Hello everyone, it's been all-too-long!
I am proud to announce the end of the semester! Exams are finally all done, but that only means the real fun can start. And so many things to come and do!

Behaim Globe with Kirigami

Kirigami is a QtQuick based components set that brings a lot of useful reusable components to QtQuick UI's. Among these we're easy to create menus, unit based scaling, drawers and all sorts of navigation options. It was a lot of fun exploring all these pieces we could fit together to create a user-friendly interface. As a way of getting to know Kirigami, I was tasked with giving the Behaim Globe app a small redesign using these components.
The info bar now comes in an overlay form (with a small black tint), which makes it clear that it's the focus point (and doesn't compete for space with the globe), and should be closed for easier navigation on the globe. It is also now flickable, which allows the user to easily close it, even with one hand, without having to find the exact button. The button to open the menu previously moved from the top left to the bottom right depending on the orientation of the screen, is now fixed at the top left to avoid confusion.

The Behaim Globe app.

The redesigned app.

Kirigami has a lot of interesting solutions and components, one of these being the OverlayDrawer, which I used to replace the old bottom menu. Below I have highlighted some other features that Kirigami offers, that may prove to be very useful.

Button styles, notifications, and menu variations, such as the OverlayDrawer.

Progression markers, and swipe-revealed secondary actions. Also note the central "Main Action" button, as another great way of guiding the user to the main purpose of the page.

Side menu, with checkable items, submenus; context-based actions that are relevant to the current page.

Kirigami provides several menu solutions, such as context-based actions, which the Kirigami Gallery app showcases better than the few examples I have provided ever could.

Once upon a time, I started an internship program. On that program, I needed to program in Python and also write tests. Based on my short experience with Python, I already hated to write tests. I didn't have enough abstraction to learn to write useful tests. After a really long and painful process of learning, I [...]

The Declaration-Use Chain

The Rust Compiler

Building the DU Chain for Rust code

 

Going forward

Hi everyone, how is it going? Fine, I hope.

Today, I will talk about my work on Krita during the week 3-4 of the coding period.

Overview

I implemented two new plugins, canvas size plugin and filter manager (applier) plugin. The first is a plugin to change image size (not scale) and to adjust the top and left edge to selected documents also. The second is a filter applier to the document or nodes, then you can select a node or the document and apply a filter to them.

Canvas Size Plugin

GUI Mockup

I drew a simple mockup to define some direction for my implementation. As you can see, it's something close to the current implementation, but without a canvas preview, we have a list of the opened documents, though.

C++ and SIP implementation

I have to provide offset properties (xOffset, yOffset) to document API and a updating to the resizeImage method to include the new parameters. I implemented these properties and your respective SIP signatures. I also wrote documentation to each method implemented in .h files. Click here to take a look.

GUI implementation with PyQt

At the end, I implemented the GUI and all your interactions and validations. How you can see below, we have a confirm button that resizes the image to selected documents.

Testing

Below, you can see the plugin working.

Before	After

Filter Manager Plugin

GUI Mockup

I didn't draw a GUI mockup, but the main idea here is to have a tree showing documents and your nodes and a list of the application's filters.

C++ and SIP implementation

I don't changed the C++ code, I fixed some bugs in the API, though.

GUI implementation with PyQt

You can see below the final result of my work. The tree was implemented using Model-View pattern. You can apply filters from the list to specific node or to all document (all top level nodes).

Testing

Below, you can see the image before and after the application of the "desaturate" filter.

Before	After

What will I do in the next week?

• Simple scripts of the previous plugins
• Plugin to take a list of images (inputted list) and apply rotate/scale
• Script to export all the layers (batch)
• Script to Duplicate image
• Script to Export to jpg X% quality.

That’s it for now, until the next week. See ya!!

There’s quite a lot of software that uses CMake as a (meta-)buildsystem. A quick count in the FreeBSD ports tree shows me 1110 ports (over a thousand) that use it. CMake generates buildsystem files which then direct the actual build — it doesn’t do building itself.

There are multiple buildsystem-backends available: in regular usage, CMake generates Makefiles (and does a reasonable job of producing Makefiles that work for GNU Make and for BSD Make). But it can generate Ninja, or Visual Studio, and other buildsystem files. It’s quite flexible in this regard.

Recently, the KDE-FreeBSD team has been working on Qt WebEngine, which is horrible. It contains a complete Chromium and who knows what else. Rebuilding it takes forever.

But Tobias (KDE-FreeBSD) and Koos (GNOME-FreeBSD) noticed that building things with the Ninja backend was considerably faster for some packages (e.g. Qt WebEngine, and Evolution data-thingy). Tobias wanted to try to extend the build-time improvements to all of the CMake-based ports in FreeBSD, and over the past few days, this has been a succes.

Ports builds using CMake now default to using Ninja as buildsystem-backend.

Here’s a bitty table of build-times. These are one-off build times, so hardly scientifically accurate — but suggestive of a slight improvement in build time.

Or here’s a much more thorough table of results from tcberner@, who did 5 builds of each with and without ninja. I’ve cut out the raw data, here are just the average-of-five results, showing usually a slight improvement in build time with Ninja.

Not everything builds properly with Ninja. This is usually due to missing dependencies that CMake does not discover; this shows up when foo depends on bar but no rule is generated for it. Depending on build order and speed, bar may be there already by the time foo gets around to being built. Doxygen showed this, where builds on 1 CPU core were all fine, but 8 cores would blow up occasionally.

