Michael Van Canneyt schrieb:
Please explain why that isn't possible to do a conversion of such an app using
Javascript ?
Are you going to compile the pascal to javascript ?
Hello *,
as I already wrote Michael in private I'm thinking about developing a
web widgetset for LCL as well.
My current considerations are these:
The application of course gets compiled as usual and runs on the server.
There is only one major issue: A web application must be prepared for
multithreading, as there is one instance of the 'main form' per user
access (or session). But, if properly written (storing data in the main
class, and not using global variables), this is not a real problem.
JavaScript will only be used for drawing and content creation, and for
event propagation of course. Communication using AJAX or JSON, but using
the synchronous version of HTTPRequest (remember that most desktop
widget toolkits are working synchronous as well, for good reason). For
example, the canvas: Drawing commands will be buffered, and as soon as
execution returned to the main loop, this command buffer will be send to
the JavaScript client. (Of course there might be special cases like
painting in a canvas and immediately reading data back from the
framebuffer. In this case it might be necesseray to emulate the whole
painting on the server using a memory image.)
Really all kinds of widgets can be emulated using JavaScript and DHTML.
This approach surely would work quite well -- but it would be quite
slow, dependent on the exact application.
Btw, what we could do is to support Microsofts Silverlight; if this
plugin is installed, create all widgets using Silverlight, where you can
use _all_ widgets which .NET's Windows.Forms support.
But back to JS/DHTML. To improve performance, I see only one way, the
way that Google's Web Toolkit is going: Analyze the source code and try
to convert single methods to JavaScript wherever possible, using some
kind of JS version of the FPC RTL. By time, this library would get
bigger and bigger, improving the performance step by step. But of course
the source analyzer has to be extremely careful about keeping the
application state in sync between client and server.
Any comments? :-)
- Sebastian
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