fb: add number to fb_fragment_t

This introduces a stricter coupling and requirement for modules
supplying a fragmenter in their prepare_frame() to only receive
fragments produced by *their* fragmenter at their render_fragment().

When modules don't explicitly perform any fragmenting they can't
really make much use of this number as it will reflect an arbitrary
fragmenting pass's perspective.

But when modules do perform their own frame fragmenting, they can
assume any fragment supplied to their render function will have been
generated by it.  This needs to be enforced a bit in the code.

The current use case is montage using a fragmenter for tiling the
montage in a threaded render.  The fragment numbers map to the
modules to be rendered in the tiles.  As long as modules can assume
their fragmenter will always be what produces their fragments, this
is perfectly fine.

2 files changed, 3 insertions, 0 deletions

diff --git a/src/fb.c b/src/fb.c
index a20fdd3..c37cc04 100644
--- a/src/fb.c
+++ b/src/fb.c
@@ -328,6 +328,7 @@ int fb_fragment_slice_single(const fb_fragment_t *fragment, unsigned n_fragments
 	res_fragment->frame_height = fragment->frame_height;
 	res_fragment->stride = fragment->stride;
 	res_fragment->pitch = fragment->pitch;
+	res_fragment->number = num;
 
 	return 1;
 }
@@ -362,6 +363,7 @@ int fb_fragment_tile_single(const fb_fragment_t *fragment, unsigned tile_size, u
 	res_fragment->frame_height = fragment->frame_height;
 	res_fragment->stride = fragment->stride + ((fragment->width - res_fragment->width) * 4);
 	res_fragment->pitch = fragment->pitch;
+	res_fragment->number = num;
 
 	return 1;
 }
diff --git a/src/fb.h b/src/fb.h
index dfd4550..300c134 100644
--- a/src/fb.h
+++ b/src/fb.h
@@ -18,6 +18,7 @@ typedef struct fb_fragment_t {
 	unsigned	frame_height;	/* height of the frame this fragment is part of */
 	unsigned	stride;		/* number of bytes from the end of one row to the start of the next */
 	unsigned	pitch;		/* number of bytes separating y from y + 1, including any padding */
+	unsigned	number;		/* this fragment's number as produced by fragmenting */
 } fb_fragment_t;
 
 /* This is a page handle object for page flip submission/life-cycle.