Improve demo script

* make sure there is a spacecenter to draw in
* make sure we handle spaces with discrete locations better

Add note about settig the previewlocation in the docs

DesignspaceEditor2.roboFontExt/html/index.html

@@ -841,6 +841,16 @@ <h3>Making a glyph</h3>
 What is happening here? Step by step: <b>CurrentDesignspace</b> returns a UFOOperator object for the current designspace.
 <b>d.newDefaultLocation()</b> creates a dict representing the default location in design coordinates. For this example it is a quick way to get a valid location, but you will probably want to see more exotic locations. Then, <b>makeOneGlyph</b> creates a new glyph object for the given glyphName and a location dict. The result is a <b>MathGlyph</b> object that can be converted to a regular RoboFont glyph object. 
 
+<h3>Setting the preview location</h3>
+
+DSE2 keeps track of the "current preview location". You can set this location with the UI and axis sliders in the Preview Window. But you can also set it with a script. 
+
+<pre><code>
+d = CurrentDesignspace()
+previewLoc = d.randomLocation()
+d.setPreviewLocation(previewLoc)</code></pre>
+
+
 <h3>Going through all designspaces</h3>
 
 You can use <code>AllDesignspaces()</code> to get a list of all open designspace documents. Optionally you can pass a font object with <code>usingFont</code> to get only the designspaces that use that font.

Scripting examples/previewFont_to_spacecenter.py

@@ -1,33 +1,48 @@
 from fontTools.designspaceLib import InstanceDescriptor
-from mojo.UI import CurrentSpaceCenter
+from mojo.UI import CurrentSpaceCenter, OpenSpaceCenter
 
 # Scripting with live designspaces
-# demo erik@letterror.com 8.12.2023
+# demo erik@letterror.com 12.12.2023
 
 # have a desigspace open in DSE2
-d = CurrentDesignspace()
-
-# have a spacecenter open
-sp = CurrentSpaceCenter()
+ds = CurrentDesignspace()
 
 # you probably want more control over what axis values to look at
 # and maybe even a fancy interface
 # but that is beyond the scope of this demo
 # so for now, a random location
-loc = d.randomLocation()
+loc = ds.randomLocation()
+# the location is just a dict with axisName: axisValue pairs.
+print("location", loc)
+
+# we can split this random location into its continuous and discrete parts
+continuousPart, discretePart = ds.splitLocation(loc)
+print("continuous part of the location:", continuousPart)
+print("discrete part of the location:", discretePart)
 
-# see the location is just a dict with axisName: axisValue pairs,
-print(loc)
+# get the default font
+# note we ask for the default of a specific discrete location here
+defaultFont = ds.findDefaultFont(discreteLocation=discretePart)
 
 # make an "instance descriptor" object to specify what we want to see
 preview = InstanceDescriptor()
-#preview.familyName = "MyPreview"
-#preview.styleName = "MyStyle"
 preview.designLocation = loc
+preview.familyName = defaultFont.info.familyName
 
 # now we're asking the designspace to make a font object with these specs
-r = d.makeInstance(preview)
-print(r)
+# This makes the whole font. If you're just looking at a couple of characters
+# there are faster ways to do that. 
+previewFont = ds.makeInstance(preview).asFontParts()
 
 # finally, we give the resulting font to the space center.
-sp.setFont(r)
+# have a spacecenter open
+sp = CurrentSpaceCenter()
+if sp is None:
+    sp = OpenSpaceCenter(previewFont)
+
+#
+sp.setFont(previewFont)
+sp.setRaw(f'HHOHOO \n {defaultFont.info.styleName}')
+
+# optionally, open the font window
+#previewFont.openInterface()