page in the IR that the @code{transparent} property is a boolean.
This
should be set to @code{#t} to make the grob transparent.
-In this next example let us make the time signature invisible
-rather than the bar lines.
+In this next example let us make the time signature invisible
+rather than the bar lines.
To do this we need to find the grob name for the time signature.
Back to
the @q{All layout objects} page in the IR to find the properties
@end lilypond
@noindent
-The time signature is gone, but this command leaves a gap where
+The time signature is gone, but this command leaves a gap where
the time signature should be. Maybe this is what is wanted for
-an exercise for the student to fill it in, but in other
-circumstances a gap might be undesirable. To remove it, the
+an exercise for the student to fill it in, but in other
+circumstances a gap might be undesirable. To remove it, the
stencil for the time signature should be set to @code{#f}
instead:
@subheading color
@cindex color property
-Finally we could make the bar lines invisible by coloring
-them white. The @code{grob-interface} specifies that the
+Finally let us try making the bar lines invisible by coloring
+them white. (There is a difficulty with this in that the
+white bar line may or may not blank out the staff lines where
+they cross. You may see in some of the examples below that this
+happens unpredictably. The details of why this is so and how to
+control it are covered in @ruser{Painting objects white}. But at
+the moment we are learning about color, so please just accept this
+limitation for now.)
+
+The @code{grob-interface} specifies that the
color property value is a list, but there is no
explanation of what that list should be. The list it
requires is actually a list of values in internal units,
a symbol, but a @emph{function}. When called, it provides
the list of internal values required to set the color to
white. The other colors in the normal list are functions
-too. To convince yourself this is working you might like
+too. To convince yourself this is working you might like
to change the color to one of the other functions in the
list.
There is yet a third function, one which converts RGB values into
internal colors -- the @code{rgb-color} function. This takes
-three arguments giving the intensities of the red, green and
+three arguments giving the intensities of the red, green and
blue colors. These take values in the range 0 to 1. So to
set the color to red the value should be @code{(rgb-color 1 0 0)}
and to white it should be @code{(rgb-color 1 1 1)}: