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UI font rendering: use available bold fonts for bold (#5675)

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A few fixes and enhancement related to bold text:
- When using bold=true with a regular font, use its bold
  variant if one exists (can be prevented by manually
  adding a setting: "use_bold_font_for_bold" = false).
- When using a bold font without bold=true, promote bold
  to true, so fallback fonts are drawn bold too.
- Whether using a bold font, or using bold=true, ensure
  fallback fonts are drawn bold, with their available bold
  variant if one exists, or with synthetized bold.
- When using a bold variant of a fallback font, keep using
  the regular variant as another fallback (as bold fonts
  may contain less glyphs than their regular counterpart).
- Allow providing bold=Font.FORCE_SYNTHETIZED_BOLD to
  get synth bold even when a bold font exists (might be
  interesting to get text in bold the same width as the
  same text non-bold).
- Use the font realname in the key when caching glyphs,
  instead of our aliases (cfont, infont...) to avoid
  duplication and wasting memory.
This commit is contained in:
poire-z
2019-12-08 20:31:27 +01:00
committed by GitHub
parent b578d8aa8b
commit 55f3575a10
4 changed files with 217 additions and 17 deletions
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196
frontend/ui/font.lua
View File

@@ -7,7 +7,35 @@ local Freetype = require("ffi/freetype")
local Screen = require("device").screen
local logger = require("logger")
-- Known regular (and italic) fonts with an available bold font file
local _bold_font_variant = {}
_bold_font_variant["NotoSans-Regular.ttf"] = "NotoSans-Bold.ttf"
_bold_font_variant["NotoSans-Italic.ttf"] = "NotoSans-BoldItalic.ttf"
_bold_font_variant["NotoSansArabicUI-Regular.ttf"] = "NotoSansArabicUI-Bold.ttf"
_bold_font_variant["NotoSerif-Regular.ttf"] = "NotoSerif-Bold.ttf"
_bold_font_variant["NotoSerif-Italic.ttf"] = "NotoSerif-BoldItalic.ttf"
-- Build the reverse mapping, so we can know a font is bold
local _regular_font_variant = {}
for regular, bold in pairs(_bold_font_variant) do
_regular_font_variant[bold] = regular
end
local Font = {
-- Make these available in the Font object, so other code
-- can complete them if needed.
bold_font_variant = _bold_font_variant,
regular_font_variant = _regular_font_variant,
-- Allow globally not promoting fonts to their bold variants
-- (and use thiner and narrower synthetized bold instead).
use_bold_font_for_bold = G_reader_settings:nilOrTrue("use_bold_font_for_bold"),
-- Widgets can provide "bold = Font.FORCE_SYNTHETIZED_BOLD" instead
-- of "bold = true" to explicitely request synthetized bold, which,
-- with XText, makes a bold string the same width as itself non-bold.
FORCE_SYNTHETIZED_BOLD = "FORCE_SYNTHETIZED_BOLD",
fontmap = {
-- default font for menu contents
cfont = "NotoSans-Regular.ttf",
@@ -74,6 +102,8 @@ local Font = {
x_smallinfofont = 20,
xx_smallinfofont = 18,
},
-- This fallback fonts list should only contain
-- regular weight (non bold) font files.
fallbacks = {
[1] = "NotoSans-Regular.ttf",
[2] = "NotoSansCJKsc-Regular.otf",
@@ -87,39 +117,89 @@ local Font = {
faces = {},
}
-- Helper functions with explicite names around
-- bold/regular_font_variant tables
function Font:hasBoldVariant(name)
return self.bold_font_variant[name] and true or false
end
function Font:getBoldVariantName(name)
return self.bold_font_variant[name]
end
function Font:isRealBoldFont(name)
return self.regular_font_variant[name] and true or false
end
function Font:getRegularVariantName(name)
return self.regular_font_variant[name] or name
end
-- Synthetized bold strength can be tuned:
-- local bold_strength_factor = 1 -- really too bold
-- local bold_strength_factor = 1/2 -- bold enough
local bold_strength_factor = 3/8 -- as crengine, lighter
-- Callback to be used by libkoreader-xtext.so to get Freetype
-- instantiated fallback fonts when needed for shaping text
local _getFallbackFont = function(face_obj, num)
if not num or num == 0 then -- return the main font
-- Add some properties to a face object as needed
local _completeFaceProperties = function(face_obj)
if not face_obj.embolden_half_strength then
-- cache this value in case we use bold, to avoid recomputation
-- Cache this value in case we use bold, to avoid recomputation
face_obj.embolden_half_strength = face_obj.ftface:getEmboldenHalfStrength(bold_strength_factor)
end
end
-- Callback to be used by libkoreader-xtext.so to get Freetype
-- instantiated fallback fonts when needed for shaping text
-- (Beware: any error in this code won't be noticed when this
-- is called from the C module...)
local _getFallbackFont = function(face_obj, num)
if not num or num == 0 then -- return the main font
_completeFaceProperties(face_obj)
return face_obj
end
if not face_obj.fallbacks then
face_obj.fallbacks = {}
end
if face_obj.fallbacks[num] ~= nil then
if face_obj.fallbacks[num] ~= nil then -- (false means: no more fallback font)
return face_obj.fallbacks[num]
end
local next_num = #face_obj.fallbacks + 1
local cur_num = 0
local realname = face_obj.realname
if face_obj.is_real_bold then
-- Get the regular name, to skip it from Font.fallbacks
realname = Font:getRegularVariantName(realname)
end
for index, fontname in pairs(Font.fallbacks) do
if fontname ~= face_obj.realname then -- Skip base one if among fallbacks
if fontname ~= realname then -- Skip base one if among fallbacks
