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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
use api::{ColorF, ColorU, FontKey, FontRenderMode, FontSize, GlyphDimensions};
use api::{FontInstanceFlags, FontVariation, NativeFontHandle};
use core_foundation::data::CFData;
use core_foundation::base::TCFType;
use core_foundation::dictionary::CFDictionary;
use core_foundation::number::{CFNumber};
use core_foundation::string::CFString;
use core_foundation::url::{CFURL, kCFURLPOSIXPathStyle};
use core_graphics::base::{kCGImageAlphaNoneSkipFirst, kCGImageAlphaPremultipliedFirst};
use core_graphics::base::{kCGBitmapByteOrder32Little};
use core_graphics::color_space::CGColorSpace;
use core_graphics::context::CGContext;
use core_graphics::context::{CGBlendMode, CGTextDrawingMode};
use core_graphics::font::{CGFont, CGGlyph};
use core_graphics::geometry::{CGAffineTransform, CGPoint, CGSize};
use core_graphics::geometry::{CG_AFFINE_TRANSFORM_IDENTITY, CGRect};
use core_text::font::CTFont;
use core_text::font_descriptor::{CTFontDescriptor, kCTFontDefaultOrientation};
use core_text::font_descriptor::{kCTFontURLAttribute, kCTFontVariationAttribute};
use core_text::font_manager;
use euclid::default::Size2D;
use crate::gamma_lut::{ColorLut, GammaLut};
use crate::rasterizer::{FontInstance, FontTransform, GlyphKey};
use crate::rasterizer::{GlyphFormat, GlyphRasterError, GlyphRasterResult, RasterizedGlyph};
use crate::types::FastHashMap;
use std::collections::hash_map::Entry;
use std::sync::Arc;
const INITIAL_CG_CONTEXT_SIDE_LENGTH: u32 = 32;
pub struct FontContext {
ct_font_descs: FastHashMap<FontKey, CTFontDescriptor>,
// Table mapping a sized font key with variations to its instantiated CoreText font.
ct_fonts: FastHashMap<(FontKey, FontSize, Vec<FontVariation>), CTFont>,
#[allow(dead_code)]
graphics_context: GraphicsContext,
#[allow(dead_code)]
gamma_lut: GammaLut,
}
// core text is safe to use on multiple threads and non-shareable resources are
// all hidden inside their font context.
unsafe impl Send for FontContext {}
struct GlyphMetrics {
rasterized_left: i32,
#[allow(dead_code)]
rasterized_descent: i32,
rasterized_ascent: i32,
rasterized_width: i32,
rasterized_height: i32,
advance: f32,
}
// There are a number of different OS prefs that control whether or not
// requesting font smoothing actually results in subpixel AA. This gets even
// murkier in newer macOS versions that deprecate subpixel AA, with the prefs
// potentially interacting and overriding each other. In an attempt to future-
// proof things against any new prefs or interpretation of those prefs in
// future macOS versions, we do a check here to request font smoothing and see
// what result it actually gives us much like Skia does. We need to check for
// each of three potential results and process them in the font backend in
// distinct ways:
// 1) subpixel AA (differing RGB channels) with dilation
// 2) grayscale AA (matching RGB channels) with dilation, a compatibility mode
// 3) grayscale AA without dilation as if font smoothing was not requested
// We can discern between case 1 and the rest by checking if the subpixels differ.
// We can discern between cases 2 and 3 by rendering with and without smoothing
// and comparing the two to determine if there was some dilation.
// This returns the actual FontRenderMode needed to support each case, if any.
