win32: fix canvas-refresh problem when a canvas is shown

and when it has been drawn onto outside of `on-paint';
 also, try to prep the content of all canvases within a
 top-level window before the window is shown (as on other
 platforms)

collects/mred/private/wx/win32/canvas.rkt

@@ -228,6 +228,13 @@
                  (get-virtual-v-pos)
                  0)))
 
+     (define/override (show-children)
+       (when (dc . is-a? . dc<%>)
+         ;; if the canvas was never shown, then it has never
+         ;; been refreshed --- but it may have been drawn
+         ;; outside `on-paint', so force a refresh
+         (reset-dc)))
+
      (define/override (get-client-hwnd)
        canvas-hwnd)
 

collects/mred/private/wx/win32/frame.rkt

@@ -177,15 +177,29 @@
 
   (define/override (show on?)
     (let ([es (get-eventspace)])
-      (when (and on?
-		 (eventspace-shutdown? es))
-	(error (string->symbol
-		(format "show method in ~a"
-			(if (is-dialog?)
-			    'dialog%
-			    'frame%)))
-	       "eventspace has been shutdown")))
-    (super show on?))
+      (when on?
+        (when (eventspace-shutdown? es)
+          (error (string->symbol
+                  (format "show method in ~a"
+                          (if (is-dialog?)
+                              'dialog%
+                              'frame%)))
+                 "eventspace has been shutdown"))
+        (when saved-child
+          (if (eq? (current-thread) (eventspace-handler-thread es))
+              (do-paint-children)
+              (let ([s (make-semaphore)])
+                (queue-callback (lambda ()
+                                  (do-paint-children)
+                                  (semaphore-post s)))
+                (sync/timeout 1 s))))))
+    ;; calling `direct-show' instead of `show' avoids
+    ;;  calling `show-children':
+    (atomically (direct-show on?)))
+
+  (define/private (do-paint-children)
+    (when saved-child
+      (send saved-child paint-children)))
 
   (define/override (direct-show on?)
     ;; atomic mode

collects/mred/private/wx/win32/panel.rkt

@@ -70,6 +70,13 @@
             #t)
           #f))
 
+    (define/override (show-children)
+      (for ([c (in-list children)])
+        (send c show-children)))
+    (define/override (paint-children)
+      (for ([c (in-list children)])
+        (send c show-children)))
+
     (define/override (wants-mouse-capture? control-hwnd)
       (ptr-equal? (get-client-hwnd) control-hwnd))
 

collects/mred/private/wx/win32/window.rkt

@@ -245,6 +245,7 @@
   (define/public (control-scrolled) #f)
 
   (define/public (show on?)
+    (when on? (show-children))
     (atomically (direct-show on?)))
 
   (define shown? #f)
@@ -295,8 +296,6 @@
   (define/public (is-shown?)
     shown?)
 
-  (define/public (paint-children) (void))
-
   (define/public (get-x)
     (let ([r (GetWindowRect hwnd)]
           [pr (GetWindowRect (send parent get-client-hwnd))])
@@ -485,6 +484,9 @@
     (when parent
       (send parent register-child this on?)))
 
+  (define/public (show-children) (void))
+  (define/public (paint-children) (void))
+
   (define/public (get-top-frame)
     (send parent get-top-frame))