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This week, I ported the remaining '''QRegExp''' uses in digiKam. There was another regression detected this week as well in class ''cameranamehelper''. The cause was not because of my mistake. We think that it is probably a bug in Qt. This regex pattern ''^(ptp|normal|mtp)(\\s+mode)?$'' was failing to give an exact match with '''QRegularExperssion''' class in ''case insensitive'' mode. I found a way to make it work by using a different construction style. The blog post has detailed information. | This week, I ported the remaining '''QRegExp''' uses in digiKam. There was another regression detected this week as well in class ''cameranamehelper''. The cause was not because of my mistake. We think that it is probably a bug in Qt. This regex pattern ''^(ptp|normal|mtp)(\\s+mode)?$'' was failing to give an exact match with '''QRegularExperssion''' class in ''case insensitive'' mode. I found a way to make it work by using a different construction style. The blog post has detailed information. | ||
===== Related Patches ===== | ===== Related Patches ===== | ||
Revision as of 09:50, 20 August 2021
digiKam: Port to Qt6 on Linux
digiKam is a professional photo management software. With the release of Qt6, digiKam needs to to adapt to many new improvements made possible with the new Qt6 framework such as code readability, better classes from Qt6 and new unit tests. Since digiKam's code-base is huge, a proper plan had to be agreed upon to achieve the goal in the GSoC timeline.
Mentors
- Gilles Caulier
- Maik Qualmann
- Thanh Trung Dinh
Links
Goals
- To build digiKam with current Qt6 stable release.
- Prepare digiKam so that it can be built with later Qt6 releases as well.
- Write new AppImage builder scripts
Status Report
Community Bonding (May 18 - June 6)
We discussed the proposal again and made some strategies on the first task and how to test the new patches.The first task was to Port digiKam to Qt 5.15. This is a sophisticated task and involves a lot of sub-steps like:
- Identifying deprecated classes and class members/functions in Qt 5.15
- Identifying their uses in digiKam code and organizing them based on which class has most uses.
- Porting the identified code. Sometimes trivial, sometimes needs reviews from mentors.
- Writing new unit test if needed.
- Running tests and check the patched code at runtime with the digiKam stable release.
We planned a safe way to introduce patches safely in the code, otherwise regressions might be introduced. Here is a list that I made of deprecated code in digiKam and sorted it according to number of usages it had.
- QTextStream::endl
- QStringList
- qrand()
- qsrand()
- QSet
- QImage
- QWheelEvent
- QMap
- QHash
- QDateTime
- QButtonGroup
- QPixmap
- QPrinter
- QProcess
- QTabletEvent
- QTimeLine
- QMutex
After identifying and listing the code that needed to be patched, I proposed two methods to approach the problem:
- We pick a source file in digiKam and make patches to it resolving all Qt deprecation warnings.
- We pick a Qt class from our list and identify it's use in all digiKam code and patch them.
The latter was safer as dealing with a lot of Qt classes in the same file might have led to regressions which were difficult to track down.
So I started early in this time only so that I don't get stuck in the coding period. I started picking Qt classes with few usages and started porting them. These were QMap, QPrinter. I faced some difficulty but my mentor's feedback helped me a lot and learnt quickly. More about this period in the blog post.
Related blog
https://anjani.live/posts/gsoc-community-bonding/
Coding Period (June 7 - August 16)
Week 1
I patched a lot of warnings mostly from Qt classes that had fewer warnings. I also wrote a new unit test for FilterAction class. This test was related to QHash warnings. The test checked if all keys are unique in a QHash in FilterAction class. In a nutshell, there were 6693 lines of build warnings on master.With the patches on my branch these warnings reduced to 1830 lines. That’s a reduction of about 73%.
Related Patches
- Fix QMap::unite() deprecation warning in presentation plugin
- Fix QProcess deprecated warning in cameracontroller backend
- Fix QHash deprecated declarations in FilterAction class
- Fix QImage deprecated transformed() usages
- New Unit test: FilterAction Unique keys test for all filters
Related Blog
https://anjani.live/posts/gsoc21-week-1/
Week 2
Continuation of work from previous week. We also discussed about introducing STL algorithms in digiKam. Though it is huge task in its own and not related to my project so we suppressed the cppcheck warnings in report and moved on.