fn determine_font_smoothing_mode() -> Option<FontRenderMode> {
let mut smooth_context = CGContext::create_bitmap_context(
None,
12,
12,
8,
12 * 4,
&CGColorSpace::create_device_rgb(),
kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Little,
);
smooth_context.set_should_smooth_fonts(true);
smooth_context.set_should_antialias(true);
smooth_context.set_rgb_fill_color(1.0, 1.0, 1.0, 1.0);
let mut gray_context = CGContext::create_bitmap_context(
None,
12,
12,
8,
12 * 4,
&CGColorSpace::create_device_rgb(),
kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Little,
);
gray_context.set_should_smooth_fonts(false);
gray_context.set_should_antialias(true);
gray_context.set_rgb_fill_color(1.0, 1.0, 1.0, 1.0);
// Autorelease pool for CTFont
objc::rc::autoreleasepool(|| {
// Lucida Grande 12 is the default fallback font in Firefox
let ct_font = core_text::font::new_from_name("Lucida Grande", 12.).unwrap();
let point = CGPoint { x: 0., y: 0. };
let glyph = 'X' as CGGlyph;
ct_font.draw_glyphs(&[glyph], &[point], smooth_context.clone());
ct_font.draw_glyphs(&[glyph], &[point], gray_context.clone());
});
let mut mode = None;
for (smooth, gray) in smooth_context.data().chunks(4).zip(gray_context.data().chunks(4)) {
if smooth[0] != smooth[1] || smooth[1] != smooth[2] {
return Some(FontRenderMode::Subpixel);
}
if smooth[0] != gray[0] || smooth[1] != gray[1] || smooth[2] != gray[2] {
mode = Some(FontRenderMode::Alpha);
}
}
return mode;
}
// We cache the font smoothing mode globally, rather than storing it in each FontContext,
// to avoid having to determine this redundantly in each context and to avoid needing to
// lock them to access this setting in prepare_font.
lazy_static! {
static ref FONT_SMOOTHING_MODE: Option<FontRenderMode> = determine_font_smoothing_mode();
}
fn should_use_white_on_black(color: ColorU) -> bool {
let (r, g, b) = (color.r as u32, color.g as u32, color.b as u32);
// These thresholds were determined on 10.12 by observing what CG does.
r >= 85 && g >= 85 && b >= 85 && r + g + b >= 2 * 255
}
fn get_glyph_metrics(
ct_font: &CTFont,
transform: Option<&CGAffineTransform>,
glyph: CGGlyph,
x_offset: f64,
y_offset: f64,
extra_width: f64,
) -> GlyphMetrics {
let mut bounds = ct_font.get_bounding_rects_for_glyphs(kCTFontDefaultOrientation, &[glyph]);
if bounds.origin.x.is_nan() || bounds.origin.y.is_nan() || bounds.size.width.is_nan() ||
bounds.size.height.is_nan()
{
// If an unexpected glyph index is requested, core text will return NaN values
// which causes us to do bad thing as the value is cast into an integer and
// overflow when expanding the bounds a few lines below.
// Instead we are better off returning zero-sized metrics because this special
// case is handled by the callers of this method.
return GlyphMetrics {
rasterized_left: 0,
rasterized_width: 0,
rasterized_height: 0,
rasterized_ascent: 0,
rasterized_descent: 0,
advance: 0.0,
};
}
let mut advance = CGSize { width: 0.0, height: 0.0 };
unsafe {
ct_font.get_advances_for_glyphs(kCTFontDefaultOrientation, &glyph, &mut advance, 1);
}
if bounds.size.width > 0.0 {
bounds.size.width += extra_width;
}
if advance.width > 0.0 {
advance.width += extra_width;
}
if let Some(transform) = transform {
bounds = bounds.apply_transform(transform);
}
// First round out to pixel boundaries
// CG Origin is bottom left
let mut left = bounds.origin.x.floor() as i32;
let mut bottom = bounds.origin.y.floor() as i32;
let mut right = (bounds.origin.x + bounds.size.width + x_offset).ceil() as i32;
let mut top = (bounds.origin.y + bounds.size.height + y_offset).ceil() as i32;
// Expand the bounds by 1 pixel, to give CG room for anti-aliasing.
// Note that this outset is to allow room for LCD smoothed glyphs. However, the correct outset
// is not currently known, as CG dilates the outlines by some percentage.
// This is taken from Skia.