-- If main font is a real bold, or if it's not but we want bold,
-- get the bold variant of the fallback if one exists.
-- But if one exists, use the regular variant as an additional
-- fallback, drawn with synthetized bold (often, bold fonts
-- have less glyphs than their regular counterpart).
if face_obj.is_real_bold or face_obj.wants_bold == true then
-- (not if wants_bold==Font.FORCE_SYNTHETIZED_BOLD)
local bold_variant_name = Font:getBoldVariantName(fontname)
if bold_variant_name then
-- There is a bold variant of that fallback font, that we can use
local fb_face = Font:getFace(bold_variant_name, face_obj.orig_size)
if fb_face ~= nil then -- valid font
cur_num = cur_num + 1
if cur_num == next_num then
_completeFaceProperties(fb_face)
face_obj.fallbacks[next_num] = fb_face
return fb_face
end
-- otherwise, go on with the regular variant
end
end
end
local fb_face = Font:getFace(fontname, face_obj.orig_size)
if fb_face ~= nil then -- valid font
cur_num = cur_num + 1
if cur_num == next_num then
_completeFaceProperties(fb_face)
face_obj.fallbacks[next_num] = fb_face
if not fb_face.embolden_half_strength then
fb_face.embolden_half_strength = fb_face.ftface:getEmboldenHalfStrength(bold_strength_factor)
end
return fb_face
end
end
@@ -143,14 +223,21 @@ function Font:getFace(font, size)
local orig_size = size
size = Screen:scaleBySize(size)
local hash = font..size
local face_obj = self.faces[hash]
-- build face if not found
if not face_obj then
local realname = self.fontmap[font]
if not realname then
realname = font
end
-- Avoid emboldening already bold fonts
local is_real_bold = self:isRealBoldFont(realname)
-- Make a hash from the realname (many fonts in our fontmap use
-- the same font file: have them share their glyphs cache)
local hash = realname..size
local face_obj = self.faces[hash]
-- build face if not found
if not face_obj then
local builtin_font_location = FontList.fontdir.."/"..realname
local ok, face = pcall(Freetype.newFace, builtin_font_location, size)
@@ -187,6 +274,7 @@ function Font:getFace(font, size)
orig_size = orig_size,
ftface = face,
hash = hash,
is_real_bold = is_real_bold,
}
self.faces[hash] = face_obj
@@ -214,4 +302,84 @@ function Font:getFace(font, size)
return face_obj
end
--- Returns an alternative face instance to be used for measuring
-- and drawing (in most cases, the one provided untouched)
--
-- If 'bold' is true, or if 'face' is a real bold face, we may need to
-- use an alternative instance of the font, with possibly the associated
-- real bold font, and/or with tweaks so fallback fonts are rendered
-- bold too, without affecting the regular 'face'.
-- (This function should only be used by TextWidget and TextBoxWidget.
-- Other widgets should not use it, and neither _getFallbackFont()
-- which will do its own processing.)
--
-- @tparam ui.font.FontFaceObj provided face font face
-- @bool bold whether bold is requested
-- @treturn ui.font.FontFaceObj face face to use for drawing
-- @treturn bool bold adjusted bold properties
function Font:getAdjustedFace(face, bold)
if face.is_real_bold then
-- No adjustment needed: main real bold font will ensure
-- fallback fonts use their associated bold font or
-- get synthetized bold - whether bold is requested or not
-- (Set returned bold to true, to force synthetized bold
-- on fallback fonts with no associated real bold)
-- (Drop bold=FORCE_SYNTHETIZED_BOLD and use 'true' if
-- we were given a real bold font.)
return face, true
end
if not bold then
-- No adjustment needed: regular main font, and regular
-- fallback fonts untouched.
return face, false
end
-- We have bold requested, and a regular/non-bold font.
if not self.use_bold_font_for_bold then
-- If promotion to real bold is not wished, force synth bold
bold = Font.FORCE_SYNTHETIZED_BOLD
end
if bold ~= Font.FORCE_SYNTHETIZED_BOLD then
-- See if a bold font file exists for that regular font.
local bold_variant_name = self:getBoldVariantName(face.realname)
if bold_variant_name then
face = Font:getFace(bold_variant_name, face.orig_size)
-- It has is_real_bold=true: no adjustment needed
return face, true
end
end
-- Only the regular font is available, and bold requested:
-- we'll have synthetized bold - but _getFallbackFont() should
-- build a list of fallback fonts either synthetized, or possibly
-- using the bold variant of a regular fallback font.
-- We don't want to collide with the regular font face_obj.fallbacks
-- so let's make a shallow clone of this face_obj, and have it cached.
-- (Different hash if real bold accepted or not, as the fallback
-- fonts list may then be different.)
local hash = face.hash..(bold == Font.FORCE_SYNTHETIZED_BOLD and "synthbold" or "realbold")
local face_obj = self.faces[hash]
if face_obj then
return face_obj, bold
end
face_obj = {
orig_font = face.orig_font,
realname = face.realname,
size = face.size,
orig_size = face.orig_size,
-- We can keep the same FT object and the same hash in this face_obj
-- (which is only used to identify cached glyphs, that we don't need
-- to distinguish as "bold" is appended when synthetized as bold)
ftface = face.ftface,
hash = face.hash,
hb_features = face.hb_features,
is_real_bold = nil,
wants_bold = bold, -- true or Font.FORCE_SYNTHETIZED_BOLD, used
-- to pick the appropritate fallback fonts
}
face_obj.getFallbackFont = function(num)
return _getFallbackFont(face_obj, num)
end
self.faces[hash] = face_obj
return face_obj, bold
end
return Font

