Asset System: Various changes to previews in preparation for Asset Browser

* Support defining (not necessarily rendering) icons in threads. Needed so the
  File Browser can expose file previews with an icon-id to scripts.
** For that, ported `icons.c` to C++, to be able to use scope based mutex locks
   (cleaner & safer code). Had to do some cleanups and minor refactoring for
   that.
* Added support for ImBuf icons, as a decent way for icons to hold the file
  preview buffers.
* Tag previews as "unfinished" while they render in a thread, for the File
  Browser to dynamically load previews as they get finished.
* Better handle cases where threaded preview generation is requested, but the
  ID type doesn't support it (fallback to single threaded). This is for general
  sanity of the code (as in, safety and cleanness)
* Enabled asset notifier for custom preview loading operator, was just disabled
  because `NC_ASSET` wasn't defined in master yet.

Part of the first Asset Browser milestone. Check the #asset_browser_milestone_1
project milestone on developer.blender.org.

Differential Revision: https://developer.blender.org/D9719

Reviewed by: Bastien Montagne, Brecht Van Lommel

1 files changed, 24 insertions, 1 deletions

diff --git a/source/blender/blenkernel/BKE_icons.h b/source/blender/blenkernel/BKE_icons.h
index cb2755d8706..5ceba4c717f 100644
--- a/source/blender/blenkernel/BKE_icons.h
+++ b/source/blender/blenkernel/BKE_icons.h
@@ -23,17 +23,26 @@
  * \ingroup bke
  *
  * Resizable Icons for Blender
+ *
+ * There is some thread safety for this API but it is rather weak. Registering or unregistering
+ * icons is thread safe, changing data of icons from multiple threads is not. Practically this
+ * should be fine since only the main thread modifies icons. Should that change, more locks or a
+ * different design need to be introduced.
  */
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+#include "BLI_compiler_attrs.h"
+
 typedef void (*DrawInfoFreeFP)(void *drawinfo);
 
 enum {
   /** ID preview: obj is #ID. */
   ICON_DATA_ID = 0,
+  /** Arbitrary Image buffer: obj is #ImBuf */
+  ICON_DATA_IMBUF,
   /** Preview: obj is #PreviewImage */
   ICON_DATA_PREVIEW,
   /** 2D triangles: obj is #Icon_Geom */
@@ -44,6 +53,9 @@ enum {
   ICON_DATA_GPLAYER,
 };
 
+/**
+ * \note See comment at the top regarding thread safety.
+ */
 struct Icon {
   void *drawinfo;
   /**
@@ -93,6 +105,9 @@ int BKE_icon_gplayer_color_ensure(struct bGPDlayer *gpl);
 
 int BKE_icon_preview_ensure(struct ID *id, struct PreviewImage *preview);
 
+int BKE_icon_imbuf_create(struct ImBuf *ibuf) ATTR_WARN_UNUSED_RESULT;
+struct ImBuf *BKE_icon_imbuf_get_buffer(int icon_id) ATTR_WARN_UNUSED_RESULT;
+
 /* retrieve icon for id */
 struct Icon *BKE_icon_get(const int icon_id);
 
@@ -131,6 +146,9 @@ void BKE_previewimg_clear_single(struct PreviewImage *prv, enum eIconSizes size)
 struct PreviewImage **BKE_previewimg_id_get_p(const struct ID *id);
 struct PreviewImage *BKE_previewimg_id_get(const struct ID *id);
 
+void BKE_previewimg_id_custom_set(struct ID *id, const char *path);
+
+bool BKE_previewimg_id_supports_jobs(const struct ID *id);
 
 /* Trigger deferred loading of a custom image file into the preview buffer. */
 void BKE_previewimg_id_custom_set(struct ID *id, const char *path);
@@ -151,6 +169,11 @@ struct PreviewImage *BKE_previewimg_id_ensure(struct ID *id);
 
 void BKE_previewimg_ensure(struct PreviewImage *prv, const int size);
 
+struct ImBuf *BKE_previewimg_to_imbuf(struct PreviewImage *prv, const int size);
+
+void BKE_previewimg_finish(struct PreviewImage *prv, const int size);
+bool BKE_previewimg_is_finished(const struct PreviewImage *prv, const int size);
+
 struct PreviewImage *BKE_previewimg_cached_get(const char *name);
 
 struct PreviewImage *BKE_previewimg_cached_ensure(const char *name);
@@ -168,7 +191,7 @@ void BKE_previewimg_blend_write(struct BlendWriter *writer, const struct Preview
 void BKE_previewimg_blend_read(struct BlendDataReader *reader, struct PreviewImage *prv);
 
 int BKE_icon_geom_ensure(struct Icon_Geom *geom);
-struct Icon_Geom *BKE_icon_geom_from_memory(const uchar *data, size_t data_len);
+struct Icon_Geom *BKE_icon_geom_from_memory(uchar *data, size_t data_len);
 struct Icon_Geom *BKE_icon_geom_from_file(const char *filename);
 
 struct ImBuf *BKE_icon_geom_rasterize(const struct Icon_Geom *geom,