In many cases, we’ve gone and fixed the missing implicit dependencies in ports and upstreams. But some things are intractable, or just really need GNU Make. For this, the FreeBSD ports infrastructure now has a knob attached to CMake for switching a port build to GNU Make.

• Normal: USES=cmake
• Out-of-source: USES=cmake:outsource
• GNU Make: USES=cmake:noninja gmake
• OoS, GMake: USES=cmake:outsource,noninja gmake
• Bad: USES=cmake gmake

For the majority of users, this has no effect, but for our package-building clusters, and for KDE-FreeBSD developers who build a lot of CMake-buildsystem software in a day it may add up to an extra coffee break. So I’ll raise a shot of espresso to friendship between daemons and ninjas.

(Image credits: Beastie by Marshall Kirk McKusick on FreeBSD.org, Ninja by irkeninvaderkit on deviantart)

Heading towards the first evaluation:

Even the exams and graduation project work this month, heading towards the first evaluation according to timeline with the planned UI ready for further development and started the search with examining a similar tool in gimp, and had more insights about the details of how the “Image Editor” works on a deeper level and how I should work to get to my next milestone of static parts cloning supporting the variable radius within the next 11 days.

For the last month the main time I took the exams, because of this I did not do much for my project. Nevertheless, I implemented the basic primitives and tested them.

Let me tell you about them.

Wet map.

Water is the main part in watercolors. That’s why I started with this.

Wet map contains 2 types of information: water value and speed vector. If the first parameter is clear, then the second one needs explanations. Speed vector needs for rewetting our splats (take it in mind, I will explain what this later).

All this values Wet map contains in KisPaintDevice:

KisPaintDeviceSP m_wetMap;

As the color space was chosen rgb16:

m_wetMap = new KisPaintDevice(KoColorSpaceRegistry::instance()->rgb16());

And there are information about water value and speed vector in pixel data.

But in this form Paint Device can’t visualize wet map correctly:

So I transorm Paint Device for visualizing wet map correctly (because it will be important for artists, I think). And now it looks like this:

Splat

My implementation is based on a procedural brush. Every brush stamp is a union of dynamic splats. Here you can see the behavior of splats:

Also I tested reweting (when splat go to flowing state from fixed state):

And as a final test I made splat generator for simulating strokes:

What next?

It’s high time to get splats to work in Krita. So I’m going to finish my plugin, and test splats behavior. But it will be primitive:

1. Clear canvas for updating splats
2. No undo/redo
3. Stupid singleton for splat storage

I was able to do major improvements to the build system of KStars. I think more and more open-source projects should pick up these low-hanging fruits with CMake and Clang:

- CCache: Speed-up the development time and working with git branches by caching the compiled object files.
- Unity Build: This simple "hack" can reduce the build time dramatically by compiling temporary C++ meta files in which the normal C++ files are included. The build time can be speeded up to 2x-3x for bigger projects.
- Clang Sanitizers: Use undefined behavior and address sanitizers to hunt down memory handling errors. Although the executable must be recompiled with Clang and special compiler flags, the resulted binary will run with minimal slowdown. It is not a complete replacement, but these sanitizers can catch most of the problems found by Valgrind during normal runtime.
- Clang Format: Format the source code with a real compiler engine.

Before writing about my actual Summer of Code experiences, I wanted to briefly share what I worked on before the official coding start.

Plasma toolicons

Can you see these ridiculously small toolicons next to the Media frame plasmoid? I’m talking about the icons which allow you to Resize, Rotate and Remove the Plasmoid. Compared with other icons, these are clearly too small.

So, as preparation for GSoC, I wanted to know why this happens, and what would be required to make them bigger. Thus my journey into the (Plasma) rabbithole began…

Tracking down where the containment is defined was relatively easy, and shortly after i found the code responsible for the ActionButton:

PlasmaCore.ToolTipArea {
    id: button

    location: PlasmaCore.Types.LeftEdge
    mainText: action !== undefined ? action.text : ""
    mainItem: toolTipDelegate

    //API
    property QtObject svg
    property alias elementId: icon.elementId
    property QtObject action
    property bool backgroundVisible: false
    property int iconSize: 32
[...]

Huh, the iconSize is 32px? Well, that was easy to fix, surely this should be set to units.iconSizes.small and this problem is gone…

… or so I thought. No, this didn’t improve the situation, back to square one.

Is it overwritten by the look and feel theme? plasma-workspace/lookandfeel/contents/components/ActionButton.qml at least doesn’t - and it also happens with the style set to Oxygen.

While looking at this, I also noticed that units.iconSizes.small returned 16px on my system. This seemed odd, because the scale factor was set to 1.8x, so I would have expected bigger icons.

Where is this icon size calculated? Ah yes, in the file units.cpp, method Units::devicePixelIconSize.

int Units::devicePixelIconSize(const int size) const
{
    /* in kiconloader.h
    enum StdSizes {
        SizeSmall=16,
        SizeSmallMedium=22,
        SizeMedium=32,
[...]
     };
    */
    // Scale the icon sizes up using the devicePixelRatio
    // This function returns the next stepping icon size
    // and multiplies the global settings with the dpi ratio.
    const qreal ratio = devicePixelRatio();

    if (ratio < 1.5) {
        return size;
     } else if (ratio < 2.0) {
         return size * 1.5;
     } else if (ratio < 2.5) {
[...]
}

Ok, my devicePixelRatio is 1.8 and therefore the icon size of a small pixmap gets multiplied by 1.5 and a request for a small (16px) pixmap should return a 24px pixmap.

