Etherpad page up/page down has a substandard user experience..

[JohnMcLear]

https://youtu.be/d-ZM8bozIQw is the video showing an example of each of the 7 tests carried out across 6 editors (some offline, some online).

Test research findings.

1. Page down from line 0

notepad => Goes to one line above expected line
winword => Incorrect, caret in wrong place
online word => same as winword
google docs=> Incorrect
etherpad=> Incorrect, Goes to one line above expected line
libreoffice=> Really weird, caret and focus in wrong place

2. page down then up from caret at [0, whatever]

notepad=> Correct
winword=> Correct
online word=> Correct
google docs=> Correct
etherpad=> Wrong, loses a line
libreoffice=> Correct	

3. page up / down over content that is a huge length line on 0,0

notepad=> Correct
winword=> Focus is correct but caret is wrong
online word=> Same as Winword
google docs=> Incorrect (2 lines too far down
etherpad=> Completely broken
libreoffice=> Really weird, caret and focus in wrong place		

4. page down / up where notion of page break exists

notepad=> Notion doesn't exist
winword=> Really bizarre user experience and loses historical references
online word=> Nearly correct (not that winword is not correct!) .. On various page downs/page up if caret lands on blank line the historical reference position is lost.
google docs=> Loses historical references on page up after just two normal page downs with no specific line breaks etc being hit.
etherpad=> Notion doesn't exist
libreoffice=> Correct

5. caret location on X axis is maintained on page down/up

notepad=> Broken, goes to character 0 on blank line
winword=> Correct!  Very impressive, keeps indentation even after hitting blank line and visiting last character in document.
online word=> Broken, goes to character 0 on blank line
google docs=> Broken, goes to character 0 on blank line
etherpad=> Broken, goes to character 0 on blank line
libreoffice=> Broken, goes to character 0 on blank line

6. Transition / lag

notepad=> Fast
winword=> Smooth, Fast.
online word=> Jerky.
google docs=> Smooth-ish, Fast-ish.  Page identifier on scroll bar begins to land behind page location on page up/down event.
etherpad=> Slow, Jerky.
libreoffice=> Fast.

7. Page down on long text content

etherpad=> Broken.
all others=> Fine.

Some rules of page up / down

• Caret should always go back to position on page up after page down event (consider if this should be position after others editing or new position take into account edits [much harder to implement].
• Should always shift focus past visible content and be within a few lines of previous viewport as per spec.
• Smooth transition is a nice to have but it should be immediate.

Aria spec https://www.w3.org/TR/wai-aria-practices-1.1/ :

Page Down (Optional): Moves focus down an author-determined number of rows, typically scrolling so the bottom row in the currently visible set of rows becomes one of the first visible rows. If focus is in the last row of the grid, focus does not move.

Page Up (Optional): Moves focus up an author-determined number of rows, typically scrolling so the top row in the currently visible set of rows becomes one of the last visible rows. If focus is in the first row of the grid, focus does not move.

[goatandsheep]

I didn't fully understood the tests, but here are my results for Zoho writer:

normal text, i.e. Roboto 12

• consistently 12 lines lower on page up
• page up and down move cursor to [0, whatever]
• tested on long lines, short lines, single character lines, lorem ipsum, paragraphed and non-paragraphed text and vertical columns of 0's
• transition is very smooth
• page down consistently lands on the next page

Monospaced 24px:

• page up and down works perfectly

Monospaced 12px:

• page up and down is 3 lines down

This is the text I used:

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Aenean quis risus in elit tempor faucibus id efficitur turpis. Donec id pharetra ante. Integer vitae mi pharetra, mollis elit non, consectetur risus. Cras malesuada faucibus odio, et hendrerit dolor viverra ut. Pellentesque eu lobortis nunc. Nunc rutrum feugiat justo ac fermentum. Donec gravida, ipsum vel varius gravida, turpis neque egestas sapien, quis hendrerit odio arcu et magna. Suspendisse hendrerit dictum venenatis. Sed id dui in est ullamcorper tempus. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Morbi leo diam, sollicitudin rutrum turpis eget, tempus viverra risus. Nulla commodo leo at accumsan blandit. Nulla massa lectus, pellentesque vitae pretium ut, porttitor sit amet velit. Nunc interdum vestibulum velit, sit amet molestie urna suscipit vitae. Ut vel augue scelerisque, viverra neque quis, fermentum arcu. 

Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Phasellus fermentum est vel vehicula pharetra. Proin lacinia arcu augue, at pellentesque justo ultrices vitae. Nullam tempor euismod lorem, sit amet hendrerit augue tristique quis. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos. Aliquam faucibus vel lacus quis condimentum. Fusce nibh elit, iaculis a consectetur eget, sodales quis lacus. In massa eros, luctus quis volutpat non, posuere sit amet neque. Donec rhoncus risus velit, eu auctor nisi egestas sit amet. Curabitur fringilla turpis nec mi iaculis rutrum.

Aenean vel auctor neque. Sed sit amet magna pulvinar, dictum nibh sed, egestas risus. Sed dignissim erat quam, sed tincidunt velit vulputate nec. Aenean rhoncus nunc tincidunt scelerisque luctus. Morbi faucibus sodales turpis, quis sollicitudin nunc congue vel. Quisque erat enim, facilisis ut diam quis, vulputate suscipit neque. Proin sed risus sit amet erat pharetra auctor. Curabitur iaculis accumsan nisi sed scelerisque. Pellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Cras lacinia interdum accumsan. Nulla malesuada est tincidunt vehicula accumsan. Praesent lobortis sagittis dapibus. 

Morbi ut enim cursus, lobortis arcu scelerisque, blandit enim. Duis efficitur ornare tellus vel finibus. Vestibulum pharetra sem ac sodales condimentum. Morbi vel dui lacinia, tincidunt quam vitae, tincidunt orci. Suspendisse finibus lacus lacus, quis faucibus sapien hendrerit vel. Integer nec tempus arcu, nec varius magna. In hendrerit et urna in convallis. Vestibulum iaculis ex at massa iaculis, vel viverra lorem consequat. In ut egestas quam. Phasellus pellentesque massa sed sapien volutpat, nec imperdiet tellus facilisis.
Nulla tempus lacus quam, vel hendrerit lectus ornare non. Orci varius natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Nulla id orci a ligula sagittis sagittis vel vel nisi. Donec eleifend non erat non dignissim. Vivamus quis nisi placerat, consequat metus vel, tempor nunc. Vivamus sollicitudin velit nisi, in ultrices quam tincidunt id. Ut condimentum nisl et justo commodo, eu gravida sapien venenatis. Etiam porttitor ligula sed lectus consequat, sit amet congue tellus convallis. Aliquam nec efficitur est. 

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[JohnMcLear]

I recorded a video of me testing zoho and added results. @goatandsheep https://youtu.be/wJ7EgU0awCY

I get WILDLY different results to you, so what's going on?

[JohnMcLear]

Results of page up / page down (no shift) Best to worst.

	page down	page up accuracy	long line	page breaks	caret offset	transition	long text
textarea(5)	y*4	y	y	x	x*3	y	y
atom(5)	x*5	y	y	x	y	y	y
ckeditor(5)	y	x*6	y	x*7	y	y	y
notepad(4)	x	y	y	x	x	y	y
winword(4)	x	y	x	x	y	y	y
libre office(4)	x	y	x	y	x	y	y
word online(3)	x	y	x	y*2	x	x	y
google docs(3)	x	y	x	x	x	y*1	y
etherpad(0)	x	x	x	x	x	x	x
zoho writer(0)	x	x	x	x	x	x	x

1 = javascript used to draw page number by scroll bar is laggy
2 = loses positioning over page breaks
3 = loses caret offset on blank line
4 = In firefox it loses line offset a little on page down but I can't consistently replicate - chrome is fine.
5 = Goes to two lines below last viewable line (should be one).
6 = Demo at https://ckeditor.com/ckeditor-5/demo/ fails going back to correct line.
7 = Demo at https://ckeditor.com/docs/ckeditor5/latest/features/page-break.html fails to have transition between pages (loses previous line numbering)

Note that I haven't included shift page up/down results.. I will do those asap.

Results of Shift page up/down

	selects to first char, first line spam PU	selects to last char, last line spam PD	shift PU after shift PD neutralizes selection	select forwards PD and PU
textarea(4)	y	y	y	y
atom(4)	y	y	y	y
winword(4)	y	y	y	y
ckeditor(0)	x	x	x	x
notepad(0)	x*1	x	x	x
word online(0)	x	x	x	x
google docs(0)	x	x	x	x
libre office(0)	x	x	x	x
etherpad(0)	x	x	x	x
zoho writer(0)	x	x	x	x

*1 doesn't work w/ out sufficient content

[JohnMcLear]

Just a note from me, waiting on @webzwo0i to do a specific part but most functionality and testing is in.

[JohnMcLear]

Fixed in PR #7437 (merged) — PageDown now advances the caret by a full page of lines instead of scrolling without moving the cursor.