'Re: Review Request 115326: fix theme cache cleanup and discarding'

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List:       kde-panel-devel
Subject:    Re: Review Request 115326: fix theme cache cleanup and discarding
From:       "Harald Sitter" <sitter () kde ! org>
Date:       2014-01-28 9:18:52
Message-ID: 20140128091852.11809.85391 () probe ! kde ! org
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> On Jan. 27, 2014, 4:30 p.m., Martin Klapetek wrote:
> > plasma/theme.cpp, lines 298-300
> > <https://git.reviewboard.kde.org/r/115326/diff/2/?file=240703#file240703line298>
> > 
> > Seems like these two could be squashed into one but...meh, up to you

ETOOLONGSTATEMENT IMO.

> On Jan. 27, 2014, 4:30 p.m., Martin Klapetek wrote:
> > plasma/theme.cpp, line 311
> > <https://git.reviewboard.kde.org/r/115326/diff/2/?file=240703#file240703line311>
> > 
> > One thing I don't understand (not related to your changes though) - why does this \
> > return cacheTheme which never ever changes inside this method? And it also never \
> > returns anywhere else, so why is it even returning a boolean value when its value \
> > is already known before this method? :O

That's the million dollar question isn't it ;)

useCache is a getter, except it's really not. It is however being (ab)used as single \
entry point for pre-cache-access conditions, and therefore a convenient lazy-init \
function. i.e. when one calls useCache() one actually does this from an effect POV:

if (d->useCache) {
 d->initPixmapCache();
 KImageCache cache = d->pixmapCache;
 [...]
}

To that extent it would really be better (for the readability) of the respective \
functions to move the lazy-init into pixmapCache() and svgElementsCache() functions \
the resulting access code remains almost the same as currently:

if (d->useCache) {
  KImageCache cache = d->pixmapCache();
  [...]
}

This way however there's no file IO in the if. Ever. Additionally right now there is \
no active lazy init for the svg elements cache it appears. The only way to get that \
cache initalized is by somehow getting a discardCache(...) call which will tear it \
down and then (re)init :/.

- Harald

-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://git.reviewboard.kde.org/r/115326/#review48389
-----------------------------------------------------------

On Jan. 28, 2014, 9:18 a.m., Harald Sitter wrote:
> 
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/115326/
> -----------------------------------------------------------
> 
> (Updated Jan. 28, 2014, 9:18 a.m.)
> 
> 
> Review request for Plasma, Aaron J. Seigo and Martin Klapetek.
> 
> 
> Repository: kdelibs
> 
> 
> Description
> -------
> 
> - introduce svgelements cache handling in useCache()
> - to decide whether or not to discard a cache type now the mtimes of \
> metadata.desktop and the respective cache file are compared (previously this was an \
>                 invalid file compared to cache change time)
> - cache cleanup now happens entirely before creation of the KImageCache instance to \
> prevent any sort of problem there 
> - add fixme comment about broken version-based cache handling. for one the version \
> specific file name is not actually used for the KImageCache and for another the \
> entire shebang is missing from svgelements all together. this has the very \
> unfortunate side effect that the *active* cache files are deleted ever so often, it \
> may be worth removing the code portions until someone finds time/interest to \
> actually implement this in a working fashion. 
> 
> Diffs
> -----
> 
> plasma/theme.cpp cb44878 
> 
> Diff: https://git.reviewboard.kde.org/r/115326/diff/
> 
> 
> Testing
> -------
> 
> upgraded from 4.8 straight to 4.12 -> theme caches correctly discarded
> 
> 
> Thanks,
> 
> Harald Sitter
> 
> 

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     <td>
      This is an automatically generated e-mail. To reply, visit:
      <a href="https://git.reviewboard.kde.org/r/115326/">https://git.reviewboard.kde.org/r/115326/</a>
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<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;">  <p style="margin-top: 0;">On January 27th, 2014, 4:30 p.m. UTC, <b>Martin \
Klapetek</b> wrote:</p>  <blockquote style="margin-left: 1em; border-left: 2px solid \
#d0d0d0; padding-left: 10px;">  

<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; \
border-collapse: collapse; margin: 2px padding: 2px;">  <thead>
  <tr>
   <th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; \
font-size: 9pt; padding: 4px 8px; text-align: left;">  <a \
href="https://git.reviewboard.kde.org/r/115326/diff/2/?file=240703#file240703line298" \
style="color: black; font-weight: bold; text-decoration: \
underline;">plasma/theme.cpp</a>  <span style="font-weight: normal;">

     (Diff revision 2)

    </span>
   </th>
  </tr>
 </thead>

 <tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
  <tr>

   <td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">const \
char *ThemePrivate::systemColorsTheme = \
&quot;internal-system-colors&quot;;</pre></td>

  </tr>
 </tbody>

 <tbody>

  <tr>
    <th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2"></font></th>  <td bgcolor="#c5ffc4" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>  <th \
bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid \
#C0C0C0;" align="right"><font size="2">293</font></th>  <td bgcolor="#c5ffc4" \
width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">              \
<span class="k">const</span> <span class="n">QString</span> <span \
class="n">svgCacheFilePath</span> <span class="o">=</span></pre></td>  </tr>

  <tr>
    <th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2"></font></th>  <td bgcolor="#c5ffc4" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>  <th \
bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid \
#C0C0C0;" align="right"><font size="2">294</font></th>  <td bgcolor="#c5ffc4" \
width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">              \
<span class="n">KStandardDirs</span><span class="o">::</span><span \
class="n">locate</span><span class="p">(</span><span \
class="s">&quot;cache&quot;</span><span class="p">,</span> <span \
class="n">svgCacheFileName</span><span class="p">);</span></pre></td>  </tr>

