v/vlib/gg/text_rendering.v

// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license that can be found in the LICENSE file.
module gg

import sokol.sfons
import sokol.sgl
import gx
import os

enum FontVariant {
	normal = 0
	bold
	mono
	italic
}

struct FT {
pub:
	fons &C.FONScontext

	font_normal int
	font_bold int
	font_mono int
	font_italic int
	scale f32 = 1.0
}

struct FTConfig {
	font_path string
	scale f32 = 1.0
	font_size int
}

fn new_ft(c FTConfig) ?&FT{
	if c.font_path == '' {
		// Load default font
	}
	$if !android {
		if c.font_path == '' || !os.exists(c.font_path) {
			println('failed to load font "$c.font_path"')
			return none
		}
	}

	mut bytes := []byte{}
	$if android {
		bytes = os.read_apk_asset(c.font_path) or {
			println('failed to load font "$c.font_path"')
			return none
		}
	} $else {
		bytes = os.read_bytes(c.font_path) or {
			println('failed to load font "$c.font_path"')
			return none
		}
	}
	bold_path := get_font_path_variant(c.font_path, .bold)
	bytes_bold := os.read_bytes(bold_path) or {
		debug_font_println('failed to load font "$bold_path"')
		bytes
	}
	mono_path := get_font_path_variant(c.font_path, .mono)
	bytes_mono:= os.read_bytes(mono_path) or {
		debug_font_println('failed to load font "$mono_path"')
		bytes
	}
	italic_path := get_font_path_variant(c.font_path, .italic)
	bytes_italic:= os.read_bytes(italic_path) or {
		debug_font_println('failed to load font "$italic_path"')
		bytes
	}
	fons := sfons.create(512, 512, 1)
	return &FT{
		fons : fons
		font_normal: C.fonsAddFontMem(fons, 'sans', bytes.data, bytes.len, false)
		font_bold: C.fonsAddFontMem(fons, 'sans', bytes_bold.data, bytes_bold.len, false)
		font_mono: C.fonsAddFontMem(fons, 'sans', bytes_mono.data, bytes_mono.len, false)
		font_italic: C.fonsAddFontMem(fons, 'sans', bytes_italic.data, bytes_italic.len, false)
		scale: c.scale
	}

}
fn (ctx &Context) set_cfg(cfg gx.TextCfg) {
	if !ctx.font_inited {
		return
	}
	if cfg.bold {
		ctx.ft.fons.set_font(ctx.ft.font_bold)
	}
	else if cfg.mono {
		ctx.ft.fons.set_font(ctx.ft.font_mono)
	}
	else if cfg.italic {
		ctx.ft.fons.set_font(ctx.ft.font_italic)
	}
	else {
		ctx.ft.fons.set_font(ctx.ft.font_normal)
	}
	scale := if ctx.ft.scale == 0 { f32(1) } else { ctx.ft.scale }
	size := if cfg.mono { cfg.size - 2 } else { cfg.size }
	ctx.ft.fons.set_size(scale * f32(size))
	C.fonsSetAlign(ctx.ft.fons, int(cfg.align) | int(cfg.vertical_align))
	color := C.sfons_rgba(cfg.color.r, cfg.color.g, cfg.color.b, cfg.color.a)
	if cfg.color.a != 255 {
		sgl.load_pipeline(ctx.timage_pip)
	}
	C.fonsSetColor(ctx.ft.fons, color)
	ascender := f32(0.0)
	descender := f32(0.0)
	lh := f32(0.0)
	ctx.ft.fons.vert_metrics(&ascender, &descender, &lh)
}

pub fn (ctx &Context) draw_text(x, y int, text_ string, cfg gx.TextCfg) {
	if !ctx.font_inited {
		eprintln('gg: draw_text(): font not initialized')
		return
	}
	//text := text_.trim_space() // TODO remove/optimize
	mut text := text_
	if text.contains('\t') {
		text = text.replace('\t', '    ')
	}
	ctx.set_cfg(cfg)
	scale := if ctx.ft.scale == 0 { f32(1) } else { ctx.ft.scale }
	C.fonsDrawText(ctx.ft.fons, x * scale, y * scale, text.str, 0) // TODO: check offsets/alignment
}

pub fn (ctx &Context) draw_text_def(x, y int, text string) {
	ctx.draw_text(x, y, text, {})
}

