Font rendering on macOS 10.14 is still too thin on Electron v4.x

[lexi-lambda]

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for an issue that matches the one I want to file, without success.

Issue Details

• Electron Version:
  • v4.2.9
• Operating System:
  • macOS 10.14.5
• Last Known Working Electron version:
  • N/A

Expected Behavior

Versions of Electron other than 4.x include a fix for font rendering on macOS 10.14. Here’s what things are supposed to look like, rendered using Electron v6.0.4:

Electron v3.1.13 is not quite as good, but it still looks fine:

Actual Behavior

On Electron v4.2.9, however, font rendering is much too thin:

Yikes!

To Reproduce

I’ve set up a repository with the above minimal example. To reproduce the issue, run the following commands on a machine running macOS 10.14:

$ git clone git@github.com:lexi-lambda/electron-4.x-font-smoothing-repro.git
$ cd electron-4.x-font-smoothing-repro
$ npm install
$ npm start

Additional Information

The original issue for this bug was #14948, and supposedly it was backported to 4.x in #17737. However, as various people have reported in microsoft/vscode#59887 (comment) and #17737 (comment), the issue is still present as of Electron v4.2.9.

[miniak]

Electron 4 is not supported anymore, this bug is not present in Electron 5+
https://electronjs.org/blog/electron-7-0#end-of-support-for-4xy

[miniak]

The problem is that https://skia-review.googlesource.com/c/skia/+/157566 wasn't back-ported properly. This is missing:

diff --git a/third_party/skia/src/ports/SkFontHost_mac.cpp b/third_party/skia/src/ports/SkFontHost_mac.cpp
index 8be3f306c1b8b1bf6609d14798860ca763f824b1..48dbf2f51d03d03863f948cdfc1aaa2dee008b29 100644
--- a/third_party/skia/src/ports/SkFontHost_mac.cpp
+++ b/third_party/skia/src/ports/SkFontHost_mac.cpp
@@ -440,6 +440,9 @@ static SmoothBehavior smooth_behavior() {
                 if (r != g || r != b) {
                     return SmoothBehavior::subpixel;
                 }
+                if (noSmoothBitmap[x][y] != smoothPixel) {
+                    smoothBehavior = SmoothBehavior::some;
+                }
             }
         }
         return smoothBehavior;