Qt

Three ways to find the location of a certain DLL at Windows

Written by  on November 11, 2019

Common problem: just using the current working directory is not sufficient, because especially for unit-tests started from the Visual Studio-testrunner the opriginal, relative path is not fitting anymore. Fallback would be check an environment variable , which is set during installation or using the WinAPI (ugh).

versioned code can be found at: github/cppcCollection

QTest: increase the timeout duration for a test-case

Written by  on October 7, 2019

Set via environment variable QTEST_FUNCTION_TIMEOUT a higher timeout duration.
qputenv sets them temporary for the run of the single test case (put this at the beginning of the test case).

nota bene: This block has to be put before qExec is ran, so put it into the constructor of the test-suite!

Qt: libpng warning (exception) about wrong color profile (sRGB)

Written by  on October 1, 2019

Problem: libpng warning: iCCP: known incorrect sRGB profile

When debugging Qt applications which load some PNG as icons at startup, it could be annoying to continue with the debugger for each thrown exception.
So, let us fix them.

Invoking $ mogrify *.png in the icon directory will fix them.

How to get mogrify? Install imagemagick.
Either manually or on macOS via homebrew: $ brew install imagemagick

libPNG in version 1.6 has to be at least installed: $ convert -list format | grep PNG

Qt: Error: Not a signal or slot declaration

Written by  on September 4, 2019

This error is too ‘good’ to be just put into “Today I learned”.

While adapting some unit-testing-code for one of the classes, I received from minGW a error stating:

What is the problem? The member-declaration looked totally valid.
Until I realized I had removed the (now commented) “private”-statement and therefore the pointers were seen by the MOC as signals/slots. Which they weren’t!

Shame on me :’)

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 ;))