haiku: Implement message box for Haiku

Add implementation for functions:

SDL_ShowSimpleMessageBox()
SDL_ShowMessageBox()

Add simple customization support also.
Fix build for x86_gcc2.

Partially fixes Bugzilla #4442.

include/SDL_syswm.h

@@ -132,7 +132,8 @@ typedef enum
     SDL_SYSWM_WINRT,
     SDL_SYSWM_ANDROID,
     SDL_SYSWM_VIVANTE,
-    SDL_SYSWM_OS2
+    SDL_SYSWM_OS2,
+    SDL_SYSWM_HAIKU
 } SDL_SYSWM_TYPE;
 
 /**

src/main/haiku/SDL_BeApp.cc

@@ -48,13 +48,14 @@ extern "C" {
 static int SDL_BeAppActive = 0;
 static SDL_Thread *SDL_AppThread = NULL;
 
+/* Default application signature */
+const char *signature = "application/x-SDL-executable";
+
 static int
 StartBeApp(void *unused)
 {
     BApplication *App;
 
-    // default application signature
-    const char *signature = "application/x-SDL-executable";
     // dig resources for correct signature
     image_info info;
     int32 cookie = 0;

src/main/haiku/SDL_BeApp.h

@@ -31,6 +31,9 @@ extern int SDL_InitBeApp(void);
 /* Quit the Be Application, if there's nothing left to do */
 extern void SDL_QuitBeApp(void);
 
+/* Be Application Signature*/
+extern const char *signature;
+
 /* vi: set ts=4 sw=4 expandtab: */
 
 #ifdef __cplusplus

src/video/SDL_video.c

@@ -3846,9 +3846,12 @@ SDL_IsScreenKeyboardShown(SDL_Window *window)
 #if SDL_VIDEO_DRIVER_X11
 #include "x11/SDL_x11messagebox.h"
 #endif
+#if SDL_VIDEO_DRIVER_HAIKU
+#include "haiku/SDL_bmessagebox.h"
+#endif
 
 
-#if SDL_VIDEO_DRIVER_WINDOWS || SDL_VIDEO_DRIVER_WINRT || SDL_VIDEO_DRIVER_COCOA || SDL_VIDEO_DRIVER_UIKIT || SDL_VIDEO_DRIVER_X11
+#if SDL_VIDEO_DRIVER_WINDOWS || SDL_VIDEO_DRIVER_WINRT || SDL_VIDEO_DRIVER_COCOA || SDL_VIDEO_DRIVER_UIKIT || SDL_VIDEO_DRIVER_X11 || SDL_VIDEO_DRIVER_HAIKU
 static SDL_bool SDL_MessageboxValidForDriver(const SDL_MessageBoxData *messageboxdata, SDL_SYSWM_TYPE drivertype)
 {
     SDL_SysWMinfo info;
@@ -3940,6 +3943,13 @@ SDL_ShowMessageBox(const SDL_MessageBoxData *messageboxdata, int *buttonid)
         X11_ShowMessageBox(messageboxdata, buttonid) == 0) {
         retval = 0;
     }
+#endif
+#if SDL_VIDEO_DRIVER_HAIKU
+    if (retval == -1 &&
+        SDL_MessageboxValidForDriver(messageboxdata, SDL_SYSWM_HAIKU) &&
+        BE_ShowMessageBox(messageboxdata, buttonid) == 0) {
+        retval = 0;
+    }
 #endif
     if (retval == -1) {
         SDL_SetError("No message system available");