v/vlib/x/ttf/ttf.v

module ttf
/**********************************************************************
*
* TrueTypeFont reader V implementation
*
* Copyright (c) 2021 Dario Deledda. All rights reserved.
* Use of this source code is governed by an MIT license
* that can be found in the LICENSE file.
*
* Note:
* - inspired by: http://stevehanov.ca/blog/?id=143 
*
* TODO: 
* - check for unicode > 0xFFFF if supported
* - evaluate use a buffer for the points in the glyph
**********************************************************************/
import strings


/******************************************************************************
*
* CMAP structs
*
******************************************************************************/
struct Segment {
mut:
	id_range_offset u32
	start_code      u16
	end_code        u16
	id_delta        u16
}

struct TrueTypeCmap {
mut:
	format   int
	cache    []int = []int{ len: 65536, init: -1 }  // for now we allocate 2^16 charcode
	segments []Segment
	arr      []int
}

/******************************************************************************
*
* TTF_File structs
*
******************************************************************************/
pub
struct TTF_File{
pub mut:
	buf            []byte
	pos            u32

	length         u16

	scalar_type    u32
	search_range   u16
	entry_selector u16
	range_shift    u16

	tables map[string]Offset_Table

	version              f32
	font_revision        f32
	checksum_adjustment  u32
	magic_number         u32
	flags                u16
	units_per_em         u16
	created              u64
	modified             u64
	x_min                f32
	y_min                f32
	x_max                f32
	y_max                f32
	mac_style            u16
	lowest_rec_ppem      u16
	font_direction_hint  i16
	index_to_loc_format  i16
	glyph_data_format    i16

	font_family          string
	font_sub_family      string
	full_name            string
	postscript_name      string

	cmaps                []TrueTypeCmap

	ascent                  i16 
	descent                 i16 
	line_gap                i16 
	advance_width_max       u16 
	min_left_side_bearing   i16 
	min_right_side_bearing  i16 
	x_max_extent            i16 
	caret_slope_rise        i16 
	caret_slope_run         i16 
	caret_offset            i16 
	metric_data_format      i16 
	num_of_long_hor_metrics u16 

	kern                    []Kern0Table
	
	// cache
	glyph_cache             map[int]Glyph
}

pub
fn (mut tf TTF_File) init() {
	tf.read_offset_tables()
	tf.read_head_table()
	//dprintln(tf.get_info_string())
	tf.read_name_table()
	tf.read_cmap_table()
	tf.read_hhea_table()
	tf.read_kern_table()
	tf.length = tf.glyph_count()
	dprintln("Number of symbols: $tf.length")
	dprintln("*****************************")
}
/******************************************************************************
*
* TTF_File Glyph Structs
*
******************************************************************************/

pub
struct Point {
pub mut:
	x        int
	y        int
	on_curve bool
}

struct Gylph_Component {
mut:
	points  []Point
}

// type of glyph
const(
	g_type_simple  = u16(1)  // simple type
	g_type_complex = u16(2)  // compound type
)

pub
struct Glyph {
pub mut:
	g_type             u16 = g_type_simple
	contour_ends       []u16
	number_of_contours i16
	points             []Point
	x_min              i16
	x_max              i16
	y_min              i16
	y_max              i16
	valid_glyph        bool
	components         []Component
}


/******************************************************************************
*
* TTF_File metrics and glyph
*
******************************************************************************/
pub
fn (mut tf TTF_File) get_horizontal_metrics(glyph_index u16) (int, int) {
	assert"hmtx" in tf.tables
	old_pos := tf.pos
	mut offset  := tf.tables["hmtx"].offset

	mut advance_width     := 0
	mut left_side_bearing := 0
	if glyph_index < tf.num_of_long_hor_metrics {
		offset += glyph_index * 4
		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")
	} else {
		// read the last entry of the hMetrics array
		tf.pos = offset + (tf.num_of_long_hor_metrics - 1) * 4
		advance_width     = tf.get_u16()
		tf.pos = offset + tf.num_of_long_hor_metrics * 4 + 2 * (glyph_index - tf.num_of_long_hor_metrics)
		left_side_bearing = tf.get_fword()
	}
	tf.pos = old_pos
	return advance_width, left_side_bearing
}

