[IronPython] Python in the Browser updates

Michael Foord fuzzyman at voidspace.org.uk
Sun Jul 20 13:53:10 CEST 2008 

Jimmy Schementi wrote:
> Michael Foord wrote:
>   
>> Jimmy Schementi wrote:
>>     
>>> Michael, question for you:
>>>
>>>
>>>       
>>>> On every keypress Javascript calls into IronPython (via the C#!).
>>>>
>>>>         
>>> How come you used C# to handle the onkeypress event? This should do
>>>       
>> it in Python:
>>     
>>>       
>> Did you look at the code to see why? I'd be really interested to know
>> if
>> I can do what I'm doing from Python inside Silverlight, but I doubt it.
>> There's not much code in total, so it should be easy to follow.
>>     
>
> Yep, I looked at it, and I'm pretty sure you can do everything from python. All the native Javascript functions are callable from python, or any .NET language, especially with HtmlPage.window.eval(), so there shouldn't be any limitation.
>
>   
>> I actually handle the onkeypress event from Javascript (onkeypress.js).
>> This calls into 'getSelection' (cursor_pos.js) to work out the current
>> selection in the textarea. Naturally this is easy to do in Firefox /
>> Safari and scarily awful in IE. :-)
>>     
>
> Attaching the event is simple:
>
> from System.Windows.Browser.HtmlPage import Document
> from System.Windows.Input import KeyEventHandler
>
> Document.myTextAreaID.AttachEvent("onkeypress", KeyEventHander(onKeyPress))
>
> def onKeyPress(sender, eventArgs):
>   # Do something with eventArgs.CharacterCode
>   pass
>
> For converting the javascript to python, there are some special javascript variables that are in different places, like "window" is HtmlPage.Window, etc.
>
>   

I've used the event attaching stuff before, but some of the Javascript 
is quite fiddly so I wasn't sure there was much benefit in moving it 
into Python.

My next version will probably be based on the Javascript UI of Try Ruby 
by Why the Luck Stiff (he has given me permission to use his JS):

http://tryruby.hobix.com/

Michael

>> Having worked these out (and shortcut a few specific scenarios - like
>> ctrl-A, ctrl-Z and ctrl-C), the Javascript then calls into IronPython
>> with the selection start, selection end, and the character that was
>> pressed. I use C# to expose a scriptable type that Javascript can call.
>>     
>
> If you hooked all the events with Python, you wouldn't need to call back into it from Javascript. This is why I prefer doing everything with Python, so I avoid having a C# shim.
>
>   
>> I use attaching events from Python to provide the sample code. There
>> are
>> three links above the console and Python handles the 'onclick' event to
>> swap the examples around.
>>     
>
> Basically, if there is something pretty basic you can't do in Python that you can do from browser Javascript, it's a bug! =)
>
>   
>> Michael Foord
>>
>>     
>>> <textarea id="code"></textarea>
>>> <div id="result"></div>
>>>
>>> from System import EventHandler
>>> from System.Windows.Browser import Htmlpage, HtmlEventArgs
>>>
>>> document = System.Windows.Browser.HtmlPage.Document
>>> def onkeypress(s, e):
>>>   document.result.innerHTML += "KeyPress<br />"
>>> document.code.AttachEvent("onkeypress",
>>>       
>> EventHandler[HtmlEventArgs](onkeypress))
>>     
>>> Anyway, just wondering if anything was blocking you from hooking HTML
>>>       
>> events with Python.
>>     
>>> ~js
>>>
>>>
>>>       
>>>> -----Original Message-----
>>>> From: users-bounces at lists.ironpython.com [mailto:users-
>>>> bounces at lists.ironpython.com] On Behalf Of Michael Foord
>>>> Sent: Tuesday, June 17, 2008 2:52 PM
>>>> To: Discussion of IronPython
>>>> Subject: Re: [IronPython] Python in the Browser updates
>>>>
>>>> Hello all,
>>>>
>>>> Sorry for the noise - but tomorrow I hope to package this for a
>>>>         
>> release
>>     
>>>> and if any of you get the chance to give me any feedback before
>>>>         
>> then.
>>     
>>>> http://www.voidspace.org.uk/ironpython/silverlight-
>>>>         
>> console/console.html
>>     
>>>> I think I have fixed all the basic usability issues (it is no longer
>>>> possible to screw up the console so that it refuses further input
>>>>         
>> for
>>     
>>>> example). To *really* fix input I ought to move execution into its
>>>>         
>> own
>>     
>>>> thread so that we can interrupt infinite loops [1] - but that is a
>>>> bigger change so I am resisting it for the moment.
>>>>
>>>> The big change is that I have added some simple code snippets - as
>>>>         
>> an
>>     
>>>> example of how it could be used in tutorials or for teaching Python.
>>>>
>>>> It is also easy to customize - the source code (200 lines of Python,
>>>>         
>> 70
>>     
>>>> lines of Javascript, 25 lines of C#) shows how to prepopulate the
>>>> execution context and show the first few lines of code in the
>>>> interpreter.
>>>>
>>>> You can get the sourcecode from the repository of course:
>>>>
>>>> http://code.google.com/p/pythoninthebrowser/
>>>>
>>>> All the best,
>>>>
>>>> Michael Foord
>>>>
>>>> [1] and then decide whether on windows a ctrl-c should send a
>>>>         
>> keyboard
>>     
>>>> interrupt or copy to the clipboard...
>>>>
>>>> Michael Foord wrote:
>>>>
>>>>         
>>>>> For those who are interested, I've updated "Python in the Browser".
>>>>>
>>>>> Both the repository:
>>>>>
>>>>> http://code.google.com/p/pythoninthebrowser/
>>>>>
>>>>> And the online demo:
>>>>>
>>>>> http://www.voidspace.org.uk/ironpython/silverlight-
>>>>>
>>>>>           
>>>> console/console.html
>>>>
>>>>         
>>>>> There are a few minor but nice improvements:
>>>>>
>>>>> * The Javascript now works with IE 7!
>>>>> * The textarea scrolls as input is printed
>>>>> * The context window is disabled to prevent you pasting over the
>>>>>
>>>>>           
>>>> input
>>>>
>>>>         
>>>>> area - not sure if this is really an improvement though...
>>>>> * The input area is cleared on load - to stop browsers like Firefox
>>>>> and Safari repopulating the textarea for us on browser refresh
>>>>> * Recursion limit is set
>>>>>
>>>>> I think it is basically in a useful state now... I might push out a
>>>>> '0.1' release from the current SVN head.
>>>>>
>>>>> All the best,
>>>>>
>>>>> Michael Foord
>>>>>
>>>>>
>>>>>           
>>>> --
>>>> http://www.ironpythoninaction.com/
>>>> http://www.theotherdelia.co.uk/
>>>> http://www.voidspace.org.uk/
>>>> http://www.ironpython.info/
>>>> http://www.resolverhacks.net/
>>>>
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