left -= 1;
bottom -= 1;
right += 1;
top += 1;
let width = right - left;
let height = top - bottom;
GlyphMetrics {
rasterized_left: left,
rasterized_width: width,
rasterized_height: height,
rasterized_ascent: top,
rasterized_descent: -bottom,
advance: advance.width as f32,
}
}
fn new_ct_font_with_variations(ct_font_desc: &CTFontDescriptor, size: f64, variations: &[FontVariation]) -> CTFont {
let ct_font = core_text::font::new_from_descriptor(ct_font_desc, size);
if variations.is_empty() {
return ct_font;
}
let mut vals: Vec<(CFNumber, CFNumber)> = Vec::with_capacity(variations.len() as usize);
for variation in variations {
vals.push((CFNumber::from(variation.tag as i64), CFNumber::from(variation.value as f64)));
}
if vals.is_empty() {
return ct_font;
}
let vals_dict = CFDictionary::from_CFType_pairs(&vals);
let variation_attribute = unsafe { CFString::wrap_under_get_rule(kCTFontVariationAttribute) };
let attrs_dict = CFDictionary::from_CFType_pairs(&[(variation_attribute, vals_dict)]);
let ct_var_font_desc = ct_font.copy_descriptor().create_copy_with_attributes(attrs_dict.to_untyped()).unwrap();
core_text::font::new_from_descriptor(&ct_var_font_desc, size)
}
// We rely on Gecko to determine whether the font may have color glyphs to avoid
// needing to load the font ahead of time to query its symbolic traits.
fn is_bitmap_font(font: &FontInstance) -> bool {
font.flags.contains(FontInstanceFlags::EMBEDDED_BITMAPS)
}
impl FontContext {
pub fn distribute_across_threads() -> bool {
true
}
pub fn new() -> FontContext {
debug!("Test for subpixel AA support: {:?}", *FONT_SMOOTHING_MODE);
// Force CG to use sRGB color space to gamma correct.
let contrast = 0.0;
let gamma = 0.0;
FontContext {
ct_font_descs: FastHashMap::default(),
ct_fonts: FastHashMap::default(),
graphics_context: GraphicsContext::new(),
gamma_lut: GammaLut::new(contrast, gamma, gamma),
}
}
pub fn add_raw_font(&mut self, font_key: &FontKey, bytes: Arc<Vec<u8>>, index: u32) {
if self.ct_font_descs.contains_key(font_key) {
return;
}
assert_eq!(index, 0);
let data = CFData::from_arc(bytes);
let ct_font_desc = match font_manager::create_font_descriptor_with_data(data) {
Err(_) => return,
Ok(cg_font) => cg_font,
};
self.ct_font_descs.insert(*font_key, ct_font_desc);
}
pub fn add_native_font(&mut self, font_key: &FontKey, native_font_handle: NativeFontHandle) {
if self.ct_font_descs.contains_key(font_key) {
return;
}
// There's no way great way to go from a CGFont to a CTFontDescriptor
// We could use the postscript name but that doesn't work for the
// system UI fonts on newer macOS versions. Instead we create a CTFont
// and use the descriptor for that. Normally we'd try to avoid new_from_CGFont
// because that adds the CGFont to the descriptor cache which can keep the CGFont
// around for a long time, but that should be ok for non-web (native) fonts.
let cf_name = CFString::new(&native_font_handle.name);
// For "hidden" system fonts, whose names start with a period,
// we can't instantiate CTFonts via a descriptor. We're really
// supposed to use CTFontCreateUIFontForLanguage, but for now
// we just use the CGFont.
let mut desc = if native_font_handle.name.starts_with('.') {
let cg_font = match CGFont::from_name(&cf_name) {
Ok(cg_font) => cg_font,
Err(_) => {
// If for some reason we failed to load a font descriptor, then our
// only options are to either abort or substitute a fallback font.
// It is preferable to use a fallback font instead so that rendering
// can at least still proceed in some fashion without erroring.
// Lucida Grande is the fallback font in Gecko, so use that here.
CGFont::from_name(&CFString::from_static_string("Lucida Grande"))
.expect("couldn't find font with postscript name and couldn't load fallback font")
}
};
core_text::font::new_from_CGFont(&cg_font, 0.).copy_descriptor()
} else {
core_text::font_descriptor::new_from_postscript_name(&cf_name)
};
// If the NativeFontHandle includes a file path, add this to the descriptor
// to disambiguate cases where multiple installed fonts have the same psname.
if native_font_handle.path.len() > 0 {
let cf_path = CFString::new(&native_font_handle.path);
let url_attribute = unsafe { CFString::wrap_under_get_rule(kCTFontURLAttribute) };
let attrs = CFDictionary::from_CFType_pairs(&[
(url_attribute, CFURL::from_file_system_path(cf_path, kCFURLPOSIXPathStyle, false)),
]);
if let Ok(desc_with_path) = desc.create_copy_with_attributes(attrs.to_untyped()) {
desc = desc_with_path;
}
}
self.ct_font_descs
.insert(*font_key, desc);
}
pub fn delete_font(&mut self, font_key: &FontKey) {
if let Some(_) = self.ct_font_descs.remove(font_key) {
self.ct_fonts.retain(|k, _| k.0 != *font_key);
}
}
pub fn delete_font_instance(&mut self, instance: &FontInstance) {
// Remove the CoreText font corresponding to this instance.
