add show-without-yield' to dialog%'

collects/mred/private/mrtop.rkt

@@ -240,6 +240,11 @@
 	  (check-style cwho #f '(no-caption resize-border no-sheet close-button) style)))
       (rename [super-on-subwindow-char on-subwindow-char])
       (private-field [wx #f])
+      (public
+        [show-without-yield (lambda () 
+                              (as-entry
+                               (lambda ()
+                                 (send wx call-show #t (lambda () (send wx show-without-yield))))))])
       (override
 	[on-subwindow-char (lambda (w event)
 			     (super-on-subwindow-char w event)

collects/mred/private/wx/common/dialog.rkt

@@ -12,6 +12,7 @@
     (super-new)
 
     (define close-sema #f)
+    (define close-sema-ready? #f)
 
     (define dialog-level 0)
     (define/override (get-dialog-level) dialog-level)
@@ -31,17 +32,32 @@
       (unless on?
         (set! dialog-level 0))
       (unless on?
-        (when close-sema
+        (when close-sema-ready?
           (semaphore-post close-sema)
-          (set! close-sema #f)))
+          (set! close-sema #f)
+          (set! close-sema-ready? #f)))
+      (when on?
+        ;; mark `close-sema' as having a corresponding `show #t'
+        ;; so that a future `show #f' can clear it; without this
+        ;; extra flag, `close-sema' could be set, `show #f' could
+        ;; post it, and then the `show #t' that created hte sema
+        ;; could happen after the `show #f'
+        (set! close-sema-ready? #t))
       (super direct-show on?))
 
+    (define/private (get-show-semaphore)
+      (atomically
+       (let ([s (or close-sema (make-semaphore))])
+         (unless close-sema (set! close-sema s))
+         (semaphore-peek-evt s))))
+
+    (define/public (show-without-yield)
+      (get-show-semaphore) ; in case some other thread wants to wait
+      (super show #t))
+
     (define/override (show on?)
       (if on?
-          (let ([s (atomically
-                    (let ([s (or close-sema (make-semaphore))])
-                      (unless close-sema (set! close-sema s))
-                      (semaphore-peek-evt s)))])
+          (let ([s (get-show-semaphore)])
             (super show on?)
             (yield s)
             (void))

collects/mred/private/wxtop.rkt

@@ -346,6 +346,17 @@
 				  1 1)
 		    (set! already-trying? #f)
 		    (resized)]))))))])
+
+      (public
+        [call-show
+	 (lambda (on? do-show)
+           (when on?
+             (position-for-initial-show))
+	   (if on?
+	       (hash-table-put! top-level-windows this #t)
+	       (hash-table-remove! top-level-windows this))
+	   (as-exit ; as-exit because there's an implicit wx:yield for dialogs
+            do-show))])
       
       (override
 	;; show: add capability to set perform-updates
@@ -356,12 +367,8 @@
 	;;          pass now to superclass's show.
 	[show
 	 (lambda (on?)
-           (when on?
-             (position-for-initial-show))
-	   (if on?
-	       (hash-table-put! top-level-windows this #t)
-	       (hash-table-remove! top-level-windows this))
-	   (as-exit ; as-exit because there's an implicit wx:yield for dialogs
+           (call-show
+            on?
 	    (lambda () (super show on?))))]
 
 	[on-visible

collects/scribblings/gui/dialog-class.scrbl

@@ -114,4 +114,11 @@ If @scheme[show?] is true, the method does not immediately return. Instead,
   method returns as soon as possible after the dialog is hidden.
 
 }
+
+@defmethod[(show-without-yield)
+           void?]{
+
+Like @racket[(send @#,this-obj[] @#,method[dialog% show] #t)], but returns
+immediately instead of @racket[yield]ing.}
+
 }