How Qt Signals and Slots Work - Part 3 - Queued and Inter Thread Connections

ABS motor fuse 6. You must store pointers. Replace the wire harness if there is an open or short circuit. See also setParent and children. I appreciate an answer, thanks. It's likely the problem is due to poor storage conditions and metal fatigue due to age. Email me at this domain and preface with zapmaker at.


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If you delete the receiver object in your eventFilter function, be sure to return true. If you return false, Qt sends the event to the deleted object and the program will crash. Note that the filtering object must be in the same thread as this object. If filterObj is in a different thread, this function does nothing. If either filterObj or this object are moved to a different thread after calling this function, the event filter will not be called until both objects have the same thread affinity again it is not removed.

See also removeEventFilter , eventFilter , and event. Calling this function is equivalent to calling inherits " QWidget " , except that it is much faster. The timer identifier is returned by startTimer when a timer event is started. See also timerEvent and startTimer. A meta-object contains information about a class that inherits QObject , e. The inherits function also makes use of the meta-object. If you have no pointer to an actual object instance but still want to access the meta-object of a class, you can use staticMetaObject.

Changes the thread affinity for this object and its children. The object cannot be moved if it has a parent. Event processing will continue in the targetThread. To move an object to the main thread, use QApplication:: Note that all active timers for the object will be reset. The timers are first stopped in the current thread and restarted with the same interval in the targetThread. As a result, constantly moving an object between threads can postpone timer events indefinitely.

ThreadChange event is sent to this object just before the thread affinity is changed. You can handle this event to perform any special processing.

Note that any new events that are posted to this object will be handled in the targetThread. This function is not thread-safe; the current thread must be same as the current thread affinity. In other words, this function can only "push" an object from the current thread to another thread, it cannot "pull" an object from any arbitrary thread to the current thread. See also setParent and children. Information about all available properties is provided through the metaObject and dynamicPropertyNames.

See also setProperty , QVariant:: Since both slots and signals can be used as receivers for signals, and the same connections can be made many times, the number of receivers is the same as the number of connections made from this signal.

As the code snippet above illustrates, you can use this function to avoid emitting a signal that nobody listens to. Removes an event filter object obj from this object. The request is ignored if such an event filter has not been installed. It is always safe to remove an event filter, even during event filter activation i. See also installEventFilter , eventFilter , and event. Returns a pointer to the object that sent the signal, if called in a slot activated by a signal; otherwise it returns 0.

The pointer is valid only during the execution of the slot that calls this function from this object's thread context. The pointer returned by this function becomes invalid if the sender is destroyed, or if the slot is disconnected from the sender's signal.

However, getting access to the sender might be useful when many signals are connected to a single slot. As mentioned above, the return value of this function is not valid when the slot is called via a Qt:: DirectConnection from a thread different from this object's thread. Do not use this function in this type of scenario. Returns the meta-method index of the signal that called the currently executing slot, which is a member of the class returned by sender. If called outside of a slot activated by a signal, -1 is returned.

For signals with default parameters, this function will always return the index with all parameters, regardless of which was used with connect. This does not apply when overloading signals with different parameters. However, getting access to the signal index might be useful when many signals are connected to a single slot. The return value of this function is not valid when the slot is called via a Qt:: See also sender , QMetaObject:: See also parent and QWidget:: Dynamic properties can be queried again using property and can be removed by setting the property value to an invalid QVariant.

Changing the value of a dynamic property causes a QDynamicPropertyChangeEvent to be sent to the object. See also property , metaObject , and dynamicPropertyNames. A timer event will occur every interval milliseconds until killTimer is called. If interval is 0, then the timer event occurs once every time there are no more window system events to process. The virtual timerEvent function is called with the QTimerEvent event parameter class when a timer event occurs. Reimplement this function to get timer events.

If multiple timers are running, the QTimerEvent:: Note that QTimer 's accuracy depends on the underlying operating system and hardware. Most platforms support an accuracy of 20 milliseconds; some provide more.

If Qt is unable to deliver the requested number of timer events, it will silently discard some. The QTimer class provides a high-level programming interface with single-shot timers and timer signals instead of events. See also timerEvent , killTimer , and QTimer:: QTimer provides a higher-level interface to the timer functionality, and also more general information about timers.

The timer event is passed in the event parameter. See also startTimer , killTimer , and event. Returns a translated version of sourceText , optionally based on a disambiguation string and value of n for strings containing plurals; otherwise returns sourceText itself if no appropriate translated string is available. If the same sourceText is used in different roles within the same context, an additional identifying string may be passed in disambiguation 0 by default.

See Writing Source Code for Translation for a detailed description of Qt's translation mechanisms in general, and the Disambiguation section for information on disambiguation. This method is reentrant only if all translators are installed before calling this method. Installing or removing translators while performing translations is not supported. Doing so will probably result in crashes or other undesirable behavior.

