Thanks. I was refering to flimage_tint which seemed to be like transparency,
but possibly it is not reversable.
xforms does support some "transparency" in supporting xor drawing.
fl_drawmode(GXxor);
and
the Positioner in xor mode (agreed not quite the same as transparency but
probably just as good for me.)
I am not sure what xor does-- are the bits in each of the colors actually
being
xored against the bits in the overlying color? But xor against black gives
black,
and since all bits
of black are 0, that does not really make sense. (or is black encoded as all
1s?)
I thought of using the GXxor in an overlay with the linewidth cranked way up
to do a "fill" but plotting on an overlay also redraws the axes of the
underlying xyplot, which makes a complete mess. (Was that how the problem of
the overlay positioner leaving ghosts behind solved-- redraw everthing in the
xyplot every time any overlay layer changes?)
On another question, how do I adjust the lines on the overlay positioner to
not extend to the edges of the positioner form? I tried setting bounds, but
that seemed
to do nothing.
On Tue, 30 Apr 2013, Jens Thoms Toerring wrote:
hi bill,
On Mon, Apr 29, 2013 at 03:29:00PM -0700, Bill Unruh wrote:
> Is there some way of putting a semi transparent box on top of an xyplot?
> In
> many programs one can select a part of the polt image-- eg for purposes
> of
> exanding the axes so as to include only that part of the image. But I
> can find
> no way of doing that in xforms. Ie, I want to put the mouse on one part
> of the
> image, hold left button down and drag it across the image. This will
> then
> change the shading of that part of the image-- either in a box whose
> corner is
> the place where the mouse was first left clicked to the current location
> of
> the mouse, or even the whole y range with x values greyed from where the
> mouse
> was first clicked to where the left botton was release. But the only
> thing
> which seems to have a "transparent" colour behaviour seems to be the
> overlay
> postioner, which is not sufficient. Is there anything else in xforms
> which
> would allow this behaviour that I have missed? (even something like "Box
> A
> lies on top of box B but is semi transparent so you can see what is
> underneath". Under "Images" the semitranparent "glass" seems to do
> something like this but
> that would not seem to be applicable to other objects.
>
>
> Some sort of overlay would parhaps work, but I have no idea how to make
> the
> colour on the overlay a transparent colour.
I fear that I have to disapoint you, but to my knowledge there's
no support for any kind of transparency in XForms. As far as I
know X itself only started to support transparency a relatively
short time ago (via some extensions), and that was quite some
time after XForms was developed. I don't know what you're refer-
ring to with "Images" and "glass", so I can't comment on this.
That doesn't necessarily mean that it's impossible to do - perhaps
someone else here on the mailing list has some nice ideas.
Best regards, Jens