Concurrency and host architecture refactoring

[tinchodias]

Key highlights:

• Singleton Hosts (#default instead of #new): Standalone hosts (BlHeadlessHost, BlOSWindowSDL2Host, BlOSSDL3Host, BlMorphicWindowHost) are now singletons accessed via #default. Sending #new now raises an explicit error ('Use #default instead'). This directly affects existing scripts that previously instantiated hosts with #new (e.g. aSpace host: BlHeadlessHost default).
• Instance-Side BlHost API & BlHostRegistry default: Replaced static class-side host APIs with instance-side host objects managing their own universe, pulse loop, and spaces.
• Converts Morphic hosts to run in a separate pulse loop process (like SDL2 and SDL3) and adds double-buffering.
• Introduce BlEventSimulator based on class-side methods of BlSpace.
• Removal of BlMockedHost (replaced by BlHeadlessHost default): Removed BlMockedHost and package BlocHost-Mock. Rather than expecting manual, explicit #pulse calls from tests, headless testing now runs on a pulse process using BlHeadlessHost default, matching how normal hosts operate. Any external script, test, or baseline referencing BlMockedHost should be updated to BlHeadlessHost default.
• Event-driven pulse synchronization in BlParallelUniverse.
• Adds synchronization methods in BlSpace (#deferAndSettle:, #defer:, #deferOrValue:, #settle, #isSettled).
• Moves eventQueue from BlHostSpace to BlSpace, and clears pending events when a window closes.
• Uses BlHost as a facade to encapsulate universe (#spaces, #closeSpaces).
• Adds #denyPulseProcess to guard against blocking calls from inside the pulse process.

[tinchodias]

Extended:

Summary

This PR proposes changes to improve concurrency and process synchronization between external processes (such as the Morphic UI process from the Playground, test runner processes in SUnit/Calypso, or background worker threads) and the Bloc host pulse loop.

Key highlights:

• Singleton Hosts (#default instead of #new): Standalone hosts (BlHeadlessHost, BlOSWindowSDL2Host, BlOSSDL3Host, BlMorphicWindowHost) are now singletons accessed via #default. Sending #new now raises an explicit error ('Use #default instead'). This directly affects existing scripts that previously instantiated hosts with #new (e.g. aSpace host: BlHeadlessHost default).
• Instance-Side BlHost API & BlHostRegistry default: Replaced static class-side host APIs with instance-side host objects managing their own universe, pulse loop, and spaces.
• Converts Morphic hosts to run in a separate pulse loop process (like SDL2 and SDL3) and adds double-buffering.
• Introduce BlEventSimulator based on class-side methods of BlSpace.
• Removal of BlMockedHost (replaced by BlHeadlessHost default): Removed BlMockedHost and package BlocHost-Mock. Rather than expecting manual, explicit #pulse calls from tests, headless testing now runs on a pulse process using BlHeadlessHost default, matching how normal hosts operate. Any external script, test, or baseline referencing BlMockedHost should be updated to BlHeadlessHost default.
• Event-driven pulse synchronization in BlParallelUniverse.
• Adds synchronization methods in BlSpace (#deferAndSettle:, #defer:, #deferOrValue:, #settle, #isSettled).
• Moves eventQueue from BlHostSpace to BlSpace, and clears pending events when a window closes.
• Uses BlHost as a facade to encapsulate universe (#spaces, #closeSpaces).
• Adds #denyPulseProcess to guard against blocking calls from inside the pulse process.

Key Changes

1. Singleton Hosts (#default instead of #new) & BlHostRegistry default:

   • Standalone hosts (BlHeadlessHost, BlOSWindowSDL2Host, BlOSSDL3Host, BlMorphicWindowHost) now use the TBlSingletonHost trait and are accessed via MyHost default.
   • Important for scripts: Sending #new to a singleton host class now explicitly raises an Error ('Use #default instead'). Scripts and tests configuring spaces must now write aSpace host: BlHeadlessHost default (or BlOSWindowSDL2Host default) instead of sending #new.
   • Removal of BlMockedHost: Removed BlMockedHost and package BlocHost-Mock. To eliminate manual, explicit #pulse sends from test suites, headless tests now run pulse-synchronized on BlHeadlessHost default. External code or baselines referencing BlMockedHost should use BlHeadlessHost default as the replacement.
   • Converted BlHost subclasses from class-side static methods to instance-side objects holding their universe, pulse loop, and host space lifecycle.
   • Introduced BlHostRegistry default to discover, prioritize, and manage host instances dynamically.
   • Registered BlHostRegistry in SessionManager (startUp: / shutDown:).
   • Added BlHostRegistry >> #closeSpaces and Bloc class >> #closeSpaces to close open spaces across active hosts.
   • Replaced BlSpace >> #ensureWindowOpen and previousVisibleStatus with clean snapshot management in BlParallelUniverse (visibleSpacesOnShutdown).

2. BlSpace Concurrency & Synchronization APIs:

   • deferAndSettle: aBlock: Runs aBlock on the host pulse loop and waits until subsequent tasks, skin passes, and layouts have settled.
   • defer: aBlock: Enqueues aBlock asynchronously to run on the pulse loop.
   • deferOrValue: aBlock: Runs immediately if already in the pulse process; otherwise defers to the pulse loop.
   • settle: Waits synchronously until deferred actions, tasks, and frame phases are idle. Guarded with #denyPulseProcess.
   • isSettled: Checks if the space and its frame phases are currently idle.
   • settleForDuration: aDuration: Time-bounded settlement waiting.

