Comparison between direction and unicode-bidi in css-CSS Tutorial-php.cn

Comparison between direction and unicode-bidi in css

黄舟

Release： 2017-06-20 10:39:19

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When making multi-language pages, students who have been exposed to Arabic and Hebrew must understand the importance of writing direction, including the writing order before the May 4th Movement, which was also from right to left. The unicode-bidi and direction attributes in css determine the direction of HTML or XML text rendering. The two attributes can be used in combination to change the text writing order

direction

direction attribute has three values

inherit uses the settings of the parent element

ltr default value, left to right, from left to right

rtl right to left from right to Left

Our default writing order is from left to right, no special settings are required, but for Arabic it is from right to left, then you need to set the direction attribute to display correctly

Prevent browser rewritingtext-alignLet’s make the default settings

<p style="direction:rtl;text-align: initial;">
    طهيس يس تآخت تهات يس وريتتآن فروم ريغت تو لآفت تهات يس وسآد    
</p>

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There is also a correspondinghtml attributedir can be set

<p dir="rtl" dtyle="text-align: initial;">
    طهيس يس تآخت تهات يس وريتتآن فروم ريغت تو لآفت تهات يس وسآد    
</p>

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The direction attribute determines the default writing order. This is different from text-align. The latter is the direction and the writing order remains unchanged.

<p style="direction: rtl;text-align: initial;">1 2 3 4 5 6。</p>
<p style="text-align:right;">1 2 3 4 5 6。</p>

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unicode-bidi

It seems that there is a direction. We can deal with the problem of writing direction. What does unicode-bidi do?

Browsers usually determine the writing direction based on the lang attribute or a special font-family, but if a sentence includes copywriting in both directions, you need to use the unicode-bidi attribute

unicode-bidi has three widely supported values

normal Use the original order in whatever order

embed acts on inline elements, and the value of the direction attribute specifies the embedding layer, which is hidden inside the object. Formula reorder

bidi-override Reorder strictly according to the value of the direction attribute. Ignore the implicit two-way operation rules

To be honest, I can’t understand this explanation. Let’s look at an example

<p style="direction:rtl;text-align: initial;">this is a test</p>
<p style="direction:rtl;unicode-bidi:bidi-override;text-align: initial;">
    this is a test
</p>
<p style="direction:rtl;unicode-bidi:bidi-override;text-align: initial;">
    this <span style="unicode-bidi:embed;">is a</span> test
</p>

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The first line is simply right-aligned, and the text will not be written backwards (Arabic Yes, there will be an explanation later)

The two attributes in the second line are combined, not only writing right to left, but also writing from right to left. This is the serious way of writing Arabic

The wonderful effect of the third line is that the style unicode-bidi:embed is added on the basis of the second line; it will not be written backwards, but written in the normal writing order

Why for Arabic The language can be displayed correctly only by setting the direction, but the English words only have a right-aligned effect and will not be written from right to left. It only works if unicode-bidi:bidi-override; is set.

This is the same as It depends on the specific language. For Arabic and Hebrew, it works automatically. If the browser cannot determine the language with a single number or letter, it uses the rtl default setting. For English, etc., the default left-to-right method is still used, and only unicode- bidi rewrite

When you specify the language as Arabic when declaring, the page will automatically write the order rtl

<html lang="ar">

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direction indicates the writing direction, which is different from writing-mode Each has its own advantages and disadvantages and can be used in combination.

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