I updated my two little Apps; Teatime and Sensors Unity to integrate with Ubuntu 18.04 and consequently with Gnome 3.

For this I ported them to the GtkApplication API which makes sure they integrate into Unity7 as well as Gnome Shell. Additionally it ensures that only one instance of the App is active at the same time.

As Dash-to-Dock implements the Unity7 D-Bus API and snaps are available everywhere this drastically widens the target audience.

To make the projects themselves more accessible, I also moved development from launchpad to github where you can now easily create pull-requests and report issues.

Furthermore the translations are managed at POEditor, where you can help translating the apps to your language. Especially Sensors Unity could use some help.

0 0

29 Apr 2018 2:00pm GMT

This is awesome:

Youtube-link

Youtube-link

Youtube-link

• Paper on the proposal
• Blog about it by Herb Sutter
• Live demo with Clang

0 0

25 Apr 2018 7:20am GMT

When I'm not in Flowhub-land, I'm used to developing software in a quite customized command line based development environment. Like for many, the cornerstones of this for me are vim and tmux.

As customization increases, it becomes important to have a way to manage that and distribute it across the different computers. For years, I've used a dotfiles repository on GitHub together with GNU Stow for this.

However, this still means I have to install all the software and tools before I can have my environment up and running.

Using Docker

Docker is a tool for building and running software in a containerized fashion. Recently Tiago gave me the inspiration to use Docker not only for distributing production software, but also for actually running my development environment.

Taking ideas from his setup, I built upon my existing dotfiles and built a reusable developer shell container.

With this, I only need Docker installed on a machine, and then I'm two commands away from having my normal development environment:

$ docker volume create workstation
$ docker run -v ~/Projects:/projects -v workstation:/root -v ~/.ssh:/keys --name workstation --rm -it bergie/shell

Here's how it looks in action:

Once I update my Docker setup (for example to install or upgrade some tool), I can get the latest version on a machine with:

$ docker pull bergie/shell

At least in theory this should give me a fully identical working environment regardless of the host machine. Linux VPS, a MacBook, or a Windows machine should all be able to run this. And soon, this should also work out of the box on Chromebooks.

Setting this up

The basics are pretty simple. I already had a repository for my dotfiles, so I only needed to write a Dockerfile to install and set up all my software.

To make things even easier, I configured Travis so that every time I push some change to the dotfiles repository, it will create and publish a new container image.

Further development ideas

So far this setup seems to work pretty well. However, here are some ideas for further improvements:

• ARM build: Sometimes I need to work on Raspberry Pis. It might be nice to cross-compile an ARM version of the same setup
• Key management: Currently I create new SSH keys for each host machine, and then upload them to the relevant places. With this setup I could use a USB stick, or maybe even a Yubikey to manage them
• Application authentication: Since the Docker image is public, it doesn't come with any secrets built in. This means I still need to authenticate with tools like NPM and Travis. It might be interesting to manage these together with my SSH keys
• SSH host: with some tweaking it might be possible to run the same container on cloud services. Then I'd need a way to get my SSH public keys there and start an SSH server

If you have ideas on how to best implement the above, please get in touch.

0 0

19 Apr 2018 12:00am GMT

0 0

14 Jan 2018 11:34pm GMT

I recently migrated a server to a new VHost that was supposed to improve the performance - however after the upgrade the performance actually was worse.

Looking at the system load I discovered that the load average was at about 3.5 - with only 2 cores available this corresponds to server overload by almost 2x.

Further looking at the logs revealed that this unfortunately was not due to the users taking interest in the site, but due to various bots hammering on the server. Actual users would be probably drawn away by the awful page load times at this point.

Asking the bots to leave

To improve page loading times, I configured my robots.txt as following

User-agent: *
Disallow: /

This effectively tells all bots to skip my site. You should not do this as you will not be discoverable at e.g. Google.

But here I just wanted to allow my existing users to use the site. Unfortunately the situation only slightly improve; the system load was still over 2.

From the logs I could tell that all bots were actually gone, except for

• SemrushBot by semrush.com
• MJ12Bot by majestic.com
• DotBot by Moz.com

But those were enough to keep the site (PHP+MySQL) overloaded.

The above bots crawl the web for their respective SEO analytics company which sell this information to webmasters. This means that unless you are already a customer of these companies, you do not benefit from having your site crawled.

In fact, if you are interested in SEO analytics for your website, you should probably look elsewhere. In the next paragraph we will block these bots and I am by far not the first one recommending this.

Making the bots leave

As the bots do not respect the robots.txt, you will have to forcefully block them. Instead of the actual webpages, we will give them a 410/ 403 which prevents them touching any PHP/ MySQL resources.

On nginx, add this to your server section:

if ($http_user_agent ~* (SemrushBot|MJ12Bot|DotBot)) {
     return 410;
}

For Apache2.4+ do:

BrowserMatchNoCase SemrushBot bad_bot
BrowserMatchNoCase MJ12Bot bad_bot
BrowserMatchNoCase DotBot bad_bot
Order Deny,Allow
Deny from env=bad_bot

For additional fun you could also given them a 307 (redirect) to their own websites here.

0 0

17 Nov 2017 8:02pm GMT

Dear Maemoans and fellow humans. The time has come again to elect a new Community Council for Q1/2018. The schedule for the voting process is as follows, according to the election rules: The nomination period of at least 2 weeks starts tomorrow, on the 8th of November 2017 and will continue until the 3rd of December 2017. The one week election starts on Friday, the 8th of December 2017 and will continue until the 14th of December 2017. In order for us to keep the community strong, it would be great to have new people with fresh ideas to carry on the torch. Please consider volunteering for the position of Maemo Council. On behalf of the outgoing Community Council, mosen0 0

07 Nov 2017 9:04pm GMT

Recently I have been look on the Ogre Matrix class which has a fairly un-optimized, but straightforward implementation, that you can see here.
I was wondering how it compares.