9
frontend/ui/rendertext.lua
View File

@@ -84,6 +84,10 @@ end
-- @bool[opt=false] bold whether the text should be measured as bold
-- @treturn glyph
function RenderText:getGlyph(face, charcode, bold)
local orig_bold = bold
if face.is_real_bold then
bold = false -- don't embolden glyphs already bold
end
local hash = "glyph|"..face.hash.."|"..charcode.."|"..(bold and 1 or 0)
local glyph = GlyphCache:check(hash)
if glyph then
@@ -98,7 +102,7 @@ function RenderText:getGlyph(face, charcode, bold)
if fb_face ~= nil then
-- for some characters it cannot find in Fallbacks, it will crash here
if fb_face.ftface:checkGlyph(charcode) ~= 0 then
rendered_glyph = fb_face.ftface:renderGlyph(charcode, bold)
rendered_glyph = fb_face.ftface:renderGlyph(charcode, orig_bold)
break
end
end
@@ -295,6 +299,9 @@ end
-- @bool[opt=false] bold whether the glyph should be artificially boldened
-- @treturn glyph
function RenderText:getGlyphByIndex(face, glyphindex, bold)
if face.is_real_bold then
bold = false -- don't embolden glyphs already bold
end
local hash = "xglyph|"..face.hash.."|"..glyphindex.."|"..(bold and 1 or 0)
local glyph = GlyphCache:check(hash)
if glyph then

