os: add font module, move from gg (#13144)

examples/gg/worker_thread.v

@@ -36,7 +36,6 @@ fn main() {
 		bg_color: bg_color
 		frame_fn: frame
 		init_fn: init
-		font_path: gg.system_font_path()
 	)
 	app.gg.run()
 }

examples/hot_reload/bounce.v

@@ -42,7 +42,6 @@ fn main() {
 		create_window: true
 		frame_fn: frame
 		bg_color: gx.white
-		font_path: gg.system_font_path()
 	)
 	// window.onkeydown(key_down)
 	println('Starting the game loop...')

examples/hot_reload/graph.v

@@ -29,7 +29,6 @@ fn main() {
 		frame_fn: frame
 		resizable: true
 		bg_color: gx.white
-		font_path: gg.system_font_path()
 	)
 	context.gg.run()
 }

vlib/gg/gg.c.v

@@ -4,6 +4,7 @@
 module gg
 
 import os
+import os.font
 import gx
 import sokol
 import sokol.sapp
@@ -182,7 +183,7 @@ fn gg_init_sokol_window(user_data voidptr) {
 			) or { panic(err) }
 			g.font_inited = true
 		} else {
-			sfont := system_font_path()
+			sfont := font.default()
 			if g.config.font_path != '' {
 				eprintln('font file "$g.config.font_path" does not exist, the system font ($sfont) was used instead.')
 			}

vlib/gg/text_rendering.c.v

@@ -7,6 +7,7 @@ import sokol.sfons
 import sokol.sgl
 import gx
 import os
+import os.font
 
 struct FT {
 pub:
@@ -83,20 +84,20 @@ fn new_ft(c FTConfig) ?&FT {
 	mut bold_path := if c.custom_bold_font_path != '' {
 		c.custom_bold_font_path
 	} else {
-		get_font_path_variant(c.font_path, .bold)
+		font.get_path_variant(c.font_path, .bold)
 	}
 	bytes_bold := os.read_bytes(bold_path) or {
 		debug_font_println('failed to load font "$bold_path"')
 		bold_path = c.font_path
 		bytes
 	}
-	mut mono_path := get_font_path_variant(c.font_path, .mono)
+	mut mono_path := font.get_path_variant(c.font_path, .mono)
 	bytes_mono := os.read_bytes(mono_path) or {
 		debug_font_println('failed to load font "$mono_path"')
 		mono_path = c.font_path
 		bytes
 	}
-	mut italic_path := get_font_path_variant(c.font_path, .italic)
+	mut italic_path := font.get_path_variant(c.font_path, .italic)
 	bytes_italic := os.read_bytes(italic_path) or {
 		debug_font_println('failed to load font "$italic_path"')
 		italic_path = c.font_path
@@ -228,113 +229,3 @@ pub fn (ctx &Context) text_size(s string) (int, int) {
 	ctx.ft.fons.text_bounds(0, 0, s, &buf[0])
 	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 {
-		debug_font_println('Using font "C:\\Windows\\Fonts\\arial.ttf"')
-		return 'C:\\Windows\\Fonts\\arial.ttf'
-	}
-	$if macos {
-		fonts := ['/System/Library/Fonts/SFNS.ttf', '/System/Library/Fonts/SFNSText.ttf',
-			'/Library/Fonts/Arial.ttf']
-		for font in fonts {
-			if os.is_file(font) {
-				debug_font_println('Using font "$font"')
-				return font
-			}
-		}
-	}
-	$if android {
-		xml_files := ['/system/etc/system_fonts.xml', '/system/etc/fonts.xml',
-			'/etc/system_fonts.xml', '/etc/fonts.xml', '/data/fonts/fonts.xml',
-			'/etc/fallback_fonts.xml']
-		font_locations := ['/system/fonts', '/data/fonts']
-		for xml_file in xml_files {
-			if os.is_file(xml_file) && os.is_readable(xml_file) {
-				xml := os.read_file(xml_file) or { continue }
-				lines := xml.split('\n')
-				mut candidate_font := ''
-				for line in lines {
-					if line.contains('<font') {
-						candidate_font = line.all_after('>').all_before('<').trim(' \n\t\r')
-						if candidate_font.contains('.ttf') {
-							for location in font_locations {
-								candidate_path := os.join_path(location, candidate_font)
-								if os.is_file(candidate_path) && os.is_readable(candidate_path) {
-									debug_font_println('Using font "$candidate_path"')
-									return candidate_path
-								}
-							}
-						}
-					}
-				}
-			}
-		}
-	}
-	mut fm := os.execute("fc-match --format='%{file}\n' -s")
-	if fm.exit_code == 0 {
-		lines := fm.output.split('\n')
-		for l in lines {
-			if !l.contains('.ttc') {
-				debug_font_println('Using font "$l"')
-				return l
-			}
-		}
-	} else {
-		panic('fc-match failed to fetch system font')
-	}
-	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 file := os.file_name(font_path)
-	mut fpath := font_path.replace(file, '')
-	file = file.replace('.ttf', '')
-
-	match variant {
-		.normal {}
-		.bold {
-			if fpath.ends_with('-Regular') {
-				file = file.replace('-Regular', '-Bold')
-			} else if file.starts_with('DejaVuSans') {
-				file += '-Bold'
-			} else if file.to_lower().starts_with('arial') {
-				file += 'bd'
-			} else {
-				file += '-bold'
-			}
-			$if macos {
-				if os.exists('SFNS-bold') {
-					file = 'SFNS-bold'
-				}
-			}
-		}
-		.italic {
-			if file.ends_with('-Regular') {
-				file = file.replace('-Regular', '-Italic')
-			} else if file.starts_with('DejaVuSans') {
-				file += '-Oblique'
-			} else if file.to_lower().starts_with('arial') {
-				file += 'i'
-			} else {
-				file += 'Italic'
-			}
-		}
-		.mono {
-			if !file.ends_with('Mono-Regular') && file.ends_with('-Regular') {
-				file = file.replace('-Regular', 'Mono-Regular')
-			} else if file.to_lower().starts_with('arial') {
-				// Arial has no mono variant
-			} else {
-				file += 'Mono'
-			}
-		}
-	}
-	return fpath + file + '.ttf'
-}

