create_font: Add minimum recommended characters

Specifically add notdef, null, CR and space. Space is hardcoded to
a width of 1024. Todo: Space width should be a config yaml option.

The font rendering systems are supposed to fallback to the space width
in the next available fallback font, but it doesn't work reliably.

Workaround for: 13rac1/emojione-color-font#2
Caused by: https://bugzilla.gnome.org/show_bug.cgi?id=757785
Related: 13rac1/emojione-color-font#17

README.md

@@ -5,7 +5,7 @@
 `scfbuild` creates *SVG in OpenType* color fonts directly from a set of source
 SVG files greatly simplifying the process of creating a custom color font.
 
-Regular color and standard character [glyph][1] are named by [Unicode][2] code
+Regular color and standard character [glyphs][1] are named by [Unicode][2] code
 point (e.g. `1f60e.svg`). [Ligatures][3] are named by code points separated
 by a hyphen `-` (e.g.`1f441-1f5e8.svg`). Note: Color glyphs cannot exist alone,
 they must replace existing standard glyphs.

scfbuild/fforge.py

@@ -40,9 +40,19 @@ def create_font():
     font.addLookup('liga', 'gsub_ligature', (), feature_script_lang)
     font.addLookupSubtable('liga', 'liga')
 
-    # Add required font characters
-    glyph = font.createChar(0x0, '.null')
+    # Add all recommended font characters
+    # Reference: https://www.microsoft.com/typography/otspec/recom.htm
+    glyph = font.createChar(-1, '.notdef')
     glyph.width = 0
+    # @todo Needs a default notdef glyph
+    glyph = font.createChar(0x0, '.null')
+    glyph.width = 1024
+    glyph = font.createChar(0xD, 'CR')
+    # @todo: Add space width to config yaml
+    glyph.width = 1024
+    glyph = font.createChar(0x20, 'space')
+    # Half-width space
+    glyph.width = 1024
     glyph = font.createChar(ZWJ_INT)
     glyph.width = 0
     glyph = font.createChar(VS16_INT)

scfbuild/main.py

@@ -70,6 +70,7 @@ def main():
     # -i --input - Input file instead of making a new one.
     # -t --type TTF/WOFF
     # --remove-unused
+    # --generate-conf
 
     args = parser.parse_args()