[digikam] [Bug 363859] digiKam core port from QWebKit to QWebEngine [patch]

[bugzilla_noreply at kde.org]

https://bugs.kde.org/show_bug.cgi?id=363859

--- Comment #27 from caulier.gilles at gmail.com ---
Some details about the problem seen with QtWebEngine port :

1/ The DK bundles explode. It's increased to 100Mb. QWebEngine
need to be optimized at compilation time. There are a lots of
possibilities due to the huge dependencies list. Also, QWebkit use 5
.pak files with binary data. It's not a negligible size. Why ? I don't
know yet.

2/ QWebEngine use a run time dependency and... dbus. This is really
weird. There is a stand alone executable dedicated to preload pages in
memory (if i well understand). This make AppImage not really easy to
run. I found a solution but i'm not happy with it. It's not really
optimum. I'm not alone with this problem. I'm in contact with AppImage
lead developer who maintain a CI suite to package application as
bundle, and most of Qt5 applications have a problem with this
QWebEngine dependency. The quick solution is to remove this dependency
and make code optional. This is not acceptable for digiKam. As i
understand, a call to Qt to make this framework better compatible with
bundle solutions was reported.

3/ There is a crash in QWebEngine when digiKam is closed. It's inside
libudev. I don't know why yet...

4/ Marble is not yet ported to QWebEngine and still use QWebkit to
render some parts inside. This will cut Marble features, and we don't want to
include both framework in the bundles.

5/ The time to compile Qt explode with QWebEngine : 1h36 with QWebkit, 3h15
with QWebEngine. Same VM under Centos 6.8 running on same computer.

So i must conclude that we need more time before to use QWebEngine
inside digiKam. The best solution is to provide code for both QWebkit
and QWebengine and to create a switch between both frameworks at
compilation time. QWebkit must be the default one. 

I propose to make another try with Qt 5.10 and DK 6.0.0

Gilles Caulier

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