let size = FontSize::from_f64_px(instance.get_transformed_size());
self.ct_fonts.remove(&(instance.font_key, size, instance.variations.clone()));
}
fn get_ct_font(
&mut self,
font_key: FontKey,
size: f64,
variations: &[FontVariation],
) -> Option<CTFont> {
// Interacting with CoreText can create autorelease garbage.
objc::rc::autoreleasepool(|| {
match self.ct_fonts.entry((font_key, FontSize::from_f64_px(size), variations.to_vec())) {
Entry::Occupied(entry) => Some((*entry.get()).clone()),
Entry::Vacant(entry) => {
let ct_font_desc = self.ct_font_descs.get(&font_key)?;
let ct_font = new_ct_font_with_variations(ct_font_desc, size, variations);
entry.insert(ct_font.clone());
Some(ct_font)
}
}
})
}
pub fn get_glyph_index(&mut self, font_key: FontKey, ch: char) -> Option<u32> {
let character = ch as u16;
let mut glyph = 0;
self.get_ct_font(font_key, 16.0, &[])
.and_then(|ct_font| {
unsafe {
let result = ct_font.get_glyphs_for_characters(&character, &mut glyph, 1);
if result {
Some(glyph as u32)
} else {
None
}
}
})
}
pub fn get_glyph_dimensions(
&mut self,
font: &FontInstance,
key: &GlyphKey,
) -> Option<GlyphDimensions> {
let (x_scale, y_scale) = font.transform.compute_scale().unwrap_or((1.0, 1.0));
let size = font.size.to_f64_px() * y_scale;
self.get_ct_font(font.font_key, size, &font.variations)
.and_then(|ct_font| {
let glyph = key.index() as CGGlyph;
let bitmap = is_bitmap_font(font);
let (mut shape, (x_offset, y_offset)) = if bitmap {
(FontTransform::identity(), (0.0, 0.0))
} else {
(font.transform.invert_scale(y_scale, y_scale), font.get_subpx_offset(key))
};
if font.flags.contains(FontInstanceFlags::FLIP_X) {
shape = shape.flip_x();
}
if font.flags.contains(FontInstanceFlags::FLIP_Y) {
shape = shape.flip_y();
}
if font.flags.contains(FontInstanceFlags::TRANSPOSE) {
shape = shape.swap_xy();
}
let (mut tx, mut ty) = (0.0, 0.0);
if font.synthetic_italics.is_enabled() {
let (shape_, (tx_, ty_)) = font.synthesize_italics(shape, size);
shape = shape_;
tx = tx_;
ty = ty_;
}
let transform = if !shape.is_identity() || (tx, ty) != (0.0, 0.0) {
Some(CGAffineTransform {
a: shape.scale_x as f64,
b: -shape.skew_y as f64,
c: -shape.skew_x as f64,
d: shape.scale_y as f64,
tx: tx,
ty: -ty,
})
} else {
None
};
let (strike_scale, pixel_step) = if bitmap {
(y_scale, 1.0)
} else {
(x_scale, y_scale / x_scale)
};
let extra_strikes = font.get_extra_strikes(
FontInstanceFlags::SYNTHETIC_BOLD | FontInstanceFlags::MULTISTRIKE_BOLD,
strike_scale,
);
let metrics = get_glyph_metrics(
&ct_font,
transform.as_ref(),
glyph,
x_offset,
y_offset,
extra_strikes as f64 * pixel_step,
);
if metrics.rasterized_width == 0 || metrics.rasterized_height == 0 {
None
} else {
Some(GlyphDimensions {
left: metrics.rasterized_left,
top: metrics.rasterized_ascent,
width: metrics.rasterized_width,
height: metrics.rasterized_height,
advance: metrics.advance,
})
}
})
}
// Assumes the pixels here are linear values from CG
fn gamma_correct_pixels(
&self,
pixels: &mut Vec<u8>,
render_mode: FontRenderMode,
color: ColorU,
) {
// Then convert back to gamma corrected values.
match render_mode {
FontRenderMode::Alpha => {
self.gamma_lut.preblend_grayscale(pixels, color);
}
FontRenderMode::Subpixel => {
self.gamma_lut.preblend(pixels, color);
}
_ => {} // Again, give mono untouched since only the alpha matters.
