Cleanup: Use enum for return values in context callbacks

Define enum `eContextResult` and use its values for returns, instead of
just returning 1, 0, or -1 (and always having some comment that explains
what -1 means).

This also cleans up the mixup between returning `0` and `false`, and `1`
and `true`. An inconsistency was discovered during this cleanup, and
marked with `TODO(sybren)`. It's not fixed here, as it would consititute
a functional change.

The enum isn't used everywhere, as enums in C and C++ can have different
storage sizes. To prevent issues, callback functions are still declared
as returning`int`. To at least make things easier to understand for
humans, I marked those with `int /*eContextResult*/`.

This is a followup of D9090, and is intended to unify how context
callbacks return values. This will make it easier to extend the approach
in D9090 to those functions.

No functional changes.

Differential Revision: https://developer.blender.org/D9095

1 files changed, 4 insertions, 2 deletions

diff --git a/source/blender/blenkernel/BKE_screen.h b/source/blender/blenkernel/BKE_screen.h
index bcc58ecf2c5..35a3d0415a8 100644
--- a/source/blender/blenkernel/BKE_screen.h
+++ b/source/blender/blenkernel/BKE_screen.h
@@ -26,6 +26,8 @@
 
 #include "RNA_types.h"
 
+#include "BKE_context.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -106,7 +108,7 @@ typedef struct SpaceType {
   void (*gizmos)(void);
 
   /* return context data */
-  int (*context)(const struct bContext *C, const char *member, struct bContextDataResult *result);
+  bContextDataCallback context;
 
   /* Used when we want to replace an ID by another (or NULL). */
   void (*id_remap)(struct ScrArea *area,
@@ -181,7 +183,7 @@ typedef struct ARegionType {
   void (*cursor)(struct wmWindow *win, struct ScrArea *area, struct ARegion *region);
 
   /* return context data */
-  int (*context)(const struct bContext *C, const char *member, struct bContextDataResult *result);
+  bContextDataCallback context;
 
   /* Is called whenever the current visible View2D's region changes.
    *