Find crappy Qt-includes

Written by marcelpetrick on February 18, 2020

Use this regular expression

[\/][q]\w+[\.][h][>]

1	[\/][q]\w+[\.][h][>]

to check for includes of the format

#include <QtCore/qdir.h> // hit
#include <QtCore/QDir> // no hit
#include <QtCore/QDir.h> // no hit

#include <QtCore/qdir.h> // hit

#include <QtCore/QDir> // no hit

#include <QtCore/QDir.h> // no hit

Test it here with regex101.com.

QDialogs receive NO close-event in case of closing via the ESC-key. Nice.

Written by marcelpetrick on February 7, 2020

At first this looked like a bug, but upon reading carefully the documentation and crawling the internet, I’ve noticed that this is
a) wanted behavior and b) I am not the first one stumbling over this issue.

So just override in the header the method for processing the QHideEvent:

protected:
    // Closing a QDialog via key 'ESC' does NOT result in a close-event.
    // Therefore we capture the QHideEvent <3
    void hideEvent(QHideEvent* eventHorizon) override;

protected:

// Closing a QDialog via key 'ESC' does NOT result in a close-event.

// Therefore we capture the QHideEvent <3

void hideEvent(QHideEvent* eventHorizon) override;

And reimplement the base-class-call with the emission of a custom signal (or triggering custom functionality) for futher processing. Like:

void
MyDialog::hideEvent(QHideEvent* eventHorizon)
{
//    emit signalDialogClosed();
    QDialog::hideEvent(eventHorizon);
}

void

MyDialog::hideEvent(QHideEvent* eventHorizon)

{

// emit signalDialogClosed();

QDialog::hideEvent(eventHorizon);

}

Edit:
Another way is to connect the QDialog’s finished-signal to your signal via DirectConnection. Less code than overriding.

qobjectdefs_impl.h:72:118: error: no type named ‘Car’ in ‘struct QtPrivate::List<>‘

Written by marcelpetrick on February 4, 2020

Bruh, wait, what?

After rebasing a bigger feature and solving all obvious conflicts, the new build threw an error like “no type names Car”. And I am currently not working in the automotive industry!
Issue was that a commit, on which was rebased, changed ‘old’ Qt4-signal-slot-syntax (with SIGNAL/SLOT keywords; the string-based connect) to the ‘new’ Qt5-version (typed and verifyable from the compiler). And one of the slots had a default parameter. This is not allowed, except you squish a lambda as intermediate layer.

// old version
//        connect( _model.get(), &AnalysisModel::signalImageChanged,
//                 this, &ImageScene::slotImageChanged );				 
				 
// ImageScene::slotImageChanged's second parameter has a default value.
// Using Qt5-connects does just work with an intermediate lambda.
connect( _model.get(), &AnalysisModel::signalImageChanged,
          this, [=](ImagePoolItem item){ ImageScene::slotImageChanged(item); } );

// old version

// connect( _model.get(), &AnalysisModel::signalImageChanged,

// this, &ImageScene::slotImageChanged );

// ImageScene::slotImageChanged's second parameter has a default value.

// Using Qt5-connects does just work with an intermediate lambda.

connect( _model.get(), &AnalysisModel::signalImageChanged,

this, [=](ImagePoolItem item){ ImageScene::slotImageChanged(item); } );

A bit more insight: Qt-docs.

edit: One of the earlier error-messags also hinted out what could be the culprit, but “no type named Car” is more funny 😉

qobject.h:239:9: error: static assertion failed: The slot requires more arguments than the signal provides.

1	qobject.h:239:9: error: static assertion failed: The slot requires more arguments than the signal provides.

Localisations

Written by marcelpetrick on January 24, 2020

The Qt framework offers a quite nice and convenient way to localize your application.
Not only how to mark inside the code translateable strings (tr(..)), but also that the translation-mappings are human-readable xml-format files (*.ts), but also their own tool to do the translation (Linguist). Linguist is quite helpful for translator who sometimes also have to have a look at the “what would you get with that translation of different size inside the widget”-result (more or less: WYSIWYG).

