Add CAIRO_INTERNAL_SURFACE_TYPE_NULL and cairo_nul_surface_create()

It creates a surface that does nothing.  This can be used with
cairo-analysis-surface, to compute bounds of cairo drawings without doing any
actual drawings.

3 files changed, 61 insertions, 1 deletions

diff --git a/src/cairo-analysis-surface-private.h b/src/cairo-analysis-surface-private.h
index dff8a873..b756a4b5 100644
--- a/src/cairo-analysis-surface-private.h
+++ b/src/cairo-analysis-surface-private.h
@@ -66,4 +66,8 @@ cairo_private void
 _cairo_analysis_surface_get_bounding_box (cairo_surface_t *surface,
 					  cairo_box_t     *bbox);
 
+
+cairo_private cairo_surface_t *
+_cairo_null_surface_create (cairo_content_t content);
+
 #endif /* CAIRO_ANALYSIS_SURFACE_H */
diff --git a/src/cairo-analysis-surface.c b/src/cairo-analysis-surface.c
index 2dc149d4..ad1ca3c9 100644
--- a/src/cairo-analysis-surface.c
+++ b/src/cairo-analysis-surface.c
@@ -748,3 +748,58 @@ _cairo_analysis_surface_get_bounding_box (cairo_surface_t *abstract_surface,
 
     *bbox = surface->page_bbox;
 }
+
+/* null surface type: a surface that does nothing (has no side effects, yay!) */
+
+static cairo_int_status_t
+_return_success (void)
+{
+    return CAIRO_STATUS_SUCCESS;
+}
+
+static const cairo_surface_backend_t cairo_null_surface_backend = {
+    CAIRO_INTERNAL_SURFACE_TYPE_NULL,
+
+    NULL, /* create_similar */
+    NULL, /* finish */
+    NULL, /* acquire_source_image */
+    NULL, /* release_source_image */
+    NULL, /* acquire_dest_image */
+    NULL, /* release_dest_image */
+    NULL, /* clone_similar */
+    NULL, /* composite */
+    NULL, /* fill_rectangles */
+    NULL, /* composite_trapezoids */
+    NULL, /* copy_page */
+    NULL, /* show_page */
+    _return_success, /* set_clip_region */
+    NULL, /* intersect_clip_path */
+    NULL, /* get_extents */
+    NULL, /* old_show_glyphs */
+    NULL, /* get_font_options */
+    NULL, /* flush */
+    NULL, /* mark_dirty_rectangle */
+    NULL, /* scaled_font_fini */
+    NULL, /* scaled_glyph_fini */
+    _return_success, /* paint */
+    _return_success, /* mask */
+    _return_success, /* stroke */
+    _return_success, /* fill */
+    _return_success, /* show_glyphs */
+    NULL  /* snapshot */
+};
+
+cairo_surface_t *
+_cairo_null_surface_create (cairo_content_t content)
+{
+    cairo_surface_t *surface;
+
+    surface = malloc (sizeof (cairo_surface_t));
+    if (surface == NULL) {
+	return _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_NO_MEMORY));
+    }
+
+    _cairo_surface_init (surface, &cairo_null_surface_backend, content);
+
+    return surface;
+}
diff --git a/src/cairo-types-private.h b/src/cairo-types-private.h
index 64f09b9f..45c158bf 100644
--- a/src/cairo-types-private.h
+++ b/src/cairo-types-private.h
@@ -148,7 +148,8 @@ typedef enum _cairo_internal_surface_type {
     CAIRO_INTERNAL_SURFACE_TYPE_ANALYSIS,
     CAIRO_INTERNAL_SURFACE_TYPE_TEST_META,
     CAIRO_INTERNAL_SURFACE_TYPE_TEST_FALLBACK,
-    CAIRO_INTERNAL_SURFACE_TYPE_TEST_PAGINATED
+    CAIRO_INTERNAL_SURFACE_TYPE_TEST_PAGINATED,
+    CAIRO_INTERNAL_SURFACE_TYPE_NULL
 } cairo_internal_surface_type_t;
 
 typedef struct _cairo_region cairo_region_t;