[webkit-dev] Settings and Preferences in layout tests

[Adam Barth]

On Wed, Sep 26, 2012 at 2:35 PM, Brady Eidson <beidson at apple.com> wrote:

>
> On Sep 26, 2012, at 2:05 PM, Adam Barth <abarth at webkit.org> wrote:
>
> [re-sent from the proper address]
>
> On Wed, Sep 26, 2012 at 2:00 PM, Adam Barth <abarth at nowhere> wrote:
>
>>
>>
>> On Wed, Sep 26, 2012 at 1:53 PM, Brady Eidson <beidson at apple.com> wrote:
>>
>>>
>>> On Sep 26, 2012, at 1:48 PM, Ryosuke Niwa <rniwa at webkit.org> wrote:
>>>
>>> On Wed, Sep 26, 2012 at 1:44 PM, Simon Fraser <simon.fraser at apple.com>wrote:
>>>
>>>>
>>>>  First, direct calls on testRunner that just set preferences should be
>>>> migrated to internals.settings or testRunner.overridePreference calls, I
>>>> think (I don't know if either is preferred).
>>>>
>>>
>>> I support the idea of unifying the approaches and just use
>>> internals.settings. However, the last time I checked, Alexey had some
>>> concerns about using internals due to settings may not be properly
>>> propagated to WebKit2 layer. Has this concern been addressed?
>>>
>>>
>>> In general I prefer the overridePreference() calls whenever they exist.
>>>
>>> internals.settings are not exposed in any real-world product whereas
>>> preferences exist in each platform's WebKit-layer API that they expose to
>>> their embedders in some form.
>>>
>>
>> The main downside of overridePreference is that it requires that you
>> expose an API for twiddling the preference on every port.  That can lead to
>> us exposing unneeded APIs (making them harder to remove) and to a bunch of
>> port-specific code in an otherwise port-independent patch.
>>
>> IMHO, we should prefer InternalSettings unless we need to test the
>> WebKit-layer code.
>>
>
> I suppose we're biased in Mac-land where the mechanism originated, but the
> "API" is simply a single string based API that only had to be implemented
> once.
>
> Your comment leads me to understand that at least one other port doesn't
> have simple string based preferences.
>
> Of course to add *any* new internal setting new code must be added
> specifically for that setting...
>
> Of course that code only has to be added once for all platforms…
>
> I would argue it's not a clear cut decision either way.
>

I'm curious whether you've added something to overridePreferences recently.
 It's a ton of port-specific work.  For example, here's the changed that
added WebKitCSSGridLayoutEnabled:  http://trac.webkit.org/changeset/117613.
 It had to change these files:

Source/WebKit/chromium/public/WebSettings.h
Source/WebKit/chromium/src/WebSettingsImpl.cpp
Source/WebKit/chromium/src/WebSettingsImpl.h
Source/WebKit/mac/WebView/WebPreferenceKeysPrivate.h
Source/WebKit/mac/WebView/WebPreferences.mm
Source/WebKit/mac/WebView/WebPreferencesPrivate.h
Source/WebKit/mac/WebView/WebView.mm
Source/WebKit2/Shared/WebPreferencesStore.h
Source/WebKit2/UIProcess/API/C/WKPreferences.cpp
Source/WebKit2/UIProcess/API/C/WKPreferencesPrivate.h
Source/WebKit2/WebProcess/InjectedBundle/InjectedBundle.cpp
Source/WebKit2/WebProcess/WebPage/WebPage.cpp
Tools/DumpRenderTree/chromium/LayoutTestController.cpp
Tools/DumpRenderTree/chromium/WebPreferences.cpp
Tools/DumpRenderTree/chromium/WebPreferences.h

... and even then, the patch only made it work in Chromium and apple-mac!

By contrast, here's a patch that adds something to InternalSettings:
http://trac.webkit.org/changeset/124372:

Source/WebCore/testing/InternalSettings.cpp
Source/WebCore/testing/InternalSettings.h
Source/WebCore/testing/InternalSettings.idl
Source/WebKit/chromium/public/WebSettings.h
Source/WebKit/chromium/src/WebSettingsImpl.cpp
Source/WebKit/chromium/src/WebSettingsImpl.h

... and now it we can run the tests on all ports.  The API for twiddling
the preference is exposed only on Chromium, which is the only port that
wishes to expose this setting at this time.

Adam
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