Education ClassRoom/Previous Logs/gsl

PhilippL	Hi everybody	10:59
* lgodard (n=lgodard@gateway.nuxeo.com) has joined #education.openoffice.org		10:59
PhilippL	I have uploaded some slides to http://gsl.openoffice.org/files/documents/16/4245/gsl_overview.odp	11:00
PhilippL	Which may be illustrating to what I'm going to say.	11:00
PhilippL	So, I'm here to talk a little about the gsl project.	11:00
ericb2	hello PhilippL , thank you very much for presenting us the GSL project	11:00
PhilippL	First, what does it mean ? GSL stands for Graphics System Layer.	11:01
PhilippL	Actually there are some modules in it that have not so much to do with graphics, but essentially GSL is about binding to the graphical	11:02
subsystems of the system OOo runs on.
* PhilippL switches to slide # 2		11:02
PhilippL	The core functionality of GSL is providing OOo's toolkit functionality.	11:02
PhilippL	Toolkit meaning what gtk is for Gnome, Qt for KDE or Swing / AWT for Java.	11:03
PhilippL	The parts of gsl I'm going to talk about a little are mainly located in the vcl, toolkit, dtrans and rsc modules of gsl.	11:03
PhilippL	VCL (Visual Control Layer) is the traditional toolkit of OOo.	11:04
PhilippL	In use basically since 1997 (meaning in StarOffice before OOo went OpenSource in 2001).	11:04
PhilippL	VCL is a C++ toolkit, based heavily on C++ inheritance mechanisms.	11:05
PhilippL	Since these are not so easily help binary compatibly.	11:05
PhilippL	toolkit was invented, which as a stable UNO API.	11:06
PhilippL	UNO meaning (Unified Network Objects)	11:06
PhilippL	which is OOo's kind of distributed objects (think Corba or .NET)	11:06
PhilippL	toolkit is supposed to be a thin wrapper around vcl that binds the (changing) vcl interface to UNO based services which stay binary	11:07
compatible.
PhilippL	Then there is the rsc (resource compiler), currently still OOo's most heavily used method of doing localization.	11:08
* PhilippL switches to slide 3		11:08
PhilippL	So let's talk a little more about vcl.	11:08
PhilippL	vcl is the core of gsl, providing the main event loop, everything that produces output (Windows, virtua devices, printers,...), most	11:09
controls (Edit fields, buttons, ...)
PhilippL	it also does a lot for reading system specific settings like theme colors, does native looking widget rendering (NWF).	11:10
PhilippL	Basically without vcl you wouldn't see a single pixel.	11:10
PhilippL	And at some point it is presumed to go away :-)	11:10
PhilippL	But more to that later.	11:10
* PhilippL switches to slide 4		11:11
PhilippL	A little more on toolkit: toolkit is your way to go if you want to write UI code that is going to be binary compatible.	11:11
PhilippL	A conditio sine qua non if you're writing extensions.	11:12
PhilippL	There are other ways, like using java, of course, but the UNO services provided by toolkit are going to stay for a while.	11:12
PhilippL	Making sure that your extension won't only run in OOo 3.0, but 3.1, 3.2 and whatever is going to follow.	11:12
* PhilippL switches to slide 5		11:13
PhilippL	Then there is clipboard and drag&drop functionality.	11:13
PhilippL	Logically and implementationwise this is tied quite closely to the main event queue, so it should belong into vcl itself.	11:14
PhilippL	That actually is where it originally was, but at the time a new implementation came around, UNO had become to get "en vogue".	11:14
PhilippL	So this functionality was put out into an own UNO service library and has staid there since.	11:15
PhilippL	If that is a good thing is open to debate, but at least it shows how much flexibility we have with the concepts of UNO. In principle you	11:16
could exchange the clipboard functionality by your own version, just replacing the service.