But it doesn’t…

Debugging suggested that my devicePixelRatio is NOT 1.8, but rather around 1.4. How did that happen, isn’t the scale factor from the KDE settings used?

Oh, the comment in updateDevicePixelRatio() mentions that QGuiApplication::devicePixelRatio() is really not used:

void Units::updateDevicePixelRatio()
{
    // Using QGuiApplication::devicePixelRatio() gives too coarse values,
    // i.e. it directly jumps from 1.0 to 2.0. We want tighter control on
    // sizing, so we compute the exact ratio and use that.
    // TODO: make it possible to adapt to the dpi for the current screen dpi
    //  instead of assuming that all of them use the same dpi which applies for
    //  X11 but not for other systems.
    QScreen *primary = QGuiApplication::primaryScreen();
    if (!primary) {
       return;
    }
    const qreal dpi = primary->logicalDotsPerInchX();
    // Usual "default" is 96 dpi
    // that magic ratio follows the definition of "device independent pixel" by Microsoft
    m_devicePixelRatio = (qreal)dpi / (qreal)96;

Hmm, yes, that was the case in earlier Qt versions when devicePixelRatio still returned an integer - but nowadays the value is a real number.

So, instead of calculating dpi / 96 I just changed it to return primary->devicePixelRatio().

Which now, finally, should return a devicePixelRatio of 1.8 and therefore result in bigger pixmaps.

Compiled it, and confident of victory restarted plasmashell… only to notice, that it still didn’t work.

What could there still go wrong?

So I got back to debugging.. to notice that primary->devicePixelRatio() returns a scale factor of 1.0. Huh? Isn’t this supposed to just use the QT_SCREEN_SCALE_FACTORS environment variable, which gets set to the value of the “Scale Display” dialog in the Systemsettings? If you want to know, the code for setting the environment variable is located in plasma-workspace/startkde/startplasmacompositor.cmake.

But why isn’t the problem gone, is there something in Plasma that overwrites this value?

Yes, of course there is!

The only way this value can be overwritten is due to the Qt attribute Qt::AA_DisableHighDpiScaling.

Grep’ing for that one pointed me to plasma-workspace/shell/main.cpp - the base file for plasmashell:

int main(int argc, char *argv[])
{
//    Devive pixel ratio has some problems in plasmashell currently.
//     - dialog continually expands (347951)
//     - Text element text is screwed (QTBUG-42606)
//     - Panel struts (350614)
//  This variable should possibly be removed when all are fixed

   qunsetenv("QT_DEVICE_PIXEL_RATIO");
   QCoreApplication::setAttribute(Qt::AA_DisableHighDpiScaling);

I looked into the mentioned bugs. What should I do now? Re-enabling the HighDpiScaling-flag so the real devicePixelRatio is returned in Qt, and therefore I can use this value to calculate the sizes icons should be and then have the bigger Plasma ToolIcons? At least QTBUG-42606 seems to be fixed…

Oh boy, what have I gotten into now…

It was time to talk to my mentor!

David Edmundson quickly noticed that there should be no mismatch with the dpi / 96 calculation. Something fishy seems to be going on here…

What is this dpi value anyway? This is the one reported by xrdb -query |grep Xft.dpi and managed in the file $HOME/.config/kcmfonts.

And that value - as you probably can guess by now - did not make any sense. It didn’t match the expectation of being scaleFactor * 96, the value it should have been set to.

On we go to the location where the scaling configuration is set - scalingconfig.cpp in the KScreen KConfig Module.

void ScalingConfig::accept()
{
[...]
   fontConfigGroup.writeEntry("forceFontDPI", scaleDPI());
[...]
}

qreal ScalingConfig::scaleDPI() const
{
    return scaleFactor() * 96.0;
}

This scaleDPI is then applied with xrdb -quiet -merge -nocpp on startup.

So Xft.dpi is set to 1.8 * 96.0, or 172.8.

Have you spotted what is going wrong?

I did not, but David noticed…

The X server can only handle real values - and therefore 172.8 is simlpy discarded!

A few moments later this patch was ready…

… and I was finally able to enjoy my icons in all their scaled glory! And you can too, because this patch is already in Plasma 5.10.

Week 2 of GSoC’s coding period was pretty dope :D. After all the hard work from the last week, I got my downloader to pull data from the website share.krita.org. As from the Week #1’s work status update, we have all discussed what all classes and functions were required to get this running. I was able to get it done and the downloader started downloading the data from the website.

PS: To get my project up and running we need KNewStuff framework version to be 5.29+. KNS team has done a lot of work in the area creating things to move pretty much good. (They have isolated KNSCore and KNS3 from then).

Before I proceed, I would love to mention the immense support and help given to me by Leinir for understanding how KNS and KNSCore works. If he didn’t notice my blog post which I posted at the starting of my project and official coding period, I would be lost at every single point of my project :P. As well as my Krita community people

As we had discussed the different classes I have created for the project to proceed, we have used certain KDE primary level framework/APIs in order to complete the GUI and get things working as planned.

Some of them, I have listed below.

• Kconfig

The KConfig framework offers functionality around reading and writing configuration. KConfig consists of two parts, KConfigCore and KConfigGui. KConfigCore offers an abstract API to configuration files. It allows grouping and transparent cascading and (de-)serialization. KConfigGui offers, on top of KConfigCore, shortcuts, and configuration for some common cases, such as session and window restoration.

