core: fix container sequence bracketing

Before this change, an error raised during the creation of a child
could leave these containers in a state where they would never update
again because the nesting depth of the sequencing could never reach 0
again.

gui-easy-lib/gui/easy/private/view/container.rkt

@@ -3,7 +3,8 @@
 (require racket/class)
 
 (provide
- container%)
+ container%
+ with-container-sequence)
 
 (define container%
   (class object%
@@ -42,3 +43,13 @@
 
     (define/private (get-children-to-widgets v)
       (send v get-context! 'children-to-widgets make-hasheq))))
+
+(define-syntax-rule (with-container-sequence container body0 body ...)
+  (dynamic-wind
+    (lambda ()
+      (send container begin-container-sequence))
+    (lambda ()
+      body0
+      body ...)
+    (lambda ()
+      (send container end-container-sequence))))

gui-easy-lib/gui/easy/private/view/if.rkt

@@ -47,16 +47,15 @@
         [@cond-e
          (define this-bool (->bool val))
          (unless (eq? (get-last-bool v) this-bool)
-           (send v begin-container-sequence)
-           (when (has-then-view? v)
-             (remove&destroy-then-view v))
-           (when (has-else-view? v)
-             (remove&destroy-else-view v))
-           (if this-bool
-               (create&add-then-view v)
-               (create&add-else-view v))
-           (send v set-context 'last-bool this-bool)
-           (send v end-container-sequence))]))
+           (with-container-sequence v
+             (when (has-then-view? v)
+               (remove&destroy-then-view v))
+             (when (has-else-view? v)
+               (remove&destroy-else-view v))
+             (if this-bool
+                 (create&add-then-view v)
+                 (create&add-else-view v))
+             (send v set-context 'last-bool this-bool)))]))
 
     (define/public (destroy v)
       (when (has-then-view? v)

gui-easy-lib/gui/easy/private/view/list.rkt

@@ -97,51 +97,49 @@
       (define keys-to-children
         (get-keys-to-children the-panel))
       (begin0 the-panel
-        (send the-panel begin-container-sequence)
-        (for ([e (in-list (peek @entries))])
-          (define k (key-proc e))
-          (define v (make-view k (make-keyed-obs k e)))
-          (define w (send v create the-panel))
-          (add-child-handlers! the-panel v)
-          (add-child the-panel v w)
-          (hash-set! keys-to-children k v))
-        (send the-panel end-container-sequence)))
+        (with-container-sequence the-panel
+          (for ([e (in-list (peek @entries))])
+            (define k (key-proc e))
+            (define v (make-view k (make-keyed-obs k e)))
+            (define w (send v create the-panel))
+            (add-child-handlers! the-panel v)
+            (add-child the-panel v w)
+            (hash-set! keys-to-children k v)))))
 
     (define/public (update v what val)
       (case/dep what
         [@entries
-         (send v begin-container-sequence)
-         (define keys-to-children
-           (get-keys-to-children v))
-         (define new-keys
-           (for/list ([e (in-list val)])
-             (define k (key-proc e))
-             (begin0 k
-               (unless (hash-has-key? keys-to-children k)
-                 (define child-v (make-view k (make-keyed-obs k e)))
-                 (define child-w (send child-v create v))
-                 (add-child-handlers! v child-v)
-                 (add-child v child-v child-w)
-                 (hash-set! keys-to-children k child-v)))))
-         (for ([(old-k old-v) (in-hash keys-to-children)])
-           (unless (member old-k new-keys)
-             (define old-w (get-child v old-v))
-             (define focused? (send old-w has-focus?))
-             (send old-v destroy old-w)
-             (send v delete-child old-w)
-             (remove-child-handlers! v old-v)
-             (remove-child v old-v)
-             (hash-remove! keys-to-children old-k)
-             (when focused?
-               (define children (send v get-children))
-               (cond
-                 [(null? children) (send v focus)]
-                 [else (send (last children) focus)]))))
-         (send v change-children
-               (λ (_)
-                 (for/list ([k (in-list new-keys)])
-                   (get-child v (hash-ref keys-to-children k)))))
-         (send v end-container-sequence)]
+         (with-container-sequence v
+           (define keys-to-children
+             (get-keys-to-children v))
+           (define new-keys
+             (for/list ([e (in-list val)])
+               (define k (key-proc e))
+               (begin0 k
+                 (unless (hash-has-key? keys-to-children k)
+                   (define child-v (make-view k (make-keyed-obs k e)))
+                   (define child-w (send child-v create v))
+                   (add-child-handlers! v child-v)
+                   (add-child v child-v child-w)
+                   (hash-set! keys-to-children k child-v)))))
+           (for ([(old-k old-v) (in-hash keys-to-children)])
+             (unless (member old-k new-keys)
+               (define old-w (get-child v old-v))
+               (define focused? (send old-w has-focus?))
+               (send old-v destroy old-w)
+               (send v delete-child old-w)
+               (remove-child-handlers! v old-v)
+               (remove-child v old-v)
+               (hash-remove! keys-to-children old-k)
+               (when focused?
+                 (define children (send v get-children))
+                 (cond
+                   [(null? children) (send v focus)]
+                   [else (send (last children) focus)]))))
+           (send v change-children
+                 (λ (_)
+                   (for/list ([k (in-list new-keys)])
+                     (get-child v (hash-ref keys-to-children k))))))]
         [@alignment
          (send/apply v set-alignment val)]
         [@enabled?

gui-easy-lib/gui/easy/private/view/observable.rkt

@@ -4,6 +4,7 @@
          (prefix-in gui: racket/gui)
          "../renderer.rkt"
          "common.rkt"
+         "container.rkt"
          "proxy.rkt"
          "view.rkt")
 
@@ -29,10 +30,9 @@
       (case/dep what
         [@data
          (unless (equal?-proc val (get-data v))
-           (send v begin-container-sequence)
-           (remove&destroy-child v)
-           (create&add-child v val)
-           (send v end-container-sequence))])
+           (with-container-sequence v
+             (remove&destroy-child v)
+             (create&add-child v val)))])
       (define child
         (send v get-context 'view #f))
       (when child

gui-easy-lib/gui/easy/private/view/panel.rkt

@@ -46,10 +46,9 @@
     (define/public (create parent)
       (define the-panel (-make-panel parent))
       (begin0 the-panel
-        (send the-panel begin-container-sequence)
-        (for ([c (in-list children)])
-          (add-child the-panel c (send c create the-panel)))
-        (send the-panel end-container-sequence)))
+        (with-container-sequence the-panel
+          (for ([c (in-list children)])
+            (add-child the-panel c (send c create the-panel))))))
 
     (define/public (update v what val)
       (case/dep what

gui-easy-lib/gui/easy/private/view/tabs.rkt

@@ -95,10 +95,9 @@
           (send the-panel set-context 'last-selection selection)
           (send the-panel set-context 'last-index index)
           (send the-panel set-selection index))
-        (send the-panel begin-container-sequence)
-        (for ([c (in-list children)])
-          (add-child the-panel c (send c create the-panel)))
-        (send the-panel end-container-sequence)))
+        (with-container-sequence the-panel
+          (for ([c (in-list children)])
+            (add-child the-panel c (send c create the-panel))))))
 
     (define/public (update v what val)
       (case/dep what

gui-easy-lib/info.rkt

@@ -1,7 +1,7 @@
 #lang info
 
 (define license 'BSD-3-Clause)
-(define version "0.16")
+(define version "0.16.1")
 (define collection "racket")
 (define deps '("base"
                "box-extra-lib"