fn (mut tf TTF_File) get_glyph_offset(index u32) u32{
	// check if needed tables exists
	assert "loca" in tf.tables
	assert "glyf" in tf.tables
	mut old_pos := tf.pos
	
	table := tf.tables["loca"]
	mut offset  := u32(0)
	mut next    := u32(0)
	if tf.index_to_loc_format == 1 {
		tf.pos = table.offset + (index << 2)
		offset  = tf.get_u32()
		next    = tf.get_u32()
	} else {
		tf.pos = table.offset + (index << 1)
		offset  = tf.get_u16() << 1
		next    = tf.get_u16() << 1
	}
	
	if offset == next {
		// indicates glyph has no outline( eg space)
		return 0
	}

	//dprintln("Offset for glyph index $index is $offset")
	tf.pos = old_pos
	return offset + tf.tables['glyf'].offset
}

fn (mut tf TTF_File) glyph_count() u16{
	assert "maxp" in tf.tables
	old_pos := tf.pos
	tf.pos = tf.tables["maxp"].offset + 4
	count := tf.get_u16()
	tf.pos = old_pos
	return count
}

pub
fn (mut tf TTF_File) read_glyph_dim(index u16) (int, int, int, int) {
	offset := tf.get_glyph_offset(index)
	//dprintln("offset: $offset")
	if offset == 0 || offset >= tf.tables["glyf"].offset + tf.tables["glyf"].length {
		dprintln("No glyph found!")
		return 0, 0, 0, 0
	}

	assert offset >= tf.tables["glyf"].offset
	assert offset < tf.tables["glyf"].offset + tf.tables["glyf"].length

	tf.pos = offset
	//dprintln("file seek read_glyph: $tf.pos")
	
	/*number_of_contours*/ _ := tf.get_i16()
	x_min := tf.get_fword()
	y_min := tf.get_fword()
	x_max := tf.get_fword()
	y_max := tf.get_fword()
	
	return x_min, x_max, y_min, y_max
}

pub
fn (mut tf TTF_File) read_glyph(index u16) Glyph {
	index_int := int(index) //index.str()
	if index_int in tf.glyph_cache{
		//dprintln("Found glyp: ${index}")
		return tf.glyph_cache[index_int]
	}
	//dprintln("Create glyp: ${index}")
	
	offset := tf.get_glyph_offset(index)
	//dprintln("offset: $offset")
	if offset == 0 || offset >= tf.tables["glyf"].offset + tf.tables["glyf"].length {
		dprintln("No glyph found!")
		return Glyph{}
	}

	assert offset >= tf.tables["glyf"].offset
	assert offset < tf.tables["glyf"].offset + tf.tables["glyf"].length

	tf.pos = offset
	//dprintln("file seek read_glyph: $tf.pos")
	
	/* ---- BUG TO SOLVE -----
	--- Order of the data if printed in the main is shuffled!! Very Strange
	mut tmp_glyph := Glyph{
		number_of_contours : tf.get_i16()
		x_min : tf.get_fword()
		y_min : tf.get_fword()
		x_max : tf.get_fword()
		y_max : tf.get_fword()
	}
	*/
	
	mut tmp_glyph := Glyph{}
	tmp_glyph.number_of_contours = tf.get_i16()
	tmp_glyph.x_min = tf.get_fword()
	tmp_glyph.y_min = tf.get_fword()
	tmp_glyph.x_max = tf.get_fword()
	tmp_glyph.y_max = tf.get_fword()
	
	//dprintln("file seek after read_glyph: $tf.pos")

	assert tmp_glyph.number_of_contours >= -1

	if tmp_glyph.number_of_contours == -1 {
		//dprintln("read_compound_glyph")
		tf.read_compound_glyph(mut tmp_glyph)
	} else {
		//dprintln("read_simple_glyph")
		tf.read_simple_glyph(mut tmp_glyph)
	}

	tf.glyph_cache[index_int] = tmp_glyph
	return tmp_glyph
}

const(
	tfk_on_curve  = 1
	tfk_x_is_byte = 2
	tfk_y_is_byte = 4
	tfk_repeat    = 8
	tfk_x_delta   = 16
	tfk_y_delta   = 32
)

fn (mut tf TTF_File) read_simple_glyph(mut in_glyph Glyph){
	if in_glyph.number_of_contours == 0 {
		return
	}

	for _ in 0..in_glyph.number_of_contours {
		in_glyph.contour_ends << tf.get_u16()
	}

