top of a couple of patches. I'm fetching them all and building in a landing PPA for testing.

This bug was fixed in the package qtbase-opensource-src - 5.2.1+dfsg-1ubuntu9

---------------
qtbase-opensource-src (5.2.1+dfsg-1ubuntu9) trusty; urgency=medium

  * debian/patches/Fix-access-after-delete-with-Harfbuzz-NG-code-path.patch
  * debian/patches/Fix-log_clusters-calculation-in-HarfBuzz-NG-code-pat.patch
  * debian/patches/HarfBuzz-NG-Hide-characters-that-should-normally-be-.patch
  * debian/patches/Minor-optimization-for-QTextEngine-shapeText.patch
    - Cherry-pick latest HarfBuzz-NG changes from upstream including the one
      fixing the glyph issue https://codereview.qt-project.org/#change,81150
      (LP: #1285184)
 -- Timo Jyrinki <email address hidden> Tue, 18 Mar 2014 06:00:49 +0000