Of course somebody had a similar question in mind before. Martin Foot that is. While the discussion still applies today, I felt like the results could have changed since 2012 as libraries and compilers have moved on.

So I forked his code to update the libs to the latest versions and came up with the following results:

The used compiler was gcc with optimization level -O2.

As we can see Eigen3 just downgrades the rest on x86_64 - probably due its explicit vectorization. Notably, CLM1 is having some issues and even falls behind the naive implementations.
On ARM the results are more tight. With Eigen3 and CLM1 being about 25% faster at addition. However CML1 again has some issues with the mult test.

We end up with Eigen3 being the overall winner and GLM being second (Ogre does not count as it is not a Math library).

Also you should migrate away from CLM1 as the development focus shifted to CLM2 and the issues found above are probably not going to be resolved.

0 0

05 Nov 2017 1:47am GMT

there are many articles on the internet telling you to switch from Apache & mod_php to nginx to get better performance.

However the main reason for performance improvement is not nginx itself but rather the way it integrates PHP.

Different ways to integrate PHP

Apache traditionally used mod_php to embed the PHP interpreter inside Apache HTTP request handler. This way it can directly interpret PHP scripts whereas with CGI it would have to start a new PHP interpreter process first - per request.

The drawback however is that the PHP interpreter is embedded in all request handlers - even those that just serve static files. This obviously blows up memory consumption which in turn can lower performance.

Nginx on the other hand uses the FCGI approach where a pool of PHP processes is started along the webserver using the FCGI process manager, FPM. The webserver then delegates individual requests using the FCGI protocol as needed.
This avoids the PHP interpreter startup costs as well as starting it without a need and is the reason nginx is faster then mod_php.

However since Apache 2.4 one can also use FCGI to integrate PHP and get virtually the same characteristics like nginx. Sticking with Apache saves you migrating all the .htaccess rules and means an easier setup for many webapps.

Furthermore since Apache 2.4.10 one can use mod_proxy_fcgi for a reverse-proxy configuration which further reduces the occupied PHP workers in the FPM pool for better performance.

Configuration on Ubuntu 16.04

Switching to FCGI on Ubuntu 16.04 is quite easy. The needed module are installed by default and just need to be enabled:

a2enmod proxy_fcgi && a2dismod php7.0

Then inside your-site.conf add

 # PHP-FPM
 <FilesMatch "\.php$">
     SetHandler "proxy:unix:/var/run/php/php7.0-fpm.sock|fcgi://localhost/"
 </FilesMatch>
 <Proxy "fcgi://localhost/">
 </Proxy>

this connects Apache in reverse proxy mode to the PHP-FPM pool using unix domain sockets for optimal performance. See the Apache Wiki for details.

Note that php-fpm by default only creates 5 PHP worker processes, which in turn limits the maximal simultaneous connections. You might want to raise this by adapting pm.max_children in /etc/php/7.0/fpm/pool.d/www.conf.

Typically you set this to RAM size / avg. process size. You can find out the latter via:

ps -ylC php-fpm7.0 --sort:rss

Performance Measurements

To measure the results I did a force reload of my single user Nextcloud instance and measured the Load time via Chrome developer tools:

as one can see depending on the amount of static/ dynamic files and internal/ external requests we can bring down the page load time by up to 15%.

0 0

27 Oct 2017 2:43pm GMT

With asynchronous commands we have typical commands from the Model View ViewModel world that return asynchronously.

Whenever that happens we want result reporting and progress reporting. We basically want something like this in QML:

Item {
  id: container
  property ViewModel viewModel: ViewModel {}

  Connections {
    target: viewModel.asyncHelloCommand
    onExecuteProgressed: {
        progressBar.value = value
        progressBar.maximumValue = maximum
    }
  }
  ProgressBar {
     id: progressBar
  }
  Button {
    enabled: viewModel.asyncHelloCommand.canExecute
    onClicked: viewModel.asyncHelloCommand.execute()
  }
}

How do we do this? First we start with defining a AbstractAsyncCommand (impl. of protected APIs here):

class AbstractAsyncCommand : public AbstractCommand {
    Q_OBJECT
public:
    AbstractAsyncCommand(QObject *parent=0);

    Q_INVOKABLE virtual QFuture<void*> executeAsync() = 0;
    virtual void execute() Q_DECL_OVERRIDE;
signals:
    void executeFinished(void* result);
    void executeProgressed(int value, int maximum);
protected:
    QSharedPointer<QFutureInterface<void*>> start();
    void progress(QSharedPointer<QFutureInterface<void*>> fut, int value, int total);
    void finish(QSharedPointer<QFutureInterface<void*>> fut, void* result);
private:
    QVector<QSharedPointer<QFutureInterface<void*>>> m_futures;
};

After that we provide an implementation:

#include <QThreadPool>
#include <QRunnable>

#include <MVVM/Commands/AbstractAsyncCommand.h>

class AsyncHelloCommand: public AbstractAsyncCommand
{
    Q_OBJECT
public:
    AsyncHelloCommand(QObject *parent=0);
    bool canExecute() const Q_DECL_OVERRIDE { return true; }
    QFuture<void*> executeAsync() Q_DECL_OVERRIDE;
private:
    void* executeAsyncTaskFunc();
    QSharedPointer<QFutureInterface<void*>> current;
    QMutex mutex;
};

#include "asynchellocommand.h"