	// skip over intructions
	tf.pos = tf.get_u16() + tf.pos 
	
	mut num_points := 0
	for ce in in_glyph.contour_ends {
		if ce > num_points {
			num_points = ce
		}
	}
	num_points++

	mut i := 0
	mut flags := []byte{}
	for i < num_points {
		flag := tf.get_u8()
		flags << flag
		in_glyph.points << Point{
			x: 0
			y: 0
			on_curve: (flag & tfk_on_curve) > 0
		}
		
		if (flag & tfk_repeat) > 0 {
			mut repeat_count := tf.get_u8()
			assert repeat_count > 0
			i += repeat_count
			for repeat_count > 0 {
				flags << flag
				in_glyph.points << Point{
					x: 0
					y: 0
					on_curve: (flag & tfk_on_curve) > 0
				}
				repeat_count--
			}
		}
		i++
	}

	// read coords x
	mut value := 0
	for i_x in 0..num_points {
		flag_x := flags[i_x]
		if (flag_x & tfk_x_is_byte) > 0 {
			if (flag_x & tfk_x_delta) > 0 {
				value += tf.get_u8()
			} else {
				value -= tf.get_u8()
			}
		} else if (~flag_x & tfk_x_delta) > 0 {
			value += tf.get_i16()
		} else {
			// value is unchanged
		}
		//dprintln("$i_x x: $value")
		in_glyph.points[i_x].x = value
	}

	// read coords y
	value = 0
	for i_y in 0..num_points {
		flag_y := flags[i_y]
		if (flag_y & tfk_y_is_byte) > 0 {
			if (flag_y & tfk_y_delta) > 0 {
				value += tf.get_u8()
			} else {
				value -= tf.get_u8()
			}
		} else if (~flag_y & tfk_y_delta) > 0 {
			value += tf.get_i16()
		} else {
			// value is unchanged
		}
		//dprintln("$i_y y: $value")
		in_glyph.points[i_y].y = value
	}

	// ok we have a valid glyph
	in_glyph.valid_glyph = true
}

const(
	tfkc_arg_1_and_2_are_words    = 1
	tfkc_args_are_xy_values       = 2
	tfkc_round_xy_to_grid         = 4
	tfkc_we_have_a_scale          = 8
	// reserved                   = 16
	tfkc_more_components          = 32
	tfkc_we_have_an_x_and_y_scale = 64
	tfkc_we_have_a_two_by_two     = 128
	tfkc_we_have_instructions     = 256
	tfkc_use_my_metrics           = 512
	tfkc_overlap_component        = 1024
)

struct Component {
mut:
	glyph_index      u16
	dest_point_index i16
	src_point_index  i16
	matrix           []f32 = [f32(1.0), 0, 0, 1.0, 0, 0]
}

fn (mut tf TTF_File) read_compound_glyph(mut in_glyph Glyph){
	in_glyph.g_type = g_type_complex
	mut component := Component{}
	mut flags := tfkc_more_components
	for (flags & tfkc_more_components) > 0 {
		mut arg1 := i16(0)
		mut arg2 := i16(0)
		
		flags = tf.get_u16()

		component.glyph_index = tf.get_u16()
		
		if (flags & tfkc_arg_1_and_2_are_words) > 0 {
			arg1 = tf.get_i16()
			arg2 = tf.get_i16()
		} else {
			arg1 = tf.get_u8()
			arg2 = tf.get_u8()
		}

		if (flags & tfkc_args_are_xy_values) > 0 {
			component.matrix[4] = arg1
			component.matrix[5] = arg2
		} else {
			component.dest_point_index = arg1
			component.src_point_index  = arg2
		}

		if (flags & tfkc_we_have_a_scale) > 0 {
			component.matrix[0] = tf.get_2dot14()
			component.matrix[3] = component.matrix[0]
		} else if (flags & tfkc_we_have_an_x_and_y_scale) > 0 {
			component.matrix[0] = tf.get_2dot14()
			component.matrix[3] = tf.get_2dot14()
		} else if (flags & tfkc_we_have_a_two_by_two) > 0 {
			component.matrix[0] = tf.get_2dot14()
			component.matrix[1] = tf.get_2dot14()
			component.matrix[2] = tf.get_2dot14()
			component.matrix[3] = tf.get_2dot14()
		}

