mailing-list for TeXmacs Users

[Henri Lesourd <address@hidden>]

David Allouche wrote:

> On Sun, Oct 26, 2008 at 20:48, Henri Lesourd <address@hidden 
> <mailto:address@hidden>> wrote:
>
>     Andrea Gamba wrote:
>
>
>         It would be also nice that the window is always centered when
>         zooming in/out.
>         Now it is aligned to the left, do you think it is possible to
>         change this
>         setting?
>
>          
>
>     No, there are no Scheme commands to change the alignment
>     of the displayed text inside the window (nor to move or
>     resize the TeXmacs window, btw).
>
>
> Henri, I think you misunderstood Andrea.
>
> What Andrea seems to have in mind is that when changing the shrinking 
> factor, the position at the center of the window should not change.
>
> In more technical terms: texmacs has a several coordinate systems: one 
> in which boxes are positioned on a page, and another in which the page 
> is positioned in the editor's viewport. When the shrinking factor is 
> changed, only one page point can have a invariant viewport position. 
> Let's call this point the "pinned point". According to Andrea, 
> currently the viewport's top-left corner is pinned. And he would like 
> to pin the center of the viewport.
>
> From the perspective of the viewport's implementor, the current 
> behaviour is the simplest fundamental one. It would be reasonable to 
> require that pinning be implemented in scheme.
>
> I expect that texmacs does not provide the necessary glue. Here's what 
> would be needed:
>
>  * getting and setting the relative position of the viewport and page 
> coordinate systems
>  * getting the size of the viewport in page coordinates
>
> Not presuming of what the actual glue should look like. This kind of 
> API is tricky to get right.

As far as I understood when looking at Joris's 
implementation
of the widgets, there is currently no API at all to scroll
the document inside the editor widget: everything is 
hardwired
inside the C++ (e.g., how it reproduces the shitty 
emacs behaviour
of jumping half a page when you want to go down (resp. 
up) when
the cursor is located at the bottom (resp. top) line 
of the editor
window).

Thus it's not a matter of the coordinate system, it's 
a matter
of having a sufficiently sophisticated control on the 
behaviour
of your UI components at the lower level. Once you 
have this,
of course you can program the nice Scheme extension 
you want.