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Anim: set Action.idroot when writing blend file, for forward compat

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When writing an Action to a blend file, for forward compatability
reasons the animation data in the first slot is also written to the old
Animato Action storage locations. That way, loading the Action in an
older version of Blender will still at least have that animation data.

However, we overlooked `Action.idroot`, which indicates which ID
type the Action is for, and therefore all Actions have an unspecified
`idroot` when loaded in pre-layered-action versions of Blender.

This PR fixes that by also setting the `idroot` to match the target ID
type of the first slot when writing to disk.

Pull Request: https://projects.blender.org/blender/blender/pulls/133819
This commit is contained in:
Nathan Vegdahl
2025-01-31 10:47:16 +01:00
committed by Nathan Vegdahl
parent 028506712d
commit b166fa46b8
2 changed files with 32 additions and 0 deletions
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8
source/blender/animrig/intern/versioning.cc
View File

@@ -35,6 +35,14 @@ constexpr const char *DEFAULT_VERSIONED_LAYER_NAME = "Legacy Layer";
bool action_is_layered(const bAction &dna_action)
{
/* NOTE: due to how forward-compatibility is handled when writing Actions to
* blend files, it is important that this function does NOT check
* `Action.idroot` as part of its determination of whether this is a layered
* action or not.
*
* See: `action_blend_write()` and `action_blend_read_data()`
*/
const animrig::Action &action = dna_action.wrap();
const bool has_layered_data = action.layer_array_num > 0 || action.slot_array_num > 0;

24
source/blender/blenkernel/intern/action.cc
View File

@@ -511,6 +511,20 @@ static void action_blend_write(BlendWriter *writer, ID *id, const void *id_addre
const animrig::Slot &first_slot = *action.slot(0);
/* The forward-compat animation data we write is for IDs of the type that
* the first slot is intended for. Therefore, the Action should have that
* `idroot` when loaded in old versions of Blender.
*
* Note that if there is no slot, this code will never run and therefore the
* action will be written with `idroot = 0`. Despite that, old
* pre-slotted-action files are still guaranteed to round-trip losslessly,
* because old actions (even when empty) are versioned to have one slot with
* `idtype` set to whatever the old action's `idroot` was. In other words,
* zero-slot actions can only be created via non-legacy features, and
* therefore represent animation data that wasn't purely from old files
* anyway. */
action.idroot = first_slot.idtype;
/* Note: channel group forward-compat data requires that fcurve
* forward-compat legacy data is also written, and vice-versa. Both have
* pointers to each other that won't resolve properly when loaded in older
@@ -531,6 +545,10 @@ static void action_blend_write(BlendWriter *writer, ID *id, const void *id_addre
write_slots(writer, action.slots());
if (do_write_forward_compat) {
/* Set the idroot back to 'unspecified', as it always should be for layered
* Actions. */
action.idroot = 0;
/* The pointers to the first/last FCurve in the `action.curves` have already
* been written as part of the Action struct data, so they can be cleared
* here, such that the code writing legacy fcurves below does nothing (as
@@ -687,6 +705,12 @@ static void action_blend_read_data(BlendDataReader *reader, ID *id)
/* Should never be stored as part of the forward-compatible data in a
* layered action, and thus should always be empty here. */
BLI_assert(BLI_listbase_is_empty(&action.chanbase));
/* Layered actions should always have `idroot == 0`, but when writing an
* action to a blend file `idroot` is typically set otherwise for forward
* compatibility reasons (see `action_blend_write()`). So we set it to zero
* here to put it back as it should be. */
action.idroot = 0;
}
else {
/* Read legacy data. */