use Sigils RChan for image messages

CHANGES.md

@@ -1,5 +1,19 @@
 # Changes
 
+## 0.41.0
+
+- Move the ownership-safe fixed-ring RChan implementation and its regression
+  suite to Sigils 0.31.0; keep a compatibility import for existing FigDraw
+  callers and exercise image-message replacement through the shared channel.
+
+- Store `RChan` messages in a fixed typed ring, transferring isolated values
+  with `swap` under the lock. Remove per-message allocations and send rollback;
+  preserve `tryTake` sources on failure and receive isolated values directly.
+  Initialize vacant slots without constructing payload field defaults.
+- Release image-message subscription channels and all ring storage. Run payload
+  hooks outside channel locks and reject reentrant operations during teardown.
+- Add Linux/macOS RSS regressions covering both `tryRecv` and blocking `recv`.
+
 ## 0.40.2
 
 - Export producer-owned `RenderFragments`, fragment handles, cursors, and their

figdraw.nimble

@@ -1,11 +1,12 @@
-version = "0.40.2"
+version = "0.41.0"
 author = "Jaremy Creechley"
 description = "UI Engine for Nim"
 license = "MIT"
 srcDir = "src"
 
 # Dependencies
 requires "nim >= 2.2"
+requires "https://github.com/elcritch/sigils#feat/rchannels"
 requires "pixie >= 5.0.1"
 requires "chroma >= 0.2.7"
 requires "bumpy"

src/figdraw/common/imgutils.nim

@@ -4,7 +4,7 @@ import std/[isolation, locks, times]
 import pkg/pixie
 import chronicles
 
-import ./rchannels
+import sigils/rchannels
 import ./formatflippy
 import ./fonttypes
 import ./shared
@@ -108,10 +108,14 @@ imageCachedLock.initLock()
 ownerTokenLock.initLock()
 imageSubscriberLock.initLock()
 
-proc `=destroy`(subscription: ImageMessageSubscriptionHandle) =
+proc `=destroy`(subscription: var ImageMessageSubscriptionHandle) =
   if subscription.id != 0'u64:
     withLock imageSubscriberLock:
       imageSubscribers.del(subscription.id)
+  # This custom destructor replaces the compiler-generated field cleanup.
+  # Release the subscription's channel owner after removing the table owner;
+  # queued ImageMsg values then get destroyed by RChan's final-owner cleanup.
+  `=destroy`(subscription.inbox)
 
 proc `==`*(a, b: ImageId): bool {.borrow.}
 proc `==`*(a, b: OwnerToken): bool {.borrow.}