• KWidgetsAddons

KWidgetAddons contains higher-level user interface elements for common tasks. KWidgetAddons contains widgets for the following areas:

• Keyboard accelerators
• Action menus and selections
• Capacity indicator
• Character selection
• Color selection
• Drag decorators
• Fonts
• Message boxes
• Passwords
• Paging of e.g. wizards
• Popups and other dialogs
• Rating
• Ruler
• Separators
• Squeezed labels
• Titles
• URL line edits with drag and drop
• View state serialization

• KRatingWidget

This class is a part of KWidgetAddons class. It displays a rating value as a row of pixmaps. The KRatingWidget displays a range of stars or other arbitrary pixmaps and allows the user to select a certain number by mouse.

Hence, till now I have implemented order by functionality to sort data items accordingly. Have included functionalities to sort according to categories. While the categories get populated according to the knsrc file. We have options to rate each item on star basis according to the likes of the user. We also have the option to see the expanded details of each item. Revised a methodology to view items in a different mode such as icon mode and list mode. Also, Function to search between the items is also working just fine.

To see all the changes and test it visually, Created a test UI and shows how things work out and pull in data from the site. I will attach it here:

Content downloader with the basic test UI, which does look like the existing KNewStuff. Next step is to change it to our own customizable UI.

Plans for Week #3

Start creating the UI for the resource downloader which will be customizable hereafter. We just need to tweak the existing UI to our need.

Here is what we actually need.

After that, This week is being followed by the first Evaluation of our work so I have mostly done my part well. Completed the tasks as required in time. So, after evaluation for the first phase gets over, I will be doing the following.

1. Give the work done till now a test run with the new and revised GUI for the content downloader.
2. Fix any bugs if there exists or noticed at the testing phase in the content downloader and fix some of the bugs which might exist in the Resource Manager after discussing it with the Krita community.
3. Meanwhile, these are going through, will be documenting the functions and classes created and changed.

Here is my branch were all the work I am done is going to.

https://cgit.kde.org/krita.git/?h=Aniketh%2FT6108-Integrate-with-share.krita.org

Will be back with more updates later next week.

Cheers.

In this week’s article for my ongoing Google Summer of Code (GSoC) project I planned on writing about the basic idea behind the project, but I reconsidered and decided to first give an overview on how Xwayland functions on a high-level and in the next week take a look at its inner workings in detail. The reason for that is, that there is not much Xwayland documentation available right now. So these two articles are meant to fill this void in order to give interested beginners a helping hand. And in two weeks I’ll catch up on explaining the project’s idea.

As we go high level this week the first question is, what is Xwayland supposed to achieve at all? You may know this. It’s something in a Wayland session ensuring that applications, which don’t support Wayland but only the old Xserver still function normally, i.e. it ensures backwards compatibility. But how does it do this? Before we go into this, there is one more thing to talk about, since I called Xwayland only something before. What is Xwayland exactly? How does it look to you on your Linux system? We’ll see in the next week that it’s not as easy to answer as the following simple explanation makes it appear, but for now this is enough: It’s a single binary containing an Xserver with a special backend written to communicate with the Wayland compositor active on your system - for example with KWin in a Plasma Wayland session.

To make it more tangible let’s take a look at Debian: There is a package called Xwayland and it consists of basically only the aforementioned binary file. This binary gets copied to /usr/bin/Xwayland. Compare this to the normal Xserver provided by X.org, which in Debian you can find in the package xserver-xorg-core. The respective binary gets put into /usr/bin/Xorg together with a symlink /usr/bin/X pointing to it.

While the latter is the central building block in an X session and therefore gets launched before anything else with graphical output, the Xserver in the Xwayland binary works differently: It is embedded in a Wayland session. And in a Wayland session the Wayland compositor is the central building block. This means in particular that the Wayland compositor also takes up the role of being the server, who talks to Wayland native applications with graphical output as its clients. They send request to it in order to present their painted stuff on the screen. The Xserver in the Xwayland binary is only a necessary link between applications, which are only able to speak to an Xserver, and the Wayland compositor/server. Therefore the Xwayland binary gets launched later on by the compositor or some other process in the workspace. In Plasma it’s launched by KWin after the compositor has initialized the rendering pipeline. You find the relevant code here.

Although in this case KWin also establishes some communication channels with the newly created Xwayland process, in general the communication between Xwayland and a Wayland server is done by the normal Wayland protocoll in the same way other native Wayland applications talk to the compositor/server. This means the windows requested by possibly several X based applications and provided by Xwayland acting as an Xserver are translated at the same time by Xwayland to Wayland compatible objects and, acting as a native Wayland client, send to the Wayland compositor via the Wayland protocol. These windows look to the Wayland compositor just like the windows - in Wayland terminology surfaces - of every other Wayland native application. When reading this keep in mind, that an application in Wayland is not limited to using only one window/surface but can create multiple at the same time, so Xwayland as a native Wayland client can do the same for all the windows created for all of its X clients.

In the second part next week we’ll have a close look at the Xwayland code to see how Xwayland fills its role as an Xserver in regards to its X based clients and at the same time acts as a Wayland client when facing the Wayland compositor.

ISO Image Writer is a tool I’m working on which writes .iso files onto a USB disk ready for installing your lovely new operating system.  Surprisingly many distros don’t have very slick recommendations for how to do this but they’re all welcome to try this.

It’s based on ROSA Image Writer which has served KDE neon and other projects well for some time.  This adds ISO verification to automatically check the digital signatures or checksums, currently supported is KDE neon, Kubuntu and Netrunner.  It also uses KAuth so it doesn’t run the UI as root, only a simple helper binary to do the writing.  And it uses KDE Frameworks goodness so the UI feels nice.

