add C++ parser for the font shorthand

This is the first part needed for the new font stack, which will
look like the FontFace-based API the browsers have. FontFace uses
a parser for font-family, font-size, etc., so I will need deeper
control over the parser.

FontFace will be implemented in C++ and I didn't want to carry
over the awkward (and slow) switching between JS and C++. So here
it is. I used Claude to generate initial classes and busy work,
but it's been heavily examined and heavily modified.

Caching aside, this is 3x faster in the benchmarks, but in some
cases was 400x faster, which IIRC is why we cached it. I expect
the C++ version to have a much more stable performance profile, so
not going to cache for now.

It's also far more correct than what we had!

Author: chearon

CHANGELOG.md

@@ -8,6 +8,8 @@ project adheres to [Semantic Versioning](http://semver.org/).
 (Unreleased)
 ==================
 ### Changed
+* `ctx.font` has a new C++ parser and is 2x-400x faster. Please file an issue if you experience different results, as caching has been removed.
+
 ### Added
 ### Fixed
 

binding.gyp

@@ -75,7 +75,8 @@
         'src/Image.cc',
         'src/ImageData.cc',
         'src/init.cc',
-        'src/register_font.cc'
+        'src/register_font.cc',
+        'src/FontParser.cc'
       ],
       'conditions': [
         ['OS=="win"', {

index.js

@@ -2,7 +2,6 @@ const Canvas = require('./lib/canvas')
 const Image = require('./lib/image')
 const CanvasRenderingContext2D = require('./lib/context2d')
 const CanvasPattern = require('./lib/pattern')
-const parseFont = require('./lib/parse-font')
 const packageJson = require('./package.json')
 const bindings = require('./lib/bindings')
 const fs = require('fs')
@@ -12,7 +11,6 @@ const JPEGStream = require('./lib/jpegstream')
 const { DOMPoint, DOMMatrix } = require('./lib/DOMMatrix')
 
 bindings.setDOMMatrix(DOMMatrix)
-bindings.setParseFont(parseFont)
 
 function createCanvas (width, height, type) {
   return new Canvas(width, height, type)
@@ -73,7 +71,6 @@ exports.DOMPoint = DOMPoint
 
 exports.registerFont = registerFont
 exports.deregisterAllFonts = deregisterAllFonts
-exports.parseFont = parseFont
 
 exports.createCanvas = createCanvas
 exports.createImageData = createImageData

lib/parse-font.js

@@ -21,6 +21,7 @@
 #include "Util.h"
 #include <vector>
 #include "node_buffer.h"
+#include "FontParser.h"
 
 #ifdef HAVE_JPEG
 #include "JPEGStream.h"
@@ -68,7 +69,8 @@ Canvas::Initialize(Napi::Env& env, Napi::Object& exports) {
     StaticValue("PNG_FILTER_PAETH", Napi::Number::New(env, PNG_FILTER_PAETH), napi_default_jsproperty),
     StaticValue("PNG_ALL_FILTERS", Napi::Number::New(env, PNG_ALL_FILTERS), napi_default_jsproperty),
     StaticMethod<&Canvas::RegisterFont>("_registerFont", napi_default_method),
-    StaticMethod<&Canvas::DeregisterAllFonts>("_deregisterAllFonts", napi_default_method)
+    StaticMethod<&Canvas::DeregisterAllFonts>("_deregisterAllFonts", napi_default_method),
+    StaticMethod<&Canvas::ParseFont>("parseFont", napi_default_method)
   });
 
   data->CanvasCtor = Napi::Persistent(ctor);
@@ -694,6 +696,7 @@ Canvas::RegisterFont(const Napi::CallbackInfo& info) {
   // now check the attrs, there are many ways to be wrong
   Napi::Object js_user_desc = info[1].As<Napi::Object>();
 
+  // TODO: use FontParser on these values just like the FontFace API works
   char *family = str_value(js_user_desc.Get("family"), NULL, false);
   char *weight = str_value(js_user_desc.Get("weight"), "normal", true);
   char *style = str_value(js_user_desc.Get("style"), "normal", false);
@@ -749,6 +752,40 @@ Canvas::DeregisterAllFonts(const Napi::CallbackInfo& info) {
   if (!success) Napi::Error::New(env, "Could not deregister one or more fonts").ThrowAsJavaScriptException();
 }
 
