From 68435c2aa880d15575e4eccbe7670439c23f97d0 Mon Sep 17 00:00:00 2001
From: Harry Jeffery <harry@exec64.co.uk>
Date: Thu, 17 Jan 2019 01:04:15 +0000
Subject: Define sources & backends

---
 src/backend.h | 30 ++++++++++++++++++++++++++++++
 src/source.h  | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 79 insertions(+)
 create mode 100644 src/backend.h
 create mode 100644 src/source.h

diff --git a/src/backend.h b/src/backend.h
new file mode 100644
index 0000000..0da2244
--- /dev/null
+++ b/src/backend.h
@@ -0,0 +1,30 @@
+#ifndef IMV_BACKEND_H
+#define IMV_BACKEND_H
+
+struct imv_source;
+
+enum backend_result {
+  BACKEND_SUCCESS = 0, /* successful load */
+  BACKEND_BAD_PATH = 1, /* no such file, bad permissions, etc. */
+  BACKEND_UNSUPPORTED = 2, /* unsupported file format */
+};
+
+/* A backend is responsible for taking a path, or a raw data pointer, and
+ * converting that into a source that imv can handle. Each backend
+ * may be powered by a different image library and support different
+ * image formats.
+ */
+struct imv_backend {
+  /* Name of the backend, for debug and user informational purposes */
+  const char *name;
+
+  /* Input: path to open
+   * Output: initialises the imv_source instance passed in
+   */
+  enum backend_result (*open_path)(const char *path, struct imv_source **src);
+
+  /* Clean up this backend */
+  void (*free)(struct imv_backend *backend);
+};
+
+#endif
diff --git a/src/source.h b/src/source.h
new file mode 100644
index 0000000..6f051e3
--- /dev/null
+++ b/src/source.h
@@ -0,0 +1,49 @@
+#ifndef IMV_SOURCE_H
+#define IMV_SOURCE_H
+
+#include <stdbool.h>
+#include "bitmap.h"
+
+/* Generic source of one or more bitmaps. Essentially a single image file */
+struct imv_source {
+  /* usually the path of the image this is the source of */
+  char *name; 
+
+  /* source's image dimensions */
+  int width;
+  int height;
+
+  /* Usually 1, more if animated */
+  int num_frames;
+
+  /* Frames are returned using SDL events. These two fields must be
+   * populated by callers before calling any frame loading functionality
+   * on the source.
+   */
+  unsigned int image_event_id;
+  unsigned int error_event_id;
+
+  /* Trigger loading of the first frame. */
+  void (*load_first_frame)(struct imv_source *src); 
+
+  /* Trigger loading of next frame.  */
+  void (*load_next_frame)(struct imv_source *src); 
+
+  /* Notify source of time passing, automatically triggers loading of
+   * the next frame when due. */
+  void (*time_passed)(struct imv_source *src, double dt); 
+
+  /* Asks the source how long we can sleep for before the next frame is due */
+  double (*time_left)(struct imv_source *src);
+
+  /* Safely free contents of this source. After this returns
+   * it is safe to dealocate/overwrite the imv_source instance.
+   */
+  void (*free)(struct imv_source *src);
+
+  /* Implementation private data */
+  void *private;
+};
+
+
+#endif
-- 
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