2.1

DanOverlay 2.1 — Performance Optimisation

Overview

Release focused exclusively on responsiveness and eliminating freezes when navigating between beatmaps. No changes to calculation logic, accuracy, or visual design.

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Problem Statement

Users reported two symptoms:

1. Freezing on rapid map switching — while scrolling through song select, the overlay would freeze showing the hint screen or the previous map's result for several seconds.
2. Slow initial load — the overlay took up to 5 seconds to appear after launching the executable.

Diagnosis

Each pipeline stage was profiled with real maps (stamina marathons, jack, tech):

Component	Average time
.osu file parsing	~0.01s
Feature extraction	~0.01s
Sunny SR (main calculation)	~0.15s
MinaCalc msd.exe (subprocess)	~0.15s
4 mode estimators	~0.01s
Full pipeline	0.15–0.34s

The calculation pipeline was not the problem. The bottleneck was in three areas completely unrelated to the mathematical logic:

1. Google Fonts blocked initial render

Every skin loaded Inter from fonts.googleapis.com synchronously. If Google's server was slow or the user was offline, the browser rendered NOTHING until the font downloaded — between 2 and 5 seconds of blank window.

2. Bridge waited up to 15s to confirm JS was ready

The communication mechanism between Python and the WebView page polled every 250ms for up to 15s. During this time, already-computed analysis results (0.3s) accumulated in a queue without being displayed, creating the illusion of freezing.

3. Every map switch spawned a new thread

The analysis coordinator created a threading.Thread for each MAP_CHANGED event. If the user scrolled through 5 maps rapidly, 5 threads ran the pipeline concurrently, competing for CPU with the overlay's UI thread.

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Changes Applied

Phase 1 — Remove blocking external dependencies

Problem	Solution	Gain
Google Fonts blocked render	Removed all <link> tags to fonts.googleapis.com from all skins. Overlay uses system-ui (OS native font) as primary, with Inter as optional fallback.	-2 to -5s on initial load

Phase 2 — Optimise Python ↔ JS communication

Problem	Solution	Gain
Bridge polling at 250ms	Reduced to 100ms	-0.3s detection
Forced-ready timeout at 15s	Reduced to 8s	-7s in worst case
Cold imports on first analysis	Expanded warmup: numpy + pandas + parser + features + classifier + rank_engine pre-imported in background at startup	-0.2s on first map

Phase 3 — Analysis thread management

Problem	Solution
Each MAP_CHANGED created a new thread	Single worker: one analysis thread handles all requests
Old analyses ran to completion even though their results were discarded	Early bailout: worker checks the cancellation token at multiple checkpoints and aborts if the map changed
Rapid switches saturated CPU	200ms debounce: if the user switches maps within 200ms, the timer resets. Only the last map is analysed

Phase 4 — Sublevel threshold consistency

Low / Mid-Low / Mid / Mid-High / High thresholds were defined inconsistently across 4 files. Unified to symmetric 20% bands:

Sublevel	Range (DP fraction)
Low	0.00 – 0.20
Mid-Low	0.20 – 0.40
Mid	0.40 – 0.60
Mid-High	0.60 – 0.80
High	0.80 – 1.00

Applies to all modes: Reform, Celestial, Signicial, Shoegazer, LN Course, and 7K.

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What Did NOT Change

• Calculation accuracy: Zero modifications to the Sunny SR algorithm, rank_engine, classifiers, or calibration profiles.
• Visual design: Skins, colours, animations, and layout intact.
• Numerical results: Same DP values, same sublevels, same classifications.

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Performance Table

Scenario	Before	After
Initial overlay load	3-8s (depending on Google Fonts connectivity)	< 1s
Single map analysis	0.3s	0.3s (unchanged — was not the bottleneck)
Rapid scroll through 10 maps	5-10 concurrent threads, overlay frozen	1 analysis, no freezing
Map switch during ongoing analysis	Previous thread kept consuming CPU	Aborts early
Sublevels (Low/High)	15/35/65/85 (asymmetric) — bars and text could mismatch	20/40/60/80 symmetric — bars and text always match