/*
pub fn (mut gg FT) init_font() {
}
*/

pub fn (ft &FT) flush(){
	sfons.flush(ft.fons)
}

pub fn (ctx &Context) text_width(s string) int {
	// ctx.set_cfg(cfg) TODO
	if !ctx.font_inited {
		return 0
	}
	mut buf := [4]f32{}
	C.fonsTextBounds(ctx.ft.fons, 0, 0, s.str, 0, buf)
	if s.ends_with(' ') {
		return int((buf[2] - buf[0]) / ctx.scale) + ctx.text_width('i') // TODO fix this in fontstash?
	}
	return int((buf[2] - buf[0]) / ctx.scale)
}

pub fn (ctx &Context) text_height(s string) int {
	// ctx.set_cfg(cfg) TODO
	if !ctx.font_inited {
		return 0
	}
	mut buf := [4]f32{}
	C.fonsTextBounds(ctx.ft.fons, 0, 0, s.str, 0, buf)
	return int((buf[3] - buf[1]) / ctx.scale)
}

pub fn (ctx &Context) text_size(s string) (int, int) {
	// ctx.set_cfg(cfg) TODO
	if !ctx.font_inited {
		return 0,0
	}
	mut buf := [4]f32{}
	C.fonsTextBounds(ctx.ft.fons, 0, 0, s.str, 0, buf)
	return int((buf[2] - buf[0]) / ctx.scale), int((buf[3] - buf[1]) / ctx.scale)
}


pub fn system_font_path() string {
	env_font := os.getenv('VUI_FONT')
	if env_font != '' && os.exists(env_font) {
		return env_font
	}
	$if windows {
		return 'C:\\Windows\\Fonts\\arial.ttf'
	}
	mut fonts := ['Ubuntu-R.ttf', 'Arial.ttf', 'LiberationSans-Regular.ttf', 'NotoSans-Regular.ttf',
	'FreeSans.ttf', 'DejaVuSans.ttf']
	$if macos {
		fonts = ['/System/Library/Fonts/SFNS.ttf', '/System/Library/Fonts/SFNSText.ttf', '/Library/Fonts/Arial.ttf']
		for font in fonts {
			if os.is_file(font) {
				return font
			}
		}
	}
	s := os.exec('fc-list') or { panic('failed to fetch system fonts') }
	system_fonts := s.output.split('\n')
	for line in system_fonts {
		for font in fonts {
			if line.contains(font) && line.contains(':') {
				res := line.all_before(':')
				println('Using font $res')
				return res
			}
		}
	}
	panic('failed to init the font')
}

fn get_font_path_variant(font_path string, variant FontVariant) string {
	// TODO: find some way to make this shorter and more eye-pleasant
	// NotoSans, LiberationSans, DejaVuSans, Arial and SFNS should work
	mut fpath := font_path.replace('.ttf', '')
	match variant {
		.normal {}
		.bold {
			if fpath.ends_with('-Regular') {
				fpath = fpath.replace('-Regular', '-Bold')
			} else if fpath.starts_with('DejaVuSans') {
				fpath += '-Bold'
			} else if fpath.to_lower().starts_with('arial') {
				fpath += 'bd'
			} else {
				fpath += '-bold'
			}
		}
		.italic {
			if fpath.ends_with('-Regular') {
				fpath = fpath.replace('-Regular', '-Italic')
			} else if fpath.starts_with('DejaVuSans') {
				fpath += '-Oblique'
			} else if fpath.to_lower().starts_with('arial') {
				fpath += 'i'
			} else {
				fpath += 'Italic'
			}
		}
		.mono {
			if fpath.ends_with('-Regular') {
				fpath = fpath.replace('-Regular', 'Mono-Regular')
			} else if fpath.to_lower().starts_with('arial') {
				// Arial has no mono variant
			} else {
				fpath += 'Mono'
			}
		}
	}
	return fpath + '.ttf'
}

fn debug_font_println(s string) {
	$if debug_font? {
		println(s)    
	}
}