fontbuild: now generating three variable fonts: complete family with two axes, italic version with weight axis and upright version with weight axis. This allows supporting browsers like MS Edge which do not correctly map italic and oblique font style properties to slnt and ital axes.

Makefile

@@ -44,7 +44,13 @@ all: all_const  all_const_hinted  all_var
 
 all_const: all_otf  all_ttf  all_web
 all_const_hinted: all_ttf_hinted  all_web_hinted
-all_var: $(FONTDIR)/var/Inter-UI.var.woff2
+all_var: \
+	$(FONTDIR)/var/Inter-UI.var.woff2 \
+	$(FONTDIR)/var/Inter-UI-upright.var.woff2 \
+	$(FONTDIR)/var/Inter-UI-italic.var.woff2 \
+	$(FONTDIR)/var/Inter-UI.var.ttf \
+	$(FONTDIR)/var/Inter-UI-upright.var.ttf \
+	$(FONTDIR)/var/Inter-UI-italic.var.ttf
 
 # Disabled. See https://github.com/rsms/inter/issues/75
 # all_var_hinted: $(FONTDIR)/var-hinted/Inter-UI.var.ttf $(FONTDIR)/var-hinted/Inter-UI.var.woff2
@@ -79,8 +85,8 @@ build/%.woff: build/%.ttf
 
 all_ufo_masters = $(Regular_ufo_d) $(Black_ufo_d) $(Italic_ufo_d) $(BlackItalic_ufo_d)
 
-$(FONTDIR)/var/Inter-UI.var.ttf: src/Inter-UI.designspace $(all_ufo_masters)
+$(FONTDIR)/var/%.var.ttf: src/%.designspace $(all_ufo_masters)
-	misc/fontbuild compile-var -o $@ src/Inter-UI.designspace
+	misc/fontbuild compile-var -o $@ $<
 
 $(FONTDIR)/const/Inter-UI-Regular.%: src/Inter-UI.designspace $(Regular_ufo_d)
 	misc/fontbuild compile -o $@ src/Inter-UI-Regular.ufo
@@ -135,7 +141,7 @@ $(FONTDIR)/const-hinted/%.ttf: $(FONTDIR)/const/%.ttf
 # 	ttfautohint --fallback-stem-width=256 --no-info --composites "$<" "$@"
 
 # make sure intermediate TTFs are not gc'd by make
-.PRECIOUS: $(FONTDIR)/const/%.ttf $(FONTDIR)/var/%.ttf
+.PRECIOUS: $(FONTDIR)/const/%.ttf $(FONTDIR)/const-hinted/%.ttf $(FONTDIR)/var/%.var.ttf
 
 # check var
 all_check_var: $(FONTDIR)/var/Inter-UI.var.ttf
@@ -235,7 +241,7 @@ docs_fonts:
 	cp -a $(FONTDIR)/const/*.woff \
 	      $(FONTDIR)/const/*.woff2 \
 	      $(FONTDIR)/const/*.otf \
-	      $(FONTDIR)/var/*.woff2 \
+	      $(FONTDIR)/var/*.* \
 	      docs/font-files/
 
 .PHONY: docs docs_info docs_fonts

misc/dist/variable.txt

@@ -1,6 +1,15 @@
 
 Variable fonts is a new technology still undergoing development.
 
+The directory named "Inter UI (TTF variable)" contains three files:
+
+- Inter-UI.var.ttf -- multi-axis complete family
+- Inter-UI-italic.var.ttf -- italic-only with variable weight axis.
+- Inter-UI-upright.var.ttf-- upright-only with variable weight axis.
+
+The "Inter UI (web)" directory contains WOFF2 versions of these same
+font files.
+
 Support for variable fonts is limited as of late 2018, but support
 is quickly arriving to web browsers, operating systems and
 design application.

misc/fontbuild

@@ -469,6 +469,47 @@ class Main(object):
     font.save(ufo_path)
 
 
+  def _genSubsetDesignSpace(self, designspace, tag, filename):
+    ds = designspace
+    italic = False
+    if tag == 'italic':
+      italic = True
+    elif tag != 'upright':
+      raise Exception('unexpected tag ' + tag)
+
+    for a in ds.axes:
+      if a.tag == "slnt":
+        ds.axes.remove(a)
+        break
+
+    rmlist = []
+    hasDefault = not italic
+    for source in designspace.sources:
+      isitalic = source.name.find('italic') != -1
+      if italic != isitalic:
+        rmlist.append(source)
+      elif italic and not hasDefault:
+        source.copyLib = True
+        source.copyInfo = True
+        source.copyGroups = True
+        source.copyFeatures = True
+        hasDefault = True
+    for source in rmlist:
+      designspace.sources.remove(source)
+
+    rmlist = []
+    for instance in designspace.instances:
+      isitalic = instance.name.find('italic') != -1
+      if italic != isitalic:
+        rmlist.append(instance)
+    for instance in rmlist:
+      designspace.instances.remove(instance)
+
+    self.log("write %s" % relpath(filename, os.getcwd()))
+    ds.write(filename)
+
+
+
   def cmd_glyphsync(self, argv):
     argparser = argparse.ArgumentParser(
       usage='%(prog)s glyphsync <glyphsfile> [options]',
@@ -557,6 +598,24 @@ class Main(object):
     self.log("write %s" % relpath(designspace_file, os.getcwd()))
     designspace.write(designspace_file)
 
+    # upright designspace
+    upright_designspace_file = pjoin(outdir, 'Inter-UI-upright.designspace')
+    p = Process(
+      target=self._genSubsetDesignSpace,
+      args=(designspace, 'upright', upright_designspace_file)
+    )
+    p.start()
+    procs.append(p)
+
+    # italic designspace
+    italic_designspace_file = pjoin(outdir, 'Inter-UI-italic.designspace')
+    p = Process(
+      target=self._genSubsetDesignSpace,
+      args=(designspace, 'italic', italic_designspace_file)
+    )
+    p.start()
+    procs.append(p)
+
     for p in procs:
       p.join()