See also trUtf8 , QApplication:: Returns a translated version of sourceText , or QString:: It is otherwise identical to tr sourceText , disambiguation , n. For portability reasons, we recommend that you use escape sequences for specifying non-ASCII characters in string literals to trUtf8.

See also tr , QApplication:: If you have a pointer to an object, you can use metaObject to retrieve the meta-object associated with that object. This function was provided as a workaround for MSVC 6 which did not support member template functions.

It is advised to use the other form in new code. Returns the given object cast to type T if the object is of type T or of a subclass ; otherwise returns 0. If object is 0 then it will also return 0. This macro associates extra information to the class, which is available using QObject:: Except for the ActiveQt extension, Qt doesn't use this information.

Instances of subclasses of QObject should not be thought of as values that can be copied or assigned, but as unique identities. This means that when you create your own subclass of QObject director or indirect , you should not give it a copy constructor or an assignment operator.

However, it may not enough to simply omit them from your class, because, if you mistakenly write some code that requires a copy constructor or an assignment operator it's easy to do , your compiler will thoughtfully create it for you. You must do more. The curious user will have seen that the Qt classes derived from QObject typically include this macro in a private section:.

It declares a copy constructor and an assignment operator in the private section, so that if you use them by mistake, the compiler will report an error. But even this might not catch absolutely every case. You might be tempted to do something like this:. First of all, don't do that.

It could generate code using neither the copy constructor nor the assignment operator we made private. In that case, no error would be reported, but your application would probably crash when you called a member function of w. If you want to register an enum that is declared in another class, the enum must be fully qualified with the name of the class defining it.

This macro registers one or several flags types to the meta-object system. It is typically used in a class definition to declare that values of a given enum can be used as flags and combined using the bitwise OR operator.

Also, mode changes are seen correct when pin addresses are changed to those demonstrated in video. I guess code was changed by site settings automatically.

Hence, copying it again here. Hi Derek, Just learning — thanks for the great write-up and video! I was wondering because every so often my code freezes and I am guessing but maybe something gets confused as to which Mode the mux is in???

Thanks for this excellent tutorial Derek. This will really help get me started with the BBB. I have been searching for a few days on how to change the pin MUX etc.

If I make an overlay following your example for a single pin, with a setting of 0x27 input with pull-down enable , it works right after boot. Same for pull-up 0x I still get high if it was initially configured with pull-up, or low if initially configured with pull-down. Is there anything in the overlay example itself that might be causing this, or is it just a bug somewhere?

I am following your instruction for gpio. I am not able to make it work.. No such file or directory. Or is the kernel using interrupt service routines to drive IO? Hi Derek, thank you very much for these tutorials, and the book which I just bought, hoping it would help with my issue.

Everything I can think to check matches what you have on this page and in the book. Even pins that are configured by default as input with pullup enabled report a value 0 but checking with the DMM, the pin is near 3. Ah, I figured it out. Hi Rick, Yes, that issue has caught many people out including me on my first pass! The book should help! Thanks for your support, Derek. Hi everybody, Thank to your explanation is now clear to me too.

But there is another problem in this site, which I cannot understand and I think it is a typo made by Mr. The former is 0x and latter is 0x0A0 in HEX. Which is the real offset of that pin? Is a mistake in this website or there is another explanation?

Hello Derek, Thaks for the tutorial. My approach was to follow your procedure to configure the mux to set the corresponding pins to GPIO output. Then set the bits within my kernel module using GPIO registers. I believe there is a broken link under Further Reading. First off, great book and blog for the BBB, I am just getting started and it has be hugely helpful. Apologies if this is redundant post, but it seems the DTO mechanism for updating the device trees at runtime has been removed from recent kernels greater than 3.

They are apparently working on something new but in the mean time do you have any suggestions? I wrote some hack code to get around this using the system command and sudo, but there must be a proper way. Then i turn off cape-bone-iio, pinmux changes propertly.

Dear Derek thank you very much for your great tutorials. They are helping me a lot in my project. Nevertheless, I am facing a problem of the cape manager. I have to unload an overlay that was already on my distribution, in order to load a custom overlay. But everytime I try to unload the specific overlay the BBB crashes and after a reboot nothing has changed.

Disabling the overlay in the uEnv. Can you help me please? Im very new to this environment.. Hi Derek First of all many thanks for the very well organized tutorial. I learned a lot. However, I am facing an issue when trying to load the newly created profile, i. My configuration seems to be ok.

The following commands react correctly. I have been documenting my project on a Blogger page, and I have just added links to your work. Thank you so much for the video! Very helpful and excellently done.

I dont know if this post is related to this topic or not but I am having some trouble connecting a flight controller to the BBB. The trouble is that these have damaged one BBB and I dont want to repeat that again. I think the problem is when the BBB is switched off these four wires going to the logic converter circuit are at 3.

