Scripting newbie...help for a "simple" crop mark script

Question

Hello,
I am after some advice or assistance on the scripting side of things for indesign please.
Basically where do you start? I'm wanting to do some scripts to speed up some repetitive processes.
What I'm trying to do initially is (what I'd think would be) a very simple script. Basically it's adding crop marks to document, with the horizontal ones running the full width of the document. I've just no idea where to start...
So, I think the process of the script would be this:
1. Find document size
2. Add a horizontal line at 0.1 pt size,
Length = document width + 20mm
X axis =  document width divided by 2 (line sits centrally, hanging 10mm over left and right edges)
Y Axis = 0mm
3. Add a horizontal line at 0.1 pt size,
Length = document width + 20mm
X axis =  document width divided by 2 (line sits centrally, hanging 10mm over left and right edges)
Y Axis = document height
4. Add a vertical line at 0.1 pt size,
Length = 10mm
X axis =  0mm
Y Axis = -2mm to -12mm (bottom line sits at -2, top of line at -12)
5. Add a vertical line at 0.1 pt size,
Length = 10mm
X axis =  document width
Y Axis = -2mm to -12mm (bottom line sits at -2, top of line at -12)
6. Add a vertical line at 0.1 pt size,
Length = 10mm
X axis =  0mm
Y Axis = document height + 2mm, to document height +12mm (top of line sits at document height +2mm, bottom of line at document height +12mm)
7. Add a vertical line at 0.1 pt size,
Length = 10mm
X axis =  document width
Y Axis = document height + 2mm to document height +12mm (top of line sits at document height +2mm, bottom of line at document height +12mm)
For the future I am wanting some more complex scripts but this will hopefully help me understand a little bit.  (I will need one with input tables where you can add variables if that's do-able, but i somehow think it wont be me doing that one!!)
Thanks in advance for any help or pointers.
Phil

Answer 1

As said above, we can walk you through a custom script step by step
Let me get you started with this: the ESTK Help -- or one of its variants -- is your biggest friend!
"1. Find document size"
Use app.activeDocument.documentPreferences.pageWidth and app.activeDocument.documentPreferences.pageWidth for these.
"2. Add a horizontal line at 0.1 pt size,
Length = document width + 20mm
X axis =  document width divided by 2 (line sits centrally, hanging 10mm over left and right edges)
Y Axis = 0mm"
app.activeDocument.graphicLines.add () adds a new graphic line on a default position. You can then move it into position.
Doing the math results in this little script to add the first line:
newLine = app.activeDocument.graphicLines.add();
newLine.paths[0].pathPoints[0].anchor = [ -20, 0 ];
newLine.paths[0].pathPoints[1].anchor = [ app.activeDocument.documentPreferences.pageWidth+20, 0 ];
newLine.strokeWeight = 0.1;
newLine.strokeColor = app.activeDocument.swatches.item("Registration");
newLine.strokeStyle = app.strokeStyles[0];
A 'line' can consist of a number of paths (consider a compound path), but usually has only one single path. A new line only has two endpoints -- the anchors --, and you can move these around by setting the coordinates with an array of [ x y ] values. Important: These values are in your current measurement units! I'm assuming, for convenience, that you have mm for this. If you see 20 inch wide lines popping up, you know why :-) Another important point: the rulers' zero point must be in the top left of your document. All "absolute" values are relative to this zero point.
It is perfectly possible to have the script set the correct measurements and move the zero point for you, but now you know why it has to do that.
Notice you don't explicitly move the center of the new line; in this case, it's easier to immediately move each end point into its correct place.
There are a few other things you can do to make the script misbehave. The new line is created with the active defaults in your document. You could have the script change the defaults to the correct settings, but that's not really user friendly. Instead, you can change everything by applying new values to the new line only. You can see I set its weight, color, and stroke style.
A few points on these latter three settings:
Didn't I just tell you all values are in current measurement units? Well, line widths are always in points (as is font size and line spacing).
The correct line color is grabbed by asking for a swatch called "Registration" -- you might want to replace this with another swatch name.
The stroke style is grabbed by blindly using the very first stroke style in InDesign. I found out the hard way using "Solid" (or what is it called) does not work across different languages. Much later I learned there is a language-independent way of using the names, but hey, that's harder to remember.