Mac: make MMTabBarView/PSMTabBarControl optional

When `MMTabBarView` and `PSMTabBarControl` are not available, the
Racket-implemented tab panel (otherwise selected by the
`'flat-portable` style or the `PLT_FLAT_PORTABLE_TAB_PANEL`
environment variable) can be used.

Closes racket/racket#5385

Author: mflatt

gui-lib/mred/private/mrpanel.rkt

@@ -11,7 +11,8 @@
          "mrwindow.rkt"
          "mrcontainer.rkt"
          "wxtabcanvas.rkt"
-         "gdi.rkt")
+         "gdi.rkt"
+         (only-in "wx/platform.rkt" tab-panel-available?))
 
 (provide pane%
          vertical-pane%
@@ -320,7 +321,8 @@
              [get-orientation (λ () (send (mred->wx this) get-orientation))])))
 
 (define list-append append)
-(define always-use-tab-canvas? (and (getenv "PLT_FLAT_PORTABLE_TAB_PANEL") #t))
+(define always-use-tab-canvas? (or (and (getenv "PLT_FLAT_PORTABLE_TAB_PANEL") #t)
+                                   (not (tab-panel-available?))))
 
 (define tab-panel%
   (class vertical-panel%

gui-lib/mred/private/wx/cocoa/platform.rkt

@@ -96,4 +96,5 @@
    key-symbol-to-menu-key
    needs-grow-box-spacer?
    graphical-system-type
-   white-on-black-panel-scheme?))
+   white-on-black-panel-scheme?
+   tab-panel-available?))

gui-lib/mred/private/wx/cocoa/tab-panel.rkt

@@ -15,7 +15,8 @@
          (for-syntax racket/base))
 
 (provide 
- (protect-out tab-panel%))
+ (protect-out tab-panel%
+              tab-panel-available?))
 
 (define-runtime-path psm-tab-bar-dir
   '(so "PSMTabBarControl.framework"))
@@ -29,23 +30,29 @@
        (directory-exists? mm-tab-bar-dir)))
 
 ;; Load MMTabBarView or PSMTabBarControl:
-(if use-mm?
-    (void (ffi-lib (build-path mm-tab-bar-dir "MMTabBarView")))
-    (void (ffi-lib (build-path psm-tab-bar-dir "PSMTabBarControl"))))
+(define tab-ok?
+  (if use-mm?
+      (and (ffi-lib (build-path mm-tab-bar-dir "MMTabBarView") #:fail (lambda () #f))
+           'mm)
+      (and (ffi-lib (build-path psm-tab-bar-dir "PSMTabBarControl") #:fail (lambda () #f))
+           'psm)))
+(define (tab-panel-available?) tab-ok?)
+
 (define NSNoTabsNoBorder 6)
 
 (define NSDefaultControlTint 0)
 (define NSClearControlTint 7)
 
 (import-class NSView NSTabView NSTabViewItem)
 (define TabBarControl
-  (if use-mm?
-      (let ()
-        (import-class MMTabBarView)
-        MMTabBarView)
-      (let ()
-        (import-class PSMTabBarControl)
-        PSMTabBarControl)))
+  (cond
+    [(not tab-ok?) #f]
+    [use-mm?
+     (import-class MMTabBarView)
+     MMTabBarView]
+    [else
+     (import-class PSMTabBarControl)
+     PSMTabBarControl]))
 (import-protocol NSTabViewDelegate)
 
 (define NSOrderedAscending -1)

gui-lib/mred/private/wx/gtk/procs.rkt

@@ -65,7 +65,8 @@
  get-color-from-user
  key-symbol-to-menu-key
  needs-grow-box-spacer?
- graphical-system-type)
+ graphical-system-type
+ tab-panel-available?)
 
 (define (find-graphical-system-path what)
   (case what
@@ -200,3 +201,5 @@
   ;; in that case we want to return #f.
   (< (luminance (get-label-background-color))
      (luminance (get-label-foreground-color))))
+
+(define (tab-panel-available?) #t)

gui-lib/mred/private/wx/platform.rkt

@@ -86,5 +86,6 @@
                 key-symbol-to-menu-key
                 needs-grow-box-spacer?
                 graphical-system-type
-                white-on-black-panel-scheme?)
+                white-on-black-panel-scheme?
+                tab-panel-available?)
   ((dynamic-require platform-lib 'platform-values)))

gui-lib/mred/private/wx/win32/platform.rkt

@@ -99,11 +99,14 @@
    key-symbol-to-menu-key
    needs-grow-box-spacer?
    graphical-system-type
-   white-on-black-panel-scheme?))
+   white-on-black-panel-scheme?
+   tab-panel-available?))
 
 (define (white-on-black-panel-scheme?)
   ;; if the background and foreground are the same
   ;; color, probably something has gone wrong;
   ;; in that case we want to return #f.
   (< (luminance (get-label-background-color))
      (luminance (get-label-foreground-color))))
+
+(define (tab-panel-available?) #t)