}
}
#[allow(dead_code)]
fn print_glyph_data(&mut self, data: &[u8], width: usize, height: usize) {
// Rust doesn't have step_by support on stable :(
debug!("Width is: {:?} height: {:?}", width, height);
for i in 0 .. height {
let current_height = i * width * 4;
for pixel in data[current_height .. current_height + (width * 4)].chunks(4) {
let b = pixel[0];
let g = pixel[1];
let r = pixel[2];
let a = pixel[3];
debug!("({}, {}, {}, {}) ", r, g, b, a);
}
}
}
pub fn prepare_font(font: &mut FontInstance) {
if is_bitmap_font(font) {
// Render mode is ignored for bitmap fonts. Also, avoid normalizing the color
// in case CoreText needs the current color for rendering glyph color layers.
font.render_mode = FontRenderMode::Mono;
font.disable_subpixel_position();
return;
}
// Sanitize the render mode for font smoothing. If font smoothing is supported,
// then we just need to ensure the render mode is limited to what is supported.
// If font smoothing is actually disabled, then we need to fall back to grayscale.
if font.flags.contains(FontInstanceFlags::FONT_SMOOTHING) ||
font.render_mode == FontRenderMode::Subpixel {
match *FONT_SMOOTHING_MODE {
Some(mode) => {
font.render_mode = font.render_mode.limit_by(mode);
font.flags.insert(FontInstanceFlags::FONT_SMOOTHING);
}
None => {
font.render_mode = font.render_mode.limit_by(FontRenderMode::Alpha);
font.flags.remove(FontInstanceFlags::FONT_SMOOTHING);
}
}
}
match font.render_mode {
FontRenderMode::Mono => {
// In mono mode the color of the font is irrelevant.
font.color = ColorU::new(255, 255, 255, 255);
// Subpixel positioning is disabled in mono mode.
font.disable_subpixel_position();
}
FontRenderMode::Alpha => {
font.color = if font.flags.contains(FontInstanceFlags::FONT_SMOOTHING) {
// Only the G channel is used to index grayscale tables,
// so use R and B to preserve light/dark determination.
let ColorU { g, a, .. } = font.color.luminance_color().quantized_ceil();
let rb = if should_use_white_on_black(font.color) { 255 } else { 0 };
ColorU::new(rb, g, rb, a)
} else {
ColorU::new(255, 255, 255, 255)
};
}
FontRenderMode::Subpixel => {
// Quantization may change the light/dark determination, so quantize in the
// direction necessary to respect the threshold.
font.color = if should_use_white_on_black(font.color) {
font.color.quantized_ceil()
} else {
font.color.quantized_floor()
};
}
}
}
pub fn begin_rasterize(_font: &FontInstance) {
}
pub fn end_rasterize(_font: &FontInstance) {
}
pub fn rasterize_glyph(&mut self, font: &FontInstance, key: &GlyphKey) -> GlyphRasterResult {
objc::rc::autoreleasepool(|| {
let (x_scale, y_scale) = font.transform.compute_scale().unwrap_or((1.0, 1.0));
let size = font.size.to_f64_px() * y_scale;
let ct_font =
self.get_ct_font(font.font_key, size, &font.variations).ok_or(GlyphRasterError::LoadFailed)?;
let glyph_type = if is_bitmap_font(font) {
GlyphType::Bitmap
} else {
GlyphType::Vector
};
let (mut shape, (x_offset, y_offset)) = match glyph_type {
GlyphType::Bitmap => (FontTransform::identity(), (0.0, 0.0)),
GlyphType::Vector => {
(font.transform.invert_scale(y_scale, y_scale), font.get_subpx_offset(key))
}
};
if font.flags.contains(FontInstanceFlags::FLIP_X) {
shape = shape.flip_x();
}
if font.flags.contains(FontInstanceFlags::FLIP_Y) {
shape = shape.flip_y();
}
if font.flags.contains(FontInstanceFlags::TRANSPOSE) {
shape = shape.swap_xy();
}
let (mut tx, mut ty) = (0.0, 0.0);
if font.synthetic_italics.is_enabled() {
let (shape_, (tx_, ty_)) = font.synthesize_italics(shape, size);
shape = shape_;
tx = tx_;
ty = ty_;
}
let transform = if !shape.is_identity() || (tx, ty) != (0.0, 0.0) {
Some(CGAffineTransform {