First alpha 0.1 is out now.

Download from https://download.kde.org/unstable/isoimagewriter/

Signed by release manager Jonathan Riddell with 0xEC94D18F7F05997E. Git tags are also signed by the same key.

It’s in KDE Git at kde:isoimagewriter and in bugs.kde.org, please do try it out and report any issues.  If you’d like a distro added to the verification please let me know and/or submit a patch. (The code to do with is a bit verbose currently, it needs tidied up.)

I’d like to work out how to make AppImages, Windows and Mac installs for this but for now it’s in KDE neon developer editions and available as source.

by

In this post, I am going to discuss about the working of a submarine and my thought process on implementing the three basic features of a submarine in the “Pilot a Submarine” activity for the Qt version of GCompris, which are:

• The Engine
• The Ballast tanks and
• The Diving Planes

The Engine

The engine of most submarines are either nuclear powered or diesel-electric engines, which are used to drive an electric motor which in turn, powers the submarine propellers. In this implementation, we will have two buttons one for increasing and another for decreasing the power generated by the submarine.

Ballast Tanks

The Ballast Tanks are the spaces in the submarine that can either be filled with water or air. It helps the submarine to dive and resurface on the water, using the concept of buouyancy. If the tanks are filled with water, the submarine dives underwater and if they are filled with air, it resurfaces on the surface of the water

Diving Planes

Once underwater, the diving planes of a submarine helps to accurately control the depth of the submarine. These are very similar to the fins present in the bodies of sharks, which helps them to swim and dive. When the planes are pointed downwards, the water flowing above the planes generate more pressure on the top surface than that on the bottom surface, forcing the submarine to dive deeper. This allows the driver to control the depth and the angle of the submarine.

Implementation

In this section I will be going through how I implemented the submarine using QML. For handling physics, I used Box2D.

The Submarine

The submarine is an QML Item element, designed as follows:

Item {
    id: submarine

    z: 1

    property point initialPosition: Qt.point(0,0)
    property bool isHit: false
    property int terminalVelocityIndex: 100
    property int resetVerticalSpeed: 500

    /* Maximum depth the submarine can dive when ballast tank is full */
    property real maximumDepthOnFullTanks: (background.height * 0.6) / 2

    /* Engine properties */
    property point velocity
    property int maximumXVelocity: 5

    /* Wings property */
    property int wingsAngle
    property int initialWingsAngle: 0
    property int maxWingsAngle: 2
    property int minWingsAngle: -2

    function destroySubmarine() {
        isHit = true
        submarineImage.broken()
    }

    function resetSubmarine() {
        isHit = false
        submarineImage.reset()

        leftBallastTank.resetBallastTanks()
        rightBallastTank.resetBallastTanks()
        centralBallastTank.resetBallastTanks()

        x = initialPosition.x
        y = initialPosition.y

        velocity = Qt.point(0,0)
        wingsAngle = initialWingsAngle
    }

	function increaseHorizontalVelocity(amt) {
        if (submarine.velocity.x + amt <= submarine.maximumXVelocity) {
            submarine.velocity.x += amt
        }
    }

    function decreaseHorizontalVelocity(amt) {
        if (submarine.velocity.x - amt >= 0) {
            submarine.velocity.x -= amt
        }
    }

    function increaseWingsAngle(amt) {
        if (wingsAngle + amt <= maxWingsAngle) {
            wingsAngle += amt
        } else {
            wingsAngle = maxWingsAngle
        }
    }

    function decreaseWingsAngle(amt) {
        if (wingsAngle - amt >= minWingsAngle) {
            wingsAngle -= amt
        } else {
            wingsAngle = minWingsAngle
        }
    }

    function changeVerticalVelocity() {
        /*
         * Movement due to planes
         * Movement is affected only when the submarine is moving forward
         * When the submarine is on the surface, the planes cannot be used
         */
        if (submarineImage.y > 0) {
            submarine.velocity.y = (submarine.velocity.x) > 0 ? wingsAngle : 0
        } else {
            submarine.velocity.y = 0
        }
        /* Movement due to Ballast tanks */
        if (wingsAngle == 0 || submarine.velocity.x == 0) {
            var yPosition = submarineImage.currentWaterLevel / submarineImage.totalWaterLevel * submarine.maximumDepthOnFullTanks

            speed.duration = submarine.terminalVelocityIndex * Math.abs(submarineImage.y - yPosition) // terminal velocity
            submarineImage.y = yPosition
        }
    }

    BallastTank {
        id: leftBallastTank

        initialWaterLevel: 0
        maxWaterLevel: 500
    }

    BallastTank {
        id: rightBallastTank

        initialWaterLevel: 0
        maxWaterLevel: 500
    }

    BallastTank {
        id: centralBallastTank

        initialWaterLevel: 0
        maxWaterLevel: 500
    }

    Image {
        id: submarineImage
        source: url + "submarine.png"

        property int currentWaterLevel: bar.level < 7 ? centralBallastTank.waterLevel : leftBallastTank.waterLevel + centralBallastTank.waterLevel + rightBallastTank.waterLevel
        property int totalWaterLevel: bar.level < 7 ? centralBallastTank.maxWaterLevel : leftBallastTank.maxWaterLevel + centralBallastTank.maxWaterLevel + rightBallastTank.maxWaterLevel

        width: background.width / 9
        height: background.height / 9

        function broken() {
            source = url + "submarine-broken.png"
        }

        function reset() {
            source = url + "submarine.png"
            speed.duration = submarine.resetVerticalSpeed
            x = submarine.initialPosition.x
            y = submarine.initialPosition.y
        }

