Re: Scrolling screen lines, I knew, it's impossible.

On 29/01/11 1:44 PM, Bram Moolenaar wrote:
> Ben Schmidt wrote:
>
>> On 27/01/11 3:38 AM, oCameLo wrote:
>>> There's so many questions and feature requests about use mouse to
>>> scroll screen lines, but until now, it's still impossible.
>>
>> Bram, you're not opposed to this kind of feature, are you? So if I did
>> some work on it, it could be included in Vim at some stage, right?
>
> This is a change that has a high probablity of introducing new bugs.

True, though if coded carefully, these bugs should only appear when the
feature is turned on.

> There are also a few questions about how to allow the user to access
> this, with an option setting or with different scroll commands?
> Probably a setting, so that it can work with scrollbars.

I think it would probably be best to do this in stages:

1. Add new commands to scroll one screen line at a time. Test it out,
including by mapping the scrollwheel to those new commands in the X
GUIs. This shouldn't be too hard, as Vim can already display lines
starting part way through; it just usually doesn't. The experience
wouldn't be very smooth yet either, but screen-line scrolling would at
least be possible, and it would pave the way for something better.

2. Add an option to make scrolling work with screen lines. The meaning
of this option would be to affect all scrolling. To start with, though,
just make it change the meaning of the scroll wheel in X GUIs (already
implemented), and where easy, the clicks of the scroll bar arrows. It
might not affect Windows yet; it depends how the scrolling works there,
and I haven't looked in any detail.

3. Make other parts of Vim, such as moving line-to-line, vertical jumps,
and scrolling for scrolloff honour the new option, too, choosing window
positions that begin with partial lines. This would make the editing
experience pretty smooth.

4. Update the code for scrollbars more thoroughly, so that dragging the
bar can work with screen lines, too. Windows should definitely benefit
by this stage and the feature would basically be finished.

5. Pick the nits of little bugs that we can't foresee.

What do you think? Would this be an OK way to proceed?

Ben.

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