Replace of (id->lib != NULL) check by meaningful macro.

Idea is to replace hard-to-track (id->lib != NULL) 'is linked datablock' check everywhere in Blender
by a macro doing the same thing. This will allow to easily spot those checks in future, and more importantly,
to easily change it (see work done in asset-engine branch).

Note: did not touch to readfile.c, since there most of the time 'id->lib' check actually concerns the pointer,
and not a check whether ID is linked or not. Will have a closer look at it later.

Reviewers: campbellbarton, brecht, sergey

Differential Revision: https://developer.blender.org/D2082

1 files changed, 1 insertions, 1 deletions

diff --git a/source/blender/editors/space_view3d/view3d_fly.c b/source/blender/editors/space_view3d/view3d_fly.c
index 8418cf0980c..31377d0fce8 100644
--- a/source/blender/editors/space_view3d/view3d_fly.c
+++ b/source/blender/editors/space_view3d/view3d_fly.c
@@ -346,7 +346,7 @@ static bool initFlyInfo(bContext *C, FlyInfo *fly, wmOperator *op, const wmEvent
 		fly->rv3d->persp = RV3D_PERSP;
 	}
 
-	if (fly->rv3d->persp == RV3D_CAMOB && fly->v3d->camera->id.lib) {
+	if (fly->rv3d->persp == RV3D_CAMOB && ID_IS_LINKED_DATABLOCK(fly->v3d->camera)) {
 		BKE_report(op->reports, RPT_ERROR, "Cannot fly a camera from an external library");
 		return false;
 	}