Fixed erroneous overwriting of temporary images inside filter effects

diff --git a/src/display/nr-filter-slot.cpp b/src/display/nr-filter-slot.cpp
index e6a78c8c7089c275fc3388f5743a0ae221e8c5a5..0cbf88e02181d12027a24ab0c572872eaf644f01 100644 (file)
--- a/src/display/nr-filter-slot.cpp
+++ b/src/display/nr-filter-slot.cpp
@@ -172,8 +172,18 @@ void FilterSlot::get_final(int slot_nr, NRPixBlock *result) {
 
 void FilterSlot::set(int slot_nr, NRPixBlock *pb)
 {
-    int index = _get_index(slot_nr);
+    /* Unnamed slot is for saving filter primitive results, when parameter
+     * 'result' is not set. Only the filter immediately after this one
+     * can access unnamed results, so we don't have to worry about overwriting
+     * previous results in filter chain. On the other hand, we may not
+     * overwrite any other image with this one, because they might be
+     * accessed later on. */
+    int index = ((slot_nr != NR_FILTER_SLOT_NOT_SET)
+                 ? _get_index(slot_nr)
+                 : _get_index(NR_FILTER_UNNAMED_SLOT));
     assert(index >= 0);
+    // Unnamed slot is only for NR::FilterSlot internal use.
+    assert(slot_nr != NR_FILTER_UNNAMED_SLOT);
     assert(slot_nr == NR_FILTER_SLOT_NOT_SET ||_slot_number[index] == slot_nr);
 
     if (slot_nr == NR_FILTER_SOURCEGRAPHIC || slot_nr == NR_FILTER_BACKGROUNDIMAGE) {
@@ -277,7 +287,8 @@ int FilterSlot::_get_index(int slot_nr)
            slot_nr == NR_FILTER_BACKGROUNDIMAGE ||
            slot_nr == NR_FILTER_BACKGROUNDALPHA ||
            slot_nr == NR_FILTER_FILLPAINT ||
-           slot_nr == NR_FILTER_STROKEPAINT);
+           slot_nr == NR_FILTER_STROKEPAINT ||
+           slot_nr == NR_FILTER_UNNAMED_SLOT);
 
     int index = -1;
     if (slot_nr == NR_FILTER_SLOT_NOT_SET) {

diff --git a/src/display/nr-filter-types.h b/src/display/nr-filter-types.h
index 0997d36f459f6af6007de419fb200d2c79c77d46..ee24840cf7def8ea5b83d80f5dfa8d52a0fda74b 100644 (file)
--- a/src/display/nr-filter-types.h
+++ b/src/display/nr-filter-types.h
@@ -31,8 +31,11 @@ enum FilterSlotType {
     NR_FILTER_BACKGROUNDIMAGE = -4,
     NR_FILTER_BACKGROUNDALPHA = -5,
     NR_FILTER_FILLPAINT = -6,
-    NR_FILTER_STROKEPAINT = -7
+    NR_FILTER_STROKEPAINT = -7,
+    NR_FILTER_UNNAMED_SLOT = -8
 };
+/* Unnamed slot is for NR::FilterSlot internal use. Passing it as
+ * parameter to NR::FilterSlot accessors may have unforeseen consequences. */
 
 } /* namespace NR */