Qt4 Hildon Legacy

Maemo Platform
The Maemo Platform is the software stack for Nokia Internet Tablets, which includes the Maemo operating system and the Maemo SDK. The Maemo Platform is mostly based on open source code, and has been developed by the Maemo Software department within Nokia in collaboration with many open source projects such as the Linux kernel, Debian, and GNOME. (from wikipedia)

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What is Hildon?
Hildon is an application framework for Linux operating system mobile devices (PDAs, mobile phones, etc), developed by Nokia for Maemo and now a part of GNOME, that focuses on providing a finger friendly interface Read more

Developing on Maemo
Developing applications for Maemo is done with the Maemo SDK. The process from creating the first prototype of your application to distributing to a wide audience consists basically of three steps:

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 * share your application project in the Maemo Garage
 * make your application easy to install and put in the Application Catalog
 * once your application has a high quality - be promoted to the Nokia user site

Maemo SDK
(from Wikipedia) The Maemo SDK is based around the Debian-oriented Scratchbox Cross Compilation Toolkit, which provides a sandbox environment in which development may take place. Scratchbox uses Qemu to emulate an ARMEL processor or sbrsh to remotely execute instructions. Scratchbox-compatible rootstraps are available for both x86 and ARMEL, so the majority of development and debugging takes place on x86, with final packaging being for ARMEL.

Watch the Maemo SDK in action!

What is Scratchbox?
Scratchbox is a cross compilation toolkit designed to make embedded Linux application development easier. It also provides a full set of tools to integrate and cross compile an entire Linux distribution. Read more...

[[Image:Rocket.png]] Getting started
To start to develop with Maemo Qt, we need to install the Maemo SDK in our linux box.

Hey, I don't have a linux box!
That's not a big problem. Maemo SDK Virtual Image project provides a programming environment for Maemo platform. You can download from here the VMWare image that you can run in VMPlayer.

Installing the Maemo SDK
If you want to install the maemo SDK on your linux box this is the page that you want to check: SDK Releases If you are on a non-debian system such as OpenSUSE you might need to perform the following command in another shell prior to logging in, in order to get ARM CPU emulation working: sudo /scratchbox/sbin/sbox_ctl start

Installing the Qt packages in Scratchbox
After Scratchbox and SDK are installed and working, you need to login, add the "extra" and "extra devel" repositories to your apt-get sources and install the Qt libs. Here's how:

> echo "# Maemo extras and extras-devel deb http://repository.maemo.org/extras/ diablo free non-free deb-src http://repository.maemo.org/extras/ diablo free deb http://repository.maemo.org/extras-devel/ diablo free non-free deb-src http://repository.maemo.org/extras-devel/ diablo free" >> /etc/apt/sources.list
 * Paste this into your Scratchbox shell (without the ">" prompt):

> apt-get update > fakeroot apt-get install libqt4-gui > fakeroot apt-get install libqt4-dev
 * Run these commands:


 * Do these steps for the DIABLO_X86 and the DIABLO_ARMEL target if you plan to build on both

How to compile a Qt application in scratchbox
All the Qt tools you need are available in scratchbox. In order to compile a Qt application you need to follow the standard Qt way: qmake -project qmake file.pro make

Running a Qt application in scratchbox
TODO

Running a Qt application into the device
To run a Qt application into the device, we need to copy it there. To do this we need to:

Installing the OpenSSH server in the device

 * Open the Application Manager
 * Enable the maemo-extras catalogue (Click the application title bar > Tools > Application catalogue...)
 * Install openssh-server from the list

Setting up a network connection
We can connect to device to our working machine via WLAN or via USB. Connecting the device to a WLAN is quite easy; a bit more tricky can be using an usb cable to set up a usb network. There is a good how-to in the maemo wiki pages. A easy way to setup the usb network in a Diablo device is installing maemo-control-usb. After the installation a new item called "USB Networking" will appear in the maemo Control Panel. Clicking it will show a dialog with a button. You need to press that button one time to raise a usb interface on your device with 192.168.2.15 as IP. After that you have to connect the device to your machine via the USB cable.

Using scp to copy the excutable on the device
Scp or secure copy is a common linux application. It can copy single/multiple files or a directory and theirs files recursively using a secure connection. To copy our application on the device we just need to run it with a syntax like this: PC_$> scp qtApplication root@DEVICE-IP:/home/user

Executing the application
Now that the application has been copied into the device, we can run it. For that we need to open the terminal or we can use ssh from our PC. PC_$> ssh root@DEVICE-IP N810_#> su - user N810_$> ./qtApplication

Intro
Porting a Qt Desktop application to Maemo requires very few efforts; This because the Maemo Qt libraries will take care of giving the Hildon Maemo look & Feel and enabling the hildon input method for your application.

