Maemo Wiki Mirror - User contributions [en]

Game development

2010-03-29T15:24:57Z

217.17.35.154: Using HAA on N900

This page contains tips on game development and SDL library usage for internet tablets.

=Useful Tips=

==Hardware notes==

* Internet tablets use a touchscreen, which enables new ways to implement game-features, such as on-screen buttons, in-game drawing, moving * character by tapping screen. etc.
* Since the device does not have any buttons on right side, implement those in software!
* Avoid using the 4 way rocker for fast and complex movements. It's not well suited for gaming.
* When using screen's vertical orientation (as in tetris) think other use for esc button than exiting game. It's so close to the rocker that accidental presses will happen.

==SDL specific notes==

Things to remember:
* The screen is natively 800x480. No resolution changes are supported. Maybe in the future we might have support for 400x240 res for faster graphics but this is quite unlikely. If trying to set fullscreen window smaller than the native screen size, you will just have black borders.
* In windowed mode matchbox will force the window to certain size (you should look at the UI specifications to see the actual window size). If your requested window is smaller than this, your window will be aligned to the upper-left and have black borders on the lower-right.
Generally SDL windows (not fullscreen) look quite bad with the theme if nothing for the theme is done inside the SDL window, but it's up to you to decide.
* Avoid full 800x480 screen updates. Memory bandwidth is limited. If you still have to do these for some reason, you should make the area smaller (eg having some statusbar or any GUI elements which doesn't need to be updated each time). Also do not use SDL_Flip(), since it will update whole screen. Use rect updating functions instead. Thank you.
* 32 bit mode doesn't work. The reason was that there was a bug that caused SDL to segfault when you had 32 bit window and you recreated the window. Since the display is only 16 bit, there is no reason to support 32 bit mode, which would just give extra round of pixel conversion and therefore slow things down. Convert your images on loading to native 16-bit with SDL.
* Mouse events. There is touchscreen, and you can't assume average end user Billy-Bob would hack the device to USB host mode and use the USB mouse. So use absolute coordinates as much as possible. One example where relative coordinates are used is scummvm. If you use keypad to move the cursor, and then use the touchscreen, the actuall cursor will be at offset from original touchpadpress. Think absolutely, not relatively ;)

==Adding support for the Task Navigator==

===Create an entry in the task list===

The Maemo Task Navigator identifies non-Maemo programs (like pure SDL applications) by matching the <code>StartupWMClass</code>-variable in the <code>.desktop</code>-file and the application "window manager class" name. By default all SDL applications have the name <code>SDL_App</code>. This can be changed with the environment variable <code>SDL_VIDEO_X11_WMCLASS</code>.

Here app.desktop is the desktop file, with:

<pre>
[Desktop Entry]
Encoding=UTF-8
Version=1.0
Type=Application
Name=The Application
Exec=/var/lib/install/usr/bin/app
Icon=app
X-Window-Icon=tn-bookmarks-link
X-Osso-Type=application/x-executable
StartupWMClass=app
Terminal=false
</pre>

* Alternative 1: Here <code>app.bin</code> is the binary executable and <code>app</code> is a wrapper script:

<pre>
#!/bin/sh
BASENAME=`basename $0`
export SDL_VIDEO_X11_WMCLASS=${BASENAME}
exec ${0}.bin "$@"
</pre>

Notice that <code>StartupWMClass == SDL_VIDEO_X11_WMCLASS</code>, and that <code>Exec</code> points to the wrapper script, not the main program.

* Alternative 2: An other possibility that doesn't need a script is the following. Put the line

<pre>
putenv("SDL_VIDEO_X11_WMCLASS=app");
</pre>

in your code. A good position is directly at the beginning of the <code>main</code> method. This way there is no need for a helper script.

