1667929 - Select[multiple][size="1"] shows scrollbars bigger than the select on Windows

Status: NEW

(Core :: Widget: Win32, defect)

Description

[Danny Lin]

Attachment: Bad controller for select[multiple][size=1] in Firefox 81

User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

Create a tag <select multiple size=1>.

Actual results:

The controller (up and down arrows) is rendered badly. It spans two rows, and the down arrow is not clickable.

Expected results:

The controller (up and down arrows) should span one row with up and down arrow taking half height, and both arrows should be clickable.

Comment 1

[Danny Lin]

Attachment: Controller for select[multiple][size=1] in Firefox 52 (no up and down arrow)

Comment 2

[Danny Lin]

Attachment: Controller for select[multiple][size=1] in Chromium 85 (good)

Comment 3

[Danny Lin]

Comment on attachment 9178387 [details]
Controller for select[multiple][size=1] in Firefox 52 (no up and down arrow)

For reference: in Firefox 52 there is no controller spanning two rows, but just no clickable controller.

Comment 4

[Danny Lin]

Comment on attachment 9178387 [details]
Controller for select[multiple][size=1] in Firefox 52 (no up and down arrow)

For reference: in Firefox 52 there is no controller spanning two rows, but just no clickable controller.

Comment 5

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

Thank you for reporting this bug!

Testcase:

data:text/html,<select multiple size="1"><option>Volvo</option><option>Audi</option></select>

Using mozregression on Windows yields this range:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=f9356df325cd5df64ef952636b788db27fbfd19f&tochange=5d4199425f57cf5657ace9e868924164286e0f43

It seems Bug 1634109 is the only bug in the range related to <select> and scrollbar. Emilio, any ideas?

Comment 6

[Emilio Cobos Álvarez (:emilio)]

Nah, that only affects dropdown selects. Bug 1365806 is the actual culprit here.

Comment 7

[Emilio Cobos Álvarez (:emilio)]

Attachment: test-case

Comment 8

[Emilio Cobos Álvarez (:emilio)]

This is a Windows theme issue, where we don't allow painting scroll arrows smaller than a certain size. Before bug 1365806 we'd suppress the scrollbars if they didn't fit, but that's not great (specially on OSes where the minimum scrollbar size is big).

The windows theme should probably not claim to have a minimum size and allow painting smaller scroll arrows. This works for me on Linux already with the non-native theme disabled (widget.disable-native-theme-for-content). Do you know if with that pref flipped on Windows the test-case behaves a bit better?

Comment 9

[Ting-Yu Lin [:TYLin] (PDT, UTC-7)]

Attachment: select-widget-comparison-win10.png

For the testcase in comment 7, flipping widget.disable-native-theme-for-content=true on Windows 10 shrinks the scroll arrows a bit, but not much.

Comment 10

[Danny Lin]

Isn't there any way to workaround this? Other browsers just don't have this issue even on Windows...