rackt/draw: fix internal error on too-large bitmap

pkgs/draw-pkgs/draw-lib/racket/draw/private/bitmap.rkt

@@ -196,17 +196,22 @@
                                               (max (*i scale h) 1))])
            (cairo_surface_flush s)
            (cond
-            [b&w?
-             ;; Init transparent white:
-             (transparent-white! s w h)]
-            [alpha?
-             ;; Init transparent:
-             (bytes-fill! (cairo_image_surface_get_data s) 0)]
+            [(cairo_image_surface_get_data s)
+             (cond
+              [b&w?
+               ;; Init transparent white:
+               (transparent-white! s w h)]
+              [alpha?
+               ;; Init transparent:
+               (bytes-fill! (cairo_image_surface_get_data s) 0)]
+              [else
+               ;; Init all white, 255 alpha:
+               (bytes-fill! (cairo_image_surface_get_data s) 255)])
+             (cairo_surface_mark_dirty s)
+             s]
             [else
-             ;; Init all white, 255 alpha:
-             (bytes-fill! (cairo_image_surface_get_data s) 255)])
-           (cairo_surface_mark_dirty s)
-           s)
+             ;; bitmap creation failed
+             #f]))
          #f
          (* 1.0 scale))]
        [([(make-alts path-string? input-port?) filename]

pkgs/gui-pkgs/gui-test/tests/gracket/dc.rktl

@@ -811,6 +811,11 @@
                    load-file
                    p)))
 
+;; ----------------------------------------
+;; No error on too-large bitmap:
+
+(st #f (make-bitmap 1000000 1000000) ok?)
+
 ;; ----------------------------------------
 
 (report-errs)