First Page Down doesn't scroll much (and cursor always on wrong line)

[peterflynn]

1. Open a file multiple screens tall. (I'm using the 'Getting Started' index.html with the window tall enough to show 72 lines of text -- window filling an entire 1920x1200 screen).
2. Put cursor at start of file
3. Page Down

Result: the viewport only scrolls 1-2 lines, so line 2 is at the top of the view and line 74 is at the bottom. The cursor stays near the bottom of the viewport as you page down.

Expected: on master, the view scrolls one whole screenful, so line 73 is at the top of the viewport. The cursor stays near the top of the viewport as you page down. This is how other editors seem to work also.

The same bug happens in reverse when you Page Up from the bottom of the file.

[peterflynn]

This sounds a little bit like #159. Marking for Sprint 20 tentatively since Page Up/Down problems have led to a lot of subtle bugs in the past (#1042, #1030, #1026, etc.).

[pthiess]

@njx : Not sure why this is a CMv3 bug ? Would be fixed with the integration? If not I would eventually remove the Sprint 20 tag and move it to S21.

[pthiess]

Reviewed.

[njx]

I'm assuming @peterflynn marked it cmv3 because it only reproduces in the cmv3 branch.

[pthiess]

Got it. I leave it up to your judgement whether it needs to be fixed this sprint.

Thanks,
Peter :)

[peterflynn]

@njx: Yes, only repros on v3 (the 'expected' description above is how v2/master behaves).

[njx]

I tested around this for awhile and didn't see any other unusual behavior. I'm guessing the heuristics have changed in CodeMirror. We should submit a patch eventually, but for now I think we can move this out to sprint 21.

[jasonsanjose]

Filed codemirror/codemirror5#1290 with a jsfiddle and boilerplate CodeMirror setup.

[jasonsanjose]

@marijnh fixed in codemirror/codemirror5@db4ad4a. I'll test this morning.

[jasonsanjose]

Looks like the cursor problem still exists. I'll file another spin off a new bug.

[jasonsanjose]

Filed #2974 for new cursor positioning issue.

[jasonsanjose]

FBNC @peterflynn. Spun off #2974 for cursor issue.

[peterflynn]

Confirmed fixed