#include <QtConcurrent/QtConcurrent>

AsyncHelloCommand::AsyncHelloCommand(QObject* parent)
    : AbstractAsyncCommand(parent) { }

void* AsyncHelloCommand::executeAsyncTaskFunc()
{
    for (int i=0; i<10; i++) {
        QThread::sleep(1);
        qDebug() << "Hello Async!";
        mutex.lock();
        progress(current, i, 10);
        mutex.unlock();
    }
    return nullptr;
}

QFuture<void*> AsyncHelloCommand::executeAsync()
{
    mutex.lock();
    current = start();
    QFutureWatcher<void*>* watcher = new QFutureWatcher<void*>(this);
    connect(watcher, &QFutureWatcher<void*>::progressValueChanged, this, [=]{
        mutex.lock();
        progress(current, watcher->progressValue(), watcher->progressMaximum());
        mutex.unlock();
    });
    connect(watcher, &QFutureWatcher<void*>::finished, this, [=]{
        void* result=watcher->result();
        mutex.lock();
        finish(current, result);
        mutex.unlock();
        watcher->deleteLater();
    });
    watcher->setFuture(QtConcurrent::run(this, &AsyncHelloCommand::executeAsyncTaskFunc));
    QFuture<void*> future = current->future();
    mutex.unlock();

    return future;
}

You can find the complete working example here.

0 0

23 Oct 2017 7:31pm GMT

This weekend I'll be in Node5 (Prague) presenting our Media Source Extensions platform implementation work in WebKit using GStreamer.

The Media Source Extensions HTML5 specification allows JavaScript to generate media streams for playback and lets the web page have more control on complex use cases such as adaptive streaming.

My plan for the talk is to start with a brief introduction about the motivation and basic usage of MSE. Next I'll show a design overview of the WebKit implementation of the spec. Then we'll go through the iterative evolution of the GStreamer platform-specific parts, as well as its implementation quirks and challenges faced during the development. The talk continues with a demo, some clues about the future work and a final round of questions.

Our recent MSE work has been on desktop WebKitGTK+ (the WebKit version powering the Epiphany, aka: GNOME Web), but we also have MSE working on WPE and optimized for a Raspberry Pi 2. We will be showing it in the Igalia booth, in case you want to see it working live.

I'll be also attending the GStreamer Hackfest the days before. There I plan to work on webm support in MSE, focusing on any issue in the Matroska demuxer or the vp9/opus/vorbis decoders breaking our use cases.

See you there!

UPDATE 2017-10-22:

The talk slides are available at https://eocanha.org/talks/gstconf2017/gstconf-2017-mse.pdf and the video is available at https://gstconf.ubicast.tv/videos/media-source-extension-on-webkit (the rest of the talks here).

0 0

17 Oct 2017 10:48am GMT

A few days ago I explained how we can do MVVM techniques like ICommand in Qt.

Today I'll explain how to make and use a simple version of the, in the XAML MVVM world quite famous, RelayCommand. In the Microsoft Prism4 & 5 world this is DelegateCommand. Both are equivalent. I will only show a non-templated RelayCommand, so no RelayCommand<T> for now. Perhaps I'll add a templated one to that mvvm project some other day.

What people call a delegate in C# is what C++ people call a Functor. Obviously we will use functors, then. Note that for people actually reading all those links: in C# the Action<T> and Func<T,G> are basically also C# delegates (or, functors, if you fancy C++'s names for this more).

Here is the RelayCommand.h:

#include <functional>
#include <QSharedPointer>
#include <MVVM/Commands/AbstractCommand.h>

class RelayCommand : public AbstractCommand
{
    Q_OBJECT
public:
    RelayCommand(std::function<void()> executeDelegatep,
                 std::function<bool()> canExecuteDelegatep,
                 QObject *parent = 0)
    : AbstractCommand(parent)
    , executeDelegate(executeDelegatep)
    , canExecuteDelegate(canExecuteDelegatep) {}

    void execute() Q_DECL_OVERRIDE;
    bool canExecute() const Q_DECL_OVERRIDE;
public slots:
    void evaluateCanExecute();
private:
    std::function<void()> executeDelegate;
    std::function<bool()> canExecuteDelegate;
};

The implementation is too simple to be true:

#include "RelayCommand.h"

bool RelayCommand::canExecute() const
{
    return canExecuteDelegate();
}

void RelayCommand::evaluateCanExecute()
{
    emit canExecuteChanged( canExecute() );
}

void RelayCommand::execute()
{
    executeDelegate();
}

Okay, so how do we use this? First we make a ViewModel. Because in this case we will define the command in C++. That probably means you want a ViewModel.

I added a CompositeCommand in the mix. For a Q_PROPERTY isn't a CommandProxy really needed, as ownership stays in C++ (when for example you pass this as parent). For a Q_INVOKABLE you would need it to wrap the QSharedPointer<AbstractCommand>.

Note. I already hear you think: wait a minute, you are not passing this to the QObject's constructor, it's not a QScopedPointer and you have a new but no delete. That's because CommandProxy converts the ownership rules to QQmlEngine::setObjectOwnership (this, QQmlEngine::JavaScriptOwnership) for itself. I don't necessarily recommend its usage here (for it's not immediately clear), but at the same time this is just a demo. You can try printing a warning in the destructor and you'll see that the QML garbage collector takes care of it.

