No subject
Wed Aug 1 07:28:53 PDT 2012
technique with respect to encapsulation in C++.
I personally believe things have two aspects, e.g. pros and cons. :)
Here pros is strongly clear.
We can save the word for encapsulation.
Then, now my question is what's the cons from this change?
It seems QT project widely uses this kind of technique called D-pointer.
Any report from them?
Kind regards,
Kangil
From: webkit-efl-bounces at lists.webkit.org
[mailto:webkit-efl-bounces at lists.webkit.org] On Behalf Of Dumez, Christophe
Sent: Thursday, October 18, 2012 5:56 PM
To: webkit-efl at lists.webkit.org
Cc: Kenneth R Christiansen
Subject: [webkit-efl] Use of pimpl idiom for Ewk classes
Hi,
Mikhail and I are currently working on refactoring the Ewk classes to make
them more C++-like, more convenience to use and less bug-prone.
As part of this work, we came out with a proposal: Use pimpl idom for Ewk
classes.
The Ewk classes are currently defined in the private headers, with all their
members public. The private headers also usually contain C-style functions
to interact with the Ewk class from inside WebKit.
Now, we would like to get rid of those private C functions and replace them
with C++ methods in the Ewk class. The issue is that the Ewk class members
are currently public meaning we can alter the members directly from outside
the Ewk class implementation and bypass those class methods.
At the same time, we don't want to make all the Ewk class members private
and create getter / setter methods for all of them. Not only this means a
lot of refactoring work and extra code, but also, this means that are public
C API implementation will need to go through those getters / setters as
well, instead of interacting with the class members directly.
We therefore thought of using the pimpl idiom so that the class members are
now stored in a POD struct in the cpp file. This effectively prevents access
to them from code other than our public C API and Ewk class methods, which
is what we want. The C API functions can still directly interact with the
Ewk class members which is convenient. We can get rid of all C functions in
the private headers and replace them with Ewk class methods. Therefore, the
coding style in WK2 EFL port implementation with be more C++ oriented.
I created a meta bug for this task:
https://bugs.webkit.org/show_bug.cgi?id=99696
I also wrote a first patch to show what the result looks like for the
Ewk_Download_Job class. The patch also adds convenience macros to
ewk_private.h to make pimpl idiom usage simpler and less error-prone:
https://bugs.webkit.org/show_bug.cgi?id=99697
We hope you like the result as much as we do.
If everyone agrees, Mikhail and I are planning to port other Ewk classes to
this proposal and update the WebKit EFL coding style.
Kr,
--
Christophe Dumez
Linux Software Engineer, PhD
Intel Finland Oy - Open Source Technology Center
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<div class=Section1>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>Hi Chris,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>FOA, thanks for the interesting topic
here. :)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>From this, I’ve learned about
useful design pattern and implementation technique with respect to
encapsulation in C++.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>I personally believe things have two
aspects, e.g. pros and cons. :)<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>Here pros is strongly clear.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>We can save the word for encapsulation.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>Then, now my question is what’s
the cons from this change?<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>It seems QT project widely uses this
kind of technique called D-pointer.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>Any report from them?<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>Kind regards,<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'>Kangil<o:p></o:p></span></p>
<p class=MsoNormal><span lang=EN-US style='font-size:10.0pt;mso-bidi-font-size:
11.0pt;font-family:"Tahoma","sans-serif";mso-fareast-font-family:"Malgun Gothic";
mso-bidi-font-family:"Times New Roman"'><o:p> </o:p></span></p>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif";mso-fareast-font-family:"Times New Roman"'>From:</span></b><span
lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif";
mso-fareast-font-family:"Times New Roman"'> webkit-efl-bounces at lists.webkit.org
[mailto:webkit-efl-bounces at lists.webkit.org] <b>On Behalf Of </b>Dumez,
Christophe<br>
<b>Sent:</b> Thursday, October 18, 2012 5:56 PM<br>
<b>To:</b> webkit-efl at lists.webkit.org<br>
<b>Cc:</b> Kenneth R Christiansen<br>
<b>Subject:</b> [webkit-efl] Use of pimpl idiom for Ewk classes<o:p></o:p></span></p>
</div>
<p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><span lang=EN-US>Hi,<br
clear=all>
<br>
Mikhail and I are currently working on refactoring the Ewk classes to make them
more C++-like, more convenience to use and less bug-prone.<br>
As part of this work, we came out with a proposal: Use pimpl idom for Ewk
classes.<br>
<br>
The Ewk classes are currently defined in the private headers, with all their
members public. The private headers also usually contain C-style functions to
interact with the Ewk class from inside WebKit.<br>
Now, we would like to get rid of those private C functions and replace them
with C++ methods in the Ewk class. The issue is that the Ewk class members are
currently public meaning we can alter the members directly from outside the Ewk
class implementation and bypass those class methods.<br>
<br>
At the same time, we don't want to make all the Ewk class members private and
create getter / setter methods for all of them. Not only this means a lot of
refactoring work and extra code, but also, this means that are public C API
implementation will need to go through those getters / setters as well, instead
of interacting with the class members directly.<br>
<br>
We therefore thought of using the pimpl idiom so that the class members are now
stored in a POD struct in the cpp file. This effectively prevents access to
them from code other than our public C API and Ewk class methods, which is what
we want. The C API functions can still directly interact with the Ewk class
members which is convenient. We can get rid of all C functions in the private
headers and replace them with Ewk class methods. Therefore, the coding style in
WK2 EFL port implementation with be more C++ oriented.<br>
<br>
I created a meta bug for this task:<br>
<a href="https://bugs.webkit.org/show_bug.cgi?id=99696">https://bugs.webkit.org/show_bug.cgi?id=99696</a><br>
<br>
I also wrote a first patch to <b>show what the result looks</b> like for the
Ewk_Download_Job class. The patch also adds convenience macros to ewk_private.h
to make pimpl idiom usage simpler and less error-prone:<br>
<b><a href="https://bugs.webkit.org/show_bug.cgi?id=99697">https://bugs.webkit.org/show_bug.cgi?id=99697</a></b><br>
<br>
We hope you like the result as much as we do.<br>
If everyone agrees, Mikhail and I are planning to port other Ewk classes to
this proposal and update the WebKit EFL coding style.<br>
<br>
Kr,<br>
-- <br>
Christophe Dumez<br>
Linux Software Engineer, PhD<br>
Intel Finland Oy - Open Source Technology Center<o:p></o:p></span></p>
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