Qt

Qt: clean includes

Written by  on May 20, 2019

(I’ve decided to follow a more agile workflow: instead of creation a “one post covers the whole topic”-post, to post also updates for each step. Article will be therefore edited while “doing”)

Last week I’ve cleaned Qt-includes for a larger project. Like #include to #include how it should be. With proper indirection, so that the Qt-library handles how and where the class is implemented.
A colleauge raised the question, why not use #include to be even more precise and to see the used module directly (needed for the CMakeLists or qmake).

First step: identify all used Qt-includes

Greps all includes starting with an uppercase Q; then split the result at the “:”; then sort und make it unique

Second step: create a replacement-list and a (python?) script which does this for all .h/.cpp-files
tdb

Advanced debugging: find call which triggers Qt-errors

Written by  on April 26, 2019

Currently the debugging version of the Qt-libraries is not available. But I receive a report "QIODevice::write (QIODevice): Called with maxSize < 0" deep within them.
Our codebase is quite large, I am more familiar with other sections and let's say it: some is 'legacy'. So, where to start looking?!?
Yesterday I remembered a trick to get via call-stack to the last-recent position where our functions trigger that mistake.

Inserted in the main.cpp after show from the MainWindow was called a

which stands for this

Add a breakpoint in the messageHandler and debug the app. Maybe disable the breakpoint until you start to trigger the critical functionality.
When it breaks, you have a nice callstack and can backtrace where it came from :)

how to resume broken downloads

Written by  on April 24, 2019

aka: fix the weird firewalling settings ..
aka: How to download the latest stable Qt SDK source code?
curl -L -O -C - http://download.qt.io/official_releases/qt/5.12/5.12.3/single/qt-everywhere-src-5.12.3.zip

Updating to the current package of Qt Charts (from the commercial version)

Written by  on February 1, 2019

Qt (or Digia? or how was the company-owning-Qt called at that time?) released in 2014 the version 1.4 of their Charts add-on for Qt. It was available only for the commercial-license and had some distinc namespace-requirements. And was also quite bare-metal.
Further development lead to more opportunities regarding the emitted signals for the cursor-handling (pressed/released instead of just clicked, for instance) and it became part of the regular package for Qt.

## Advice for a CMake-based project ##

If you want to maintain and upgrade your legacy code, then:

  1. add “Charts” to your find_package:
  2. change the namespace inside the CMakeLists from “former naming” to “Qt5::Charts”
  3. remove the dependency to the old package in the top-level CMakeLists.txt
  4. replace inside the h/cpp all occurences of “QtCommercialChart::” with “QtCharts::”
  5. replace inside the h/cpp all occurences of “QTCOMMERCIALCHART_USE_NAMESPACE” with “using namespace QtCharts;”
  6. update the installer-creator-script(s) to include the Qt5Charts.dll

Et voilà , it should build now.

Retrospective view at 2018

Written by  on February 1, 2019

The first month of 2019 already passed. And we passed it with flying colors!
But let’s have a look at 2018 – a year full of challenges and success: I’ve worked full-time, organized and participated in advanced courses for Python and in Requirements Engineering (officially: IREB Requirements Engineering Foundation Level-approved) and pursued a new employment as software engineer.

And I wrote some software in my spare-time, as you can see in the graph for the public github-repositories. The gaps in the commits can be explained with the birth of my daughter and the time where I acquired the new job and moved nearly 900 km across the country. Yay! Nice personal projects were and are Cullendula and the Daily Coding Challenges, which I solve mostly with fully Unit-tested Python (3).

More new, hands-on knowledge was gained in the area of CMake and Qt-charts.
Well – 2018 was great. Let me make 2019 greater! 💪

Fixing ~crappy~ no-good Qt-includes

Written by  on January 29, 2019

How to locate all includes of that style:

with proper

Fired up https://regex101.com/ and set it to PHP and created an expression, which matches:
starting with slash, then a q, then characters, then . then h

(Replace & check has to be done by YOU ;))

Qt5: connect: How to use ‘connect’ in case the slot has less parameters than the signal

Written by  on September 18, 2018

Task is to connect from one signal with one parameter to a slot with zero parameters. With the “old” Qt4-way of connect it works like this

But what if I want to use the type-safe Qt5-connects?

The documentation just mentions the cases with:
* connect to default parameters in slot
* and (for example) using the above-mentioned way of the string-based connect.

My idea was to use a lambda to fix this:

But it turned out in in this thread that

is possible! 🙂

First pull-request on github, yay!

Written by  on August 5, 2018

Searched for a usable NTP-library, which assorts well with Qt and stumbled over qntp. While fiddling around I noticed in their source some opportunities to improve the code. So I cloned the repo, did them and created my very first pull-request for open-source 🙂
(Side-note: currently mostly Python-code is pushed due to the daily coding-challenge. But C++/Qt is still my carthorse.)

MPC: adding additional DEFINES

Written by  on May 25, 2018

Some weeks ago I noticed how the qDebug()-output could be enriched, so that in bigger solutions with a lot of different “unknown” components a reported error could be immediately pinned. And you save writing always __FILE__ and __LINE__. Referres to this post.
But the problem was that with the mpc-buildsystem it was unknown to me how to force it to put this DEFINE into the vcxproj-files.

It can be done via the “macros”-statement!

So I worked on my Python-skills and wrote a short script which iterates the given path recursively and fixes all mpc-files by checking for the position of the line with the last closingbrace “}” and then it adds before that position the line. Of course, the experts know several thousand ways to improve that script – but I am currently happy with it. It works, it is debug-able (.sh, I look at you!) and I will use the skeleton also for some other tasks.
It can be found (like most Python-snippets) at: https://github.com/marcelpetrick/pythonCollection

QT_MESSAGELOGCONTEXT: more detailed qDebug()

Written by  on April 19, 2018

Add to your environment:

Windows: set either via “set” or via RapidEnvironmentEditor.
In case of a no-debug-build, add QT_MESSAGELOGCONTEXT to DEFINES in the pro-file.

(Open question: if there are just mpc/vcxproj-files, then how to trigger?)

related sources:
* https://woboq.com/blog/nice-debug-output-with-qt.html
* https://fecub.wordpress.com/2015/11/04/better-debug-output-using-qt_message_pattern/
* http://doc.qt.io/qt-5/qmessagelogcontext.html#details