#include <QObject>
#include <QScopedPointer>

#include <MVVM/Commands/CommandProxy.h>
#include <MVVM/Commands/CompositeCommand.h>
#include <MVVM/Commands/RelayCommand.h>
#include <MVVM/Models/CommandListModel.h>

class ViewModel: public QObject
{
    Q_OBJECT

    Q_PROPERTY(CommandProxy* helloCommand READ helloCommand CONSTANT)
public:
    ViewModel(QObject *parent=0):QObject(parent),
        helloCmd(new CompositeCommand()){

        QSharedPointer<CompositeCommand> cCmd = helloCmd.dynamicCast<CompositeCommand>();
        cCmd->add( new RelayCommand ([=] { qWarning() << "Hello1 from C++ RelayCommand"; },
                            [=]{ return true; }));
        cCmd->add( new RelayCommand ([=] { qWarning() << "Hello2 from C++ RelayCommand"; },
                            [=]{ return true; }));
        proxyCmd = new CommandProxy (helloCmd);
    }
    CommandProxy* helloCommand() {
        return proxyCmd;
    }
private:
    QSharedPointer<AbstractCommand> helloCmd;
    CommandProxy *proxyCmd;
};

Let's also make a very simple View.qml that uses the ViewModel

import QtQuick 2.3
import QtQuick.Window 2.0
import QtQuick.Controls 1.2

import Example 1.0

Item {
    property ViewModel viewModel: ViewModel {}

    Button {
        enabled: viewModel.helloCommand.canExecute
        onClicked: viewModel.helloCommand.execute()
    }
}

0 0

24 Aug 2017 6:57pm GMT

In the .NET XAML world, you have the ICommand, the CompositeCommand and the DelegateCommand. You use these commands to in a declarative way bind them as properties to XAML components like menu items and buttons. You can find an excellent book on this titled Prism 5.0 for WPF.

The ICommand defines two things: a canExecute property and an execute() method. The CompositeCommand allows you to combine multiple commands together, the DelegateCommand makes it possible to pass two delegates (functors or lambda's); one for the canExecute evaluation and one for the execute() method.

The idea here is that you want to make it possible to put said commands in a ViewModel and then data bind them to your View (so in QML that's with Q_INVOKABLE and Q_PROPERTY). Meaning that the action of the component in the view results in execute() being called, and the component in the view being enabled or not is bound to the canExecute bool property.

In QML that of course corresponds to a ViewModel.cpp for a View.qml. Meanwhile you also want to make it possible to in a declarative way use certain commands in the View.qml without involving the ViewModel.cpp.

So I tried making exactly that. I've placed it on github in a project I plan to use more often to collect MVVM techniques I come up with. And in this article I'll explain how and what. I'll stick to the header files and the QML file.

We start with defining a AbstractCommand interface. This is very much like .NET's ICommand, of course:

#include <QObject>

class AbstractCommand : public QObject {
    Q_OBJECT
    Q_PROPERTY(bool canExecute READ canExecute NOTIFY canExecuteChanged)
public:
    AbstractCommand(QObject *parent = 0):QObject(parent){}
    Q_INVOKABLE virtual void execute() = 0;
    virtual bool canExecute() const = 0;
signals:
    void canExecuteChanged(bool canExecute);
};

We will also make a command that is very easy to use in QML, the EmitCommand:

#include <MVVM/Commands/AbstractCommand.h>

class EmitCommand : public AbstractCommand
{
    Q_OBJECT
    Q_PROPERTY(bool canExecute READ canExecute WRITE setCanExecute NOTIFY privateCanExecuteChanged)
public:
    EmitCommand(QObject *parent=0):AbstractCommand(parent){}

    void execute() Q_DECL_OVERRIDE;
    bool canExecute() const Q_DECL_OVERRIDE;
public slots:
    void setCanExecute(bool canExecute);
signals:
    void executes();
    void privateCanExecuteChanged();
private:
    bool canExe = false;
};

We make a command that allows us to combine multiple commands together as one. This is the equivalent of .NET's CompositeCommand, here you have our own:

#include <QSharedPointer>
#include <QQmlListProperty>

#include <MVVM/Commands/AbstractCommand.h>
#include <MVVM/Commands/ListCommand.h>

class CompositeCommand : public AbstractCommand {
    Q_OBJECT

    Q_PROPERTY(QQmlListProperty<AbstractCommand> commands READ commands NOTIFY commandsChanged )
    Q_CLASSINFO("DefaultProperty", "commands")
public:
    CompositeCommand(QObject *parent = 0):AbstractCommand (parent) {}
    CompositeCommand(QList<QSharedPointer<AbstractCommand> > cmds, QObject *parent=0);
    ~CompositeCommand();
    void execute() Q_DECL_OVERRIDE;
    bool canExecute() const Q_DECL_OVERRIDE;
    void remove(const QSharedPointer<AbstractCommand> &cmd);
    void add(const QSharedPointer<AbstractCommand> &cmd);

    void add(AbstractCommand *cmd);
    void clearCommands();
    QQmlListProperty<AbstractCommand> commands();

signals:
    void commandsChanged();
private slots:
    void onCanExecuteChanged(bool canExecute);
private:
    QList<QSharedPointer<AbstractCommand> > cmds;
    static void appendCommand(QQmlListProperty<AbstractCommand> *lst, AbstractCommand *cmd);
    static AbstractCommand* command(QQmlListProperty<AbstractCommand> *lst, int idx);
    static void clearCommands(QQmlListProperty<AbstractCommand> *lst);
    static int commandCount(QQmlListProperty<AbstractCommand> *lst);
};

We also make a command that looks a lot like ListElement in QML's ListModel:

#include <MVVM/Commands/AbstractCommand.h>

class ListCommand : public AbstractCommand
{
    Q_OBJECT
    Q_PROPERTY(AbstractCommand *command READ command WRITE setCommand NOTIFY commandChanged)
    Q_PROPERTY(QString text READ text WRITE setText NOTIFY textChanged)
public:
    ListCommand(QObject *parent = 0):AbstractCommand(parent){}
    void execute() Q_DECL_OVERRIDE;
    bool canExecute() const Q_DECL_OVERRIDE;
    AbstractCommand* command() const;
    void setCommand(AbstractCommand *newCommand);
    void setCommand(const QSharedPointer<AbstractCommand> &newCommand);
    QString text() const;
    void setText(const QString &newValue);
signals:
    void commandChanged();
    void textChanged();
private:
    QSharedPointer<AbstractCommand> cmd;
    QString txt;
};

Let's now also make the equivalent for QML's ListModel, CommandListModel:

#include <QObject>
#include <QQmlListProperty>

#include <MVVM/Commands/ListCommand.h>

class CommandListModel:public QObject {
    Q_OBJECT
    Q_PROPERTY(QQmlListProperty<ListCommand> commands READ commands NOTIFY commandsChanged )
    Q_CLASSINFO("DefaultProperty", "commands")
public:
    CommandListModel(QObject *parent = 0):QObject(parent){}
    void clearCommands();
    int commandCount() const;
    QQmlListProperty<ListCommand> commands();
    void appendCommand(ListCommand *command);
    ListCommand* command(int idx) const;
signals:
    void commandsChanged();
private:
    static void appendCommand(QQmlListProperty<ListCommand> *lst, ListCommand *cmd);
    static ListCommand* command(QQmlListProperty<ListCommand> *lst, int idx);
    static void clearCommands(QQmlListProperty<ListCommand> *lst);
    static int commandCount(QQmlListProperty<ListCommand> *lst);

    QList<ListCommand* > cmds;
};

Okay, let's now put all this together in a simple example QML:

import QtQuick 2.3
import QtQuick.Window 2.0
import QtQuick.Controls 1.2

import be.codeminded.mvvm 1.0

import Example 1.0 as A

Window {
    width: 360
    height: 360
    visible: true

    ListView {
        id: listView
        anchors.fill: parent

        delegate: Item {
            height: 20
            width: listView.width
            MouseArea {
                anchors.fill: parent
                onClicked: if (modelData.canExecute) modelData.execute()
            }
            Text {
                anchors.fill: parent
                text: modelData.text
                color: modelData.canExecute ? "black" : "grey"
            }
        }

        model: comsModel.commands

        property bool combineCanExecute: false

        CommandListModel {
            id: comsModel

            ListCommand {
                text: "C++ Lambda command"
                command:  A.LambdaCommand
            }

            ListCommand {
                text: "Enable combined"
                command: EmitCommand {
                    onExecutes: { console.warn( "Hello1");
                        listView.combineCanExecute=true; }
                    canExecute: true
                }
            }

            ListCommand {
                text: "Disable combined"
                command: EmitCommand {
                    onExecutes: { console.warn( "Hello2");
                        listView.combineCanExecute=false; }
                    canExecute: true
                }
            }

            ListCommand {
                text: "Combined emit commands"
                command: CompositeCommand {
                    EmitCommand {
                        onExecutes: console.warn( "Emit command 1");
                        canExecute: listView.combineCanExecute
                    }
                    EmitCommand {
                        onExecutes: console.warn( "Emit command 2");
                        canExecute: listView.combineCanExecute
                    }
                }
            }
        }
    }
}

I made a task-bug for this on Qt, here.

0 0

18 Aug 2017 8:06pm GMT

Recently the Meson Build System gained some momentum. It is time to stop that.
Not that Meson is a bad piece of software - on the contrary, it is quite well designed.
Still it makes building C/C++ applications worse, by (quoting xkcd) basically creating this:

It sets out to create a cross-platform, more readable and faster alternative to autotools. But there is already CMake that solves this.

You might say that CMake is ugly, but note that the CMake 2.x you might have tried is not the same CMake 3.x that is available today. Many patterns have improved and are now both more logical and more readable.

Nowadays the difference between Meson and CMake is just a matter of syntactic preference. The Meson authors seem to agree here.

The actual criterion for selecting a build system however should be tooling support and community spread. CMake easily wins here:

After the introduction of the server mode it got native support by QtCreator, CLion, Android Studio (NDK) and even Microsofts Visual Studio. Native means that you do not have to generate any intermediate project files, but the CMakeLists.txt is used directly by the IDE.

On the community spread side we got e.g. KDE, OpenCV, zlib, libpng, freetype and as of recently Boost. These projects using CMake not only guarantees that you can easily use them, but that you can also include them in your build via add_subdirectory such that the become part of your project. This is especially useful if you are cross-compiling - for instance to a Raspberry Pi.

On the other hand, reinventing a wheel that is tailored to the needs of a specific community (Gnome), means that it will fall behind and eventually die. This is what is currently happening to the Vala language that had a similar birth to Meson.

The meson devs might object that Meson generates build files that run faster on a Raspberry Pi. However if your cross compiling is working you do not need that. And honestly, that particular improvement could have been also achieved by providing a patch to the CMake Ninja generator..

Addendum 15-06-2018
A new guide for CMake called CGold can be found here, which is of comparable quality to the Meson docs.

Addendum 4-1-2018
Some comments (rightfully) note that Meson has generally a better documentation and avoids some of its pitfalls. However this is mostly due to Meson not being around long enough such that the way you do things in Meson changed. Neither did it see such a widespread use like CMake yet. (think of corner-cases)

But even if you argue that this is precisely the point why you should use Meson, I would argue that improving the existing documentation in CMake and adding more educational warnings is easier then writing something from scratch.

0 0

25 Jul 2017 2:05pm GMT

Dear Maemo community, I have the great honor of introducing the new Community Council for the upcoming Q2/2017 period.