vlib/gg/text_rendering.v

@@ -4,13 +4,6 @@ module gg
 
 import gx
 
-enum FontVariant {
-	normal = 0
-	bold
-	mono
-	italic
-}
-
 struct FTConfig {
 	font_path             string
 	custom_bold_font_path string

vlib/os/font/font.v

@@ -0,0 +1,135 @@
+// Copyright (c) 2019-2022 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 font
+
+import os
+
+// Variant enumerates the different variants a font can have.
+pub enum Variant {
+	normal = 0
+	bold
+	mono
+	italic
+}
+
+[if debug_font ?]
+fn debug_font_println(s string) {
+	println(s)
+}
+
+// default returns an absolute path the default system TTF font.
+// If the env variable `VUI_FONT` is set this is used instead.
+// NOTE that, in some cases, the function calls out to external OS programs
+// so running this in a hot loop is not advised.
+pub fn default() string {
+	env_font := os.getenv('VUI_FONT')
+	if env_font != '' && os.exists(env_font) {
+		return env_font
+	}
+	$if windows {
+		debug_font_println('Using font "C:\\Windows\\Fonts\\arial.ttf"')
+		return 'C:\\Windows\\Fonts\\arial.ttf'
+	}
+	$if macos {
+		fonts := ['/System/Library/Fonts/SFNS.ttf', '/System/Library/Fonts/SFNSText.ttf',
+			'/Library/Fonts/Arial.ttf']
+		for font in fonts {
+			if os.is_file(font) {
+				debug_font_println('Using font "$font"')
+				return font
+			}
+		}
+	}
+	$if android {
+		xml_files := ['/system/etc/system_fonts.xml', '/system/etc/fonts.xml',
+			'/etc/system_fonts.xml', '/etc/fonts.xml', '/data/fonts/fonts.xml',
+			'/etc/fallback_fonts.xml']
+		font_locations := ['/system/fonts', '/data/fonts']
+		for xml_file in xml_files {
+			if os.is_file(xml_file) && os.is_readable(xml_file) {
+				xml := os.read_file(xml_file) or { continue }
+				lines := xml.split('\n')
+				mut candidate_font := ''
+				for line in lines {
+					if line.contains('<font') {
+						candidate_font = line.all_after('>').all_before('<').trim(' \n\t\r')
+						if candidate_font.contains('.ttf') {
+							for location in font_locations {
+								candidate_path := os.join_path(location, candidate_font)
+								if os.is_file(candidate_path) && os.is_readable(candidate_path) {
+									debug_font_println('Using font "$candidate_path"')
+									return candidate_path
+								}
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	mut fm := os.execute("fc-match --format='%{file}\n' -s")
+	if fm.exit_code == 0 {
+		lines := fm.output.split('\n')
+		for l in lines {
+			if !l.contains('.ttc') {
+				debug_font_println('Using font "$l"')
+				return l
+			}
+		}
+	} else {
+		panic('fc-match failed to fetch system font')
+	}
+	panic('failed to init the font')
+}
+
+// get_path_variant returns the `font_path` file name replaced with the
+// file name of the font's `variant` version if it exists.
+pub fn get_path_variant(font_path string, variant Variant) string {
+	// TODO: find some way to make this shorter and more eye-pleasant
+	// NotoSans, LiberationSans, DejaVuSans, Arial and SFNS should work
+	mut file := os.file_name(font_path)
+	mut fpath := font_path.replace(file, '')
+	file = file.replace('.ttf', '')
+
+	match variant {
+		.normal {}
+		.bold {
+			if fpath.ends_with('-Regular') {
+				file = file.replace('-Regular', '-Bold')
+			} else if file.starts_with('DejaVuSans') {
+				file += '-Bold'
+			} else if file.to_lower().starts_with('arial') {
+				file += 'bd'
+			} else {
+				file += '-bold'
+			}
+			$if macos {
+				if os.exists('SFNS-bold') {
+					file = 'SFNS-bold'
+				}
+			}
+		}
+		.italic {
+			if file.ends_with('-Regular') {
+				file = file.replace('-Regular', '-Italic')
+			} else if file.starts_with('DejaVuSans') {
+				file += '-Oblique'
+			} else if file.to_lower().starts_with('arial') {
+				file += 'i'
+			} else {
+				file += 'Italic'
+			}
+		}
+		.mono {
+			if !file.ends_with('Mono-Regular') && file.ends_with('-Regular') {
+				file = file.replace('-Regular', 'Mono-Regular')
+			} else if file.to_lower().starts_with('arial') {
+				// Arial has no mono variant
+			} else {
+				file += 'Mono'
+			}
+		}
+	}
+	return fpath + file + '.ttf'
+}