[Webkit-unassigned] [Bug 153405] [GTK] Implement overlay scrollbars

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=153405

--- Comment #2 from Darin Adler <darin at apple.com> ---
Comment on attachment 269692
  --> https://bugs.webkit.org/attachment.cgi?id=269692
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=269692&action=review

I have some comments, but I’m not sure enough about everything for either a review+ or a review-.

Generally looks good. I am a bit confused by some of the critical details, though.

> Source/WebCore/platform/ScrollAnimatorNone.cpp:54
> +static const double kFrameRate = 60;
> +static const double kTickTime = 1 / kFrameRate;
> +static const double kMinimumTimerInterval = .001;
> +static const double kOverflowScrollbarsAnimationDuration = 1;
> +static const double kOverflowScrollbarsAnimationHideDelay = 2;

This (existing, not new) use of k prefixes doesn’t seem right for WebKit coding style.

> Source/WebCore/platform/ScrollAnimatorNone.cpp:631
> +    gdouble progress = 1;

All the rest are using double, but this one place uses gdouble. Surprised this compiles at all on non-GTK platforms.

> Source/WebCore/platform/ScrollAnimatorNone.h:53
>      explicit ScrollAnimatorNone(ScrollableArea&);

I don’t understand how ScrollAnimatorNone is still the right name for this class, now that it’s implementing scrollbar appear/disappear animations. Is this the right way to factor this.

> Source/WebCore/platform/ScrollAnimatorNone.h:188
> +    Scrollbar* m_horizontalOverlayScrollbar { nullptr };
> +    Scrollbar* m_verticalOverlayScrollbar { nullptr };
> +    bool m_overlayScrollbarsLocked { false };
> +    Timer m_overlayScrollbarAnimationTimer;
> +    double m_overlayScrollbarAnimationSource { 0 };
> +    double m_overlayScrollbarAnimationTarget { 0 };
> +    double m_overlayScrollbarAnimationCurrent { 0 };
> +    double m_overlayScrollbarAnimationStartTime { 0 };
> +    double m_overlayScrollbarAnimationEndTime { 0 };

That looks like a lot of unconditional overhead for ports that never use this, which currently includes EFL at least, perhaps also Mac and iOS? Or maybe not? Is there a way to make this cost conditional?

In new code we are trying to use std::chrono for time, rather than plain doubles.

> Source/WebCore/platform/Scrollbar.h:134
> +    double opacity() const { return m_opacity; }
> +    void setOpacity(double opacity) { m_opacity = opacity; }

A little strange to use double for this. Don’t we use float for this kind of thing elsewhere?

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