font/plan9font: look for subfont ".0" suffixes.
Change-Id: Id8aadd846311fd621b47912d7b426d6a2d17a594
Reviewed-on: https://go-review.googlesource.com/25560
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/font/plan9font/plan9font.go b/font/plan9font/plan9font.go
index af57c55..315e793 100644
--- a/font/plan9font/plan9font.go
+++ b/font/plan9font/plan9font.go
@@ -174,6 +174,31 @@
return 0, false
}
+// For subfont files, if reading the given file name fails, we try appending
+// ".n" where n is the log2 of the grayscale depth in bits (so at most 3) and
+// then work down to 0. This was done in Plan 9 when antialiased fonts were
+// introduced so that the 1-bit displays could keep using the 1-bit forms but
+// higher depth displays could use the antialiased forms.
+var subfontSuffixes = [...]string{
+ "",
+ ".3",
+ ".2",
+ ".1",
+ ".0",
+}
+
+func (f *face) readSubfontFile(name string) ([]byte, error) {
+ var firstErr error
+ for _, suffix := range subfontSuffixes {
+ if b, err := f.readFile(name + suffix); err == nil {
+ return b, nil
+ } else if firstErr == nil {
+ firstErr = err
+ }
+ }
+ return nil, firstErr
+}
+
func (f *face) subface(r rune) (*subface, rune) {
// Fall back on U+FFFD if we can't find r.
for _, rr := range [2]rune{r, '\ufffd'} {
@@ -188,7 +213,7 @@
continue
}
if x.subface == nil {
- data, err := f.readFile(x.relFilename)
+ data, err := f.readSubfontFile(x.relFilename)
if err != nil {
log.Printf("plan9font: couldn't read subfont %q: %v", x.relFilename, err)
x.bad = true