===Set the window title===

If you see "unknown" title in task list (OS2008 bug/feature), you can set it by using:

<pre>
#include <SDL/SDL_syswm.h>
#include <X11/Xutil.h>

SDL_SysWMinfo info;
SDL_VERSION(&info.version);
if ( SDL_GetWMInfo(&info) ) {
Display *dpy = info.info.x11.display;
Window win;

if (Video.FullScreen)
win = info.info.x11.fswindow;
else
win = info.info.x11.wmwindow;
if (dpy && win) XStoreName(dpy, win, "Title");
}
</pre>
Alternatively you can try to set title for both windows no matter if fullscreen or not. This seems to work and saves you setting the title again after fullscreen switch.
<pre>
Display *dpy = info.info.x11.display;
Window win;
if (dpy){
win = info.info.x11.fswindow;
if (win) XStoreName(dpy, win, "Title");
win = info.info.x11.wmwindow;
if (win) XStoreName(dpy, win, "Title");
}
</pre>

If SDL_WM_SetCaption is present in the code, add the code above after that call. Or, just remove SDL_WM_SetCaption as the code above will set the window title and the icon for the window is handled by hildon-desktop using the Icon field in your desktop file.

If you wish for text to appear in the task navigator on the second line corresponding to your game; make "Title" be: "'text to display on first line' - 'text to display on second line'". The " - " (with spaces) are important.

==Utilizing pixel doubling inside SDL==

As there is support for pixel-doubled drawing to the screen inside the HW, there is implementations to utilize that up to X. So if you want to use it you have to do some xlib code, therefore it might be a good idea to put this small piece of code to switch pixel doubling mode to a separate file.

'''NOTE:''' There is no Xsp scaling on N900 anymore. You might want to use Hildon Animation Actor to scale the pixmap. Either with [http://git.maemo.org/git/sdlhildon/?p=sdlhildon;a=tree;f=sdlhaa SDL_haa] or [http://wiki.maemo.org/Documentation/Maemo_5_Developer_Guide/Porting_Software/Scaling_Fixed_Size_Windows directly].
====What is pixel doubling?====

Pixel doubling is a feature of the Xsp extension of the tablet's X server. When enabled, all draws to the display are doubled in size with a smoothing filter. This reduces required bandwidth for screen updates by a factor of 4, making full-motion fullscreen animation possible. This also allows lower-quality graphics to be drawn to portions of the screen (for example a low-res game area and a high-res status bar).

====Pixel doubling problems and workarounds====

* Be aware that Xsp pixel doubling feature was designed for scaling video-player videos (drawn by dsp, not X) and is not officially supported.
* Don't update areas which would exceed doubled coordinates 400x240.
* If possible, disable doubling when not drawing, because if another process draws to screen (like infoprints) while the Xsp doubling is active, results can be quite "artistic".
* If mouse pointer is enabled, it will break pixel doubling. Disable it before turning on doubling with SDL_ShowCursor(0);.
* Many SDL games that draw several small updaterects will break Xsp pixel doubling, causing flicker. This has been discussed at length on the maemo-developer list without a resolution. If pixel doubling is causing areas to flicker, change the code from individual updated rectangles for sprites to one updaterect for your entire game screen, for example region (0,0,320,240).
* If your game crashes or exits before disabling pixel doubling, it will be left on until some application switches it off. This means that you will have 'artistic desktop' or a white screen or reboot. This can be avoided by reacting to SDL active events, if somebody else gets active status, immediately switch doubling off.

====Howto use it====

There exists one X extension (Xsp), which can be used for that. Sample piece of code with SDL:

<pre>
#include <X11/Xlib.h>
#include <X11/extensions/Xsp.h>

#include <SDL/SDL.h>
#include <SDL/SDL_syswm.h>

void set_doubling(unsigned char enable)
{
SDL_SysWMinfo wminfo;
SDL_VERSION(&wminfo.version);
SDL_GetWMInfo(&wminfo);
XSPSetPixelDoubling(wminfo.info.x11.display, 0, enable);
}
</pre>

Note that when you compile it you have to include X include path and link this with libXsp (-lXsp).

=External Links=

[http://www.libsdl.org/ Simple DirectMedia Layer Homepage]

[http://www.gamedev.net/ Game Development Resources]

[[Category:Development]]
[[Category:Games]]

Open development/Why the closed packages

2009-12-14T17:50:55Z

217.17.35.154: /* Waiting list */

==Reasons==

Open source is the licensing model preferred by Nokia in the development of Maemo. There are some reasons to have exceptions, though.