Related Patches
- Fix QSet issues by using only QSet constructor to make QSet objects
- Version check for QButtonGroup
- Version check for QWheelEvent
- Version check for QLabel
- Version check for QFlag
- Macro for Qt::endl
- Macro for Qt::SplitBehavior
Related Blog
https://anjani.live/posts/gsoc21-week-2/
Week 3
During this week I patched the very old random number generators and qsrand()/qrand() in digiKam. As a result we were able to drop Boost::Random dependency. I also ported Qt X11 Extras module code. A very detailed report is in the blog post.
Related patches
- Remove qsrand
- Remove qrand
- Port class RandomNumberGenerator to drop boost::random
- Remove Qt X11Extras module
- Remove deprecated QMutex usage
Related Blog
https://anjani.live/posts/gsoc21-week-3/
Week 4
In this week, digiKam was fully ported to Qt 5.15. We also started discussion on now introducing Qt6 this week. I tried building it for the first time with Qt6, it failed(no surprises here). We ran into a problem that digiKam depends on Qt WebEngine which would only be stable in Qt 6.2 in September. We discussed about possible solutions. I tried building the alpha Qt 6.2 but it doesn't build.
Related Patches
- Replace removed QDateTime constructor with new function
- Port dbjobsthread.cpp to not use deprecated const_iterator “+” operator
- Isolate rajce plugin
Week 5
I found the solution to problem from last week. Gilles also helped me to get started. This week I worked on porting the build system to Qt6. digiKam is huge and we have successfully branched the build process if no web module is found. A more detailed report is in the blog.
Related Patches
Related Blog
https://anjani.live/posts/gsoc21-week-5/
Week 6
This week our goal was to port the build system in such a way that it can detect a Qt installation 5/6 and adjust accordingly. Our goal was to preserve the functionality of current Qt5 pipelines and tests. We used cmake variables and patched hardcoded Qt versions in the cmake with dynamically set variables enabling cmake configuration with both Qt5 and Qt6.
Related Patches
and many more can be found in the work branch.
Related Blog
https://anjani.live/posts/gsoc21-week-6/
Week 7
This week I worked on building digiKam with Qt6. To do this, I had to build KF5 components with Qt6 first as they are currently built with Qt5 which was a problem. I built a few modules with Qt6 but it was taking some time. If I had more time in my hands I could have completed building all required modules but we decided that we can do this later and move to work on the next task.
Now I had to port Core5Compat module code to Qt6 Core code. I have explained all the work in detail in the blog post.
Related Patches
- Port QRegExp to QRegularExpression in dplugins
- Port QRegExp to QRegularExpression in libs/database
- Port QRegExp to QRegularExpression in core/libs
- Port QStringRef to QStringView
- Port QRegExp::exactMatch()
Related Blog
https://anjani.live/posts/gsoc21-week-7/
Week 8
Most of this week's work was debugging the regression in Porting QRegExp to QRegularExpression in advancedrename tool. The regression was caught by advancedrename_utest. The regression was fixed by patching the advancedrename digiKam API itself. I have explained the regression and my process of fixing in the blog post so do refer that.
Another patch was the porting of QTextCodec class. It was trivial. I had to leave two instances because of no clear alternatives were available. These are:
For the time being, we will use Core5Compat module to keep this code working.
Related Patches
Related Blog
https://anjani.live/posts/gsoc21-week8/
Week 9
This week, I ported the remaining QRegExp uses in digiKam. There was another regression detected this week as well in class cameranamehelper. The cause was not because of my mistake. We think that it is probably a bug in Qt. This regex pattern ^(ptp|normal|mtp)(\\s+mode)?$ was failing to give an exact match with QRegularExperssion class in case insensitive mode. I found a way to make it work by using a different construction style. The blog post has detailed information.