		//dprintln("Read component glyph index ${component.glyph_index}")
		//dprintln("Transform: ${component.matrix}")

		old_pos := tf.pos

		simple_glyph := tf.read_glyph(component.glyph_index)
		if simple_glyph.valid_glyph {
			point_offset := in_glyph.points.len
			for i in 0..simple_glyph.contour_ends.len {
				in_glyph.contour_ends << u16(simple_glyph.contour_ends[i] + point_offset)
			}

			for p in simple_glyph.points {
				mut x := f32(p.x)
				mut y := f32(p.y)
				x = component.matrix[0] * x + component.matrix[1] * y + component.matrix[4]
				y = component.matrix[2] * x + component.matrix[3] * y + component.matrix[5]            	
				in_glyph.points << Point{
					x: int(x)
					y: int(y)
					on_curve: p.on_curve
				}
			}
		}
		tf.pos = old_pos
	}

	in_glyph.number_of_contours = i16(in_glyph.contour_ends.len)

	if (flags & tfkc_we_have_instructions) > 0 {
		tf.pos = tf.get_u16() + tf.pos
	}

	// ok we have a valid glyph
	in_glyph.valid_glyph = true
}

/******************************************************************************
*
* TTF_File get functions
*
******************************************************************************/
fn (mut tf TTF_File) get_u8() byte {
	x := tf.buf[tf.pos]
	tf.pos++
	return byte(x)
}

fn (mut tf TTF_File) get_i8() i8 {
	return i8(tf.get_u8())
}

fn (mut tf TTF_File) get_u16() u16 {
	x := u16(tf.buf[tf.pos] << u16(8)) | u16(tf.buf[tf.pos + 1])
	tf.pos += 2
	return x
}

fn (mut tf TTF_File) get_ufword() u16 {
	return tf.get_u16()
}

fn (mut tf TTF_File) get_i16() i16 {
	return i16(tf.get_u16())
}

fn (mut tf TTF_File) get_fword() i16 {
	return tf.get_i16()
}

fn (mut tf TTF_File) get_u32() u32 {
	x :=(u32(tf.buf[tf.pos]) << u32(24)) | 
		(u32(tf.buf[tf.pos + 1]) << u32(16)) | 
		(u32(tf.buf[tf.pos + 2]) << u32(8)) | 
		u32(tf.buf[tf.pos + 3])
	tf.pos += 4
	return x
}

fn (mut tf TTF_File) get_i32() int {
	return int(tf.get_u32())
}

fn (mut tf TTF_File) get_2dot14() f32 {
	return f32(tf.get_i16()) / f32(i16(1 << 14))
}

fn (mut tf TTF_File) get_fixed() f32 {
	return f32(tf.get_i32() / f32(1 << 16))
}

/*---- restore when MSVC will work again! ----
fn (mut tf TTF_File) get_string(length int) string {
	tmp_pos := tf.pos
	tf.pos += u32(length)
	unsafe{
		return tos(&tf.buf.data[tmp_pos], length)
	}
}
*/

fn (mut tf TTF_File) get_string(length int) string {
	tmp_pos := tf.pos
	mut tmp_txt := strings.new_builder(length)
	for _ in 0..length {
		tmp_txt.write_b(tf.get_u8())
	}
	res_txt := tmp_txt.str()
	tf.pos = tmp_pos + u32(length)
	return res_txt
}

fn (mut tf TTF_File) get_unicode_string(length int) string {
	mut tmp_txt := strings.new_builder(length)
	mut real_len := 0
	
