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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - [GTK] Add kinetic scrolling"
href="https://bugs.webkit.org/show_bug.cgi?id=155750#c8">Comment # 8</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - [GTK] Add kinetic scrolling"
href="https://bugs.webkit.org/show_bug.cgi?id=155750">bug 155750</a>
from <span class="vcard"><a class="email" href="mailto:cgarcia@igalia.com" title="Carlos Garcia Campos <cgarcia@igalia.com>"> <span class="fn">Carlos Garcia Campos</span></a>
</span></b>
<pre>Comment on <span class=""><a href="attachment.cgi?id=276397&action=diff" name="attach_276397" title="WIP patch">attachment 276397</a> <a href="attachment.cgi?id=276397&action=edit" title="WIP patch">[details]</a></span>
WIP patch
View in context: <a href="https://bugs.webkit.org/attachment.cgi?id=276397&action=review">https://bugs.webkit.org/attachment.cgi?id=276397&action=review</a>
Some general comments only for now.
<span class="quote">> Source/WTF/wtf/FeatureDefines.h:320
> +#if !defined(ENABLE_KINETIC_SCROLLING)
> +#define ENABLE_KINETIC_SCROLLING 1
> +#endif</span >
We don't need any compile option for this, just add the ScrollAnimationKinetic.cpp to the GTK compilation.
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:87
> +ScrollAnimationKinetic::PerAxisData::PerAxisData()
> + : PerAxisData(0, 0, 0, 0)
> +{
> +}</span >
Initialize the members when declared in the header file and remove the explicit constructor
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:96
> + , m_equilibriumPosition(0)
> + , m_t(0)</span >
Initialize constant values in the header when declared.
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:104
> + m_t += timeDelta;</span >
Do not use abbreviations for members, what does t mean?
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:138
> + if (animationTimerActive())
> + stop();</span >
stop already checks if the animation is active.
<span class="quote">>> Source/WebCore/platform/ScrollAnimationKinetic.cpp:144
>> + m_scrollHistory.append(ScrollEvent(orientation, step * multiplier, currentTime));
>
> What about letting ScrollAnimatorGtk handle the scrolling history and passing the computed inertia to ScrollAnimationKinetic when triggering inertial scrolling? This may help using the velocity values from the swipe gesture directly.</span >
Sounds good.
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:165
> +void ScrollAnimationKinetic::serviceAnimation()</span >
serviceAnimation comes from RAf when not using a timer, but we are using a timer. See ScrollAnimatorSmooth, we are not actually using serviceAnimation in GTK port.
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:172
> + FloatPoint accumDelta(0, 0);</span >
The default constructor already initializes its member to 0, so you don't need (0, 0);
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:186
> + if (velocity == FloatPoint(0, 0))</span >
Ditto.
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:196
> + animationTimerFired();</span >
I'm not sure I understand this, serviceAnimation should be equivalent to animationTimerFired().
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:228
> +void ScrollAnimationKinetic::startNextTimer(double delay)
> +{
> + m_animationTimer.startOneShot(delay);
> +}</span >
We have this in ScrollAnimationSmooth because we support RAF without the timer option, but in this case we can just use m_animationTimer.startOneShot(delay) directly.
<span class="quote">> Source/WebCore/platform/ScrollAnimationKinetic.cpp:233
> +bool ScrollAnimationKinetic::animationTimerActive() const
> +{
> + return m_animationTimer.isActive();
> +}</span >
Ditto.
<span class="quote">>> Source/WebKit2/UIProcess/gtk/GestureController.cpp:218
>> +void GestureController::SwipeGesture::swipe(SwipeGesture* swipeGesture, double x, double y, GtkGesture* gesture)
>
> x and y (which should probably be named velocityX and velocityY) could (should?) be used to trigger inertial scrolling.</span >
Indeed.</pre>
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