From: Ben Harris <bjh21@bjh21.me.uk>
Date: Fri, 8 Nov 2024 00:42:42 +0000 (+0000)
Subject: Very rough but apparently functional 'palt' support
X-Git-Tag: bedstead-3.246~45
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=b83edc5cc062fa16260c845113c4a6365a5380ed;p=bedstead-debian.git

Very rough but apparently functional 'palt' support
---

diff --git a/bedstead.c b/bedstead.c
index 9f6c809..a88e0b3 100644
--- a/bedstead.c
+++ b/bedstead.c
@@ -3053,6 +3053,13 @@ main(int argc, char **argv)
 	TTXI("minMemType1", 0); TTXI("maxMemType1", 0);
 	printf(" </post>\n");
 
+	for (i = 0; i < nglyphs; i++)
+		glyphs_by_name[i] = glyphs + i;
+	qsort(glyphs_by_name, nglyphs, sizeof(glyphs_by_name[0]),
+	      &compare_glyphs_by_name);
+
+	dogpos(); /* Must be before 'CFF ' because it uses glyph bitmaps. */
+
 	printf(" <CFF>\n");
 	TTXI("major", 1); TTXI("minor", 0);
 	printf("  <CFFFont name='%s'>\n",
@@ -3085,13 +3092,6 @@ main(int argc, char **argv)
 	/* 	printf("StrokedFont: 1\n"); */
 	/* 	printf("StrokeWidth: 50\n"); */
 	/* } */
-	/* printf("Lookup: 257 0 0 \"palt: proportional metrics\" {\"palt\"} " */
-	/*     "['palt' ('DFLT' <'dflt'> 'latn' <'dflt'>)]\n"); */
-	for (i = 0; i < nglyphs; i++)
-		glyphs_by_name[i] = glyphs + i;
-	qsort(glyphs_by_name, nglyphs, sizeof(glyphs_by_name[0]),
-	      &compare_glyphs_by_name);
-	/* Scan for aliased glyphs to turn into subroutines. */
 	printf("    <Subrs>\n");
 	nsubrs = 0;
 	for (i = 0; i < nglyphs; i++) {
@@ -3128,7 +3128,6 @@ main(int argc, char **argv)
 		       (int)realglyph(&glyphs[i])->left_sidebearing);
 	printf(" </hmtx>\n");
 	dogsub();
-	dogpos();
 	printf("</ttFont>\n");
 	return EXIT_SUCCESS;
 }
@@ -3408,10 +3407,20 @@ dosinglesubs(char const *suffix)
 			       glyphs[i].name, glyphs[i].name);
 }
 
+static int
+glyph_footprint(char data[XSIZE-1])
+{
+	int i;
+	int footprint = 0;
+
+	for (i = 0; i < YSIZE-1; i++) footprint |= data[i];
+	return footprint;
+}
 
 static void
 dogpos(void)
 {
+	int dx, dh, i;
 
 	/* We only support one 'GPOS' lookup, 'palt'. */
 	printf(" <GPOS>\n");
@@ -3424,6 +3433,13 @@ dogpos(void)
 	TTXI("FeatureIndex", 0);
 	printf("    </DefaultLangSys></Script>\n");
 	printf("   </ScriptRecord>\n");
+	printf("   <ScriptRecord>\n");
+	TTXS("ScriptTag", "latn");
+	printf("    <Script><DefaultLangSys>\n");
+	TTXI("ReqFeatureIndex", 0xffff); /* No required feature. */
+	TTXI("FeatureIndex", 0);
+	printf("    </DefaultLangSys></Script>\n");
+	printf("   </ScriptRecord>\n");
 	printf("  </ScriptList>\n");
 	printf("  <FeatureList>\n");
 	printf("   <FeatureRecord>\n");
@@ -3437,6 +3453,37 @@ dogpos(void)
 	printf("   <Lookup>\n");
 	TTXI("LookupType", 1);
 	TTXI("LookupFlag", 0);
+	/*
+	 * We have only a few dx/dh combinations, so it makes sense to
+	 * organise by that rather than spitting out a separate value
+	 * for each glyph.
+	 */
+	for (dx = 0; dx < XSIZE - 1; dx++)
+		for (dh = (dx == 0 ? 1 : dx); dh < XSIZE - 1; dh++) {
+			printf("       <SinglePos Format='1'>\n");
+			printf("<!-- dx = %d; dh = %d -->\n", dx, dh);
+			printf("        <Coverage>\n");
+			for (i = 0; i < nglyphs; i++) {
+				struct glyph *g = realglyph(&glyphs[i]);
+				if (g->flags & (MOS6|MOS4)) continue;
+				int fp = glyph_footprint(g->data);
+				if ((fp & (0xff << (XSIZE-dx-1))) == 0 &&
+				    (fp & (0xff << (XSIZE-dx-2))) != 0 &&
+				    (fp & ((1 << (dh - dx)) - 1)) == 0 &&
+				    (fp & ((1 << (dh - dx + 1)) - 1)) != 0 ||
+				    fp == 0 && dx == 0 && dh == 3) {
+					printf("<!-- fp = 0%o -->\n", fp);
+					TTXS("Glyph", glyphs[i].name);
+				}
+			}
+			printf("        </Coverage>\n");
+			TTXI("ValueFormat", 5);
+			printf("        <Value XPlacement='%i' "
+			       "XAdvance='%i'/>\n",
+			       (int)(-dx * XPIX), (int)(-dh * XPIX));
+			printf("       </SinglePos>\n");
+		}
+			
 	printf("   </Lookup>\n");
 	printf("  </LookupList>\n");
 	printf(" </GPOS>\n");
@@ -3461,40 +3508,6 @@ doglyph(struct glyph *g)
 		dochar(g);
 }
 
-static void
-dopalt(struct glyph *g)
-{
-	int i;
-	unsigned char cols = 0;
-	int dx = 0, dh = 0;
-
-	g = realglyph(g);
-	if (g->flags & (MOS6|MOS4)) return;
-	/*
-	 * For proportional layout, we'd like a left side-bearing of
-	 * one pixel, and a right side-bearing of zero.  Space
-	 * characters get an advance width of three pixels.
-	 */
-	for (i = 0; i < YSIZE - 1; i++)
-		cols |= g->data[i] & ((1 << XSIZE) - 1);
-	if (cols == 0)
-		dh = 3 - XSIZE;
-	else {
-		while (!(cols & 1 << (XSIZE - 2))) {
-			cols <<= 1;
-			dx--;
-		}
-		while (!(cols & 1)) {
-			cols >>= 1;
-			dh--;
-		}
-	}
-	if (dx || dh)
-		printf("Position2: \"palt\" dx=%d dy=0 dh=%d dv=0\n",
-		       (int)(dx * XPIX), (int)(dh * XPIX));
-}
-
-
 typedef struct vec {
 	int x, y;
 } vec;