3. eventQueue Migration to BlSpace & Clearing Events on Window Close:

   • Moved eventQueue from BlHostSpace directly into BlSpace (BlSpace >> #eventQueue, BlSpace >> #enqueueEvent:), so that events, tasks, layout, and drawing phases are all handled directly on BlSpace.
   • When a host window closes (hostSpaceClose), pending events in eventQueue are cleared (eventQueue removeAll). This prevents old hardware events from being replayed if the space is reopened or moved to another host.

4. Host as Facade Encapsulating universe (#spaces, #closeSpaces):

   • Uses BlHost as a facade between BlSpace and platform runtime execution (#openSpace:, #closeSpace:, #hasSpace:, #isSettled, #isPulsing, #defer:, #spaces, #closeSpaces).
   • Senders no longer need to access self host universe or self host universe spaces directly.
   • Standardized BlHost >> #spaces and BlHost >> #closeSpaces.
   • Renamed internal host-space management to hostSpaceOpen and hostSpaceClose under #'host space - accessing' to keep space public autocompletion clean.
   • Decoupling BlSpace from the in-image universe also facilitates future work on subprocess/IPC hosts.

5. Pulse Process Helpers & Deadlock Guard (#denyPulseProcess):

   • Harmonized process terminology across Bloc: pulseProcess, deferOrValue: (replacing older uiProcessDo: and inUIProcessDo:).
   • Added #denyPulseProcess on BlHost (used by BlParallelUniverse and BlEventSimulator). It raises an error if blocking synchronization (settle, waitUntil:) is called from within the pulse loop process itself, avoiding deadlocks.

6. Morphic Hosts on a Separate Pulse Process (Like SDL2 and SDL3) & Double-Buffering:

   • Converted Morphic hosts so their window spaces run in an independent pulse loop process, matching the behavior of SDL2 and SDL3 hosts.
   • Implemented double-buffering (backBuffer, frontBuffer) in BlAbstractMorphicHostSpace, preventing tearing and blank forms when embedding spaces in Morphic or Spec2 presenters (SpBlSpaceInMorphPresenter, BlDemoPresenter).
   • Calls currentWorld defer: [ self changed ] from BlMorphicSpaceHostMorph >> #form: to wake up the Morphic UI stepping loop from the pulse process.
   • Added synchronous morphicWindow fullBounds in BlMorphicWindowHostSpace >> #show to prevent initial 0@0 extent issues.
   • Cleaned up Morphic window close handling so closing a window does not reopen it on the next pulse.

7. Guarded Layout & Concurrency Safety (#forceLayout, Text, Export):

   • Guarded BlElement >> #forceLayout against execution on attached elements (signaling an Error directing senders to space settle or space deferAndSettle:).
   • Guarded BlTextElement >> #onPostMeasure: with a local paragraph copy and nil-check against concurrent text release/invalidation.
   • Updated BlElement >> #aeAsForm and BAExporter >> #export to synchronize with the space (space settle) when attached, and force layout synchronously when detached.

8. Testing Modernization (BlSpaceTestCase, BlEventSimulator, BlParameterizedHostTest):

   • Introduced BlSpaceTestCase as a lightweight base class for fast, headless unit tests with automatic cleanup.
   • Refactored BlParameterizedHostTest to parameterize on host instances (BlHostRegistry default availableHosts).
   • Extracted event simulation into BlEventSimulator in Bloc-Simulation with stateful modifiers and #denyPulseProcess guard.

Related Issues

• Concurrency problem when element is exported to Form while its space is opened #560 (Concurrency when exporting element to Form)
• Execute inUIProcessDo: when even there is no process #642 (Execute inUIProcessDo: when there is no process)
• BlProportionalLayout strange behaviour when exported as Form while opened in space #561 (BlProportionalLayout strange behavior when exported)
• BlHost: implement singleton in stateless subclasses? #816 (BlHost: implement singleton in stateless subclasses?)
• Can BlHostEventFetcher be merged into host spaces? #625 (Can BlHostEventFetcher be merged into host spaces?)
• Smoke tests in Ubuntu fail too often #783 (ubuntu fails too often)

[tinchodias]

BARenderTest's buildVariantsOfRoundedRectangleAndOutskirts fails on mac due to recent change in the libraries versions, but windows libraries are still the old versions:

Mac:

Cairo: 1.18.4
Freetype: 2.13.3
Harfbuzz: 11.0.0

Windows:

Cairo: 1.17.4
Freetype: 2.12.1
Harfbuzz: 5.3.1

[tinchodias]

This PR introduces a new System Setting for subclasses of BlParameterizedHostTest:

"All available hosts" means running each of the tests in BlHeadlessHost, BlMorphicWindowHost and BlOSWindowSDL2Host, while the other option means running only on BlHeadlessHost, which is faster.

In my image with Bloc, Album and Toplo, this changes from running around 5000 tests to 3500 test.