Trim trailing zeroes in ttconv output

jkseppan · jkseppan · commit e78d502867e8 · 2020-08-01T11:58:12.000+03:00
These could increase the file length in case of fonts with
many composite glyphs.
diff --git a/extern/ttconv/pprdrv_tt.cpp b/extern/ttconv/pprdrv_tt.cpp
@@ -109,6 +109,13 @@ Fixed getFixed(BYTE *s)
 
 /*
 ** Get a 16 bit fixed point (2.14) number.
+**
+** The value range is from -2.0 to a little under 2.0.  The two
+** most-significant bits encode the whole part in two's-complement
+** format and the remaining 14 bits encode the numerator n of the
+** fraction n/16384 to be added to the whole part.
+**
+** https://docs.microsoft.com/en-us/typography/opentype/otspec181/otff#data-types
 */
 F2DOT14 getF2DOT14(BYTE *s)
 {
@@ -126,9 +133,32 @@ F2DOT14 getF2DOT14(BYTE *s)
     return val;
 }
 
-float F2DOT14value(F2DOT14 f)
+/*
+** Convert a fixed-point 2.14 number to a newly-allocated string.
+** Use at most six decimals but remove trailing zeroes and possibly
+** the decimal point.
+*/
+char* F2DOT14value(F2DOT14 f)
 {
-    return f.whole + (float)f.fraction/16384;
+    const size_t maxlen = strlen("-1.234567") + 1;
+    char *value = (char*)calloc(sizeof(char), maxlen);
+    if (value == NULL ||
+        snprintf(value, maxlen, "%.6f", f.whole + (float)f.fraction/16384) < 0) {
+        abort();
+    }
+
+    char *ptr = &value[maxlen-1];
+    while (ptr > value && *ptr == '\0') {
+        ptr--;
+    }
+    while (ptr > value && *ptr == '0') {
+        *ptr-- = '\0';
+    }
+    if (ptr > value && *ptr == '.') {
+        *ptr = '\0';
+    }
+
+    return value;
 }
 
 
diff --git a/extern/ttconv/pprdrv_tt2.cpp b/extern/ttconv/pprdrv_tt2.cpp
@@ -409,7 +409,9 @@ void GlyphToType3::load_char(TTFONT* font, BYTE *glyph)
 } /* end of load_char() */
 
 /*
-** Emmit PostScript code for a composite character.
+** Emit PostScript code for a composite character.
+**
+** https://docs.microsoft.com/en-us/typography/opentype/spec/glyf#composite-glyph-description
 */
 void GlyphToType3::do_composite(TTStreamWriter& stream, struct TTFONT *font, BYTE *glyph)
 {
@@ -480,10 +482,15 @@ void GlyphToType3::do_composite(TTStreamWriter& stream, struct TTFONT *font, BYT
                    subglyph here.  However, that doesn't seem to work with
                    xpdf or gs (only acrobat), so instead, this just includes
                    the subglyph here inline. */
-                stream.printf("q %.6f %.6f %.6f %.6f %d %d cm\n",
-                              F2DOT14value(mat00), F2DOT14value(mat01),
-                              F2DOT14value(mat10), F2DOT14value(mat11),
-                              topost(arg1), topost(arg2));
+                char *s00 = F2DOT14value(mat00), *s01 = F2DOT14value(mat01),
+                    *s10 = F2DOT14value(mat10), *s11 = F2DOT14value(mat11);
+
+                stream.printf("q %s %s %s %s %d %d cm\n",
+                              s00, s01, s10, s11, topost(arg1), topost(arg2));
+                free(s00);
+                free(s01);
+                free(s10);
+                free(s11);
             }
             else
             {
diff --git a/extern/ttconv/truetype.h b/extern/ttconv/truetype.h
@@ -94,7 +94,7 @@ ULONG getULONG(BYTE *p);
 USHORT getUSHORT(BYTE *p);
 Fixed getFixed(BYTE *p);
 F2DOT14 getF2DOT14(BYTE *p);
-float F2DOT14value(F2DOT14 f);
+char *F2DOT14value(F2DOT14 f);
 
 /*
 ** Get an funits word.
