Replace ab_glyph with Skrifa + vello_cpu; enable font hinting (#7694)

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I'll probably come back to this and clean it up a bit. This PR
reimplements ab_glyph's functionality on top of Skrifa, a somewhat
lower-level font API that's being used in Chrome now.

Skrifa doesn't perform rasterization itself, so I'm using
[vello_cpu](https://github.com/linebender/vello) from the Linebender
project for rasterization. It's still in its early days, but I believe
it's already quite fast. It also supports color and gradient fills, so
color emoji support will be easier.

Skrifa also supports font hinting, which should make text look a bit
nicer / less blurry.

Here's the current ab_glyph rendering:

<img width="1592" height="1068" alt="image"
src="https://github.com/user-attachments/assets/2385b66e-23f8-4c6e-b8c2-ea90e0eea4e4"
/>

Here's Skrifa *without* hinting--it looks almost identical, but there
are some subpixel differences, probably due to rasterizer behavior:

<img width="1592" height="1068" alt="image"
src="https://github.com/user-attachments/assets/a815f3e9-65ac-4940-bc00-571177bef53d"
/>

Here's Skrifa  *with* hinting:

<img width="1592" height="1068" alt="image"
src="https://github.com/user-attachments/assets/d6cc0669-3537-4377-bba9-ed5ef09664db"
/>

Hinting does make the horizontal strokes look a bit bolder, which makes
me wonder once again about increasing the font weight from "light" to
"regular".

---------

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

Cargo.lock

@@ -863,6 +863,15 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "color"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a18ef4657441fb193b65f34dc39b3781f0dfec23d3bd94d0eeb4e88cde421edb"
+dependencies = [
+ "bytemuck",
+]
+
 [[package]]
 name = "color-hex"
 version = "0.2.0"
@@ -1595,7 +1604,6 @@ dependencies = [
 name = "epaint"
 version = "0.33.2"
 dependencies = [
- "ab_glyph",
  "ahash",
  "bytemuck",
  "criterion",
@@ -1609,8 +1617,11 @@ dependencies = [
  "parking_lot",
  "profiling",
  "rayon",
+ "self_cell",
  "serde",
  "similar-asserts",
+ "skrifa",
+ "vello_cpu",
 ]
 
 [[package]]
@@ -1639,6 +1650,15 @@ version = "3.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a5d9305ccc6942a704f4335694ecd3de2ea531b114ac2d51f5f843750787a92f"
 
+[[package]]
+name = "euclid"
+version = "0.22.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ad9cdb4b747e485a12abb0e6566612956c7a1bafa3bdb8d682c5b6d403589e48"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "event-listener"
 version = "5.3.1"
@@ -1706,6 +1726,15 @@ dependencies = [
  "simd-adler32",
 ]
 
+[[package]]
+name = "fearless_simd"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8fb2907d1f08b2b316b9223ced5b0e89d87028ba8deae9764741dba8ff7f3903"
+dependencies = [
+ "bytemuck",
+]
+
 [[package]]
 name = "file_dialog"
 version = "0.1.0"
@@ -1749,6 +1778,15 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "77ce24cb58228fbb8aa041425bb1050850ac19177686ea6e0f41a70416f56fdb"
 
+[[package]]
+name = "font-types"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "39a654f404bbcbd48ea58c617c2993ee91d1cb63727a37bf2323a4edeed1b8c5"
+dependencies = [
+ "bytemuck",
+]
+
 [[package]]
 name = "fontconfig-parser"
 version = "0.5.7"
@@ -2528,6 +2566,17 @@ dependencies = [
  "smallvec",
 ]
 
+[[package]]
+name = "kurbo"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ce9729cc38c18d86123ab736fd2e7151763ba226ac2490ec092d1dd148825e32"
+dependencies = [
+ "arrayvec",
+ "euclid",
+ "smallvec",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.5.0"
@@ -2577,6 +2626,12 @@ dependencies = [
  "redox_syscall 0.5.7",
 ]
 
+[[package]]
+name = "linebender_resource_handle"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d4a5ff6bcca6c4867b1c4fd4ef63e4db7436ef363e0ad7531d1558856bae64f4"
+
 [[package]]
 name = "linked-hash-map"
 version = "0.5.6"
@@ -3253,6 +3308,19 @@ version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "df94ce210e5bc13cb6651479fa48d14f601d9858cfe0467f43ae157023b938d3"
 
+[[package]]
+name = "peniko"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3c76095c9a636173600478e0373218c7b955335048c2bcd12dc6a79657649d8"
+dependencies = [
+ "bytemuck",
+ "color",
+ "kurbo 0.12.0",
+ "linebender_resource_handle",
+ "smallvec",
+]
+
 [[package]]
 name = "percent-encoding"
 version = "2.3.2"
@@ -3383,9 +3451,9 @@ dependencies = [
 
 [[package]]
 name = "png"
-version = "0.17.14"
+version = "0.17.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "52f9d46a34a05a6a57566bc2bfae066ef07585a6e3fa30fbbdff5936380623f0"
+checksum = "82151a2fc869e011c153adc57cf2789ccb8d9906ce52c0b39a6b5697749d7526"
 dependencies = [
  "bitflags 1.3.2",
  "crc32fast",
@@ -3692,6 +3760,16 @@ dependencies = [
  "crossbeam-utils",
 ]
 
+[[package]]
+name = "read-fonts"
+version = "0.35.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6717cf23b488adf64b9d711329542ba34de147df262370221940dfabc2c91358"
+dependencies = [
+ "bytemuck",
+ "font-types",
+]
+
 [[package]]
 name = "redox_syscall"
 version = "0.4.1"
@@ -3985,6 +4063,12 @@ dependencies = [
  "tiny-skia",
 ]
 
+[[package]]
+name = "self_cell"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "16c2f82143577edb4921b71ede051dac62ca3c16084e918bf7b40c96ae10eb33"
+
 [[package]]
 name = "serde"
 version = "1.0.228"
@@ -4112,6 +4196,16 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "56199f7ddabf13fe5074ce809e7d3f42b42ae711800501b5b16ea82ad029c39d"
 
+[[package]]
+name = "skrifa"
+version = "0.37.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8c31071dedf532758ecf3fed987cdb4bd9509f900e026ab684b4ecb81ea49841"
+dependencies = [
+ "bytemuck",
+ "read-fonts",
+]
+
 [[package]]
 name = "slab"
 version = "0.4.9"
@@ -4233,7 +4327,7 @@ version = "0.15.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "68c7541fff44b35860c1a7a47a7cadf3e4a304c457b58f9870d9706ece028afc"
 dependencies = [
- "kurbo",
+ "kurbo 0.11.1",
  "siphasher",
 ]
 
@@ -4735,7 +4829,7 @@ dependencies = [
  "flate2",
  "fontdb",
  "imagesize",
- "kurbo",
+ "kurbo 0.11.1",
  "log",
  "pico-args",
  "roxmltree",
@@ -4763,6 +4857,30 @@ version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
 
+[[package]]
+name = "vello_common"
+version = "0.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a235ba928b3109ad9e7696270edb09445a52ae1c7c08e6d31a19b1cdd6cbc24a"
+dependencies = [
+ "bytemuck",
+ "fearless_simd",
+ "log",
+ "peniko",
+ "skrifa",
+ "smallvec",
+]
+
+[[package]]
+name = "vello_cpu"
+version = "0.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0bd1fcf9c1814f17a491e07113623d44e3ec1125a9f3401f5e047d6d326da21"
+dependencies = [
+ "bytemuck",
+ "vello_common",
+]
+
 [[package]]
 name = "version_check"
 version = "0.9.5"