Add terminal hook query_frame_background_color

* src/termhooks.c (query_frame_background_color): New terminal hook.

* src/image.c (image_query_frame_background_color): Remove. Use the
terminal hook instead.

* src/nsterm.m:
* src/w32term.c:
* src/xterm.c: Implement and set the new terminal hook.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/termhooks.h b/src/termhooks.h
index fbc37261330..54f09e03033 100644
--- a/src/termhooks.h
+++ b/src/termhooks.h
@@ -513,6 +513,10 @@ struct terminal
 
    */
 
+  /* This hook is called to store the frame's background color into
+     BGCOLOR.  */
+  void (*query_frame_background_color) (struct frame *f, XColor *bgcolor);
+
 #if defined (HAVE_X_WINDOWS) || defined (HAVE_NTGUI)
   /* On frame F, translate pixel colors to RGB values for the NCOLORS
      colors in COLORS.  Use cached information, if available.  */