+/*
+ * Do not use! This is only exported for testing
+ */
+Napi::Value
+Canvas::ParseFont(const Napi::CallbackInfo& info) {
+  Napi::Env env = info.Env();
+
+  if (info.Length() != 1) return env.Undefined();
+
+  Napi::String str;
+  if (!info[0].ToString().UnwrapTo(&str)) return env.Undefined();
+
+  bool ok;
+  auto props = FontParser::parse(str, &ok);
+  if (!ok) return env.Undefined();
+
+  Napi::Object obj = Napi::Object::New(env);
+  obj.Set("size", Napi::Number::New(env, props.fontSize));
+  Napi::Array families = Napi::Array::New(env);
+  obj.Set("families", families);
+
+  unsigned int index = 0;
+
+  for (auto& family : props.fontFamily) {
+    families[index++] = Napi::String::New(env, family);
+  }
+
+  obj.Set("weight", Napi::Number::New(env, props.fontWeight));
+  obj.Set("variant", Napi::Number::New(env, static_cast<int>(props.fontVariant)));
+  obj.Set("style", Napi::Number::New(env, static_cast<int>(props.fontStyle)));
+
+  return obj;
+}
+
 /*
  * Get a PangoStyle from a CSS string (like "italic")
  */

src/Canvas.cc

@@ -68,6 +68,7 @@ class Canvas : public Napi::ObjectWrap<Canvas> {
     void StreamJPEGSync(const Napi::CallbackInfo& info);
     static void RegisterFont(const Napi::CallbackInfo& info);
     static void DeregisterAllFonts(const Napi::CallbackInfo& info);
+    static Napi::Value ParseFont(const Napi::CallbackInfo& info);
     Napi::Error CairoError(cairo_status_t status);
     static void ToPngBufferAsync(Closure* closure);
     static void ToJpegBufferAsync(Closure* closure);

src/Canvas.h

@@ -9,6 +9,7 @@
 #include "CanvasGradient.h"
 #include "CanvasPattern.h"
 #include "InstanceData.h"
+#include "FontParser.h"
 #include <cmath>
 #include <cstdlib>
 #include "Image.h"
@@ -2575,34 +2576,29 @@ Context2d::GetFont(const Napi::CallbackInfo& info) {
 
 void
 Context2d::SetFont(const Napi::CallbackInfo& info, const Napi::Value& value) {
-  InstanceData* data = env.GetInstanceData<InstanceData>();
-
   if (!value.IsString()) return;
 
-  if (!value.As<Napi::String>().Utf8Value().length()) return;
-
-  Napi::Value mparsed;
+  std::string str = value.As<Napi::String>().Utf8Value();
+  if (!str.length()) return;
 
-  // parseFont returns undefined for invalid CSS font strings
-  if (!data->parseFont.Call({ value }).UnwrapTo(&mparsed) || mparsed.IsUndefined()) return;
-
-  Napi::Object font = mparsed.As<Napi::Object>();
-
-  Napi::String empty = Napi::String::New(env, "");
-  Napi::Number zero = Napi::Number::New(env, 0);
-
-  std::string weight = font.Get("weight").UnwrapOr(empty).ToString().UnwrapOr(empty).Utf8Value();
-  std::string style = font.Get("style").UnwrapOr(empty).ToString().UnwrapOr(empty).Utf8Value();
-  double size = font.Get("size").UnwrapOr(zero).ToNumber().UnwrapOr(zero).DoubleValue();
-  std::string unit = font.Get("unit").UnwrapOr(empty).ToString().UnwrapOr(empty).Utf8Value();
-  std::string family = font.Get("family").UnwrapOr(empty).ToString().UnwrapOr(empty).Utf8Value();
+  bool success;
+  auto props = FontParser::parse(str, &success);
+  if (!success) return;
 
   PangoFontDescription *desc = pango_font_description_copy(state->fontDescription);
   pango_font_description_free(state->fontDescription);
 
-  pango_font_description_set_style(desc, Canvas::GetStyleFromCSSString(style.c_str()));
-  pango_font_description_set_weight(desc, Canvas::GetWeightFromCSSString(weight.c_str()));
+  PangoStyle style = props.fontStyle == FontStyle::Italic ? PANGO_STYLE_ITALIC
+    : props.fontStyle == FontStyle::Oblique ? PANGO_STYLE_OBLIQUE
+    : PANGO_STYLE_NORMAL;
+  pango_font_description_set_style(desc, style);
 
+  pango_font_description_set_weight(desc, static_cast<PangoWeight>(props.fontWeight));
+
+  std::string family = props.fontFamily.empty() ? "" : props.fontFamily[0];
+  for (size_t i = 1; i < props.fontFamily.size(); i++) {
+    family += "," + props.fontFamily[i];
+  }
   if (family.length() > 0) {
     // See #1643 - Pango understands "sans" whereas CSS uses "sans-serif"
     std::string s1(family);
@@ -2617,12 +2613,12 @@ Context2d::SetFont(const Napi::CallbackInfo& info, const Napi::Value& value) {
   PangoFontDescription *sys_desc = Canvas::ResolveFontDescription(desc);
   pango_font_description_free(desc);
 
-  if (size > 0) pango_font_description_set_absolute_size(sys_desc, size * PANGO_SCALE);
+  if (props.fontSize > 0) pango_font_description_set_absolute_size(sys_desc, props.fontSize * PANGO_SCALE);
 
   state->fontDescription = sys_desc;
   pango_layout_set_font_description(_layout, sys_desc);
 
-  state->font = value.As<Napi::String>().Utf8Value().c_str();
+  state->font = str;
 }
 
 /*