[webkit-dev] Scrollbar Changes

Darin Fisher darin at chromium.org
Sat Sep 13 17:56:22 PDT 2008

Don't forget that scroll arrows need to change state when you hover
over the scroll thumb in Vista.  (That's a Vista-ism that many custom
scroll bar implementations--for example IE8--miss.)


On Fri, Sep 12, 2008 at 12:06 PM, Dave Hyatt <hyatt at apple.com> wrote:
> Scrollbars are going to be changing substantially in the next couple of
> weeks.
> Right now several ports have their own versions of PlatformScrollbar
> that all clone the same logic (with the only difference between the
> classes being metrics and rendering).
> The current plan for refactoring is to eliminate PlatformScrollbar and
> make Scrollbar into a class that handles scrolling using a non-native
> cross-platform implementation.  The Scrollbar class will be talking to a
> new ScrollbarTheme interface that will be platform-specific.
> ScrollbarTheme will be responsible for rendering scrollbars (and
> providing metrics for scrollbars).
> If any ports have special needs for this Scrollbar class (or for
> ScrollbarTheme), send me email or respond in this thread.  I know that
> both WebKit on OS X and Google Chrome have need of tickmarks support on
> scrollbars, so this will ultimately need to be built into the rendering
> model.
> Classes that still require truly native scrollbars can subclass
> Scrollbar (with the only cost being a handful of wasted member variables
> in Scrollbar), although we would strongly encourage ports not to use
> native scrollbars.  We will even be abandoning the native
> PlatformScrollbar implementation on the Mac.
> The new cross-platform Scrollbar class is going to support styling via
> CSS (initially for overflow sections only).  If your port doesn't use
> this class, then you won't get the upcoming CSS styling support.
> dave
> (hyatt at apple.com)
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