  <tr>
    <th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2"></font></th>  <td bgcolor="#c5ffc4" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>  <th \
bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid \
#C0C0C0;" align="right"><font size="2">295</font></th>  <td bgcolor="#c5ffc4" \
width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">              \
<span class="k">const</span> <span class="n">QFileInfo</span> <span \
class="nf">svgCacheFileInfo</span><span class="p">(</span><span \
class="n">svgCacheFilePath</span><span class="p">);</span></pre></td>  </tr>

 </tbody>

</table>

  <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Seems like these two \
could be squashed into one but...meh, up to you</pre>  </blockquote>

</blockquote>
<pre style="margin-left: 1em; white-space: pre-wrap; white-space: -moz-pre-wrap; \
white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">ETOOLONGSTATEMENT IMO.</pre> <br />

<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;">  <p style="margin-top: 0;">On January 27th, 2014, 4:30 p.m. UTC, <b>Martin \
Klapetek</b> wrote:</p>  <blockquote style="margin-left: 1em; border-left: 2px solid \
#d0d0d0; padding-left: 10px;">  

<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; \
border-collapse: collapse; margin: 2px padding: 2px;">  <thead>
  <tr>
   <th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; \
font-size: 9pt; padding: 4px 8px; text-align: left;">  <a \
href="https://git.reviewboard.kde.org/r/115326/diff/2/?file=240703#file240703line311" \
style="color: black; font-weight: bold; text-decoration: \
underline;">plasma/theme.cpp</a>  <span style="font-weight: normal;">

     (Diff revision 2)

    </span>
   </th>
  </tr>
 </thead>

 <tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
  <tr>

   <td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">const \
char *ThemePrivate::systemColorsTheme = \
&quot;internal-system-colors&quot;;</pre></td>

  </tr>
 </tbody>

 <tbody>

  <tr>
    <th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2">268</font></th>  <td bgcolor="#ffffff" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; ">    <span \
class="k">return</span> <span class="n">cacheTheme</span><span \
class="p">;</span></pre></td>  <th bgcolor="#f0f0f0" style="border-left: 1px solid \
#C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font \
size="2">306</font></th>  <td bgcolor="#ffffff" width="50%"><pre style="font-size: \
8pt; line-height: 140%; margin: 0; ">    <span class="k">return</span> <span \
class="n">cacheTheme</span><span class="p">;</span></pre></td>  </tr>

 </tbody>

</table>

  <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">One thing I don&#39;t \
understand (not related to your changes though) - why does this return cacheTheme \
which never ever changes inside this method? And it also never returns anywhere else, \
so why is it even returning a boolean value when its value is already known before \
this method? :O</pre>  </blockquote>

</blockquote>
<pre style="margin-left: 1em; white-space: pre-wrap; white-space: -moz-pre-wrap; \
white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">That&#39;s \
the million dollar question isn&#39;t it ;)

useCache is a getter, except it&#39;s really not. It is however being (ab)used as \
single entry point for pre-cache-access conditions, and therefore a convenient \
lazy-init function. i.e. when one calls useCache() one actually does this from an \
effect POV:

if (d-&gt;useCache) {
 d-&gt;initPixmapCache();
 KImageCache cache = d-&gt;pixmapCache;
 [...]
}

To that extent it would really be better (for the readability) of the respective \
functions to move the lazy-init into pixmapCache() and svgElementsCache() functions \
the resulting access code remains almost the same as currently:

if (d-&gt;useCache) {
  KImageCache cache = d-&gt;pixmapCache();
  [...]
}

This way however there&#39;s no file IO in the if. Ever. Additionally right now there \
is no active lazy init for the svg elements cache it appears. The only way to get \
that cache initalized is by somehow getting a discardCache(...) call which will tear \
it down and then (re)init :/.</pre> <br />

<p>- Harald</p>

<br />
<p>On January 28th, 2014, 9:18 a.m. UTC, Harald Sitter wrote:</p>

<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="8" \
style="background-image: \
url('https://git.reviewboard.kde.org/static/rb/images/review_request_box_top_bg.ab6f3b1072c9.png'); \
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solid;">  <tr>
  <td>

<div>Review request for Plasma, Aaron J. Seigo and Martin Klapetek.</div>
<div>By Harald Sitter.</div>

<p style="color: grey;"><i>Updated Jan. 28, 2014, 9:18 a.m.</i></p>

<div style="margin-top: 1.5em;">
 <b style="color: #575012; font-size: 10pt;">Repository: </b>
kdelibs
</div>

<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
 <table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" \
style="border: 1px solid #b8b5a0">  <tr>
  <td>
   <pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
                break-word;">- introduce svgelements cache handling in useCache()
- to decide whether or not to discard a cache type now the mtimes of metadata.desktop \
and the respective cache file are compared (previously this was an invalid file \
                compared to cache change time)
- cache cleanup now happens entirely before creation of the KImageCache instance to \
prevent any sort of problem there

- add fixme comment about broken version-based cache handling. for one the version \
specific file name is not actually used for the KImageCache and for another the \
entire shebang is missing from svgelements all together. this has the very \
unfortunate side effect that the *active* cache files are deleted ever so often, it \
may be worth removing the code portions until someone finds time/interest to actually \
implement this in a working fashion.</pre>  </td>
 </tr>
</table>

<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: \
1px solid #b8b5a0">  <tr>
  <td>
   <pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">upgraded from 4.8 straight to 4.12 -&gt; theme caches correctly \
discarded</pre>  </td>
 </tr>
</table>

<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">

 <li>plasma/theme.cpp <span style="color: grey">(cb44878)</span></li>

</ul>

<p><a href="https://git.reviewboard.kde.org/r/115326/diff/" style="margin-left: \
3em;">View Diff</a></p>

  </td>
 </tr>
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