Re: Setting X-offset and Y-offset graphically.

[Richard Shann]

On Tue, 2013-04-23 at 17:49 +0200, Janek Warchoł wrote:
> 2013/4/23 Richard Shann <address@hidden>:
> > On Tue, 2013-04-23 at 17:16 +0200, Urs Liska wrote:
> >> David Nalesnik <address@hidden> schrieb:
> >> >I'm a little confused here too.  I watched the demo (very cool, BTW!)
> >> >and you are starting with a default curve, if I'm not mistaken.
> >
> > Well, only if the user clicks accurately on the control points marked
> > with the red crosses. The user has set up the coordinate system with the
> > first cross-hair click on the center staff line, and then the rest is
> > relative to that.
> >
> >> >Couldn'tthe
> >> >results of dragging the various control points be expressed as
> >> >displacements to the curve you started with, rather than as absolute
> >> >values?  Then adjustments would be made automatically with a
> >> >change in layout.
> >>
> >> That's what I thought initially too.
> >> But maybe this default curve isn't Lilypond's? Then he'd be out of luck.
> >
> > What would be needed is to get the user to click on the control points
> > accurately and then work out the differences from there. That could be
> > done...
> 
> What about this: ask the user to drag the control points.  Then he
> doesn't have to click precisely on the control point.

... well, continuing from my email in response to Urs
Denemo does not know where anything is until told. So if you click near
the first control point Denemo cannot draw the curve, so you get no
visualization of the shape...


> In more detail:
> - user enters slur editing mode, control points appear.
> - user clicks near first control point
> - holding the mouse button down, he moves the cursor 2 units
> horizontally and 1 unit vertically, then he releases the button.
this is the point where no newly drawn curve can be shown by Denemo
because it does not know where the other control points are.
> - this becomes \shape #'((2 . 1) ... )
> - similarly for other control points.
> 
> This way it doesn't matter how precisely he clicked on the control
> point, because we don't have to set up any absolute coordinate system
> - we just measure the displacement he did when mouse button was held
> down.  All is relative!
> Actually, the same mechanism could be applied to moving grobs you
> showed before.
This is what is being done for moving e.g. Rehearsal Marks... you just
click on the mark and then click where you want it to go to.

Richard

>   Things should become way simpler and more precise, and
> won't even need showing refpoints.
> 
> Does this make things clearer?
> Janek