* '''Brand''': Nokia wants to keep a strong brand and identity avoiding any risks of dilution.
* '''Differentiation''': Nokia wants to gain competitive advantage in certain areas by keeping the related software closed.
* '''Legacy''': Nokia keeps some components minimally maintained - the work of opening them has an unclear outcome.
* '''IPR & licensing issues''': Nokia avoids serious risks brought by patents, copyrights or complicated licensing situations.
* '''Security''': Nokia avoids safety risks and liabilities that could be caused by freeing access to certain hardware components.
* '''Third party''': Nokia does not own the code and therefore does not decide on the license.

== Specific reasons for packages ==
This list needs update as it mostly refers to Maemo 4.1.

* '''[https://bugs.maemo.org/show_bug.cgi?id=1832 tablet-browser-ui]''': At the beginning there was a proprietary browser. In Maemo 4.0 the Mozilla based browser came, with an open engine (MicroB) but still a closed UI provided by tablet-browser. The main reason was the default rule to have the Maemo applications UI closed for differentiation. The context in mobile browsing has changed significantly and now there are better reasons to offer also an open browser UI. This is the plan for Fremantle.
* '''[[Questions_for_Nokia#Bookmark_manager_engine|Bookmark manager]]''': Closed because of legacy and the default rule to have the UI application layer closed. However, the licensing of this component is being reviewed and it could be opened in Fremantle. Filing an enhancement request and seeing the interest and potential use cases would be something the community could do. Deadline: Fremantle beta SDK release.
* '''[https://bugs.maemo.org/show_bug.cgi?id=1235 Media player]''': Currently closed because of the default criteria of UI differentiation. In progress, though. The engine is being opened in Fremantle, in the form of a Media Application Framework also available for third parties. The UI is open for discussion, as you can see in the Comment #5 of the enhancement request. For instance, it would count a lot seeing a will to converge efforts and contribution from the many third party media player projects.
* '''[https://bugs.maemo.org/show_bug.cgi?id=3195 Connection applet]''': Legacy. The applet itself is not much but it unveils all the Connectivity middleware which is also closed. The whole Connectivity framework is having major changes in Fremantle and Harmattan, and the resould ''could'' be a much open framework altogether (applet included). Too soon to tell.
* '''[https://bugs.maemo.org/show_bug.cgi?id=3199 Display applet]''': Legacy. Opening it could be considered if really needed. From the comments in the bug report it looks like the need is not that big though?
* '''Location framework''': Differentiation. Nokia is investing heavily in location software and services, that are planned to be implemented in Maemo during Fremantle and Harmattan.
* '''libmetalayer''': Legacy. Substituted in Fremantle by open source upstream Meta Tracker. See [https://bugs.maemo.org/show_bug.cgi?id=2836#c16 this comment] about the possibility to open it still.
* '''osso-dsp-modules''': DSP component provided by Texas Instruments. Note that the DSP packages provided by Nokia are open source: osso-dsp-loader, osso-dsp-headers. If you are interested in open source DSP development then [http://dspgateway.sourceforge.net/ DSP Gateway] (developed by Nokia) might get your attention. However, the introduction of PulseAudio in Fremantle gives an opportunity to platform developers to forget about the DSP completely.
* '''dsme''': This component covered many areas including power management, which is considered a differentiation area by Nokia. The component has been redesigned and the sensitive functionality has moved to mce, allowing to distribute dsme (soon) with an open license together with related tools and plugins: bootstate, dsmetool, waitfordsme, libdsme.so, libhwwd.so, liblifeguard.so, libprocesswd.so, libstartup.so and libstate.so. Then libtemperature.so will be replaced by another component consisting of several dsme open source plugins. Finally, libcalmodule.so will be dropped.
* '''bme - Battery Management Entity''': Security. A misuse of the could lead to serious battery damages that could result in liabilities for Nokia. hald-addon-bme is a related package, also closed.
* '''mce - Mode Control Entity''': Initially closed for differentiation because of its impact in battery life, an area where Nokia strives to excel. Nowadays the differentiation aspect is lighter but legacy plays a role as well.

