libstage: expose struct stage_t size publiclypublic-size

The existing stage.h has been renamed to stage-public.h, and stage.h
is now generated as part of the build.

The generated stage.h now declares a padded struct stage_t after
including the original stage.h as stage-public.h.

The real struct stage_t has moved out of stage.c into stage-private.h,
which is very similar to the generated stage.h but declares a the real
struct stage_t instaed of the padded one.  The internal code while
building libstage.a simply includes stage-private.h to get the real
struct and everything from stage-public.h.

My main annoyance with this approach is it leaves stage.h and
libstage.a in @top_builddir@/src, but stage-public.h at
@top_srcdir@/src.  I generally use this library in a vendored form,
without performing any `make install` step.  Currently, when I use it,
my outer autotools project vendoring this library adds
-I@top_srcdir@/libstage/src to get the headers, and it looks like it
will need to *add* -I@top_builddir@/libstage/src to get the generated
stage.h while keeping the -I@top_srcdir@/libstage/src for
stage-public.h.

Sigh, there's probably a simple way to make the build simply copy
the stage-public.h to @top_builddir@/src.  I made some experiments
with that, and at least when using the same filename, it seemed to
get confused because the file existed in @top_srcdir@/src despite
being in BUILT_SOURCES and CLEANFILES, and it tended to clobber
the copy in @top_srcdir@/src.  Leaving that as a TODO for a future
day.

4 files changed, 38 insertions, 22 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index de38d5f..400a0fb 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -1,3 +1,14 @@
 noinst_LIBRARIES = libstage.a
-libstage_a_SOURCES = ../include/dll_h/dll.h stage.c stage.h
+noinst_PROGRAMS = stage-header
+
+libstage_a_SOURCES = ../include/dll_h/dll.h stage-private.h stage-public.h stage.c
 libstage_a_CPPFLAGS = -I@top_srcdir@/include
+
+stage_header_SOURCES = ../include/dll_h/dll.h stage-private.h stage-header.c
+stage_header_CPPFLAGS = -I@top_srcdir@/include
+
+BUILT_SOURCES = stage.h
+CLEANFILES = stage.h
+
+stage.h: Makefile stage-header
+	@top_builddir@/src/stage-header >$@
diff --git a/src/stage-private.h b/src/stage-private.h
new file mode 100644
index 0000000..ac045a4
--- /dev/null
+++ b/src/stage-private.h
@@ -0,0 +1,23 @@
+#ifndef _STAGE_PRIVATE_H
+#define _STAGE_PRIVATE_H
+
+#include <dll_h/dll.h>
+
+#include "stage-public.h"
+
+struct stage_t {
+       stage_t                 *parent;        /* NULL when root stage */
+       dll_t                   layer;          /* node on parent->layers[layer] when parent != NULL */
+       dll_t                   layers[STAGE_LAYERS_MAX];
+       char                    name[STAGE_NAME_MAX];
+       float                   alpha;          /* alpha for the stage */
+       unsigned                active:1;       /* stage is active */
+       unsigned                locked:1;       /* stage is locked */
+       unsigned                dirty:1;        /* stage is dirty (since last render) */
+       unsigned                allocated:1;    /* stage is allocated by libstage, needs freeing. */
+
+       const stage_ops_t       *ops;           /* ops for operating on this stage's object */
+       void                    *object;        /* this stage's object */
+};
+
+#endif
diff --git a/src/stage.h b/src/stage-public.h
index 40f2057..d7bd4fe 100644
--- a/src/stage.h
+++ b/src/stage-public.h
@@ -14,8 +14,8 @@
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-#ifndef _STAGE_H
-#define _STAGE_H
+#ifndef _STAGE_PUBLIC_H
+#define _STAGE_PUBLIC_H
 
 #define STAGE_NAME_MAX		16
 #define STAGE_LAYERS_MAX	10
diff --git a/src/stage.c b/src/stage.c
index a714f1f..106186e 100644
--- a/src/stage.c
+++ b/src/stage.c
@@ -18,25 +18,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include <dll_h/dll.h>
-
-#include "stage.h"
-
-
-struct stage_t {
-	stage_t			*parent;	/* NULL when root stage */
-	dll_t			layer;		/* node on parent->layers[layer] when parent != NULL */
-	dll_t			layers[STAGE_LAYERS_MAX];
-	char			name[STAGE_NAME_MAX];
-	float			alpha;		/* alpha for the stage */
-	unsigned		active:1;	/* stage is active */
-	unsigned		locked:1;	/* stage is locked */
-	unsigned		dirty:1;	/* stage is dirty (since last render) */
-	unsigned		allocated:1;	/* stage is allocated by libstage, needs freeing. */
-
-	const stage_ops_t	*ops;		/* ops for operating on this stage's object */
-	void			*object;	/* this stage's object */
-};
+#include "stage-private.h"
 
 
 /* minimally initialize a stage to carry an object */