Maemo Style
The Maemo style is the default style of the Qt applications that run in Maemo. The other styles available in Qt 4.4 maemo are QCleanLooks, Windows and Plastique (It will be available in the next packages of Qt).

You can force your application to use another style in several way:

1. Running your application with the flag -style  $> ./qt-test-application -style windows

HINT: You can put this flag in the Exec field of the desktop file that launch the application.

2. If you want to change your code, you can use this static function:QApplication::setStyle( QStyle * style )

3. If you want to change the style only for a particular widget, you can call this function in the widget constructor: QWidget::setStyle( QStyle * style )

Showing the status bar
The hildon applications don't have a stuatus bar. Qt for maemo hide the status bar by default. You can show it again modifying your code. TODO

Adding Maemo changes to a Qt Application
Some methods of Qt for Maemo are not available in the "standard" Qt libs. Then a Qt application with specific Maemo Qt code can't be built outside the Maemo SDK. To avoid this issue, the developer can use the preprocessor directives, for example:

//Specific hildon code here
 * 1) ifdef Q_WS_HILDON
 * 1) endif

Limitations
TODO

Intro
The Gnu Project Debugger, or gdb for short, is a general purpose debugger that can be used for various debugging purposes.

Debugging a Qt application into scratchbox
TODO

Debugging a Qt application into the device
1. Installing gdb into the device A. add the sdk tools repository to the catalogue list B. install gdb by using apt-get (require around 6 Mb of space)

2. Install the debug symbols files in scratchbox (ARMEL target) apt-get install libqt4-dbg

3. Run the application (device side) $gdbserver 0.0.0.0:1234 ./qtApplication

4. Run the gdb client on your host PC (scratchbox side) [sbox-DIABLO_ARMEL: ~/TEST/svn/qt4-x11-4.4.0/examples/widgets/tablet] > gdb ./qtApplication

5. Set the target of gdb (gdb) target remote 172.21.37.117:1234

6. Tell to gdb to continue to debug the application on the device (gdb) continue

7. Wait some moments...

8. Your application will appear on the device screen.

9. Happy debugging!

Links
GDB documentation & Tutorials

GDBServer man page

maemo debugging guide

gdb debian package for Diablo

OProfile
Oprofile is a low overhead system-wide profiler for linux. It can be used to find CPU usage bottlenecks in the whole system and within processes. It works fine in the device, but viewing the reports can take quite a long time (10 minutes) when fired up on N800/N810 devices. Therefore, it often makes sense to run opreport in scratchbox.

If you want to know more about OProfile in Maemo click here to read a good how to.

Valgrind
TODO

[[Image:package.png]] Packaging a Qt application for Maemo
Find out more..

[[Image:Helmet.png]] Maemo Qt API Reference
Maemo Qt is based on Qt for X11. It shares the same API avoiding API breaks. In this way every Qt application that runs in other platforms (Windows, MacOS X, Linux, S60) can run also into the Maemo devices.

To Develop a Qt application you can use the Official Qt 4.4 API Documentation and the list below to see what are the Maemo changes.

QString QDesktopServices::storageLocation(StandardLocation type) returns specific Maemo locations for these types: - DesktopLocation:  QDir::homePath + QLatin1String("/MyDocs"),            instead of QDir::homePath + QLatin1String("/Desktop") - DocumentsLocation: QDir::homePath + QLatin1String("/MyDocs/.documents"), instead of QDir::homePath + QLatin1String("/MyDocs/.documents") - PicturesLocation: QDir::homePath + QLatin1String("/MyDocs/.images"),    instead of QDir::homePath + QLatin1String("/Pictures") - MusicLocation:    QDir::homePath + QLatin1String("/MyDocs/.sounds"),    instead of QDir::homePath + QLatin1String("/Music") - MoviesLocation:   QDir::homePath + QLatin1String("/MyDocs/.videos"),    instead of QDir::homePath + QLatin1String("/MyDocs/.videos")

QTabletEvents are able to get the pressure value from the touchscreen. - The eventdeviceType is for the touchscreen is set to QTabletEvent::Stylus. - QTabletEvents won't be used anymore in Fremantle Finger poke is emulated in scratchbox by the Middle Mouse button (NOTE: There is no Fullscreen VKB in scratchbox)

QInputEvents don't move the cursor. It's mandatory to get working the HIM moving the cursor via QInputMethodEvents. Why is it mandatory? Because if the user select text with the finger from the right to the left, we are able to remove the highlighted text, but the cursor will be moved on the last char instead to stay on the first one. To do that some changes has been added to some widget function like: widget::inputMethodEvent(QInputMethodEvent *e). Modifing that function in some custom widgets may be necessary. Don't reimplementing that function will break some fullscreen virtual keyboard features.