**The members of the new council are (in alphabetical order):**

• Juiceme (Jussi Ohenoja)
• Mosen (Timo Könnecke)
• Sicelo (Sicelo Mhlongo)

The voting results can be seen on the [voting page]

I want to thank warmly all the members of the community who participated in this most important action of choosing a new council for us!

The new council shall meet on the #maemo-meeting IRC channel next tuesday 18.06 at 20:00 UTC for the formal handover with the passing council.

Jussi Ohenoja, On behalf of the outgoing Maemo Community Council

0 0

11 Jul 2017 8:17pm GMT

I'm at home now. I don't do non-public unpaid work. So let's blog the example I'm making for him.

workplace.h

#ifndef Workplace_H
#define Workplace_H

#include <QObject>
#include <QFuture>
#include <QWaitCondition>
#include <QMutex>
#include <QStack>
#include <QList>
#include <QThread>
#include <QFutureWatcher>

class Workplace;

typedef enum {
    WT_INSERTS,
    WT_QUERY
} WorkplaceWorkType;

typedef struct {
    WorkplaceWorkType type;
    QList<int> values;
    QString query;
    QFutureInterface<bool> insertIface;
    QFutureInterface<QList<QStringList> > queryIface;
} WorkplaceWork;

class WorkplaceWorker: public QThread {
    Q_OBJECT
public:
    WorkplaceWorker(QObject *parent = NULL)
        : QThread(parent), m_running(false) { }
    void run() Q_DECL_OVERRIDE;
    void pushWork(WorkplaceWork *a_work);
private:
    QStack<WorkplaceWork*> m_ongoing;
    QMutex m_mutex;
    QWaitCondition m_waitCondition;
    bool m_running;
};

class Workplace: public QObject {
    Q_OBJECT
public:
    explicit Workplace(QObject *a_parent=0) : QObject (a_parent) {}
    bool insert(QList<int> a_values);
    QList<QStringList> query(const QString &a_param);
    QFuture<bool> insertAsync(QList<int> a_values);
    QFuture<QList<QStringList> > queryAsync(const QString &a_param);
private:
    WorkplaceWorker m_worker;
};

class App: public QObject {
    Q_OBJECT
public slots:
    void perform();
    void onFinished();
private:
    Workplace m_workplace;
};

#endif// Workplace_H

workplace.cpp

#include "workplace.h"

void App::onFinished()
{
    QFutureWatcher<bool> *watcher = static_cast<QFutureWatcher<bool>* > ( sender() );
    delete watcher;
}

void App::perform()
{
    for (int i=0; i<10; i++) {
       QList<int> vals;
       vals.append(1);
       vals.append(2);
       QFutureWatcher<bool> *watcher = new QFutureWatcher<bool>;
       connect (watcher, &QFutureWatcher<bool>::finished, this, &App::onFinished);
       watcher->setFuture( m_workplace.insertAsync( vals ) );
    }

    for (int i=0; i<10; i++) {
       QList<int> vals;
       vals.append(1);
       vals.append(2);
       qWarning() << m_workplace.insert( vals );
       qWarning() << m_workplace.query("test");
    }
}

void WorkplaceWorker::pushWork(WorkplaceWork *a_work)
{
    if (!m_running) {
        start();
    }

    m_mutex.lock();
    switch (a_work->type) {
    case WT_QUERY:
        m_ongoing.push_front( a_work );
    break;
    default:
        m_ongoing.push_back( a_work );
    }
    m_waitCondition.wakeAll();
    m_mutex.unlock();
}

void WorkplaceWorker::run()
{
    m_mutex.lock();
    m_running = true;
    while ( m_running ) {
        m_mutex.unlock();
        m_mutex.lock();
        if ( m_ongoing.isEmpty() ) {
            m_waitCondition.wait(&m_mutex);
        }
        WorkplaceWork *work = m_ongoing.pop();
        m_mutex.unlock();

        // Do work here and report progress
        sleep(1);

        switch (work->type) {
        case WT_QUERY: {
            // Report result here
            QList<QStringList> result;
            QStringList row;
            row.append("abc"); row.append("def");
            result.append(row);
            work->queryIface.reportFinished( &result );
            } break;

        case WT_INSERTS:
        default: {
            // Report result here
            bool result = true;
            work->insertIface.reportFinished( &result );
            } break;
        }

        m_mutex.lock();
        delete work;
    }
    m_mutex.unlock();
}

bool Workplace::insert(QList<int> a_values)
{
    WorkplaceWork *work = new WorkplaceWork;;
    QFutureWatcher<bool> watcher;
    work->type = WT_INSERTS;
    work->values = a_values;
    work->insertIface.reportStarted();
    watcher.setFuture ( work->insertIface.future() );
    m_worker.pushWork( work );
    watcher.waitForFinished();
    return watcher.result();
}

QList<QStringList> Workplace::query(const QString &a_param)
{
    WorkplaceWork *work = new WorkplaceWork;
    QFutureWatcher<QList<QStringList> > watcher;
    work->type = WT_QUERY;
    work->query = a_param;
    work->queryIface.reportStarted();
    watcher.setFuture ( work->queryIface.future() );
    m_worker.pushWork( work );
    watcher.waitForFinished();
    return watcher.result();
}

QFuture<bool> Workplace::insertAsync(QList<int> a_values)
{
    WorkplaceWork *work = new WorkplaceWork;
    work->type = WT_INSERTS;
    work->values = a_values;
    work->insertIface.reportStarted();
    QFuture<bool> future = work->insertIface.future();
    m_worker.pushWork( work );
    return future;
}

QFuture<QList<QStringList> > Workplace::queryAsync(const QString &a_param)
{
    WorkplaceWork *work = new WorkplaceWork;
    work->type = WT_QUERY;
    work->query = a_param;
    work->queryIface.reportStarted();
    QFuture<QList<QStringList> > future = work->queryIface.future();
    m_worker.pushWork( work );
    return future;
}

0 0

06 Jul 2017 7:49pm GMT

Imagine we want an editor that has undo and redo capability. But the operations on the editor are all asynchronous. This implies that also undo and redo are asynchronous operations.