        Behavior on y {
            NumberAnimation {
                id: speed
                duration: 500
            }
        }

        onXChanged: {
            if (submarineImage.x >= background.width) {
                Activity.finishLevel(true)
            }
        }
    }

    Body {
        id: submarineBody
        target: submarineImage
        bodyType: Body.Dynamic
        fixedRotation: true
        linearDamping: 0
        linearVelocity: submarine.isHit ? Qt.point(0,0) : submarine.velocity

        fixtures: Box {
            id: submarineFixer
            width: submarineImage.width
            height: submarineImage.height
            categories: items.submarineCategory
            collidesWith: Fixture.All
            density: 1
            friction: 0
            restitution: 0
            onBeginContact: {
                var collidedObject = other.getBody().target

                if (collidedObject == whale) {
                    whale.hit()
                }
                if (collidedObject == crown) {
                    crown.captureCrown()
                } else {
                    Activity.finishLevel(false)
                }
            }
        }
    }
    Timer {
        id: updateVerticalVelocity
        interval: 50
        running: true
        repeat: true

        onTriggered: submarine.changeVerticalVelocity()
    }
}

The Item is a parent object to hold all the different components of the submarine (the Image BallastTank and the Box2D component). It also contains the functions and the variables that are global to the submarine.

The Engine

The engine is a very straightforward implementation via the linearVelocity component of the Box2D element. We have two variables global to the submarine for handling the engine component, defined as follows:

property point velocity
property int maximumXVelocity: 5

which are pretty much self-explanatory, the velocity holds the current velocity of the submarine, both horizontal and vertical and the maximumXVelocity holds the maximum horizontal speed the submarine can achieve.

For increasing or decreasing the velocity of the submarine, we have two functions global to the submarine, as follows:

function increaseHorizontalVelocity(amt) {
    if (submarine.velocity.x + amt <= submarine.maximumXVelocity) {
        submarine.velocity.x += amt
    }
}

function decreaseHorizontalVelocity(amt) {
    if (submarine.velocity.x - amt >= 0) {
        submarine.velocity.x -= amt
    }
}

which essentially gets the amount by which the velocity.x component needs to be increased or decreased, checks whether it crosses the range or not, and makes the necessary changes likewise.

The actual applying of the velocity is very straightforward, which takes place in the Body component of the submarine as follows:

Body {
	...
	linearVelocity: submarine.isHit ? Qt.point(0,0) : submarine.velocity
	...

The submarine.isHit component, as the name suggests holds whether the submarine is hit by any object or not (except the pickups). If so, the velocity is reset to (0,0)

Thus, for increasing or decreasing the engine power, we just have to call one of the two functions anywhere from the code:

submarine.increaseHorizontalVelocity(1); /* For increasing H velocity */
submarine.decreaseHorizontalVelocity(1); /* For decreasing H velocity */

The Ballast Tanks

The Ballast Tanks are implemented separately in BallastTank.qml, since it will be implemented more that once. It looks like the following:

Item {
    property int initialWaterLevel
    property int waterLevel: 0
    property int maxWaterLevel
    property int waterRate: 10
    property bool waterFilling: false
    property bool waterFlushing: false

    function fillBallastTanks() {
        waterFilling = !waterFilling

        if (waterFilling) {
            fillBallastTanks.start()
        } else {
            fillBallastTanks.stop()
        }
    }

    function flushBallastTanks() {
        waterFlushing = !waterFlushing

        if (waterFlushing) {
            flushBallastTanks.start()
        } else {
            flushBallastTanks.stop()
        }
    }

    function updateWaterLevel(isInflow) {
        if (isInflow) {
            if (waterLevel < maxWaterLevel) {
                waterLevel += waterRate

            }
        } else {
            if (waterLevel > 0) {
                waterLevel -= waterRate
            }
        }

        if (waterLevel > maxWaterLevel) {
            waterLevel = maxWaterLevel
        }

        if (waterLevel < 0) {
            waterLevel = 0
        }
    }

    function resetBallastTanks() {
        waterFilling = false
        waterFlushing = false

        waterLevel = initialWaterLevel

        fillBallastTanks.stop()
        flushBallastTanks.stop()
    }

    Timer {
        id: fillBallastTanks
        interval: 500
        running: false
        repeat: true

        onTriggered: updateWaterLevel(true)
    }

    Timer {
        id: flushBallastTanks
        interval: 500
        running: false
        repeat: true

        onTriggered: updateWaterLevel(false)
    }
}

What they essentially does is:

• fillBallastTanks: Fills up the Ballast tanks upto maxWaterLevel. Sets the flag waterFilling to true if the Ballast is to be filled with water, and the timer fillBallastTanks is set to start(), which will increase the water level in the tank after every 500 millisecond.
• flushBallastTanks: Flushes the Ballast tanks down to 0. Sets the flag waterFlushing to true if the Ballast is to be flushed out of water, and the timer flushBallastTanks is set to start(), which will decrease the water level in the tank after every 500 millisecond.
• resetBallastTanks: Resets the water level in the ballast tanks to it’s initial values

In the Submarine Item, we just use three instances of the BallastTank object, for left, right and central ballast tanks, setting up it’s initial and maximum water level.

