x.ttf: fix a bug in TTF fixed point data management (#14987)

vlib/x/ttf/ttf.v

@@ -90,6 +90,8 @@ pub mut:
 	kern                    []Kern0Table
 	// cache
 	glyph_cache map[int]Glyph
+	// font widths array scale for PDF export
+	width_scale f32 = 1.0
 }
 
 pub fn (mut tf TTF_File) init() {
@@ -103,6 +105,8 @@ pub fn (mut tf TTF_File) init() {
 	tf.length = tf.glyph_count()
 	dprintln('Number of symbols: $tf.length')
 	dprintln('*****************************')
+	dprintln('Unit per em: $tf.units_per_em')
+	dprintln('advance_width_max: $tf.advance_width_max')
 }
 
 /******************************************************************************
@@ -159,7 +163,7 @@ pub fn (mut tf TTF_File) get_horizontal_metrics(glyph_index u16) (int, int) {
 		tf.pos = offset
 		advance_width = tf.get_u16()
 		left_side_bearing = tf.get_i16()
-		// dprintln("Found h_metric aw: $advance_width lsb: $left_side_bearing")
+		// dprintln("${glyph_index} aw:${advance_width} lsb:${left_side_bearing}")
 	} else {
 		// read the last entry of the hMetrics array
 		tf.pos = offset + (tf.num_of_long_hor_metrics - 1) * 4
@@ -200,7 +204,7 @@ fn (mut tf TTF_File) get_glyph_offset(index u32) u32 {
 	return offset + tf.tables['glyf'].offset
 }
 
-fn (mut tf TTF_File) glyph_count() u16 {
+pub fn (mut tf TTF_File) glyph_count() u16 {
 	assert 'maxp' in tf.tables
 	old_pos := tf.pos
 	tf.pos = tf.tables['maxp'].offset + 4
@@ -233,6 +237,58 @@ pub fn (mut tf TTF_File) read_glyph_dim(index u16) (int, int, int, int) {
 	return x_min, x_max, y_min, y_max
 }
 
+pub fn (mut tf TTF_File) get_ttf_widths() ([]int, int, int) {
+	mut space_cw, _ := tf.get_horizontal_metrics(u16(` `))
+	// div_space_cw := int((f32(space_cw) * 0.3))
+
+	// count := int(tf.glyph_count())
+	mut min_code := 0xFFFF + 1
+	mut max_code := 0
+	for i in 0 .. 300 {
+		glyph_index := tf.map_code(i)
+		if glyph_index == 0 {
+			continue
+		}
+		// dprintln("$i = glyph_index: $glyph_index ${i:c}")
+		if i > max_code {
+			max_code = i
+		}
+		if i < min_code {
+			min_code = i
+		}
+	}
+	// dprintln("min_code: $min_code max_code: $max_code")
+	mut widths := []int{len: max_code - min_code + 1, init: 0}
+
+	for i in min_code .. max_code {
+		pos := i - min_code
+		glyph_index := tf.map_code(i)
+
+		if glyph_index == 0 || i == 32 {
+			widths[pos] = space_cw
+			continue
+		}
+
+		x_min, x_max, _, _ := tf.read_glyph_dim(glyph_index)
+		aw, lsb := tf.get_horizontal_metrics(u16(glyph_index))
+		w := x_max - x_min
+		rsb := aw - (lsb + w)
+
+		// pp1 := x_min - lsb
+		// pp2 := pp1 + aw
+
+		w1 := w + lsb + rsb
+
+		widths[pos] = int(w1 / tf.width_scale)
+		// if i >= int(`A`) && i <= int(`Z`) {
+		//	dprintln("${i:c}|$glyph_index [$pos] =>  width:${x_max-x_min} aw:${aw}|w1:${w1} lsb:${lsb} rsb:${rsb} pp1:${pp1} pp2:${pp2}")
+		//}
+	}
+
+	// dprintln("Widths: ${widths.len}")
+	return widths, min_code, max_code
+}
+
 pub fn (mut tf TTF_File) read_glyph(index u16) Glyph {
 	index_int := int(index) // index.str()
 	if index_int in tf.glyph_cache {
@@ -511,7 +567,12 @@ fn (mut tf TTF_File) get_ufword() u16 {
 }
 
 fn (mut tf TTF_File) get_i16() i16 {
-	return i16(tf.get_u16())
+	// return i16(tf.get_u16())
+	mut res := u32(tf.get_u16())
+	if (res & 0x8000) > 0 {
+		res -= (u32(1) << 16)
+	}
+	return i16(res)
 }
 
 fn (mut tf TTF_File) get_fword() i16 {
@@ -526,7 +587,11 @@ fn (mut tf TTF_File) get_u32() u32 {
 }
 
 fn (mut tf TTF_File) get_i32() int {
-	return int(tf.get_u32())
+	mut res := u64(tf.get_u32())
+	if (res & 0x8000_0000) > 0 {
+		res -= (u64(1) << 32)
+	}
+	return int(res)
 }
 
 fn (mut tf TTF_File) get_2dot14() f32 {