Optimize lookups in FontEmbeddingManager, use HashSet over Dictionary

[h3xds1nz]

Description

Optimizes methods in FontEmbeddingManager, using HashSet<ushort> over Dictionary<ushort, bool> since the bool is useless and as the comment says, it was always the plan anyways.

• GetUsedGlyphs throws KeyNotFoundException over ArgumentException but that bug was already present.
  • I'll log an issue for this later.

3 Different faces, 9 Glyph Runs

Method	Mean [ns]	Error [ns]	StdDev [ns]	Gen0	Code Size [B]	Allocated [B]
Original	1,344.4 ns	13.79 ns	12.23 ns	0.1507	1,066 B	2544 B
PR_EDIT	850.7 ns	11.54 ns	10.23 ns	0.1297	1,577 B	2184 B

Benchmark data source

yield return new List<GlyphRun>() { giveme("Consolas", "hello"), giveme("Arial", "hannah"), giveme("Consolas", "test"),
                                    giveme("Arial", "hello"), giveme("Consolas", "hannah"), giveme("Arial", "test"),
                                    giveme("Times New Roman", "hello"), giveme("Times New Roman", "hannah"), giveme("Times New Roman", "test") };

1 font, 9 Glyph Runs (XpsFontSubsetter scenario)

Method	Mean [ns]	Error [ns]	StdDev [ns]	Gen0	Code Size [B]	Allocated [B]
Original	1,401.2 ns	5.46 ns	5.11 ns	0.1087	1,063 B	1832 B
PR_EDIT	878.1 ns	3.87 ns	3.43 ns	0.1020	1,394 B	1712 B

Benchmark data source

yield return new List<GlyphRun>() { giveme("Consolas", "hello"), giveme("Consolas", "hannah"), giveme("Consolas", "test"),
                                    giveme("Consolas", "hello"), giveme("Consolas", "hannah"), giveme("Consolas", "test"),
                                    giveme("Consolas", "hello"), giveme("Consolas", "hannah"), giveme("Consolas", "Okay, lets change this a bit!") };

Customer Impact

Improved performance, slightly decreased allocations. This is used by the XpsFontSubsetter, so it could gain a bit of perf.

Regression

No.

Testing

Local build.

Risk

Low, just a simple swap.

Microsoft Reviewers: Open in CodeFlow