From 47f98a38d0f8a83648c13a54adc717d49d0898f1 Mon Sep 17 00:00:00 2001
From: Richard Antalik <richardantalik@gmail.com>
Date: Thu, 18 Jun 2020 05:25:20 +0200
Subject: VSE: Fix assigning effect strip inputs

Partialy fixes T73828

Currently all 3 effect inputs were assigned even if not all 3 were used.
This causes problems with reassigning effects in python, because 3rd input is
not accessible.

This patch will only assign inputs that are necessary for effect to work
properly.

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D6868
---
 source/blender/blenkernel/intern/sequencer.c       | 40 +++++++++-------------
 .../editors/space_sequencer/sequencer_edit.c       | 13 +++++++
 2 files changed, 29 insertions(+), 24 deletions(-)

diff --git a/source/blender/blenkernel/intern/sequencer.c b/source/blender/blenkernel/intern/sequencer.c
index 019d4fff0e5..7ec4797a998 100644
--- a/source/blender/blenkernel/intern/sequencer.c
+++ b/source/blender/blenkernel/intern/sequencer.c
@@ -842,30 +842,22 @@ void BKE_sequence_calc(Scene *scene, Sequence *seq)
   }
 
   /* effects and meta: automatic start and end */
-
   if (seq->type & SEQ_TYPE_EFFECT) {
-    /* pointers */
-    if (seq->seq2 == NULL) {
-      seq->seq2 = seq->seq1;
-    }
-    if (seq->seq3 == NULL) {
-      seq->seq3 = seq->seq1;
-    }
-
-    /* effecten go from seq1 -> seq2: test */
-
-    /* we take the largest start and smallest end */
-
-    // seq->start = seq->startdisp = MAX2(seq->seq1->startdisp, seq->seq2->startdisp);
-    // seq->enddisp = MIN2(seq->seq1->enddisp, seq->seq2->enddisp);
-
     if (seq->seq1) {
-      /* XXX These resets should not be necessary, but users used to be able to
-       *     edit effect's length, leading to strange results. See [#29190] */
       seq->startofs = seq->endofs = seq->startstill = seq->endstill = 0;
-      seq->start = seq->startdisp = max_iii(
-          seq->seq1->startdisp, seq->seq2->startdisp, seq->seq3->startdisp);
-      seq->enddisp = min_iii(seq->seq1->enddisp, seq->seq2->enddisp, seq->seq3->enddisp);
+      if (seq->seq3) {
+        seq->start = seq->startdisp = max_iii(
+            seq->seq1->startdisp, seq->seq2->startdisp, seq->seq3->startdisp);
+        seq->enddisp = min_iii(seq->seq1->enddisp, seq->seq2->enddisp, seq->seq3->enddisp);
+      }
+      else if (seq->seq2) {
+        seq->start = seq->startdisp = max_ii(seq->seq1->startdisp, seq->seq2->startdisp);
+        seq->enddisp = min_ii(seq->seq1->enddisp, seq->seq2->enddisp);
+      }
+      else {
+        seq->start = seq->startdisp = seq->seq1->startdisp;
+        seq->enddisp = seq->seq1->enddisp;
+      }
       /* we cant help if strips don't overlap, it wont give useful results.
        * but at least ensure 'len' is never negative which causes bad bugs elsewhere. */
       if (seq->enddisp < seq->startdisp) {
@@ -2949,9 +2941,9 @@ static ImBuf *seq_render_effect_strip_impl(const SeqRenderData *context,
     case EARLY_DO_EFFECT:
       for (i = 0; i < 3; i++) {
         /* Speed effect requires time remapping of cfra for input(s). */
-        if (input[1] && seq->type == SEQ_TYPE_SPEED) {
+        if (input[0] && seq->type == SEQ_TYPE_SPEED) {
           float target_frame = BKE_sequencer_speed_effect_target_frame_get(context, seq, cfra, i);
-          ibuf[i] = seq_render_strip(context, state, input[i], target_frame);
+          ibuf[i] = seq_render_strip(context, state, input[0], target_frame);
         }
         else { /* Other effects. */
           if (input[i]) {
@@ -2960,7 +2952,7 @@ static ImBuf *seq_render_effect_strip_impl(const SeqRenderData *context,
         }
       }
 
-      if (ibuf[0] && ibuf[1]) {
+      if (ibuf[0] && (ibuf[1] || BKE_sequence_effect_get_num_inputs(seq->type) == 1)) {
         if (sh.multithreaded) {
           out = BKE_sequencer_effect_execute_threaded(
               &sh, context, seq, cfra, fac, facf, ibuf[0], ibuf[1], ibuf[2]);
diff --git a/source/blender/editors/space_sequencer/sequencer_edit.c b/source/blender/editors/space_sequencer/sequencer_edit.c
index 4a8bea11b41..cbc4d9e51f1 100644
--- a/source/blender/editors/space_sequencer/sequencer_edit.c
+++ b/source/blender/editors/space_sequencer/sequencer_edit.c
@@ -673,6 +673,14 @@ int seq_effect_find_selected(Scene *scene,
   *r_selseq2 = seq2;
   *r_selseq3 = seq3;
 
+  /* TODO(Richard): This function needs some refactoring, this is just quick hack for T73828. */
+  if (BKE_sequence_effect_get_num_inputs(type) < 3) {
+    *r_selseq3 = NULL;
+  }
+  if (BKE_sequence_effect_get_num_inputs(type) < 2) {
+    *r_selseq2 = NULL;
+  }
+
   return 1;
 }
 
@@ -2222,6 +2230,11 @@ static int sequencer_reassign_inputs_exec(bContext *C, wmOperator *op)
   Sequence *seq1, *seq2, *seq3, *last_seq = BKE_sequencer_active_get(scene);
   const char *error_msg;
 
+  if (BKE_sequence_effect_get_num_inputs(last_seq->type) != 0) {
+    BKE_report(op->reports, RPT_ERROR, "Cannot reassign inputs: strip has no inputs");
+    return OPERATOR_CANCELLED;
+  }
+
   if (!seq_effect_find_selected(
           scene, last_seq, last_seq->type, &seq1, &seq2, &seq3, &error_msg)) {
     BKE_report(op->reports, RPT_ERROR, error_msg);
-- 
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