Noticed today some flaws in the localisation of MTuner (nice memory profiler) and offered some help.
This is what I love about OSS: you don’t just take, but can also lend a helping hand and improve the quality 🙂

QtCreator: add online-help if the SDK is not coming from an official package

Written by marcelpetrick on January 1, 2020

~problem~ challenge:

having some Qt-SDK without help files. Using help inside a browser is possible, but cumbersome. and local help would be nice for quick parameter-checks.

solution:

Go to some repo for Ubuntu-packages for Qt and get the “qtdoc-archive”: in my case qt512doc-5.12.0-1basyskom1.
(Notice: the Qt-ressources at doc.qt.io fail miserably. Unless you run some installer, you would not get any online-help.)
Then add it via QtCreator > Tools > Options > Help > Documentation > “add the QCH files there”.

Edit: found also the official docu at: http://download.qt-project.org/online/qtsdkrepository/windows_x86/desktop/qt5_5121_src_doc_examples/qt.qt5.5121.doc/ as 7z-archive.

QtCreator: SpellChecker – how to set up

Written by marcelpetrick on December 22, 2019

The plan is to use the spellchecker from https://github.com/CJCombrink/SpellChecker-Plugin
Let’s be honest: it is quite hard to extract the needed information for a proper setup of the spellchecker. I took me on first try several guesses, which files to download, where to put them and how to configure the dictionary.
Since the process is a bit tricky, my two cents:

download the current version for Win10 x64 from this page: https://github.com/CJCombrink/SpellChecker-Plugin/releases (currently “SpellChecker-Plugin_v2.0.5_x64.zip”)
extract
copy&paste the two folders “bin” and “lib” into the current QtCreator 4.11-directory (it has to be that version 4.11 else the plugin fails to load!): for me this is “C:\Qt\Tools\QtCreator”)
download the proper .aff and .dic files for the dictionary from: https://cgit.freedesktop.org/libreoffice/dictionaries/tree/en – for me “en_US”
start QtCreator and you should have under “tools > options” a new entry for “SpellChecker” … configure there the dictionary-usage
restart QtCreator (again!)
done 🙂

Qt: custom-class and specialities for QVariant and QSettings

Written by marcelpetrick on December 11, 2019

While implementing some custom-class (C++17; Qt5.12) some specialities became (painfully) noticeable.
The guide at the Qt-source is quite well written.

ctor, copy-ctor and dtor are all required and have to be public
add Q_DECLARE_METATYPE(CustomClass)
QDebug-stream-operator in case of simple debugging-messages
if the QVariant-version of the CustomClass shall be written to QSettings, then implement also the two streaming operators: << and >> (else crash with Assert “unable to save type”): howto

block ads on music videos on youtube

Written by marcelpetrick on December 9, 2019

Task: youtube has annyoing ads at certain music-videos, which are set as playback-version for last.fm. I like to stream some music while programming, but I hate getting conditioned by advertisments.

Situation: Firefox 71.0, 64 bit, Win10

Solution: install “AdBlocker for YouTube™von AdblockLite” and configure it like this:

MicroPython (uPython) – the future is here

Written by marcelpetrick on November 27, 2019

My activity with the ESP8266/ESP32 boards had somehow fallen asleep after I set up one of the ESP8266 as Wifi-repeater. It worked, but creating own devices was too cumbersome. Firing up the ArduinoStudio took ages, building and downloading the firmware in C++ was error-prone, took ages (seriously, this is a tiny program, what the hell happens in the background?).
But I knew there exists a path, which could save some time: µPython (micropython). It runs a firmware, you just deploy your “code”. In my case now a tiny hello-world-like program.

I used this and that tutorial and the uPyCraft-IDE. Got it working with an ESP8266 in minutes.

Seriously: goodbye crappy, non-structured and slow-to-build C/C++ for my microcontrollers. The future is here o/

By the way: the motivation also comes from my current daily practice of Python (of course, I still contribute to C++/Qt-based projects), but my current flame is Python (for Project Euler and daily coding challenges).

C++ name demangling

Written by marcelpetrick on November 20, 2019

Like described in “Today I learned” (TIL): c++filt is quite helpful for demangling:

But what if you have none readily available? -> c++filtjs