Refactor cefclient sample application

[magreenblatt]

Original report by me.

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Original issue 1500 created by magreenblatt on 2015-01-22T00:57:21.000Z:

The cefclient sample application has evolved incrementally and haphazardly since the CEF project was first started. It's now time to refactor cefclient so that it better reflects good application design principles. This includes:

File/code organization:

• Make file extensions consistent with other CEF targets (use .cc instead of .cpp).
• Use namespaces to wrap cefclient classes/functions (all cefclient sources in 'client' namespace, specific tests in `_test' nested namespace).

General design principles:

• Classes should have well-defined lifespans and access patterns. For example, helper classes should be scoped to the parent class' lifespan and only accessed on a single thread where possible.
• Use delegates and observers to limit explicit dependencies on other class types.
  -- Delegates are generally passed to the class constructor and guaranteed to outlive the class instance.
  -- Multiple observers might be registered on the same class instance and should unregister themselves before destruction.
  -- Document the thread on which delegate/observer methods will be called.
• Use smart pointer types (scoped_ptr, scoped_refptr, WeakPtr) instead of T* where possible.
• When using T* (with delegates, for example) add comments and assertions to document/check expected lifespan.
• Use protected/private destructors where possible to compile-time check that instances are only deleted via the associated smart pointer types.
• Use DISALLOW_COPY_AND_ASSIGN and similar macros as appropriate.
• Access class members on a single thread and use posted tasks instead of locking to protect access where possible.
  -- Class methods can internally post to the correct thread when setting members.
  -- Use asynchronous callbacks for accessing members that may live on a different thread.

Application structure:

• Use a singleton global context class whose lifespan is scoped to main() instead of multiple global functions/variables for managing shared state (list of existing windows, common file paths, etc).
• Use an abstraction for message loop functionality (Run/Quit/PostTask) instead of implementing the same logic multiple times in platform-specific files (CefRunMessageLoop vs CefDoMessageLoopWork vs multi-threaded message loop on Windows).

Window creation/management:

• Create a class structure to represent different types of native windows and browser windows (windowed vs off-screen) with specialized CefClient hierarchy/sub-classes.
• Create a root window class representing a native window with title bar and resize browser.
  -- Optionally show/hide controls (url bar and back/forward/stop/reload buttons).
  -- Optionally create as a top-level window or popup window.
  -- Optionally create with a windowed browser (created/managed by CEF) or off-screen browser (native window with GL context + CefRenderHandler).
  -- Create/manage root windows via the singleton global context class.
• Window class implementations will likely be platform-specific (WinAPI vs Cocoa vs GTK/X11) while CefClient implementations will likely be shared across platforms.

[magreenblatt]

Comment 1. originally posted by magreenblatt on 2015-01-22T01:57:06.000Z:

File extensions changed from .cpp to .cc in trunk revision 1981.

[magreenblatt]

Comment 2. originally posted by magreenblatt on 2015-01-22T17:56:29.000Z:

An abstraction for message loop functionality has been added in trunk revision 1982.

[magreenblatt]

Comment 3. originally posted by magreenblatt on 2015-01-22T19:54:31.000Z:

On Mac we should also remove the helper target build dependencies on code that does not actually run in that process (*_test, client_handler, etc).

[magreenblatt]

Comment 4. originally posted by magreenblatt on 2015-01-22T20:21:51.000Z:

Add test_runner as the single entry point for running test-related code and move test implementations to the client namespace in trunk revision 1983.

[magreenblatt]

Comment 5. originally posted by magreenblatt on 2015-01-22T21:40:04.000Z:

Use test_runner::Alert instead of platform-specific notifications in trunk revision 1984.

[magreenblatt]

Comment 6. originally posted by magreenblatt on 2015-01-22T23:11:57.000Z:

Replace global App* functions with singleton MainContext instance in trunk revision 1985.

[magreenblatt]

Comment 7. originally posted by magreenblatt on 2015-01-23T16:21:23.000Z:

Don't specify `virtual` in combination with `OVERRIDE` since it's redundant in trunk revision 1986 and revision 1987.

[magreenblatt]

Comment 8. originally posted by magreenblatt on 2015-01-23T19:12:51.000Z:

All files moved to the `client` namespace in trunk revision 1988 and revision 1989.

[magreenblatt]

Comment 9. originally posted by magreenblatt on 2015-01-23T20:07:08.000Z:

Additional `client` namespace changes in trunk revision 1990. Move Linux GTK dialog handlers from ClientHandler into a separate class in trunk revision 1991.

[magreenblatt]

Comment 10. originally posted by magreenblatt on 2015-01-27T00:05:12.000Z:

Trunk revision 1999:

• Split ClientHandler into an abstract base class and a concrete implementation for shared usage.
• Show an alert box when selecting Tests > Popup Window while running in off-screen rendering mode.
• Mac: Enable/disable UX buttons to match loading state.

Trunk revision 2001:

• Windows: Introduce RootWindow concept and associated window/client object hierarchy.
• Remove locking from ClientHandlerShared that was only required for the Windows implementation.
• Add CefDeleteOnThread helper for deleting ref-counted types on a named CEF thread.

[magreenblatt]

Comment 11. originally posted by magreenblatt on 2015-01-30T19:11:21.000Z:

Trunk revision 2004:

• Introduce RootWindow concept and associated window/client object hierarchy on Linux.

Trunk revision 2006:

• Introduce RootWindow concept and associated window/client object hierarchy on Mac.

Trunk revision 2008:

• Remove ClientHandler abstraction that is no longer necessary now that all platforms use RootWindow

Trunk revision 2009:

• Simplify TempWindow usage.

[magreenblatt]

Comment 12. originally posted by magreenblatt on 2015-01-31T04:49:19.000Z:

Trunk revision 2010, revision 2011, revision 2012, revision 2013 and revision 2014:

• Restructure files into browser/, common/, renderer/ and resources/ directories.
• Mac: Reduce helper process file dependencies.

Trunk revision 2015:

• Split ClientApp into process-specific types.

[magreenblatt]

Comment 13. originally posted by magreenblatt on 2015-02-02T22:36:36.000Z:

Trunk revision 2017:

• Restructure file lists in CMakeLists.txt.in to generate nicer output.

Trunk revision 2018:

• Move files containing the main() program entry point to the top-level cefclient directory.

[magreenblatt]

• set state to "resolved"