a: shape.scale_x as f64,
b: -shape.skew_y as f64,
c: -shape.skew_x as f64,
d: shape.scale_y as f64,
tx: tx,
ty: -ty,
})
} else {
None
};
let glyph = key.index() as CGGlyph;
let (strike_scale, pixel_step) = if glyph_type == GlyphType::Bitmap {
(y_scale, 1.0)
} else {
(x_scale, y_scale / x_scale)
};
let extra_strikes = font.get_extra_strikes(
FontInstanceFlags::SYNTHETIC_BOLD | FontInstanceFlags::MULTISTRIKE_BOLD,
strike_scale,
);
let metrics = get_glyph_metrics(
&ct_font,
transform.as_ref(),
glyph,
x_offset,
y_offset,
extra_strikes as f64 * pixel_step,
);
if metrics.rasterized_width == 0 || metrics.rasterized_height == 0 {
return Err(GlyphRasterError::LoadFailed);
}
let raster_size = Size2D::new(
metrics.rasterized_width as u32,
metrics.rasterized_height as u32
);
// If the font render mode is Alpha, we support two different ways to
// compute the grayscale mask, depending on the value of the platform
// options' font_smoothing flag:
// - Alpha + smoothing:
// We will recover a grayscale mask from a subpixel rasterization, in
// such a way that the result looks as close to subpixel text
// blending as we can make it. This involves gamma correction,
// luminance computations and preblending based on the text color,
// just like with the Subpixel render mode.
// - Alpha without smoothing:
// We will ask CoreGraphics to rasterize the text with font_smoothing
// off. This will cause it to use grayscale anti-aliasing with
// comparatively thin text. This method of text rendering is not
// gamma-aware.
//
// For subpixel rasterization, starting with macOS 10.11, CoreGraphics
// uses different glyph dilation based on the text color. Bright text
// uses less font dilation (looks thinner) than dark text.
// As a consequence, when we ask CG to rasterize with subpixel AA, we
// will render white-on-black text as opposed to black-on-white text if
// the text color brightness exceeds a certain threshold. This applies
// to both the Subpixel and the "Alpha + smoothing" modes, but not to
// the "Alpha without smoothing" and Mono modes.
//
// Fonts with color glyphs may, depending on the state within per-glyph
// table data, require the current font color to determine the output
// color. For such fonts we must thus supply the current font color just
// in case it is necessary.
let use_white_on_black = should_use_white_on_black(font.color);
let use_font_smoothing = font.flags.contains(FontInstanceFlags::FONT_SMOOTHING);
let (antialias, smooth, text_color, bg_color, invert) = match glyph_type {
GlyphType::Bitmap => (true, false, ColorF::from(font.color), ColorF::TRANSPARENT, false),
GlyphType::Vector => {
match (font.render_mode, use_font_smoothing) {
(FontRenderMode::Subpixel, _) |
(FontRenderMode::Alpha, true) => if use_white_on_black {
(true, true, ColorF::WHITE, ColorF::BLACK, false)
} else {
(true, true, ColorF::BLACK, ColorF::WHITE, true)
},
(FontRenderMode::Alpha, false) => (true, false, ColorF::BLACK, ColorF::WHITE, true),
(FontRenderMode::Mono, _) => (false, false, ColorF::BLACK, ColorF::WHITE, true),
}
}
};
{
let cg_context = self.graphics_context.get_context(&raster_size, glyph_type);
// These are always true in Gecko, even for non-AA fonts
cg_context.set_allows_font_subpixel_positioning(true);
cg_context.set_should_subpixel_position_fonts(true);
// Don't quantize because we're doing it already.
cg_context.set_allows_font_subpixel_quantization(false);
cg_context.set_should_subpixel_quantize_fonts(false);
cg_context.set_should_smooth_fonts(smooth);
cg_context.set_should_antialias(antialias);
// Fill the background. This could be opaque white, opaque black, or
// transparency.
