Re: Data engine update issue in Javascript

[Maik Beckmann]

For the sake of completeness, here github repo of the applet in question

 - http://github.com/MaikBeckmann/plasma-textmon

and the  docs I wrote on it so far

 - http://maikbeckmann.github.com/plasma-textmon/

Comments are especially welcome in regards to
http://maikbeckmann.github.com/plasma-textmon/prelude.html


There is more content in that isn't exported to browesable html

 - http://raw.github.com/MaikBeckmann/plasma-textmon/gh-pages/dataengines.org
(staring from * COMMENT The systemmonitor date engine)
 - http://github.com/MaikBeckmann/plasma-textmon/blob/gh-pages/UI.org

because I haven't gotten around to get it into a presentable state yet.


I've spend a fair amount of time on this during the last days.  I'll
continue to work now and then on evenings hanging out in #plasma .

See you there,
Maik
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Re: Data engine update issue in Javascript

[Maik Beckmann]

I figured the problem(s) out. Here it goes..

Here source code from the initial email without the print statements.

  var layout = new LinearLayout(plasmoid);
  l =  new Label();
  l.text = ---;
  layout.addItem(l);

  var smDataEngine = dataEngine(systemmonitor)

  smDataEngine.sourceAdded.connect(function(name) {
if (name.toString() == cpu/system/TotalLoad) {
  smDataEngine.connectSource(name, plasmoid, 1000);
  });

  plasmoid.dataUpdated = function(name, d) {
if ( d[value] ) {
  l.text = d[value];
}
  };

There are three bugs in there, where the first hides the remaining two.

The first bug is that sourceAdded isn't called when the applet is added to a
running plasma-desktop session.  If you'd restart plasma-deskop, then it works
as advertised.  I assume that the the process loads all applet and then starts
the data engines, which then causes the sourceAdded slot to be called.  Adding
a new applet ofc doesn't restart the data engines and there we have it.  Note
that for the same reason this bug doesn't show up when you're using
plasmoidviewer (which is why it took me a while to figure it out).

Now lets change the source code to work around this problem.  I'll get rid of
sourceAdded altogether, since it's unlikely that the CPU will be plugged out at
runtime.

  var layout = new LinearLayout(plasmoid);
  l =  new Label();
  l.text = ---;
  layout.addItem(l);

  var smDataEngine = dataEngine(systemmonitor)

  smDataEngine.connectSource(cpu/system/TotalLoad, plasmoid, 1000);

  plasmoid.dataUpdated = function(name, d) {
if ( d[value] ) {
  l.text = d[value];
}
  };

This reliably _never_ works, because the second bug kicks in.  When
connetSource is called the updateData slot isn't filled yet.  This causes
connetSource to fail.  This failure doesn't cause an debug message to be
emitted (which is good IMO), but connectSource returns 'undefined' rather than
'true'. So the two remaining bugs are:
 1. 'plasmoid.dataUpdated = ..' isn't located before
'smDataEngine.connectSource(..)' in the source file.
 2. The return value of connectSource isn't checked.

Here the final and hopefully correct version

  var layout = new LinearLayout(plasmoid);
  l =  new Label();
  l.text = ---;
  layout.addItem(l);

  plasmoid.dataUpdated = function(name, d) {
if ( d[value] ) {
  l.text = d[value];
}
  };

  var smDataEngine = dataEngine(systemmonitor);
  if (!smDataEngine.connectSource(cpu/system/TotalLoad, plasmoid, 1000)) {
throw(connecting to data source failed.);
  }



Thanks for your attention,
Maik
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Re: Data engine update issue in Javascript

[Maik Beckmann]

https://www.dropbox.com/s/omnt27sor7d99zl/textmondebug.plasmoid
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Data engine update issue in Javascript

[Maik Beckmann]

Hello,

Forever ago when I switched (back) from the awesome window manager to KDE I've
done a textual system monitor applet in javascript, which shows the most
important system parameters (cpu, memory, network, hdd).  I've cleaned the
source up and decided it might of interested to others.   But there is
an issue I
wasn't able to solve yet: When the applet is added to the desktop or panel,
then the systemmonitor doesn't respond.  Only when the plasma-desktop process
is restarted, it starts working.

The following screenshot visualizes the effect.
 - http://wstaw.org/m/2012/02/08/plasma-desktopZ29288.png
In there two applet instances are shown.  The one on top was added followed by
 : kquitapp plasma-desktop
 : plasma-desktop
The one beneath was just added without restarting plasma.

The code in this paste is a condenced version that reproduces the problem
 - http://paste.kde.org/205478/
(and the matching metadata.desktop http://paste.kde.org/205490/ ).  Here a
screenshot that is the equivalent to the one above for the complete applet
 - http://wstaw.org/m/2012/02/08/plasma-desktopl30563.png
Note the problem doesn't occur with plasmoidviewer, only with the actually
running plasma-desktop.


My question: Is this a bug or am I doing something wrong?


Best,
Maik
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