	for _ in 0..(length>>1) {
		c := tf.get_u16()
		c_len := ((0xe5000000>>((c>>3) & 0x1e)) & 3) + 1
		real_len += c_len
		if c_len == 1 {
			tmp_txt.write_b(byte(c & 0xff))
		} else {
			tmp_txt.write_b(byte((c >> 8) & 0xff))
			tmp_txt.write_b(byte(c & 0xff))
		}
		//dprintln("c: ${c:c}|${ byte(c &0xff) :c} c_len: ${c_len} str_len: ${real_len} in_len: ${length}")
	}
	tf.pos += u32(real_len)
	res_txt := tmp_txt.str()
	//dprintln("get_unicode_string: ${res_txt}")
	return res_txt
}

fn (mut tf TTF_File) get_date() u64 {
	// var macTime = this.getUint32() * 0x100000000 + this.getUint32();
	// utcTime = macTime * 1000 + Date.UTC(1904, 1, 1);
	// return new Date(utcTime);

	mac_time := u64( (tf.get_u32()) << 32) + u64(tf.get_u32())
	return mac_time
}

fn (mut tf TTF_File) calc_checksum(offset u32, length u32) u32 {
	old_index  := tf.pos
	mut sum    := u64(0)
	mut nlongs := int((length + 3) >> 2)
	tf.pos = offset
	//dprintln("offs: $offset nlongs: $nlongs")
	for nlongs > 0 {
		sum = sum + u64(tf.get_u32())
		nlongs--
	}
	tf.pos = old_index
	return u32(sum & u64(0xffff_ffff))
}

/******************************************************************************
*
* Offset_Table
*
******************************************************************************/
struct Offset_Table {
mut:
	checksum u32
	offset   u32
	length   u32
}

fn (mut tf TTF_File) read_offset_tables() {
	dprintln("*** READ TABLES OFFSET ***")
	tf.pos = 0
	tf.scalar_type   = tf.get_u32()
	num_tables       := tf.get_u16()
	tf.search_range  = tf.get_u16()
	tf.entry_selector= tf.get_u16()
	tf.range_shift   = tf.get_u16()

	dprintln("scalar_type   : [0x$tf.scalar_type.hex()]")
	dprintln("num tables    : [$num_tables]")
	dprintln("search_range  : [0x$tf.search_range.hex()]")
	dprintln("entry_selector: [0x$tf.entry_selector.hex()]")
	dprintln("range_shift   : [0x$tf.range_shift.hex()]")

	mut i:= 0
	for i < num_tables {
		tag := tf.get_string(4)
		tf.tables[tag] = {
			checksum: tf.get_u32()
			offset:   tf.get_u32()
			length:   tf.get_u32()
		}
		dprintln("Table: [$tag]")
		//dprintln("${tf.tables[tag]}")

		if tag != 'head' {
			assert tf.calc_checksum(tf.tables[tag].offset, tf.tables[tag].length) == tf.tables[tag].checksum
		}
		i++
	}
	dprintln("*** END READ TABLES OFFSET ***")
}

/******************************************************************************
*
* Head_Table
*
******************************************************************************/
fn (mut tf TTF_File) read_head_table() {
	dprintln("*** READ HEAD TABLE ***")
	tf.pos = tf.tables["head"].offset
	dprintln("Offset: $tf.pos")

	tf.version             = tf.get_fixed()
	tf.font_revision       = tf.get_fixed()
	tf.checksum_adjustment = tf.get_u32()
	tf.magic_number        = tf.get_u32()
	assert tf.magic_number == 0x5f0f3cf5
	tf.flags               = tf.get_u16()
	tf.units_per_em        = tf.get_u16()
	tf.created             = tf.get_date()
	tf.modified            = tf.get_date()
	tf.x_min               = tf.get_i16()
	tf.y_min               = tf.get_i16()
	tf.x_max               = tf.get_i16()
	tf.y_max               = tf.get_i16()
	tf.mac_style           = tf.get_u16()
	tf.lowest_rec_ppem     = tf.get_u16()
	tf.font_direction_hint = tf.get_i16()
	tf.index_to_loc_format = tf.get_i16()
	tf.glyph_data_format   = tf.get_i16()
}