cg_context.set_rgb_fill_color(
bg_color.r.into(),
bg_color.g.into(),
bg_color.b.into(),
bg_color.a.into(),
);
let rect = CGRect {
origin: CGPoint { x: 0.0, y: 0.0 },
size: CGSize {
width: metrics.rasterized_width as f64,
height: metrics.rasterized_height as f64,
},
};
// Make sure we use the Copy blend mode, or else we'll get the Porter-Duff OVER
// operator, which can't clear to the transparent color!
cg_context.set_blend_mode(CGBlendMode::Copy);
cg_context.fill_rect(rect);
cg_context.set_blend_mode(CGBlendMode::Normal);
// Set the text color and draw the glyphs.
cg_context.set_rgb_fill_color(
text_color.r.into(),
text_color.g.into(),
text_color.b.into(),
1.0,
);
cg_context.set_text_drawing_mode(CGTextDrawingMode::CGTextFill);
// CG Origin is bottom left, WR is top left. Need -y offset
let mut draw_origin = CGPoint {
x: -metrics.rasterized_left as f64 + x_offset + tx,
y: metrics.rasterized_descent as f64 - y_offset - ty,
};
if let Some(transform) = transform {
cg_context.set_text_matrix(&transform);
draw_origin = draw_origin.apply_transform(&transform.invert());
} else {
// Make sure to reset this because some previous glyph rasterization might have
// changed it.
cg_context.set_text_matrix(&CG_AFFINE_TRANSFORM_IDENTITY);
}
ct_font.draw_glyphs(&[glyph], &[draw_origin], cg_context.clone());
// We'd like to render all the strikes in a single ct_font.draw_glyphs call,
// passing an array of glyph IDs and an array of origins, but unfortunately
// with some fonts, Core Text may inappropriately pixel-snap the rasterization,
// such that the strikes overprint instead of being offset. Rendering the
// strikes with individual draw_glyphs calls avoids this.
for i in 1 ..= extra_strikes {
let origin = CGPoint {
x: draw_origin.x + i as f64 * pixel_step,
y: draw_origin.y,
};
ct_font.draw_glyphs(&[glyph], &[origin], cg_context.clone());
}
}
let mut rasterized_pixels = self.graphics_context
.get_rasterized_pixels(&raster_size, glyph_type);
if glyph_type == GlyphType::Vector {
// We rendered text into an opaque surface. The code below needs to
// ignore the current value of each pixel's alpha channel. But it's
// allowed to write to the alpha channel, because we're done calling
// CG functions now.
if smooth {
// Convert to linear space for subpixel AA.
// We explicitly do not do this for grayscale AA ("Alpha without
// smoothing" or Mono) because those rendering modes are not
// gamma-aware in CoreGraphics.
self.gamma_lut.coregraphics_convert_to_linear(
&mut rasterized_pixels,
);
}
for pixel in rasterized_pixels.chunks_mut(4) {
if invert {
pixel[0] = 255 - pixel[0];
pixel[1] = 255 - pixel[1];
pixel[2] = 255 - pixel[2];
}
// Set alpha to the value of the green channel. For grayscale
// text, all three channels have the same value anyway.
// For subpixel text, the mask's alpha only makes a difference
// when computing the destination alpha on destination pixels
// that are not completely opaque. Picking an alpha value
// that's somehow based on the mask at least ensures that text
// blending doesn't modify the destination alpha on pixels where
// the mask is entirely zero.
pixel[3] = pixel[1];
}
if smooth {
// Convert back from linear space into device space, and perform
// some "preblending" based on the text color.
// In Alpha + smoothing mode, this will also convert subpixel AA
// into grayscale AA.
self.gamma_correct_pixels(
&mut rasterized_pixels,
font.render_mode,
font.color,
);
}
}
Ok(RasterizedGlyph {
left: metrics.rasterized_left as f32,
top: metrics.rasterized_ascent as f32,
width: metrics.rasterized_width,
height: metrics.rasterized_height,
scale: match glyph_type {
GlyphType::Bitmap => y_scale.recip() as f32,
GlyphType::Vector => 1.0,
},
format: match glyph_type {
GlyphType::Bitmap => GlyphFormat::ColorBitmap,
GlyphType::Vector => font.get_glyph_format(),
},
bytes: rasterized_pixels,
})})
}
}
// Avoids taking locks by recycling Core Graphics contexts.
