Drivers: ensure Python expressions are cached with copy-on-write.

Store the compiled expressions on the original driver.

Ref T55442.

3 files changed, 14 insertions, 11 deletions

diff --git a/source/blender/blenkernel/BKE_fcurve.h b/source/blender/blenkernel/BKE_fcurve.h
index 09f5ecce050..dbe325b2056 100644
--- a/source/blender/blenkernel/BKE_fcurve.h
+++ b/source/blender/blenkernel/BKE_fcurve.h
@@ -108,7 +108,8 @@ bool  driver_get_variable_property(
         struct ChannelDriver *driver, struct DriverTarget *dtar,
         struct PointerRNA *r_ptr, struct PropertyRNA **r_prop, int *r_index);
 
-float evaluate_driver(struct PathResolvedRNA *anim_rna, struct ChannelDriver *driver, const float evaltime);
+float evaluate_driver(struct PathResolvedRNA *anim_rna, struct ChannelDriver *driver,
+                      struct ChannelDriver *driver_orig, const float evaltime);
 
 /* ************** F-Curve Modifiers *************** */
 
@@ -282,7 +283,8 @@ void correct_bezpart(float v1[2], float v2[2], float v3[2], float v4[2]);
 
 /* evaluate fcurve */
 float evaluate_fcurve(struct FCurve *fcu, float evaltime);
-float evaluate_fcurve_driver(struct PathResolvedRNA *anim_rna, struct FCurve *fcu, float evaltime);
+float evaluate_fcurve_driver(struct PathResolvedRNA *anim_rna, struct FCurve *fcu,
+                             struct ChannelDriver *driver_orig, float evaltime);
 /* evaluate fcurve and store value */
 float calculate_fcurve(struct PathResolvedRNA *anim_rna, struct FCurve *fcu, float evaltime);
 
diff --git a/source/blender/blenkernel/intern/anim_sys.c b/source/blender/blenkernel/intern/anim_sys.c
index e5a68fa7476..0867170611f 100644
--- a/source/blender/blenkernel/intern/anim_sys.c
+++ b/source/blender/blenkernel/intern/anim_sys.c
@@ -3017,7 +3017,7 @@ void BKE_animsys_eval_driver(Depsgraph *depsgraph,
 			PathResolvedRNA anim_rna;
 			if (animsys_store_rna_setting(&id_ptr, NULL, fcu->rna_path, fcu->array_index, &anim_rna)) {
 				const float ctime = DEG_get_ctime(depsgraph);
-				const float curval = calculate_fcurve(&anim_rna, fcu, ctime);
+				const float curval = evaluate_fcurve_driver(&anim_rna, fcu, driver_orig, ctime);
 				ok = animsys_write_rna_setting(&anim_rna, curval);
 				if (ok && DEG_is_active(depsgraph)) {
 					animsys_write_orig_anim_rna(&id_ptr, NULL, fcu, curval);
diff --git a/source/blender/blenkernel/intern/fcurve.c b/source/blender/blenkernel/intern/fcurve.c
index 0de04e31be9..0ffc9054ddd 100644
--- a/source/blender/blenkernel/intern/fcurve.c
+++ b/source/blender/blenkernel/intern/fcurve.c
@@ -1922,13 +1922,14 @@ float driver_get_variable_value(ChannelDriver *driver, DriverVar *dvar)
 /* Evaluate an Channel-Driver to get a 'time' value to use instead of "evaltime"
  *	- "evaltime" is the frame at which F-Curve is being evaluated
  *  - has to return a float value
+ *  - driver_orig is where we cache Python expressions, in case of COW
  */
-float evaluate_driver(PathResolvedRNA *anim_rna, ChannelDriver *driver, const float evaltime)
+float evaluate_driver(PathResolvedRNA *anim_rna, ChannelDriver *driver, ChannelDriver *driver_orig, const float evaltime)
 {
 	DriverVar *dvar;
 	
 	/* check if driver can be evaluated */
-	if (driver->flag & DRIVER_FLAG_INVALID)
+	if (driver_orig->flag & DRIVER_FLAG_INVALID)
 		return 0.0f;
 	
 	switch (driver->type) {
@@ -1998,8 +1999,8 @@ float evaluate_driver(PathResolvedRNA *anim_rna, ChannelDriver *driver, const fl
 		{
 #ifdef WITH_PYTHON
 			/* check for empty or invalid expression */
-			if ( (driver->expression[0] == '\0') ||
-			     (driver->flag & DRIVER_FLAG_INVALID) )
+			if ( (driver_orig->expression[0] == '\0') ||
+			     (driver_orig->flag & DRIVER_FLAG_INVALID) )
 			{
 				driver->curval = 0.0f;
 			}
@@ -2009,7 +2010,7 @@ float evaluate_driver(PathResolvedRNA *anim_rna, ChannelDriver *driver, const fl
 				 */
 				BLI_mutex_lock(&python_driver_lock);
 
-				driver->curval = BPY_driver_exec(anim_rna, driver, evaltime);
+				driver->curval = BPY_driver_exec(anim_rna, driver, driver_orig, evaltime);
 
 				BLI_mutex_unlock(&python_driver_lock);
 			}
@@ -2705,7 +2706,7 @@ float evaluate_fcurve(FCurve *fcu, float evaltime)
 	return evaluate_fcurve_ex(fcu, evaltime, 0.0);
 }
 
-float evaluate_fcurve_driver(PathResolvedRNA *anim_rna, FCurve *fcu, float evaltime)
+float evaluate_fcurve_driver(PathResolvedRNA *anim_rna, FCurve *fcu, ChannelDriver *driver_orig, float evaltime)
 {
 	BLI_assert(fcu->driver != NULL);
 	float cvalue = 0.0f;
@@ -2715,7 +2716,7 @@ float evaluate_fcurve_driver(PathResolvedRNA *anim_rna, FCurve *fcu, float evalt
 	 */
 	if (fcu->driver) {
 		/* evaltime now serves as input for the curve */
-		evaltime = evaluate_driver(anim_rna, fcu->driver, evaltime);
+		evaltime = evaluate_driver(anim_rna, fcu->driver, driver_orig, evaltime);
 
 		/* only do a default 1-1 mapping if it's unlikely that anything else will set a value... */
 		if (fcu->totvert == 0) {
@@ -2762,7 +2763,7 @@ float calculate_fcurve(PathResolvedRNA *anim_rna, FCurve *fcu, float evaltime)
 		/* calculate and set curval (evaluates driver too if necessary) */
 		float curval;
 		if (fcu->driver) {
-			curval = evaluate_fcurve_driver(anim_rna, fcu, evaltime);
+			curval = evaluate_fcurve_driver(anim_rna, fcu, fcu->driver, evaltime);
 		}
 		else {
 			curval = evaluate_fcurve(fcu, evaltime);