/******************************************************************************
*
* Name_Table
*
******************************************************************************/
fn (mut tf TTF_File) read_name_table() {
	dprintln("*** READ NAME TABLE ***")
	assert "name" in tf.tables
	table_offset := tf.tables["name"].offset
	tf.pos = tf.tables["name"].offset
	
	format        := tf.get_u16() // must be 0
	assert format == 0
	count         := tf.get_u16()
	string_offset := tf.get_u16()

	for _ in 0..count {
		platform_id          := tf.get_u16()
		/*platform_specific_id :=*/ tf.get_u16()
		/*language_id          :=*/ tf.get_u16()
		name_id              := tf.get_u16()
		length               := tf.get_u16()
		offset               := tf.get_u16()

		old_pos              := tf.pos
		tf.pos = table_offset + string_offset + offset

		mut name := ""
		if platform_id == 0 || platform_id == 3 {
			name = tf.get_unicode_string(length)
		} else {
			name = tf.get_string(length)
		}
		//dprintln("Name [${platform_id} / ${platform_specific_id}] id:[$name_id] language:[$language_id] [$name]")
		tf.pos = old_pos

		match name_id {
			1 {
				tf.font_family = name
			}
			2 {
				tf.font_sub_family = name
			}
			4 {
				tf.full_name  = name
			}
			6 {
				tf.postscript_name = name
			}
			else {}
		}
	}
}

/******************************************************************************
*
* Cmap_Table
*
******************************************************************************/
fn (mut tf TTF_File) read_cmap_table() {
	dprintln("*** READ CMAP TABLE ***")
	assert "cmap" in tf.tables
	table_offset := tf.tables["cmap"].offset
	tf.pos = table_offset

	version           := tf.get_u16() // must be 0
	assert version == 0
	number_sub_tables := tf.get_u16()

	// tables must be sorted by platform id and then platform specific
	// encoding.
	for _ in 0..number_sub_tables {
		// platforms are:
		// 0 - Unicode -- use specific id 6 for full coverage. 0/4 common.
		// 1 - Macintosh (Discouraged)
		// 2 - reserved
		// 3 - Microsoft
		platform_id          := tf.get_u16()
		platform_specific_id := tf.get_u16()
		offset               := tf.get_u32()
		dprintln("CMap platform_id=${platform_id} specific_id=${platform_specific_id} offset=${offset}")
		if platform_id == 3 && platform_specific_id <= 1 {
			tf.read_cmap(table_offset + offset)
		}
	}
}

fn (mut tf TTF_File) read_cmap(offset u32) {
	old_pos := tf.pos
	tf.pos  = offset
	format   := tf.get_u16()
	length   := tf.get_u16()
	language := tf.get_u16()

	dprintln("  Cmap format: $format length: $length language: $language")
	if format == 0 {
		dprintln("  Cmap 0 Init...")
		mut cmap := TrueTypeCmap{}
		cmap.init_0(mut tf)
		tf.cmaps << cmap
	} else if format == 4 {
		dprintln("  Cmap 4 Init...")
		mut cmap := TrueTypeCmap{}
		cmap.init_4(mut tf)
		tf.cmaps << cmap
	}

	tf.pos = old_pos
}

/******************************************************************************
*
* CMAPS 0/4
*
******************************************************************************/
fn (mut tf TTF_File) map_code(char_code int) u16{
	mut index := 0
	for i in 0..tf.cmaps.len {
		mut cmap := tf.cmaps[i]
		if cmap.format == 0 {
			//dprintln("format 0")
			index = cmap.map_0(char_code)
		} else if cmap.format == 4 {
			//dprintln("format 4")
			index = cmap.map_4(char_code, mut tf)
		}
	}
	return u16(index)
}

fn (mut tm TrueTypeCmap) init_0(mut tf TTF_File) {
	tm.format = 0
	for i in 0..256 {
		glyph_index := tf.get_u8()
		dprintln("   Glyph[$i] = %glyph_index")
		tm.arr << glyph_index
	}
}

fn (mut tm TrueTypeCmap) map_0(char_code int) int {
	if char_code >= 0 && char_code <= 255 {
		//dprintln("charCode $char_code maps to ${tm.arr[char_code]}")
		return tm.arr[char_code]
	}
	return 0
}

fn (mut tm TrueTypeCmap) init_4(mut tf TTF_File) {
	tm.format = 4

	// 2x segcount
	seg_count      := tf.get_u16() >> 1
	/*search_range   :=*/ tf.get_u16()
	/*entry_selector :=*/ tf.get_u16()
	/*range_shift    :=*/ tf.get_u16()


