add make-platform-bitmap

also: use it in pict's rendering and
remove redex's platform-specific font choice
(going back to using 'modern on all platforms)

closes PR 12554

original commit: 1945ff270962679e13f66131c5b3eb91cc1edb2f

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

@@ -5,13 +5,13 @@
          racket/draw
          racket/draw/private/gl-context
          racket/draw/private/color
+         racket/draw/private/bitmap
          "pool.rkt"
          "utils.rkt"
          "const.rkt"
          "types.rkt"
          "window.rkt"
          "dc.rkt"
-         "bitmap.rkt"
          "cg.rkt"
          "queue.rkt"
          "item.rkt"

collects/mred/private/wx/cocoa/dc.rkt

@@ -8,7 +8,6 @@
          racket/draw/private/gl-context
          "types.rkt"
          "utils.rkt"
-         "bitmap.rkt"
          "window.rkt"
          "../../lock.rkt"
          "../common/queue.rkt"

collects/mred/private/wx/cocoa/image.rkt

@@ -5,11 +5,11 @@
          racket/draw/unsafe/cairo
          racket/draw/private/local
          racket/draw/unsafe/bstr
+         racket/draw/private/bitmap
          "utils.rkt"
          "types.rkt"
          "const.rkt"
          "cg.rkt"
-         "bitmap.rkt"
          "../../lock.rkt"
          (only-in '#%foreign ffi-callback))
 

collects/mred/private/wx/cocoa/printer-dc.rkt

@@ -13,7 +13,6 @@
          "../../lock.rkt"
          "dc.rkt"
          "frame.rkt"
-         "bitmap.rkt"
          "cg.rkt"
          "utils.rkt"
          "types.rkt")

collects/mred/private/wx/cocoa/procs.rkt

@@ -2,6 +2,7 @@
 (require "../../syntax.rkt"
          racket/class
          racket/draw
+         racket/draw/private/bitmap
          ffi/unsafe
          ffi/unsafe/objc
          "utils.rkt"
@@ -12,7 +13,6 @@
          "filedialog.rkt"
          "colordialog.rkt"
          "dc.rkt"
-         "bitmap.rkt"
          "printer-dc.rkt"
          "menu-bar.rkt"
          "agl.rkt"

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

@@ -23,46 +23,33 @@
 
 (define-gdi32 SelectClipRgn (_wfun _pointer _pointer -> _int))
 
-(define win32-bitmap%
-  (class bitmap%
-    (init w h hwnd [gl-config #f])
-    (super-make-object (make-alternate-bitmap-kind w h))
+(define hwnd-param (make-parameter #f))
 
-    (define s
-      (let ([s
-             (if (not hwnd)
-                 (cairo_win32_surface_create_with_dib CAIRO_FORMAT_RGB24 w h)
-                 (atomically
-                  (let ([hdc (GetDC hwnd)])
-                    (begin0
-                     (cairo_win32_surface_create_with_ddb hdc
-                                                          CAIRO_FORMAT_RGB24 w h)
-                     (ReleaseDC hwnd hdc)))))])
-        ;; initialize bitmap to white:
-        (let ([cr (cairo_create s)])
-          (cairo_set_source_rgba cr 1.0 1.0 1.0 1.0)
-          (cairo_paint cr)
-          (cairo_destroy cr))
-        s))
+(define win32-bitmap%
+  (class win32-no-hwnd-bitmap%
+    (init w h hwnd [gl-config #f])
+    (inherit get-cairo-surface)
+    (parameterize ([hwnd-param hwnd])
+      (super-new [w w] [h h]))
+    
+    (define/override (build-cairo-surface w h) 
+      (define hwnd (hwnd-param))
+      (if hwnd
+          (atomically
+           (let ([hdc (GetDC hwnd)])
+             (begin0
+               (cairo_win32_surface_create_with_ddb hdc
+                                                    CAIRO_FORMAT_RGB24 w h)
+               (ReleaseDC hwnd hdc))))
+          (super build-cairo-surface)))
     
     (define gl (and gl-config
-                    (let ([hdc (cairo_win32_surface_get_dc s)])
+                    (let ([hdc (cairo_win32_surface_get_dc (get-cairo-surface))])
                       (set-cpointer-tag! hdc 'HDC)
                       (create-gl-context hdc 
                                          gl-config
                                          #t))))
-    (define/override (get-bitmap-gl-context) gl)
-
-    (define/override (ok?) #t)
-    (define/override (is-color?) #t)
-    (define/override (has-alpha-channel?) #f)
-
-    (define/override (get-cairo-surface) s)
-
-    (define/override (release-bitmap-storage)
-      (atomically
-       (cairo_surface_destroy s)
-       (set! s #f)))))
+    (define/override (get-bitmap-gl-context) gl)))
 
 (define dc%
   (class backing-dc%

collects/scribblings/gui/miscwin-funcs.scrbl

@@ -253,7 +253,10 @@ Creates a bitmap that draws in a way that is the same as drawing to a
 canvas in its default configuration.
 
 A normal @racket[bitmap%] draws in a more platform-independent way and
-may use fewer constrained resources, particularly on Windows.}
+may use fewer constrained resources, particularly on Windows.
+
+See also @racket[make-platform-bitmap].
+}
 
 
 @defproc[(play-sound [filename path-string?]