Smooth scrolling

[Mark Smith]

Very nice. Thanks Panos

> On Feb 2, 2021, at 2:54 PM, panagiotis merakos via use-livecode <use-livecode at lists.runrev.com> wrote:
> 
> Hello folks,
> 
> This bug report contains a workaround for smooth scrolling - hope it helps.
> 
> https://quality.livecode.com/show_bug.cgi?id=19759
> 
> Cheers,
> Panos
> --
> 
> On Tue, 2 Feb 2021 at 16:17, Craig newman via use-livecode <
> use-livecode at lists.runrev.com> wrote:
> 
>> On a Mac, I made a field with 25000 words or so. Certainly dragging the
>> thumb is jerky.
>> 
>> But dragging the thumb forces the field's scroll  to track the thumbPos, as
>> it relates to the number of lines and the total "pixel" travel available to
>> that thumb. I don't see how a field could scroll smoothly at all, since the
>> thumb and the scroll are locked together.
>> 
>> In other words, how can it "glide" from one line (scroll position) to
>> another, since the thumbPos has a finite number of possible locations, and
>> if there are a LOT of lines, each location may be several lines away?
>> 
>> Craig
>> 
>> -----Original Message-----
>> From: use-livecode [mailto:use-livecode-bounces at lists.runrev.com] On
>> Behalf
>> Of Richard Gaskin via use-livecode
>> Sent: Monday, February 01, 2021 10:11 PM
>> To: use-livecode at lists.runrev.com
>> Cc: Richard Gaskin <ambassador at fourthworld.com>
>> Subject: Re: Smooth scrolling
>> 
>> David Epstein wrote:
>> 
>>> My impression is that a LiveCode field scrolls less smoothly than  > a
>> comparable field in some other programs, such as MS Word and  > Scrivener.
>> If I paste about 25,000 words into a word wrapped  > scrolling field, and
>> then drag the scrolling thumb up and down  > there is much more jumpiness
>> than I see when I do the same thing  > to the same text in those other
>> programs.  (LC 9.6 on Mac OS 10.12.6).
>>> Do others see the same thing?  Does anyone know the underlying cause  >
>> of this, or a remedy?
>> 
>> Nice to hear the name Scrivener. Blount did some good rethinking of how
>> words are managed when he came up with that app.
>> 
>> In the olden days I remember being impressed with how smoothly LC scrolled
>> vs things like Word, which wasn't all that surprising given that LC buffers
>> the whole field in RAM while Word pages from disk.
>> 
>> A lot's changed since then. Not only have SSDs taken over to narrow the
>> gap,
>> but I no longer have a copy of Word to compare anything to. :)
>> 
>> But I did just do a quick test of LC v9.6.2rc2 vs LibreOffice Write on
>> Ubuntu 18.04, using Kafka's Metamorphosis to get a reasonably close number
>> of words to your test (Gutenberg Project RTF is 25,180 words:
>> http://www.gutenberg.org/files/5200/5200-r.rtf ).
>> 
>> Very different setup of course, but FWIW LC and LibreOffice are quite close
>> in scrolling, though LC seems noticeably smoother.
>> 
>> Of course Ubuntu and macOS couldn't be more different from top to bottom,
>> with different font managers, buffering APIs, compositors, etc., so while
>> it
>> was easy for me to do this quick test it's almost entirely useless.
>> 
>> What might be nice would be someone with good knowledge of Apple low-level
>> tools, similar to the ones we see for Android or to some degree strace,
>> where graphical UI stuff can be profiled so we can see what Word and LC are
>> doing differently.
>> 
>> It might also be worth setting the field's layerMode to "scrolling" and the
>> stack's compositorType to "CoreGraphics" to see if that improves things.
>> 
>> --
>>  Richard Gaskin
>>  Fourth World Systems
>>  Software Design and Development for the Desktop, Mobile, and the Web
>>  ____________________________________________________________________
>>  Ambassador at FourthWorld.com                http://www.FourthWorld.com
>> 
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