	// Ending character code for each segment, last is 0xffff
	for _ in 0..seg_count {
	tm.segments << Segment{0, 0, tf.get_u16(), 0}
	}

	// reservePAD
	tf.get_u16()

	// starting character code for each segment
	for i in 0..seg_count {
	tm.segments[i].start_code = tf.get_u16()
	}

	// Delta for all character codes in segment
	for i in 0..seg_count {
	tm.segments[i].id_delta = tf.get_u16()
	}

	// offset in bytes to glyph indexArray, or 0
	for i in 0..seg_count {
		ro := u32(tf.get_u16())
		if ro != 0 {
		tm.segments[i].id_range_offset = tf.pos - 2 + ro
		} else {
		tm.segments[i].id_range_offset = 0
		}
	}
/*
	// DEBUG LOG
	for i in 0..seg_count {
	seg := tm.segments[i]
	dprintln("    segments[$i] = $seg.start_code $seg.end_code $seg.id_delta $seg.id_range_offset")
	}
*/
}

fn (mut tm TrueTypeCmap) map_4(char_code int, mut tf TTF_File) int {
	//dprintln("HERE map_4 for char [$char_code]")
	old_pos := tf.pos
	if tm.cache[char_code] == -1 {
		//dprintln("Not found, search for it!")
		mut found := false
		for segment in tm.segments {
			if segment.start_code <= char_code && segment.end_code >= char_code {
				mut index := (segment.id_delta + char_code) & 0xffff
				if segment.id_range_offset > 0 {
					glyph_index_address := segment.id_range_offset + 2 * u32(char_code - segment.start_code)
					tf.pos = glyph_index_address
					index = tf.get_u16()
				}

				tm.cache[char_code] = index
				found = true
				break
			}
		}
		if !found {
			tm.cache[char_code] = 0
		}
	}
	tf.pos = old_pos
	return tm.cache[char_code]
}

/******************************************************************************
*
* Hhea table
*
******************************************************************************/
fn (mut tf TTF_File) read_hhea_table() {
	dprintln("*** READ HHEA TABLE ***")
	assert "hhea" in tf.tables
	table_offset := tf.tables["hhea"].offset
	tf.pos = table_offset

	/*version :=*/ tf.get_fixed() // 0x00010000
	
	tf.ascent                  = tf.get_fword()
	tf.descent                 = tf.get_fword()
	tf.line_gap                = tf.get_fword()
	tf.advance_width_max       = tf.get_ufword()
	tf.min_left_side_bearing   = tf.get_fword()
	tf.min_right_side_bearing  = tf.get_fword()
	tf.x_max_extent            = tf.get_fword()
	tf.caret_slope_rise        = tf.get_i16()
	tf.caret_slope_run         = tf.get_i16()
	tf.caret_offset            = tf.get_fword()
	tf.get_i16() // reserved
	tf.get_i16() // reserved
	tf.get_i16() // reserved
	tf.get_i16() // reserved
	tf.metric_data_format      = tf.get_i16()
	tf.num_of_long_hor_metrics = tf.get_u16()
}

/******************************************************************************
*
* Kern table
*
******************************************************************************/
struct Kern0Table {
mut:
	swap       bool
	offset     u32
	n_pairs    int
	kmap       map[u32]i16
	old_index  int = -1
}

fn (mut kt Kern0Table) reset() {
	kt.old_index = -1
}

fn (mut kt Kern0Table) get(glyph_index int) (int, int) {
	mut x := 0

	if kt.old_index >= 0 {
		ch := ((u32(kt.old_index & 0xFFFF) << 16) | u32(glyph_index & 0xFFFF))
		//dprintln("kern_get: $ch")
		if ch in kt.kmap {
			x = int(kt.kmap[ch])
		}
	}
	kt.old_index = glyph_index
	if kt.swap {
		return 0 , x
	}
	return x, 0
}

