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Re: display question: should ^N and \NNN widths be fixed?

From: Eli Zaretskii
Subject: Re: display question: should ^N and \NNN widths be fixed?
Date: Mon, 27 May 2002 10:33:13 +0300 (IDT)

On 27 May 2002, Thien-Thi Nguyen wrote:

>    The current code in indent.c assumes that buffer positions increase 
>    monotonically with screen positions.  I'm not saying that you should do 
>    my job of lifting that limitation, but please keep this in mind when you 
>    design and code the new indent.c, so that changing it for bidi Emacs 
>    would not be harder than it is today.
> what makes it difficult to support this lifting, today?

Just a lot of coding ;-)

The problem is that with bidi display, the relationship between buffer 
positions and screen positions is no longer a simple monotonically 
increasing function.  For example, if the buffer's contents is this:


where upper-case letters stand for right-to-left characters, then it is 
displayed as


and thus you cannot simply walk the buffer one character at a time and 
add their display widths to compute the display column.  For example, the 
column of C is 3 (zero-based), not 5.

Again, I'm not saying you should solve this problem when you work on your 
changes.  I'm just asking to keep this at the back of your mind when you 
make design decisions.

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