BallastTank {
    id: leftBallastTank

    initialWaterLevel: 0
    maxWaterLevel: 500
}

BallastTank {
    id: rightBallastTank

    initialWaterLevel: 0
    maxWaterLevel: 500
}

BallastTank {
    id: centralBallastTank

    initialWaterLevel: 0
    maxWaterLevel: 500
}

For filling up or flushing the ballast tanks (centralBallastTank in this case), we just have two call either of the following two functions:

centralBallastTank.fillBallastTanks() /* For filling */
centralBallastTank.flushBallastTanks() /* For flushing */

I will be discussing about how the depth is maintained using the ballast tanks in the next section.

The Diving Planes

The diving planes will be used to control the depth of the submarine once it is moving underwater. Keeping that in mind, along with the fact that it needs to be effectively integrated with the ballast tanks. This is implemented in the changeVerticalVelocity() function, which is discussed as follows:

/*
 * Movement due to planes
 * Movement is affected only when the submarine is moving forward
 * When the submarine is on the surface, the planes cannot be used
 */
if (submarineImage.y > 0) {
    submarine.velocity.y = (submarine.velocity.x) > 0 ? wingsAngle : 0
} else {
    submarine.velocity.y = 0
}

However, under the following conditions:

• the angle of the planes is reduced to 0
• the horizontal velocity of the submarine is 0,

the ballast tanks will take over. Which is implemented as:

/* Movement due to Ballast tanks */
if (wingsAngle == 0 || submarine.velocity.x == 0) {
    var yPosition = submarineImage.currentWaterLevel / submarineImage.totalWaterLevel * submarine.maximumDepthOnFullTanks

    speed.duration = submarine.terminalVelocityIndex * Math.abs(submarineImage.y - yPosition) // terminal velocity
    submarineImage.y = yPosition
}

yPosition calculates how much percentage of the tank is filled with water, and likewise it determines the depth to which it will dive. The speed.duration is the duration of the transition animation, and the duration depends directly on how much the submarine will have to cover up along the Y axis, to avoid a steep rise or fall of the submarine.

For increasing or decreasing the angle of the diving planes, we just need to call either of the following two functions:

submarine.increaseWinglsAngle(1) /* For increasing */
submarine.decreaseWingsAngle(1) /* For decerasing */

That’s it for now! The two major goals to be completed next are the rotation of the submarine (in case more than one tanks are used and they are unequally filled up) and the UI for controlling the submarine. Will provide an update on it once it is completed.

It is a long time since I posted on my blog and frankly, i missed it. I’ve been busy with school: courses, tones of homework, projects and presentations.

Since last year i had a great experience with GCompris and KDE in general, i decided to apply in this year’s GSoC as well, only this time, i chose another project from KDE: Minuet.

Minuet is part of KDE-edu and its goal is helping teachers and students both novice and experienced teach and respectively learn and exercise their music skills. It is primarily focused on ear-training exercises and other areas will soon be available.

Minuet includes a virtual piano keyboard, displayed at the bottom of the screen, on which users can visualize the exercises. Using a piano keyboard is a good starting point for anyone who wants to learn the basics of musical theory: intervals, chords, scales etc. Minuet is currently based on the piano keyboard for all its ear training exercises. While this is a great feature, some may find it not quite suitable to their musical instrument.

My project aims to deliver to the user a framework which will support the implementation of multiple instrument views as Minuet plugins. Furthermore, apart from the piano keyboard, I will implement another instrument for playing the exercise questions and user’s answers.

This mechanism should allow new instruments to be integrated as Minuet plugins. After downloading the preferred instrument plugin, the user would then be able to switch between instruments. It will allow him to enhance his musical knowledge by training his skills using that particular instrument.

At the end of summer, I intend to have changed the current architecture to allow multiple-instrument visualization framework and refactor the piano keyboard view as a separate plugin. I also intend to have implemented a plugin for at least one new instrument: a guitar.

A mock up on the new guitar is shown below:

I hope it will be a great summer for me, my mentor and the users of Minuet, whom i want to offer a better experience by using my work.

Sounds like déjà vu? You are right! We used to have Facebook Event sync in KOrganizer back in KDE 4 days thanks to Martin Klapetek. The Facebook Akonadi resource, unfortunately, did not survive through Facebook API changes and our switch to KF5/Qt5.

I’m using a Facebook event sync app on my Android phone, which is very convenient as I get to see all events I am attending, interested in or just invited to directly in my phone’s calendar and I can schedule my other events with those in mind. Now I finally grew tired of having to check my phone or Facebook whenever I wanted to schedule event through KOrganizer and I spent a few evenings writing a brand new Facebook Event resource.

Inspired by the Android app the new resource creates several calendars – for events you are attending, events you are interested in, events you have declined and invitations you have not responded to yet. You can configure if you want to receive reminders for each of those.

Additionally, the resource fetches a list of all your friend’s birthdays (at least of those who have their birthday visible to their friends) and puts them into a Birthday calendar. You can also configure reminders for those separately.

The Facebook Sync resource will be available in the next KDE Applications feature release in August.

Hello readers

I’m glad to share this opportunity to be selected 2 times for Google Summer of Code project under KDE. It’s my second consecutive year working with DigiKam team.

DigiKam is an advanced digital photo management  application which enables user to view, manage, edit, organise, tag and share photographs under Linux systems. DigiKam has a feature to search items by similarity. This require to compute image fingerprints stored in main database. These data can take space on disk especially with huge collection and bloat the main database a lots and increase complexity to backup main database which include all main information for each item registered, as tags, label, comments, etc.

The goal of this proposal is to store the similarity fingerprints must be stored in a dedicated database. This would be a big relief for the end users as image fingerprints are around few KB of raw data for each image. And storing all of them takes huge disk space, increases time latency for huge collections.

