Web Assembly and decalarative-camera example.

[Julian Guarin 0]

Hey, recently I've been interested in learning web assembly with qt.

So I followed the tutorial on building an app by @morten-sorvig to build and run classic QtQuick's declarative camera example :
https://blog.qt.io/blog/2018/11/19/getting-started-qt-webassembly/

I tweaked the Makefile produced by qmake, just to avoid some nasty error:

em++ -s WASM=1 -s FULL_ES2=1 -s ALLOW_MEMORY_GROWTH=1 -s USE_WEBGL2=1 -s NO_EXIT_RUNTIME=0 -s ERROR_ON_UNDEFINED_SYMBOLS=1 --bind -s "BINARYEN_TRAP_MODE='clamp'" -O3 -L/home/jg/opensource/qt/5.12.0/m/qtbase/lib -lqtfreetype -s USE_LIBPNG=1 -o declarative-camera.js qmlcamera.o declarative-camera.js_plugin_import.o declarative-camera.js_qml_plugin_import.o qrc_declarative-camera.o   -L/home/jg/opensource/qt/5.12.0/m/qtbase/plugins/platforms -L/home/jg/opensource/qt/5.12.0/m/qtbase/lib -s USE_ZLIB=1 -s USE_LIBPNG=1 -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -L/home/jg/opensource/qt/5.12.0/m/qtbase/plugins/mediaservice -lqtmedia_audioengine -s -s -s -s -s -s -s -s -s -s -s -s -L/home/jg/opensource/qt/5.12.0/m/qtbase/plugins/video/videonode -leglvideonode -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -L/home/jg/opensource/qt/5.12.0/m/qtbase/plugins/playlistformats -lqtmultimedia_m3u -s -s -s -s -s -s -s -s -s -s -s -s -lwasm -lQt5EventDispatcherSupport -s -s -s -s -lQt5FontDatabaseSupport -s -s -s -s -lqtfreetype -s -s -lQt5EglSupport -s -s -s -s -s -s -s -s -L/home/jg/opensource/qt/5.12.0/m/qtbase/plugins/imageformats -lqgif -s -s -s -s -lqicns -s -s -s -s -lqico -s -s -s -s -lqjpeg -s -s -s -s -lqtga -s -s -s -s -lqtiff -s -s -s -s -s -lqwbmp -s -s -s -s -lqwebp -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -L/home/jg/opensource/qt/5.12.0/m/qtbase/qml/QtQuick.2 -lqtquick2plugin -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -L/home/jg/opensource/qt/5.12.0/m/qtbase/qml/QtMultimedia -ldeclarative_multimedia -lQt5MultimediaQuick -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -s -lQt5Quick -s -s -s -s -s -s -s -s -s -s -s -s -lQt5Multimedia -s -s -s -s -s -s -lQt5Gui -s -s -lqtharfbuzz -s -lQt5Qml -s -s -s -lQt5Network -s -s -lQt5Core -s -lqtpcre2   
emcc: warning: cannot represent a NaN literal '0x1fda4c40' with custom bit pattern in NaN-canonicalizing JS engines (e.g. Firefox and Safari) without erasing bits!
  in   ret double 0x7FF4000000000000 in _Z5qSNaNv() 
emcc: warning: cannot represent a NaN literal '0x1fda4c40' with custom bit pattern in NaN-canonicalizing JS engines (e.g. Firefox and Safari) without erasing bits!
  in   store double 0x7FF4000000000000, double* %37, align 8, !tbaa !15 in _Z16qt_asciiToDoublePKciRbRi18StrayCharacterMode() 
emcc: warning: cannot represent a NaN literal '0x1fda4c40' with custom bit pattern in NaN-canonicalizing JS engines (e.g. Firefox and Safari) without erasing bits!
emcc: warning: cannot represent a NaN literal '0x1fda4c40' with custom bit pattern in NaN-canonicalizing JS engines (e.g. Firefox and Safari) without erasing bits!
emcc: warning: cannot represent a NaN literal '0x216f45a0' with custom bit pattern in NaN-canonicalizing JS engines (e.g. Firefox and Safari) without erasing bits!
  in   %177 = select i1 %.0187.off0, double 0xFFF8000000000000, double 0x7FF8000000000000 in _ZNK17double_conversion23StringToDoubleConverter12StringToIeeeIPKcEEdT_ibPi() 
error: undefined symbol: _ZN7QThread4exitEi
warning: To disable errors for undefined symbols use `-s ERROR_ON_UNDEFINED_SYMBOLS=0`
Error: Aborting compilation due to previous errors
shared:ERROR: '/home/jg/opensource/em/node/8.9.1_64bit/bin/node /home/jg/opensource/em/emscripten/1.38.25/src/compiler.js /tmp/tmpi_PmAI.txt /home/jg/opensource/em/emscripten/1.38.25/src/embind/emval.js /home/jg/opensource/em/emscripten/1.38.25/src/embind/embind.js /home/jg/opensource/em/emscripten/1.38.25/src/library_pthread_stub.js' failed (1) 

Ok, then I ran the emscripten server... :

$[12:18:jg]@webcam[master !?]> emrun --no_browser --port 8081 .
Web server root directory: /home/jg/Code/hacks/wasm/qml/webcam
Now listening at http://localhost:8081/
The html page you are running is not emrun-capable. Stdout, stderr and exit(returncode) capture will not work. Recompile the application with the --emrun linker flag to enable this, or pass --no_emrun_detect to emrun to hide this check.

And I got the application to run!!!!
However.... camera is not being accessed by the application:

So I'm almost there!!! However... .would like to understand why the camera is not being accessed, my guess is this is related to browser authorizations to use the camera etc....

Any clues?
Any help @morten-sorvig or anyone greatly appreciated.....

[raven-worx]

@Julian-Guarin-0
i would be suprised if the QtMultimedia module (and a backend) was ported for the QtWebAssembly module.
I guess a special backend would be needed which accesses the browser capabilities.

I might be wrong though, but i couldn't find any info at a quick glance which proves me wrong.

[Julian Guarin 0]

Ok, however when I've configured Qt to be built from sources I can see the following modules in Qt:

Qt Multimedia:
ALSA ................................... no
GStreamer 1.0 .......................... no
GStreamer 0.10 ......................... no
Video for Linux ........................ no
OpenAL ................................. yes
PulseAudio ............................. no
Resource Policy (libresourceqt5) ....... no
Windows Audio Services ................. no
DirectShow ............................. no
Windows Media Foundation ............... no

So I guess you are right. Does this confirm what you did see?

[raven-worx]

@Julian-Guarin-0 said in Web Assembly and decalarative-camera example.:

So I guess you are right. Does this confirm what you did see?

as i said, i didnt see anything ;)
But the configure clearly shows that you might only be possible to play sound files, i don't know if thats really true though for QtWebAssembly.