* PhilippL switches to slide 6		11:16
PhilippL	The resource compiler	11:16
PhilippL	I mention it mainly because it will come up in an example I will come to later.	11:17
PhilippL	RSC is a compiler taking in a "resource source" file containg UI descriptions.	11:17
PhilippL	It also contains localizations of everything that needs to be localized (Strings, bitmaps, potentially whole elements).	11:18
PhilippL	it compiles this source into a multitude of binary output files, one for each locale requested.	11:18
PhilippL	So you end up with one resource file for english, french, german, whatever each.	11:19
* PhilippL switches to slide 7		11:19
PhilippL	There is so many stuff in gsl, let's pick one concrete example.	11:19
PhilippL	What you're first going to see when starting OOo is always a Window.	11:20
PhilippL	So how does it work ?	11:20
PhilippL	From the system point of view, exactly one window is involved here.	11:20
PhilippL	This is abstracted using per system implementation in vcl's system dependent layer called SAL: System Abstraction Layer.	11:21
PhilippL	Incidentally there is another sal in the porting project.	11:21
PhilippL	That one is OOo's equivalent to the C runtime library.	11:21
PhilippL	It also means (you guessed it) System Abstraction Layer.	11:22
PhilippL	The same name is a historical accident, however vcl's sal layer existed first :-)	11:22
PhilippL	So this one system window will usually contain multiple vcl Windows.	11:22
PhilippL	That is because vcl uses "soft windows" or "gadgets" as they are e.g. called in the X11 toolkit.	11:23
PhilippL	Basically a gadget is only a clip region that confines drawing of a logical window into its own borders.	11:23
PhilippL	The management of these gadgets is done by vcl's independent layer.	11:24
PhilippL	SAL usually does not need to know about any specific soft child windows that may or may not be children of its one real system window.	11:25
* PhilippL switches to slide 8		11:25
PhilippL	so if you have your typical dialog, the system (X11, Windows, Aqua, whatever) actually knows just one window there, although there are usually many more UI elements which are drawn by vcl's independent layer.	11:26
PhilippL	for those seeing the presentation: the "soft" windows are marked in red on the slide.	11:27
* PhilippL switches to slide 9		11:27
PhilippL	So SAL cares about system specific things on our window (positioning, sizing, giving a title) as well as the events that are sent by the system to our window.	11:28
PhilippL	It abstracts these events into a common form understood by the independent layer and then defers these abstracted events to it.	11:29
PhilippL	The independent layer then cares for transforming the events appropriately for the soft windows that are actually involved.	11:29
PhilippL	e.g. it will paint those soft windows that are in the area the system notified us for the system window that needs to be drawn.	11:30
* PhilippL switches to slide 10		11:30
PhilippL	So a more practical question: how do I create a dialog using vcl ?	11:31
PhilippL	Typically you create a new class representing your dialog.	11:31
PhilippL	This new class inherits form vcl's ModalDialog class.	11:31
PhilippL	As data members you include the controls you want to show in your dialog.	11:32
PhilippL	The dialog needs a constructor which can take the dialog's parent window as argument.	11:32
PhilippL	(the parent window being the one the dialog is supposed to me modal for).	11:32
PhilippL	The dialog itself is then the parent of the controls it contains.	11:33
PhilippL	running it is then as simple as instantiating your new class and then calling the Execute method inherited from the dialog super class.	11:34
* mynfred has quit ()		11:34
PhilippL	on slide number 11 you can see an example of a very simple dialog containing two radio buttons, an OK and a Cancel button.	11:35
* PhilippL switches to slide 12		11:35
PhilippL	The good sides: you write abstracted code, all that is necessari	11:36
PhilippL	oops	11:36
PhilippL	necessary to do on a specific platform will be done automatically for you.	11:36
PhilippL	Write once, run anywhere	11:36
PhilippL	There is a provend localization mechanism that works the same on all platforms, no need to be involved in one localization mechanism for every platform.	11:37
* PhilippL switches to slide 13		11:37
PhilippL	So what is "bad" about vcl ?	11:38
ericb2	:-)	11:38
PhilippL	For even the most simple dialog you need to create new c++ code.	11:38
PhilippL	There is no UI editor currently, all controls are hand positioned.	11:38
PhilippL	There is no layouting capability, which OOo is quite suffering from.	11:39
PhilippL	However there is an effort underway to correct this via a new toolkit service.	11:39
PhilippL	vcl uses its own controls, not native widgets -> you'll have perhaps the system look (if NWF works right) but won't have the system "feel"	11:40
PhilippL	So is this going to change.	11:40
PhilippL	In short we plan to ...	11:40
PhilippL	... for the last five years ...	11:41
PhilippL	The amount involved would be staggering since virtually the whole office would have to be recoded.	11:41
PhilippL	At some point we still hope to do this transformation, though.	11:42
PhilippL	Which is why vcl is sometimes considered "dead".	11:42
PhilippL	In short, if you create new UI, the most reliable way currently (if you don't want to do code maintanance very often) is to use the UNO based toolkit.	11:43
PhilippL	This is going to stay for a while.	11:43
PhilippL	Seeing that I'll have to go in about 15 minutes, are there any questions ?	11:44
ericb2	I have some, but I'll ask you later (very specific)	11:45
PhilippL	BTW: if you have questions, you can usually find me on #dev.openoffice.org	11:45
ericb2	was awesome :)	11:45
* ericb2 learned a lot		11:45
PhilippL	or you can mail me directly (address is in the presentation).	11:45
ericb2	PhilippL: I just regret not much attendees joined the channel. I know for sure a lot of people read the log, but this is damage, to see a so	11:46
valuable developer like you with so few people asking for questions :/
PhilippL	I mean "send a mail to me", not "mail me" of course :-)	11:46
PhilippL	not a problem, as I said I have to go for a while anyway :-)	11:47
PhilippL	So it seems that's it for today.	11:48
ericb2	PhilippL: ok, then if there are no questions, I'll ask on the list. Thank you very much for your presentation: I'd really have been glad to find it several years ago, when I started to contribute for Mac OS X port	11:48
PhilippL	Have a nice day everyone and don't hesitate to ask on #dev.openoffice.org or dev@gsl.openoffice.orf mailing list.	11:48

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