QColor stores RGB colour with 16 bits per channel, so "0.5" would
convert to 32768 (i.e. round(0.5 * 65535)), or 0x8000.

If you convert down to 8 bits per channel, you'll have 0x80.  If you
convert that value back up to 16 bits per channel, you'll have 0x8080.
And finally, converting that to floating point gives you 0.50196.

So you'll probably need to adjust the tests to accept an error on the
order of 1/(2*255) in these values.

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src in Ubuntu.

  Text.color can't be compared reliably

Status in qtdeclarative-opensource-src package in Ubuntu:

Bug description:
  Given the below QML:

  import QtQuick 2.4

  Text {
      id: text
      text: 'foobar'
      color: foobar

      property color foobar: Qt.rgba(0, 0, 0, 0.5)
      property color foobar2: foobar

      Component.onCompleted: {
          console.log("text:", text.color, foobar, Qt.colorEqual(text.color, 
foobar), text.color.a);
          console.log("property:", foobar2, foobar, Qt.colorEqual(foobar2, 
foobar), foobar2.a);
              qml: text: #80000000 #80000000 false 0.5019607843137255
              qml: property: #80000000 #80000000 true 0.5000076295109483

  Seems that Text.color stores the colour with a different precision,
  resulting in Qt.colorEqual() returning false.

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: libqt5quick5 5.6.1-4ubuntu3~xenialoverlay1~1 [origin: 
  ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
  Uname: Linux 4.4.0-36-generic x86_64
  NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
  ApportVersion: 2.20.1-0ubuntu2.1
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Thu Sep  1 14:40:27 2016
  InstallationDate: Installed on 2016-05-06 (117 days ago)
  InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 
  SourcePackage: qtdeclarative-opensource-src
  UpgradeStatus: No upgrade log present (probably fresh install)

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