1394708 - <input> is too wide in nightly57.0a1 on Windows10 Japanese Edition

Status: NEW

(Core :: Layout: Form Controls, defect, P3)

Description

[Alice0775 White]

Attachment: screenshot

Steps To Reproduce:
0. Windows10 home 64bit CU, Japanese Edition
1. Open https://docs.python.org/2/library/abc.html

Actual Results:
See attached screenshot

Comment 1

[Alice0775 White]

Attachment: testcase html

Comment 2

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

Well, the causes of this difference with Edge and Chrome are different.

Edge treats the generic font family, "sans-serif", not as "Meiryo". Actually, ASCII characters are not displayed with Meiryo, but Japanese characters are displayed with Meiryo. So, if you change the font-family of the <input> to "Meiryo" or "メイリオ", you can see same result. So, the generic font family handling is different from Gecko.

On the other hand, Chrome behaves odd. Even if you change the font-family to "Meiryo" or "メイリオ", you don't see wider <input> element but the <input> element is displayed with Meiryo. So, the behavior is really odd to me. Chrome might not use Meiryo's metrics to compute <input> element size.

I guess this may not be so major problem since this is caused by incomplete style rules. If web designers change font of <input>, they should specify <input> element size with CSS rather than using size attribute or not specifying anything for avoiding too long/short <input> element.

On the other hand, if we could change <input size> computation or default size of <input>, we may have avoided this issue forever. However, it may cause other issues like too short <input> element for specific fonts.


This issue might have been discussed in other bugs, but I don't know that. Any ideas?

Comment 3

[Alice0775 White]

Attachment: testcase html

Comment 4

[Alice0775 White]

Attachment: screenshot of testcase html

Nightly57.0a1 : approx 22 chars
Beta56.0b6    : approx 12 chars

It is too wide in Nightly57.0a1.

Comment 5

[Alice0775 White]

The width of the span element does not differ greatly between nightly and release.
However, the width of the input element is doubled....
why?

Comment 6

[Alice0775 White]

Attachment: testcase 2

Comment 7

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

The width is computed with average character width of the font that is stored in font metrics, not actual width:
https://searchfox.org/mozilla-central/rev/cd82cacec2cf734768827ff85ba2dba90a534c5e/layout/forms/nsTextControlFrame.cpp#141,157,161-162

And the default size attribute value of Gecko is 20:
https://searchfox.org/mozilla-central/rev/cd82cacec2cf734768827ff85ba2dba90a534c5e/dom/html/nsITextControlElement.h#218

Comment 8

[Alice0775 White]

Attachment: testcase 3 html, font specified on ancestor

This seems to be as expected if font specified on ancestor element.

Comment 9

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

(In reply to Alice0775 White from comment #8)
> This seems to be as expected if font specified on ancestor element.

Yes, web designers need to specify font-family to <input> directly since we specify it directly in default stylesheet. Therefore, this should not be so major.
https://searchfox.org/mozilla-central/rev/cd82cacec2cf734768827ff85ba2dba90a534c5e/layout/style/res/forms.css#89,98

Comment 10

[Jonathan Watt [:jwatt]]

Mass bug change to replace various 'parity' whiteboard flags with the new canonical keywords. (See bug 1443764 comment 13.)