We want all this to be available in QML, we want to use QFuture for the asynchronous stuff and we want to use QUndoCommand for the undo and redo capability.

But how do they do it?

First of all we will make a status object, to put the status of the asynchronous operations in (asyncundoable.h).

class AbstractAsyncStatus: public QObject
{
    Q_OBJECT

    Q_PROPERTY(bool success READ success CONSTANT)
    Q_PROPERTY(int extra READ extra CONSTANT)
public:
    AbstractAsyncStatus(QObject *parent):QObject (parent) {}
    virtual bool success() = 0;
    virtual int extra() = 0;
};

We will be passing it around as a QSharedPointer, so that lifetime management becomes easy. But typing that out is going to give us long APIs. So let's make a typedef for that (asyncundoable.h).

typedef QSharedPointer<AbstractAsyncStatus> AsyncStatusPointer;

Now let's make ourselves an undo command that allows us to wait for asynchronous undo and asynchronous redo. We're combining QUndoCommand and QFutureInterface here (asyncundoable.h).

class AbstractAsyncUndoable: public QUndoCommand
{
public:
    AbstractAsyncUndoable( QUndoCommand *parent = nullptr )
        : QUndoCommand ( parent )
        , m_undoFuture ( new QFutureInterface<AsyncStatusPointer>() )
        , m_redoFuture ( new QFutureInterface<AsyncStatusPointer>() ) {}
    QFuture<AsyncStatusPointer> undoFuture()
        { return m_undoFuture->future(); }
    QFuture<AsyncStatusPointer> redoFuture()
        { return m_redoFuture->future(); }

protected:
    QScopedPointer<QFutureInterface<AsyncStatusPointer> > m_undoFuture;
    QScopedPointer<QFutureInterface<AsyncStatusPointer> > m_redoFuture;

};

Okay, let's implement these with an example operation. First the concrete status object (asyncexample1command.h).

class AsyncExample1Status: public AbstractAsyncStatus
{
    Q_OBJECT
    Q_PROPERTY(bool example1 READ example1 CONSTANT)
public:
    AsyncExample1Status ( bool success, int extra, bool example1,
                          QObject *parent = nullptr )
        : AbstractAsyncStatus(parent)
        , m_example1 ( example1 )
        , m_success ( success )
        , m_extra ( extra ) {}
    bool example1() { return m_example1; }
    bool success() Q_DECL_OVERRIDE { return m_success; }
    int extra() Q_DECL_OVERRIDE { return m_extra; }
private:
    bool m_example1 = false;
    bool m_success = false;
    int m_extra = -1;
};

Let's make a QUndoCommand that uses a timer to simulate asynchronous behavior. We could also use QtConcurrent's run function to use a QThreadPool and QRunnable instances that also implement QFutureInterface, of course. Seasoned Qt developers know what I mean. For the sake of example, I wanted to illustrate that QFuture can also be used for asynchronous things that aren't threads. We'll use the lambda because QUndoCommand isn't a QObject, so no easy slots. That's the only reason (asyncexample1command.h).

class AsyncExample1Command: public AbstractAsyncUndoable
{
public:
    AsyncExample1Command(bool example1, QUndoCommand *parent = nullptr)
        : AbstractAsyncUndoable ( parent ), m_example1(example1) {}
    void undo() Q_DECL_OVERRIDE {
        m_undoFuture->reportStarted();
        QTimer *timer = new QTimer();
        timer->setSingleShot(true);
        QObject::connect(timer, &QTimer::timeout, [=]() {
            QSharedPointer<AbstractAsyncStatus> result;
            result.reset(new AsyncExample1Status ( true, 1, m_example1 ));
            m_undoFuture->reportFinished(&result);
            timer->deleteLater();
        } );
        timer->start(1000);
    }
    void redo() Q_DECL_OVERRIDE {
        m_redoFuture->reportStarted();
        QTimer *timer = new QTimer();
        timer->setSingleShot(true);
        QObject::connect(timer, &QTimer::timeout, [=]() {
            QSharedPointer<AbstractAsyncStatus> result;
            result.reset(new AsyncExample1Status ( true, 2, m_example1 ));
            m_redoFuture->reportFinished(&result);
            timer->deleteLater();
        } );
        timer->start(1000);
    }
private:
    QTimer m_timer;
    bool m_example1;
};

Let's now define something we get from the strategy design pattern; a editor behavior. Implementations provide an editor all its editing behaviors (abtracteditorbehavior.h).

class AbstractEditorBehavior : public QObject
{
    Q_OBJECT
public:
    AbstractEditorBehavior( QObject *parent) : QObject (parent) {}

    virtual QFuture<AsyncStatusPointer> performExample1( bool example1 ) = 0;
    virtual QFuture<AsyncStatusPointer> performUndo() = 0;
    virtual QFuture<AsyncStatusPointer> performRedo() = 0;
    virtual bool canRedo() = 0;
    virtual bool canUndo() = 0;
};

So far so good, so let's make an implementation that has a QUndoStack and that therefor is undoable (undoableeditorbehavior.h).