Not in the device but also relevant:
* '''Flasher''': Utility to flash the device from a Linux computer. Currently closed for legacy, considering the move to an open project to ease and encourage the development of versions not supported by Nokia e.g. [https://bugs.maemo.org/show_bug.cgi?id=1100 Mac OS X] and [https://bugs.maemo.org/show_bug.cgi?id=1013 PowerPC].

== Requesting the opening of closed components ==
If you want a Nokia closed component to be open use the Brainstorm to file a proposal adding the opening of the component as one solutions (others might want to add other potential solutions, like using an alternative component).

The chances of success of your proposal will probably depend on how it fits within the following reasons for a relicensing:

# '''Fixing a bug''': The package is in non-free although it looks like it's actually an open piece of software. In this case forget about Brainstorm and simply [http://bugs.maemo.org file a bug].
# '''Nurturing application development''': There is a strong argument proving that opening a component will bring more and better apps for end users.
# '''Spread of Maemo driven technologies to other platforms''': A component fits well in a gap existing in other Linux/OSS based projects and there is a concrete interest on collaborating and contributing to a component if it's opened.
# '''Community maintenance''': A component is receiving low attention from the official maintainers even if it has high attention from the community and there are developers volunteering to contribute to it if the source code is available.
# '''Better architecture''': Probably covered by 2 or 3 but just in case. A closed component is sitting in the midle of open components making things more difficult that needed to developers interested in that area.

== Waiting list ==

If you want to know the specific reasons for a package to be closed please list it below and the Maemo team will answer as time permits. You can also add comments to a certain package to drive attention/priority to it.

Requested at [https://bugs.maemo.org/show_bug.cgi?id=1584 Bug 1584] including comments:
* File Manager
* activate_panel
* bt-cal
* cal-tool
* fb-chaimage
* text2screen
* wlan-cal
* wlan-fw-update
* retu-time
* show_image
* battest
* dspctl
* the script linuxrc
* libbmeic.so
* libcal.so
* libppu.so
* libactivitymonitor.so
* libinactivity-blank.so
* libperipheral.so
* BME
* libi18n-locale-resolver0

These packages are included in the nokia-binaries metapackage offered with the Maemo SDK:

* hildon-task-navigator-bookmarks
* osso-bookmark-menu->osso-bookmark-engine->osso-bookmark-user
* osso-browser-translations-dev
* libaccounts-dev ->libaccounts0
* libaccounts-doc
* libosso-abook-dev ->libosso-abook
* libosso-rtcom-accounts-dev ->libosso-rtcom-accounts0
* libosso-rtcom-accounts-doc
* osso-addressbook ->libcontact-importexport
* osso-contact-plugin-dev ->osso-contact-plugin
* osso-mission-control ->libplayback-1-0 ->libimlogger0
* libconbtui0 ->
* liblocation-dev ->liblocation0
* libossoproductinfo0 ->libdsme0
* libgpsbt-dev ->libgpsbt
* libgpsmgr-dev ->libgpsmgr
* libogs1.2-dev ->libogs1.2-1 ->libosso-filemanager-interface
* id3search -> libmetalayer0 ->libgisds-gtk-dialog0 ->libgisds0
* osso-global-search
* osso-applet-certman ->certs ->osso-clock
* libosso-certman-dev ->libosso-certman1
* osso-help-ui

Other Requests:
* mnotify (Webmail Notifier) - Open source could allow it to support other webmail providers, and fix minor issues like [https://bugs.maemo.org/show_bug.cgi?id=2066 bug 2066] as it is apparantly low priority for Nokia. Update - according to several bugs this has now been dropped by Nokia.
* telepathy-spirit - This connection manager might be useful for people using Telepathy framework and Skype on desktop computer.

== Opened ==

* [https://bugs.maemo.org/show_bug.cgi?id=3635 Alarm framework] is open source, but apparently the sources are lost/missing as explained in the bug.

[[Category:Development]]
[[Category:Community]]