Hardcoded Keys: In the QMainWindow: - F6 - Toggle fullscreen the application - F4 - Shows/Hides the application context menu - Zoom in - is a standard key sequence QKeySequence::ZoomIn - Zoom out - is a standard key sequence QKeySequence::ZoomOut

Input Method: Maemo Qt uses the Hildon IM as default Input method. Each kind of widget can set the IM mode. This allows the input method to focus on the type of input that the application is expecting. Eg: spinboxes can receive only numeric characters (1-9). NOTE: Qt widgets like QTextEdit, QLineEdit... set the right input method mode automatically. A developer can change it by using: void QInputContext::setInputMode(int mode); It will update immediately the Hildon Input method to use the selected IM mode. HIC Modes: HILDON_GTK_INPUT_MODE_ALPHA 	alphabetical characters and whitespace HILDON_GTK_INPUT_MODE_NUMERIC 	numbers 0-9 and the '-' character HILDON_GTK_INPUT_MODE_SPECIAL 	special characters HILDON_GTK_INPUT_MODE_HEXA 	hexadecimal characters; numbers 0-9, characters a-f, and A-F HILDON_GTK_INPUT_MODE_TELE 	telephone numbers; numbers 0-9, whitespace, and the characters "pwPW/.-+*#?," HILDON_GTK_INPUT_MODE_FULL 	unrestricted entry mode, combination of the alpha, numeric and special modes. HILDON_GTK_INPUT_MODE_MULTILINE 	the client contains multiple lines of text or accepts linebreaks in the input. HILDON_GTK_INPUT_MODE_INVISIBLE 	do not echo or save the input in the IM when entering sensitive information such as passwords. HILDON_GTK_INPUT_MODE_AUTOCAP 	automatically capitalize the first letter at the start of a sentence. HILDON_GTK_INPUT_MODE_DICTIONARY 	enable predictive dictionaries and learning based on the input. Example: For a password field we need to set a specific IM mode: int mode = HILDON_GTK_INPUT_MODE_FULL | HILDON_GTK_INPUT_MODE_INVISIBLE QInputContext qic = widget->inputContext; qic->setInputMode(mode); If you are developing a Custom widget able to receive input text, you can instruct your widget to use the right IM Mode just returning the mode. - How does it work? The Hildon IM sends a XMessage to pop up the "Virtual Keyboard" (or better the Main HIM UI) when an input widget receive the focus. The IM before to raise the VKB, makes an inputMethodQuery to the widget retrieving the IM mode. If the developer of the custom widget doesn't set the mode property, the IM will use HILDON_GTK_INPUT_MODE_FULL (the default mode) for that widget. Setting the ImMode is quite easy. Check the code below for more understanding. #ifdef Q_WS_HILDON #include  #endif QVariant QAbstractSpinBox::inputMethodQuery(Qt::InputMethodQuery query) const {       Q_D(const QAbstractSpinBox); switch(query) { case Qt::ImMode:{ int mode = HILDON_GTK_INPUT_MODE_NUMERIC; return QVariant(mode); }       default: return d->edit->inputMethodQuery(query); } }

[[Image:Helmet.png]] Contributing to the Maemo Qt Project
Maemo Qt is a community project. Contributing to the forum, sending us patches, give us feedbacks, tracking bugs are all activities that help us to improve the quality of our work.

Commit changes in SVN
If you are a maemo Qt developer and you want to save your changes in the garage SVN but your project is not ready to go to the main line (trunk/qt-x11), you should create a your private branch and then work there until the merging with the mainline.

For that you have to create a your directory in branches/ named developer_name-qt. After that you can copy trunk/qt-x11 in your directory. svn copy --username developer_name https://garage.maemo.org/svn/qt4/trunk/qt-x11 https://garage.maemo.org/svn/qt4/branches/developer_name-qt -m "Creating private branch of trunk/qt-x11" NOTE: Subversion uses cheap copy, so them don't increase the size of the repository. Then feel free to create your own branch.

Merging branche changes in the mainline
Before to merge your changes in the mainline, the code must be full working, cleaned and tested. A review from another developer is also needed in order to reduce the possibility to add errors.

Be updated
Any Maemo Qt developer should be updated and should participate to the discussions, for that he must join the Mailing list.

[[Image:Help-contents.png]] F.A.Q.

 * I'm tring to compile a Qt application for ARMEL, but I got the error below. What's wrong?

/targets/FREMANTLE_X86/usr/include/qt4/QtCore/qatomic_i386.h:127: error: impossible constraint in 'asm'

You are using X86 include files, then you have to update your Makefile. Running qmake before run make will be solve this issue.