How do you suggest that I connect these circuits so that they are always powered on after the BBB finishes booting up and powered down before it switches off. This is the circuit that I have implemented. The low side is connected to the BBB and the high side is connected to inputs on the flight controller. But when I connect the voltage source to 3V3 it works. Could you suggest me a better option that I can use universally wherever I need to convert 3.

Thank you so much for these tutorials. I am trying to follow the example above for deployment of an overlay. Attempts to load the overlay result in the following error message in dmesg…. I think the only choice in recent versions is to recompile a full DTC and load it at boot up. Derek, I really like your book. And kernel Linux beaglebone 4.

Most of the literature out there is for Angstrom and Debian Wheezy. Hi Derek, first of all, thank you for the amazing content. To this point I have spend quite sometime trying to figure out how to get it working with the latest Debian image Jessie.

Could you please share what version of Debian you where using when writing the book? Thank for great tutorials. I am new in embedded Linux and I have a problem with understanding Device tree overlay I just need to change default state of the I2C pins P9.

Is there quick path without be a PhD to do it I think it will be useful for all users like me. First, congratulations for your blog! Well, I have a doubt. In the video, it was presented one mode to set the pins at your own device tree cape.

Is make difference if I use the OS in emmc or sd-card? It also has channels at social media sites for communication and promotion.

They also attend conference events. They support community members by providing information, navigating bureaucracies, and matching research partners. The HIG provides a standardized layout.

The KDE Women help women to contribute and encourage women to give talks at conferences. The Release team defines and executes the official software releases.

The Team is responsible for setting release schedules for the official releases. This includes release dates, deadlines for individual release steps and restrictions for code changes. The release team is composed of Module Coordinators, Marketing Team liaison, and the people who actually do the work of tagging and creating the releases.

Each event is on a large scale, both thematically and geographically. Akademy-BR and Akademy-es are local community events. Akademy is the annual world summit, held each summer at varying venues in Europe. Secondary goals are to engage local people, and to provide space for getting together to write code. Akademy including conference, KDE e. BOFs are meet to discuss specific sub-projects or issues. Initially, each conference was numbered after the release, and not regular held.

Since the conferences were held once a year. And they were named Akademy since Their purpose is to recognize outstanding contribution to KDE. There are three awards, best application, best non-application and jury's award. As always the winners are chosen by the winners from the previous year. The event provides a regional opportunity for contributors and enthusiasts to gather and share their experiences. It is free to all participants. It is intended to ensure that KDE in the world is not simply seen as being Euro-centric.

It is held in the North America since In January , KDE 4. The event included 1—2 days of presentations, BoF meetings and hackathon sessions. The schedule included presentations, BoFs, hackathons and a day trip. It started with a short introduction by Jeff Mitchell, who was the principal organizer of the conference, talked a bit of history about Camp KDE and some statistics about the KDE community. The talks of the event were relatively well attended, and an increase over the previous year to around 70 people.

The schedule included presentations, hackathons and a party at Noisebridge. The conference opened with an introduction spoken by Celeste Lyn Paul. Akademy-es is a conference for Spanish community since , aimed at Spanish speakers. The event is organized by Spanish local organization. There were approximately 80 participants. The event was held in two different locations: Akademy-BR is addressed to Brazilian community since The purpose of the meeting is to gather and organize ideas Brazilian developers on how to help KDE in Brazil.

Akademy-BR was organized by the local group named LiveBlue. There were thirty participants from all over Brazil. College of Engineering in Bangalore, India. The first three days of the event had talks, tutorials and interactive sessions. The last two days were a focused code sprint. The Lighting of the Auspicious Lamp ceremony was performed to open the conference. The first session was by Lydia Pintscher who talk "So much to do — so little time". It gives talks and workshops. The purpose of the event are: The event is free.

On 12 July the first version of the desktop environment, called KDE 1. The original GPL licensed version of this toolkit only existed for platforms which used the X11 display server, but with the release of Qt 4, LGPL licensed versions are available for more platforms. KDE Plasma provides a unified environment for running and managing applications on different form factors like desktops, netbooks, tablets or smartphones. Its successor KDE Plasma 5 was released on July 15, and currently features the following workspaces:.

Solid , Nepomuk , Phonon , etc. Stable and mature bindings available for the following programming languages: KDE applications can potentially be portable between operating systems and independent of a particular workspace or desktop environment.

Some applications are part of the regular Software Compilation releases, others are part of Extragear and release to their own schedule. It aims to provide the users with rapidly updated Qt and KDE software, while updating the rest of the OS components from the Ubuntu repositories at the normal pace. It is a wiki based on MediaWiki , like Wikipedia that provides a platform to create and share open source textbooks. The idea is to have a massive library of textbooks for anyone and everyone to use and create.

Its roots lay in University of Milan , where a group of physics majors wanted to share notes—then decided that it was for everyone and not just their internal friend group.

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