Re: Mixed L2R and R2L paragraphs and horizontal scroll

[martin rudalics]

>> Because it's no more a window but a line property, IIUC.  When, after
>> scrolling the first line, you move `point' to show another portion of
>> the second line like this
>>
>>        +---------+---------+-------------------+
>>        |$ijk     |abcdefgh$|abcdefghijk        |
>>        |KJIHGFED$|$HGFEDCBA|        KJIHGFEDCBA|
>>        |         |         |                   |
>>        +---------+---------+-------------------+
>>
>> you get two different non-zero values of `window-hscroll'.
>
> No, you don't necessarily get two different values.  The value from
> the second line defines a scroll from the right margin, not from the
> left.  (Which probably means it's not a good idea to have
> window-hscroll return a negative value in that case.)

When you hscroll the second line we must be able to return that somehow
- otherwise how would we know?  So either we have to invent a new
function like `window-RL-hscroll' or interpret the return value of
`window-hscroll' appropriately.  And this function must probably handle
lines containing both LR and RL text correctly.

>>  >       +---------+---------+-------------------+
>>  >       |$ijk     |abcdefgh$|abcdefghijk        |
>>  >       |     KJI$|$HGFEDCBA|        KJIHGFEDCBA|
>>  >       |         |         |                   |
>>  >       +---------+---------+-------------------+
>>  >
>>  > Is this what you are suggesting?
>>
>> This would be needlessly inconvenient.
>
> Why inconvenient?

Inconvenient for the user.  Why scroll something out of view if there's
no urgent need to do so.  (Although a similar argument could be made for
pure LR text as well - why scroll the entire window when I want to see
the last characters of the single overlong line in my entire text.  With
automatic line-wrapping turned off, I mean.)

> That's what would happen if the second line was
> displayed at the left margin, like this:
>
>       +---------+---------+-------------------+
>       |$ijk     |abcdefgh$|abcdefghijk        |
>       |$IJK     |$HGFEDCBA|        KJIHGFEDCBA|
         ^^^^^^^^^
>       |         |         |                   |
>       +---------+---------+-------------------+

I fail to understand the marked text in your example.

> The advantage is that all the lines scroll in lockstep, albeit in two
> different directions, and `window-hscroll' can still return a single
> value whose meaning is well defined.

So it would be convenient for the designer.

>> Hence, `window-hscroll' should probably return the value for the
>> line `window-point' is on.
>
> That's also possible.  Are the users of this function normally
> interested only in the amount of scroll of the current line?

Mostly for calculating the argument of `set-window-hscroll' I suppose.
But I have never looked into this.

martin