fn (mut tf TTF_File) create_kern_table0(vertical bool, cross bool) Kern0Table {
	offset         := tf.pos
	n_pairs        := tf.get_u16()
	search_range   := tf.get_u16()
	entry_selector := tf.get_u16()
	range_shift    := tf.get_u16()
	dprintln("n_pairs: $n_pairs search_range: $search_range entry_selector: $entry_selector range_shift: $range_shift")

	mut kt0 := Kern0Table{
		swap: (vertical && !cross) || (!vertical && cross)
		offset: offset
		n_pairs: n_pairs
	}

	for _ in 0..n_pairs {
		left  := tf.get_u16()
		right := tf.get_u16()
		value := tf.get_fword()
		tmp_index := (u32(left) << 16) | u32(right)
		kt0.kmap[tmp_index] = value
		//dprintln("index: ${tmp_index.hex()} val: ${value.hex()}")
	}
	kt0.old_index = -1
	return kt0
}

fn (mut tf TTF_File) read_kern_table() {
	dprintln("*** READ KERN TABLE ***")
	if !("kern" in tf.tables){
		return
	}
	table_offset := tf.tables["kern"].offset
	tf.pos = table_offset

	version           := tf.get_u16() // must be 0
	assert version == 0 // must be 0
	n_tables          := tf.get_u16()

	dprintln("Kern Table version: $version Kern nTables: $n_tables")

	for _ in 0..n_tables{
		st_version := tf.get_u16() // sub table version
		length     := tf.get_u16()
		coverage   := tf.get_u16()
		format     := coverage >> 8
		cross      := coverage & 4
		vertical   := (coverage & 0x1) == 0
		dprintln("Kerning subtable version [$st_version] format [$format] length [$length] coverage: [${coverage.hex()}]")
		if format == 0 {
			dprintln("kern format: 0")
			kern := tf.create_kern_table0(vertical, cross != 0)
			tf.kern << kern
		} else {
			dprintln("Unknown format -- skip")
			tf.pos = tf.pos + length
		}
	}
}

fn (mut tf TTF_File) reset_kern() {
	for i in 0..tf.kern.len {
		tf.kern[i].reset()
	}
}

fn (mut tf TTF_File) next_kern(glyph_index int) (int, int){
	mut x := 0
	mut y := 0
	for i in 0..tf.kern.len {
		tmp_x, tmp_y := tf.kern[i].get(glyph_index)
		x = x + tmp_x
		y = y + tmp_y
	}
	return x, y
}


/******************************************************************************
*
* TTF_File Utility
*
******************************************************************************/
/*
fn (tf TTF_File) get_info_string() string{
	txt := "----- Font Info -----
version: $tf.version
font_revision: $tf.font_revision
magic_number : ${tf.magic_number.hex()}
flags        : ${tf.flags.hex()}
created      : ${tf.created}
modified     : ${tf.modified}
box          : [xm:${tf.x_min}, ym:${tf.y_min}, xM:${tf.x_max}, yM:${tf.y_max}]
mac_style    : ${tf.mac_style}
-----------------------
"
	return txt
}
*/


/******************************************************************************
*
* TTF_File test
*
******************************************************************************/
fn tst(){
	mut tf := TTF_File{}

	tf.buf = [
		byte(0xFF),              // 8  bit
		0xF1, 0xF2,              // 16 bit
		0x81, 0x23, 0x45, 0x67,  // 32 bit
		0x12, 0x34, 0x12, 0x34,  // get_2dot14 16 bit
		0x12, 0x34, 0x12, 0x34   // get_fixed 32 bit int
	]
	assert tf.get_u8().hex() == "ff"
	assert tf.get_u16().hex() == "f1f2"
	assert tf.get_u32().hex() == "81234567"

	dprintln("buf len: ${tf.buf.len}")
	//dprintln( tf.get_u8().hex() )
	//dprintln( tf.get_u16().hex() )
	//dprintln( tf.get_u32().hex() )
	//dprintln( tf.get_2dot14() )
	//dprintln( tf.get_fixed() )
}