Thus, to overcome all the above issues, a new DB interface would be created. {This work has already been done for thumbnail and face fingerprints}. Also, from backup point of view, it’s easy to have separate files to optimise.

I’ll add keep you guys updated with my work in upcoming posts.

Till then, I encourage you to use the software. It’s easy to install and use. (You can find cheat sheet to build DigiKam in my previous post! )

Happy DigiKaming!

Following the 5th release 5.5.0 published in March 2017, the digiKam team is proud to announce the new release 5.6.0 of digiKam Software Collection. With this version the HTML gallery and the video slideshow tools are back, database shrinking (e.g. purging stale thumbnails) is also supported on MySQL, grouping items feature has been improved, the support for custom sidecars type-mime have been added, the geolocation bookmarks introduce fixes to be fully functional with bundles, the support for custom sidecars, and of course a lots of bug has been fixed.

HTML Gallery Tool

The HTML gallery is accessible through the tools menu in the main bar of both digiKam and showFoto. It allows you to create a a web gallery with a selection of photos or a set of albums, that you can open in any web browser. There are many themes to select and you can create your own as well. Javascript support is also available.

Video Slideshow Tool

The Video Slideshow is accessible also through the tools menu in the main bar of both digiKam and showFoto. It allows you to create a video slide with a selection of photos or albums. The generated video file can be view in any media player, as phones, tablets, Blue Ray reader, etc. There are many settings to customize the format, the codec, the resolution, and the transition (as for ex the famous Kens-Burn effect).

Database Integrity Tool

Already in 5.5.0 release, the tool dedicated to tests for database integrity and obsolete information have been improved. Besides obvious data safety improvements this can free up quite a lot of space in the digiKam databases. For technical reasons only SQLite database were shrunk to this smaller size in 5.5.0 release. Now this is also possible for MySQL databases with 5.6.0.

Items Grouping Features

Earlier changes to the grouping behaviour proved that digiKam users have quite diverse workflows - so with the current change we try to represent that diversity.

Originally grouped items were basically hidden away. Due to requests to include grouped items in certain operations, this was changed entirely to include grouped items in (almost) all operations. Needless to say, this wasn’t such a good idea either. So now you can choose which operations should be performed on all images in a group or just the first one.

The corresponding settings live in the configuration wizard under Miscellaneous in the Grouping tab. By default all operations are set to Ask, which will open a dialog whenever you perform this operation and grouped items are involved.

Extra Sidecars Support

Another new capability is to recognise additional sidecars. Under the new Sidecars tab in the Metadata part of the configuration wizard you can specify any additional extension that you want digiKam to recognise as a sidecar. These files will neither be read from nor written to, but they will be moved/rename/deleted/… together with the item that they belong to.

Geolocation Bookmarks

Another important change done for this new version is to restore the geolocation bookmarks feature which did not work with bundle versions of digiKam (AppImage, MacOS, and Windows). The new bookmarker has been fully re-written and is still compatible with previous geolocation bookmarks settings. It is now able to display the bookmark GPS information over a map for a better usability while editing your collection.

Google Summer of Code 2017 Students

This summer the team is proud to assist 4 students to work on separate projects:

Swati Lodha is back in the team. As in 2016, she will work to improve the Database interface. After having fixed and improved the MySQL support in digiKam, she has the task this year to isolate all the database contents dedicated to manage the similarity finger-prints matrix. As for thumbnails and face recognition, these elements will be stored in a new dedicated database. The goal is to reduce the core database size, simplify the maintenance and decrease the core database time-latencies.

Yingjie Liu is a Chinese student, mainly specialized with math and algorithms who will add a new efficient face recognition algorithm and will try to introduce some AI solution to simplify the face tag workflow.

Ahmed Fathi is an Egyptian student who will work to restore and improve the DLNA support in digiKam, to be able to stream collections contents through the network with compatible UPNP device as the Smart TV, tablets or cellulars.

Shaza Ismail is an another Egyptian student who will work to an ambitious project to create a tool for image editor to be used for healing image stains with the use of another part of the image by coloring by the use of one part over the other, mainly testing on dust spots, but can be used for other particles hiding as well.

Final Words

The next main digiKam version 6.0.0 is planned for the end of this year, when all Google Summer of Code projects will be ready to be backported for a beta release. In September, we will release a maintenance version 5.7.0 with a set of bugfixes as usual.

For further information about 5.6.0, take a look at the list of more than 81 issues closed in Bugzilla.

digiKam 5.6.0 Software collection source code tarball, Linux 32/64 bits AppImage bundles, MacOS package, and Windows 32/64 bits installers can be downloaded from this repository.

Happy digiKaming while this summer!

Set up the arcanist for Koko

• It was pretty much easy to install. For my Archlinux just below command did the work for me.

  yaourt -S arcanist-git

• Then I had to add .arcconfig to the Koko repository so that arc could point to the link where it should publish the changes

  { “phabricator.uri”:”https://phabricator.kde.org/” }

• The only problem is with the SSL certificates, as the university campus wireless network uses its own self-signed certificate. This will create problem to access the ssl encrypted web content, pretty much everything related to development :P
• Also university campus network does not allow SSH over it’s network. This will prohibit me from committing the changes to the git repository.
• Hence to use the arcanist, everytime I will have to check for the curl.cainfo in the /etc/php/php.ini and set/unset the environment variable GIT_SSL_CAINFO depending on the network I am using.