More common video code

* Provide new function to get current common framebuffer
    * Migrates non-X11 video_setpage routine

src/video/video.h

@@ -97,8 +97,8 @@ void video_loadfont_int(int first, int qty, const unsigned char *data);
  */
 void video_plotchar(int row, int col, int color, unsigned char code);
 
-/* Called at about 30Hz (this may change in future), and when waiting in
- * the interface screens.
+/*
+ * Draws video and possibly handles keyboard input.
  *
  * Should flush any video data to the real screen (if any kind of caching
  * is in use), check for keyboard input (presently reported via
@@ -108,6 +108,11 @@ void video_sync(int block);
 
 void video_set_mode(a2_video_mode_t mode);
 
+/*
+ * Get a reference to current internal framebuffer
+ */
+const uint8_t * const video_current_framebuffer();
+
 #endif /* !__ASSEMBLER__ */
 
 /**** Private stuff follows *****/

src/video/xvideo.c

@@ -67,14 +67,6 @@ typedef struct {
     unsigned long status;
 } FullScreenHints;
 
-/* -------------------------------------------------------------------------
-    video_setpage(p):    Switch to screen page p
-   ------------------------------------------------------------------------- */
-void video_setpage(int p)
-{
-    video__current_page = p;
-}
-
 #ifdef HAVE_X11_SHM
 /*
  * XShm code influenced from the DOOM source code.

src/vidsup.c

@@ -724,3 +724,15 @@ void video_shutdown(void)
 #endif
 }
 
+/* -------------------------------------------------------------------------
+    video_setpage(p):    Switch to screen page p
+   ------------------------------------------------------------------------- */
+void video_setpage(int p)
+{
+    video__current_page = p;
+}
+
+const uint8_t * const video_current_framebuffer() {
+    return !video__current_page ? video__fb1 : video__fb2;
+}
+