Core - Add AddPreferenceObserver support.

[SLT-World]

Fixes: -

Summary:

• Added support for listening to modifications of preferences exposing AddPreferenceObserver to RequestContext.

Changes:

• I have modified IRequestContext.cs, RequestContext.cpp, RequestContext.h, CefSharp.Core.Runtime.netcore.cs, created IPreferenceObserver.cs and PreferenceObserverAdapter.h.
  • Added AddPreferenceObserver to RequestContext.
  • Created IPreferenceObserver.

How Has This Been Tested?
Operating System: Windows 11
Environment: Visual Studio 2022
Setup:

await Cef.UIThreadTaskFactory.StartNew(async delegate
{
    IRequestContext GlobalRequestContext = Cef.GetGlobalRequestContext();
    GlobalRequestContext.SetPreference("autofill.enabled", true, out _);
    GlobalRequestContext.AddPreferenceObserver("autofill.enabled", new AutofillPreferenceObserver());
});

public class AutofillPreferenceObserver : IPreferenceObserver
{
    public void Dispose() { }

    public void OnPreferenceChanged(string Name)
    {
        IRequestContext GlobalRequestContext = Cef.GetGlobalRequestContext();
        object Value = GlobalRequestContext.GetPreference(Name);
        MessageBox.Show($"Autofill preference change detected. {Name} = {Value}");
    }
}

Alternated the autofill preference with a button:

bool AutofillState = false;

private async void Button_Click(object sender, RoutedEventArgs e)
{
    bool AutofillStateChange = AutofillState;
    AutofillState = !AutofillState;
    MessageBox.Show($"Changing autofill preference to {AutofillStateChange}.");
    await Cef.UIThreadTaskFactory.StartNew(async delegate
    {
        IRequestContext GlobalRequestContext = Cef.GetGlobalRequestContext();
        GlobalRequestContext.SetPreference("autofill.enabled", AutofillStateChange, out _);
    });
}

The Changing autofill... message box is displayed first, followed by Autofill preference change detected shortly, confirming the functionality.

I'm not clear on why the first line of CefSharp.Core.Runtime.RefAssembly/CefSharp.Core.Runtime.netcore.cs is once more labeled as a change by GitHub.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Updated documentation

Checklist:

• Tested the code(if applicable)
• Commented my code
• Changed the documentation(if applicable)
• New files have a license disclaimer
• The formatting is consistent with the project (project supports .editorconfig)

Summary by CodeRabbit

• New Features
  • Added support for monitoring browser preference changes through IRequestContext.
  • Preference observers receive notifications when the specified preference changes.
  • Added registration management so observers can be removed when no longer needed.
  • Added a dedicated observer callback interface for handling preference updates.
  • Documented callback behavior, including browser UI-thread execution and performance considerations.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 61563473-9aff-410b-a33c-07dcdd75bc0a

📥 Commits

Reviewing files that changed from the base of the PR and between b1236dd and 9ac6b42.

📒 Files selected for processing (1)

• CefSharp.Core/RequestContext.cs

🚧 Files skipped from review as they are similar to previous changes (1)

• CefSharp.Core/RequestContext.cs

---

📝 Walkthrough

Walkthrough

The PR adds IPreferenceObserver and AddPreferenceObserver to the public API. The C++/CLI runtime adapts managed observers to CEF callbacks, returns registration wrappers, and includes the adapter in both runtime projects.

Changes

Preference Observer Registration

Layer / File(s)	Summary
Observer API contract CefSharp/Callback/IPreferenceObserver.cs, CefSharp/IRequestContext.cs, CefSharp.Core.Runtime/RequestContext.h, CefSharp.Core.Runtime.RefAssembly/CefSharp.Core.Runtime.netcore.cs, CefSharp.Core/RequestContext.cs	Adds the disposable observer contract and the AddPreferenceObserver declarations and wrapper. The API supports one preference or all preferences and returns IRegistration.
Runtime callback registration CefSharp.Core.Runtime/Internals/PreferenceObserverAdapter.h, CefSharp.Core.Runtime/RequestContext.cpp	Adapts managed callbacks to CEF, forwards preference changes, validates disposal and UI-thread state, and wraps the native registration.
Runtime project inclusion CefSharp.Core.Runtime/*.vcxproj, CefSharp.Core.Runtime/*.vcxproj.filters	Adds PreferenceObserverAdapter.h to both projects and their header filters.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant RequestContext
  participant RuntimeRequestContext
  participant PreferenceObserverAdapter
  participant CefRequestContext
  RequestContext->>RuntimeRequestContext: AddPreferenceObserver(name, observer)
  RuntimeRequestContext->>PreferenceObserverAdapter: Create adapter
  RuntimeRequestContext->>CefRequestContext: Register observer
  CefRequestContext-->>PreferenceObserverAdapter: Notify preference change
  PreferenceObserverAdapter-->>RequestContext: OnPreferenceChanged(name)
  RuntimeRequestContext-->>RequestContext: Return IRegistration

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 21.43% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: adding AddPreferenceObserver support to Core.
Description check	✅ Passed	The description covers the change, testing environment, test procedure, change types, and checklist; the empty issue reference is non-critical.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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[AppVeyorBot]

❌ Build CefSharp 151.3.140-CI5579 failed (commit 11c80442a2 by @SLT-World)

[AppVeyorBot]

❌ Build CefSharp 151.3.140-CI5580 failed (commit cd4fc073c3 by @SLT-World)

[AppVeyorBot]

✅ Build CefSharp 151.3.140-CI5581 completed (commit 1b974755d8 by @SLT-World)