#[allow(dead_code)]
struct GraphicsContext {
vector_context: CGContext,
vector_context_size: Size2D<u32>,
bitmap_context: CGContext,
bitmap_context_size: Size2D<u32>,
}
impl GraphicsContext {
fn new() -> GraphicsContext {
let size = Size2D::new(INITIAL_CG_CONTEXT_SIDE_LENGTH, INITIAL_CG_CONTEXT_SIDE_LENGTH);
GraphicsContext {
vector_context: GraphicsContext::create_cg_context(&size, GlyphType::Vector),
vector_context_size: size,
bitmap_context: GraphicsContext::create_cg_context(&size, GlyphType::Bitmap),
bitmap_context_size: size,
}
}
#[allow(dead_code)]
fn get_context(&mut self, size: &Size2D<u32>, glyph_type: GlyphType)
-> &mut CGContext {
let (cached_context, cached_size) = match glyph_type {
GlyphType::Vector => {
(&mut self.vector_context, &mut self.vector_context_size)
}
GlyphType::Bitmap => {
(&mut self.bitmap_context, &mut self.bitmap_context_size)
}
};
let rounded_size = Size2D::new(size.width.next_power_of_two(),
size.height.next_power_of_two());
if rounded_size.width > cached_size.width || rounded_size.height > cached_size.height {
*cached_size = Size2D::new(u32::max(cached_size.width, rounded_size.width),
u32::max(cached_size.height, rounded_size.height));
*cached_context = GraphicsContext::create_cg_context(cached_size, glyph_type);
}
cached_context
}
#[allow(dead_code)]
fn get_rasterized_pixels(&mut self, size: &Size2D<u32>, glyph_type: GlyphType)
-> Vec<u8> {
let (cached_context, cached_size) = match glyph_type {
GlyphType::Vector => (&mut self.vector_context, &self.vector_context_size),
GlyphType::Bitmap => (&mut self.bitmap_context, &self.bitmap_context_size),
};
let cached_data = cached_context.data();
let cached_stride = cached_size.width as usize * 4;
let result_len = size.width as usize * size.height as usize * 4;
let mut result = Vec::with_capacity(result_len);
for y in (cached_size.height - size.height)..cached_size.height {
let cached_start = y as usize * cached_stride;
let cached_end = cached_start + size.width as usize * 4;
result.extend_from_slice(&cached_data[cached_start..cached_end]);
}
debug_assert_eq!(result.len(), result_len);
result
}
fn create_cg_context(size: &Size2D<u32>, glyph_type: GlyphType) -> CGContext {
// The result of rasterization, in all render modes, is going to be a
// BGRA surface with white text on transparency using premultiplied
// alpha. For subpixel text, the RGB values will be the mask value for
// the individual components. For bitmap glyphs, the RGB values will be
// the (premultiplied) color of the pixel. For Alpha and Mono, each
// pixel will have R==G==B==A at the end of this function.
// We access the color channels in little-endian order.
// The CGContext will create and own our pixel buffer.
// In the non-Bitmap cases, we will ask CoreGraphics to draw text onto
// an opaque background. In order to hit the most efficient path in CG
// for this, we will tell CG that the CGContext is opaque, by passing
// an "[...]AlphaNone[...]" context flag. This creates a slight
// contradiction to the way we use the buffer after CG is done with it,
// because we will convert it into text-on-transparency. But that's ok;
// we still get four bytes per pixel and CG won't mess with the alpha
// channel after we've stopped calling CG functions. We just need to
// make sure that we don't look at the alpha values of the pixels that
// we get from CG, and compute our own alpha value only from RGB.
// Note that CG requires kCGBitmapByteOrder32Little in order to do
// subpixel AA at all (which we need it to do in both Subpixel and
// Alpha+smoothing mode). But little-endian is what we want anyway, so
// this works out nicely.
let color_type = match glyph_type {
GlyphType::Vector => kCGImageAlphaNoneSkipFirst,
GlyphType::Bitmap => kCGImageAlphaPremultipliedFirst,
};
CGContext::create_bitmap_context(None,
size.width as usize,
size.height as usize,
8,
size.width as usize * 4,
&CGColorSpace::create_device_rgb(),
kCGBitmapByteOrder32Little | color_type)
}
}
#[derive(Clone, Copy, PartialEq, Debug)]
enum GlyphType {
Vector,
Bitmap,
}