class UndoableEditorBehavior: public AbstractEditorBehavior
{
public:
    UndoableEditorBehavior(QObject *parent = nullptr)
        : AbstractEditorBehavior (parent)
        , m_undoStack ( new QUndoStack ){}

    QFuture<AsyncStatusPointer> performExample1( bool example1 ) Q_DECL_OVERRIDE {
        AsyncExample1Command *command = new AsyncExample1Command ( example1 );
        m_undoStack->push(command);
        return command->redoFuture();
    }
    QFuture<AsyncStatusPointer> performUndo() {
        const AbstractAsyncUndoable *undoable =
            dynamic_cast<const AbstractAsyncUndoable *>(
                    m_undoStack->command( m_undoStack->index() - 1));
        m_undoStack->undo();
        return const_cast<AbstractAsyncUndoable*>(undoable)->undoFuture();
    }
    QFuture<AsyncStatusPointer> performRedo() {
        const AbstractAsyncUndoable *undoable =
            dynamic_cast<const AbstractAsyncUndoable *>(
                    m_undoStack->command( m_undoStack->index() ));
        m_undoStack->redo();
        return const_cast<AbstractAsyncUndoable*>(undoable)->redoFuture();
    }
    bool canRedo() Q_DECL_OVERRIDE { return m_undoStack->canRedo(); }
    bool canUndo() Q_DECL_OVERRIDE { return m_undoStack->canUndo(); }
private:
    QScopedPointer<QUndoStack> m_undoStack;
};

Now we only need an editor, right (editor.h)?

class Editor: public QObject
{
    Q_OBJECT
    Q_PROPERTY(AbstractEditorBehavior* editorBehavior READ editorBehavior CONSTANT)
public:
    Editor(QObject *parent=nullptr) : QObject(parent)
        , m_editorBehavior ( new UndoableEditorBehavior ) { }
    AbstractEditorBehavior* editorBehavior() { return m_editorBehavior.data(); }
    Q_INVOKABLE void example1Async(bool example1) {
        QFutureWatcher<AsyncStatusPointer> *watcher = new QFutureWatcher<AsyncStatusPointer>(this);
        connect(watcher, &QFutureWatcher<AsyncStatusPointer>::finished,
                this, &Editor::onExample1Finished);
        watcher->setFuture ( m_editorBehavior->performExample1(example1) );
    }
    Q_INVOKABLE void undoAsync() {
        if (m_editorBehavior->canUndo()) {
            QFutureWatcher<AsyncStatusPointer> *watcher = new QFutureWatcher<AsyncStatusPointer>(this);
            connect(watcher, &QFutureWatcher<AsyncStatusPointer>::finished,
                    this, &Editor::onUndoFinished);
            watcher->setFuture ( m_editorBehavior->performUndo() );
        }
    }
    Q_INVOKABLE void redoAsync() {
        if (m_editorBehavior->canRedo()) {
            QFutureWatcher<AsyncStatusPointer> *watcher = new QFutureWatcher<AsyncStatusPointer>(this);
            connect(watcher, &QFutureWatcher<AsyncStatusPointer>::finished,
                    this, &Editor::onRedoFinished);
            watcher->setFuture ( m_editorBehavior->performRedo() );
        }
    }
signals:
    void example1Finished( AsyncExample1Status *status );
    void undoFinished( AbstractAsyncStatus *status );
    void redoFinished( AbstractAsyncStatus *status );
private slots:
    void onExample1Finished() {
        QFutureWatcher<AsyncStatusPointer> *watcher =
                dynamic_cast<QFutureWatcher<AsyncStatusPointer>*> (sender());
        emit example1Finished( watcher->result().objectCast<AsyncExample1Status>().data() );
        watcher->deleteLater();
    }
    void onUndoFinished() {
        QFutureWatcher<AsyncStatusPointer> *watcher =
                dynamic_cast<QFutureWatcher<AsyncStatusPointer>*> (sender());
        emit undoFinished( watcher->result().objectCast<AbstractAsyncStatus>().data() );
        watcher->deleteLater();
    }
    void onRedoFinished() {
        QFutureWatcher<AsyncStatusPointer> *watcher =
                dynamic_cast<QFutureWatcher<AsyncStatusPointer>*> (sender());
        emit redoFinished( watcher->result().objectCast<AbstractAsyncStatus>().data() );
        watcher->deleteLater();
    }
private:
    QScopedPointer<AbstractEditorBehavior> m_editorBehavior;
};

Okay, let's register this up to make it known in QML and make ourselves a main function (main.cpp).

#include <QtQml>
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <editor.h>
int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);
    QQmlApplicationEngine engine;
    qmlRegisterType<Editor>("be.codeminded.asyncundo", 1, 0, "Editor");
    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    return app.exec();
}

Now, let's make ourselves a simple QML UI to use this with (main.qml).

import QtQuick 2.3
import QtQuick.Window 2.2
import QtQuick.Controls 1.2
import be.codeminded.asyncundo 1.0
Window {
    visible: true
    width: 360
    height: 360
    Editor {
        id: editor
        onUndoFinished: text.text = "undo"
        onRedoFinished: text.text = "redo"
        onExample1Finished: text.text = "whoohoo " + status.example1
    }
    Text {
        id: text
        text: qsTr("Hello World")
        anchors.centerIn: parent
    }
    Action {
        shortcut: "Ctrl+z"
        onTriggered: editor.undoAsync()
    }
    Action {
        shortcut: "Ctrl+y"
        onTriggered: editor.redoAsync()
    }
    Button  {
        onClicked: editor.example1Async(99);
    }
}

You can find the sources of this complete example at github. Enjoy!

0 0

11 May 2017 8:09pm GMT