14
frontend/ui/widget/textboxwidget.lua
View File

@@ -38,7 +38,9 @@ local TextBoxWidget = InputContainer:new{
alignment = "left", -- or "center", "right"
dialog = nil, -- parent dialog that will be set dirty
face = nil,
bold = nil,
bold = nil, -- use bold=true to use a real bold font (or synthetized if not available),
-- or bold=Font.FORCE_SYNTHETIZED_BOLD to force using synthetized bold,
-- which, with XText, makes a bold string the same width as it non-bolded.
line_height = 0.3, -- in em
fgcolor = Blitbuffer.COLOR_BLACK,
width = Screen:scaleBySize(400), -- in pixels
@@ -59,6 +61,7 @@ local TextBoxWidget = InputContainer:new{
text_height = nil, -- adjusted height to visible text (lines_per_page*line_height_px)
cursor_line = nil, -- LineWidget to draw the vertical cursor.
_bb = nil,
_face_adjusted = nil,
-- We can provide a list of images: each image will be displayed on each
-- scrolled page, in its top right corner (if more images than pages, remaining
@@ -99,6 +102,15 @@ local TextBoxWidget = InputContainer:new{
}
function TextBoxWidget:init()
if not self._face_adjusted then
self._face_adjusted = true -- only do that once
-- If self.bold, or if self.face is a real bold face, we may need to use
-- an alternative instance of self.face, with possibly the associated
-- real bold font, and/or with tweaks so fallback fonts are rendered bold
-- too, without affecting the regular self.face
self.face, self.bold = Font:getAdjustedFace(self.face, self.bold)
end
self.line_height_px = Math.round( (1 + self.line_height) * self.face.size )
self.cursor_line = LineWidget:new{
dimen = Geom:new{

15
frontend/ui/widget/textwidget.lua
View File

@@ -13,6 +13,7 @@ Example:
--]]
local Blitbuffer = require("ffi/blitbuffer")
local Font = require("ui/font")
local Geom = require("ui/geometry")
local Math = require("optmath")
local RenderText = require("ui/rendertext")
@@ -25,7 +26,9 @@ local util = require("util")
local TextWidget = Widget:new{
text = nil,
face = nil,
bold = false, -- synthetized/fake bold (use a bold face for nicer bold)
bold = false, -- use bold=true to use a real bold font (or synthetized if not available),
-- or bold=Font.FORCE_SYNTHETIZED_BOLD to force using synthetized bold,
-- which, with XText, makes a bold string the same width as it non-bolded.
fgcolor = Blitbuffer.COLOR_BLACK,
padding = Size.padding.small, -- vertical padding (should it be function of face.size ?)
-- (no horizontal padding is added)
@@ -35,6 +38,7 @@ local TextWidget = Widget:new{
-- for internal use
_updated = nil,
_face_adjusted = nil,
_text_to_draw = nil,
_length = 0,
_height = 0,
@@ -58,6 +62,15 @@ function TextWidget:updateSize()
end
self._updated = true
if not self._face_adjusted then
self._face_adjusted = true -- only do that once
-- If self.bold, or if self.face is a real bold face, we may need to use
-- an alternative instance of self.face, with possibly the associated
-- real bold font, and/or with tweaks so fallback fonts are rendered bold
-- too, without affecting the regular self.face
self.face, self.bold = Font:getAdjustedFace(self.face, self.bold)
end
-- Compute height:
-- Used to be:
-- self._height = math.ceil(self.face.size * 1.5)