1080830 - Scroll amount is very small or big

Status: NEW

(Core :: Layout, defect)

Description

[Alice0775 White]

Attachment: testcase scroll amount is very small

IE and Chrome does not have the problem.

Steps To Reproduce:
1. Open attached
2. Click upper pane and Attempt to scroll by mouse wheel or arrow key
   --- You can see the problem. Scroll amount is very small.

3. Click lower pane and Attempt to scroll by mouse wheel or arrow key
   --- This seems to be correct behavior.

Actual Results:
Scroll amount of the upper pane is very small.

Expected Results:
Scroll amount should be same as other place.

Comment 1

[Olli Pettay [:smaug][[e-mail]]]

To me Gecko's behavior is the expected one.
I wonder what heuristics IE and Chrome use in this kind of case.

Comment 2

[Timothy Nikkel (:tnikkel)]

Currently, the font size of the scrollable element is used to determine how much to scroll. For "content" the fontsize is 1px (even though it contains elements that have fontsize 18px), and the "content2" the fontsize is 16px.

Comment 3

[Timothy Nikkel (:tnikkel)]

Does anyone have a proposal of what to do instead?

Comment 4

[Masayuki Nakano [:masayuki] (he/him)(JST, +0900)]

Yeah, for mouse wheel scroll amount, we have mousewheel.min_line_scroll_amount pref whose value is minimum line height in pixels. When actual line height is smaller than the value, Gecko use the value as line height as to scroll.

If we make this value larger, somebody may feel it's too fast, though.

Comment 5

[Alice0775 White]

Attachment: testcase scroll amount is too big