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Cleanup: Improvements to Outliner tree writing code, add assert 

Comments there weren't really helpful, took me a while to get what they
try to say. This attempts to add a better explanation. Also add an
assert for a previous, implicit (but commented) assumption, and some
minor cleanups.
This commit is contained in:
Julian Eisel 2022-08-17 19:20:52 +02:00
parent ecf4a7835d
commit d8223bdc38
1 changed files with 21 additions and 10 deletions
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31
source/blender/blenkernel/intern/screen.c
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@ -1123,32 +1123,43 @@ static void write_uilist(BlendWriter *writer, uiList *ui_list)
}
}
static void write_space_outliner(BlendWriter *writer, SpaceOutliner *space_outliner)
static void write_space_outliner(BlendWriter *writer, const SpaceOutliner *space_outliner)
{
BLI_mempool *ts = space_outliner->treestore;
if (ts) {
int elems = BLI_mempool_len(ts);
const int elems = BLI_mempool_len(ts);
/* linearize mempool to array */
TreeStoreElem *data = elems ? BLI_mempool_as_arrayN(ts, "TreeStoreElem") : NULL;
if (data) {
/* In this block we use the memory location of the treestore
* but _not_ its data, the addresses in this case are UUID's,
* since we can't rely on malloc giving us different values each time.
BLO_write_struct(writer, SpaceOutliner, space_outliner);
/* To store #TreeStore (instead of the mempool), two unique memory addresses are needed,
* which can be used to identify the data on read:
* 1) One for the #TreeStore data itself.
* 2) One for the array of #TreeStoreElem's inside #TreeStore (#TreeStore.data).
*
* For 1) we just use the mempool's address (#SpaceOutliner::treestore).
* For 2) we don't have such a direct choice. We can't just use the array's address from
* above, since that may not be unique over all Outliners. So instead use an address relative
* to 1).
*/
TreeStore ts_flat = {0};
/* TODO the mempool could be moved to #SpaceOutliner_Runtime so that #SpaceOutliner could
* hold the #TreeStore directly. */
/* we know the treestore is at least as big as a pointer,
* so offsetting works to give us a UUID. */
/* Address relative to the tree-store, as noted above. */
void *data_addr = (void *)POINTER_OFFSET(ts, sizeof(void *));
/* There should be plenty of memory addresses within the mempool data that we can point into,
* just double-check we don't potentially end up with a memory address that another DNA
* struct might use. Assumes BLI_mempool uses the guarded allocator. */
BLI_assert(MEM_allocN_len(ts) >= sizeof(void *) * 2);
TreeStore ts_flat = {0};
ts_flat.usedelem = elems;
ts_flat.totelem = elems;
ts_flat.data = data_addr;
BLO_write_struct(writer, SpaceOutliner, space_outliner);
BLO_write_struct_at_address(writer, TreeStore, ts, &ts_flat);
BLO_write_struct_array_at_address(writer, TreeStoreElem, elems, data_addr, data);