perf: Reduce allocations across Shimmer, Popup, TabView, and TextInputLayout

[PaulAndersonS]

Root Cause of the Issue

Multiple controls have unnecessary object allocations, redundant method calls, and expensive reflection operations in hot paths that negatively impact runtime performance.

Description of Change

This PR implements 5 targeted performance improvements across 4 controls:

1. Shimmer – Cache Point allocations as static readonly fields

   • CreateWavePaint() previously created 2 new Point objects on every call. Since the values are constants (e.g., (0,0), (1,0), (0,1), (1,1)), they are now cached as static readonly fields, eliminating per-call heap allocations.

2. Shimmer – Remove Cast<View>() LINQ allocation in DrawCustomViewChildren

   • The recursive DrawCustomViewChildren method called .Cast<View>() on layout.Children, which allocates an enumerator wrapper on every call. Replaced with direct iteration and type checking.

3. Popup – Eliminate redundant null check and unnecessary new Page() allocations

   • GetMainPage() had a duplicate if (windowPage is not null) check (dead code).
   • Both GetMainPage() and GetMainWindowPage() returned new Page() as a fallback, creating garbage that callers immediately discarded. Now returns null, with callers updated for null-safety.

4. TabView (iOS) – Cache GetProperties().Any() reflection result per-type

   • On every touch event, the handler called touchViewType.GetProperties().Any(...) which uses reflection to scan all properties. Added a ConcurrentDictionary<Type, bool> cache so reflection happens only once per type.

5. TextInputLayout – Consolidate multiple InvalidateDrawable() calls

   • OnTextInputViewTextChanged could call InvalidateDrawable() up to 2 times in a single invocation (once for hint state change + once for clear icon). Consolidated into a single deferred call using a needsRedraw flag.

Issues Fixed

N/A – Proactive performance improvement.

Unit Tests

Added 11 unit tests in PerformanceOptimizationTests.cs covering:

• Shimmer gradient point correctness for all wave directions
• Shimmer cached static point verification
• Popup null return behavior (no more unnecessary Page allocations)
• TextInputLayout text change handler functionality
• TabView type accessibility verification

[naveenkumar-sanjeevirayan]

Tab View and Text Input Layout changes are fine

[Karthickmani97]

Shimmer control changes are fine

[AmalRajUmapathySelvam]

Popup changes are fine.