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

Store the compiled expressions on the original driver.

Ref T55442.

7 files changed, 42 insertions, 39 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);
diff --git a/source/blender/editors/animation/keyframing.c b/source/blender/editors/animation/keyframing.c
index 1913eb944d9..fe5714aba2e 100644
--- a/source/blender/editors/animation/keyframing.c
+++ b/source/blender/editors/animation/keyframing.c
@@ -954,7 +954,7 @@ bool insert_keyframe_direct(Depsgraph *depsgraph, ReportList *reports, PointerRN
 
 		if (RNA_path_resolved_create(&ptr, prop, fcu->array_index, &anim_rna)) {
 			/* for making it easier to add corrective drivers... */
-			cfra = evaluate_driver(&anim_rna, fcu->driver, cfra);
+			cfra = evaluate_driver(&anim_rna, fcu->driver, fcu->driver, cfra);
 		}
 		else {
 			cfra = 0.0f;
diff --git a/source/blender/python/BPY_extern.h b/source/blender/python/BPY_extern.h
index b4c36a7c516..da1b031f1c0 100644
--- a/source/blender/python/BPY_extern.h
+++ b/source/blender/python/BPY_extern.h
@@ -87,7 +87,8 @@ void	BPY_modules_load_user(struct bContext *C);
 void	BPY_app_handlers_reset(const short do_all);
 
 void	BPY_driver_reset(void);
-float	BPY_driver_exec(struct PathResolvedRNA *anim_rna, struct ChannelDriver *driver, const float evaltime);
+float	BPY_driver_exec(struct PathResolvedRNA *anim_rna, struct ChannelDriver *driver,
+                        struct ChannelDriver *driver_orig, const float evaltime);
 
 void	BPY_DECREF(void *pyob_ptr);	/* Py_DECREF() */
 void	BPY_DECREF_RNA_INVALIDATE(void *pyob_ptr);
diff --git a/source/blender/python/intern/bpy_driver.c b/source/blender/python/intern/bpy_driver.c
index 215a64a4449..96bfa9f26d3 100644
--- a/source/blender/python/intern/bpy_driver.c
+++ b/source/blender/python/intern/bpy_driver.c
@@ -48,6 +48,8 @@
 
 #include "bpy_driver.h"
 
+#include "BPY_extern.h"
+
 extern void BPY_update_rna_module(void);
 
 #define USE_RNA_AS_PYOBJECT
@@ -196,8 +198,12 @@ static void pydriver_error(ChannelDriver *driver)
  * (new)note: checking if python is running is not threadsafe [#28114]
  * now release the GIL on python operator execution instead, using
  * PyEval_SaveThread() / PyEval_RestoreThread() so we don't lock up blender.
+ *
+ * For copy-on-write we always cache expressions and write errors in the
+ * original driver, otherwise these would get freed while editing. Due to
+ * the GIL this is thread-safe.
  */
-float BPY_driver_exec(struct PathResolvedRNA *anim_rna, ChannelDriver *driver, const float evaltime)
+float BPY_driver_exec(struct PathResolvedRNA *anim_rna, ChannelDriver *driver, ChannelDriver *driver_orig, const float evaltime)
 {
 	PyObject *driver_vars = NULL;
 	PyObject *retval = NULL;
@@ -213,7 +219,7 @@ float BPY_driver_exec(struct PathResolvedRNA *anim_rna, ChannelDriver *driver, c
 	int i;
 
 	/* get the py expression to be evaluated */
-	expr = driver->expression;
+	expr = driver_orig->expression;
 	if (expr[0] == '\0')
 		return 0.0f;
 
@@ -249,47 +255,47 @@ float BPY_driver_exec(struct PathResolvedRNA *anim_rna, ChannelDriver *driver, c
 	/* update global namespace */
 	bpy_pydriver_namespace_update_frame(evaltime);
 
-	if (driver->flag & DRIVER_FLAG_USE_SELF) {
+	if (driver_orig->flag & DRIVER_FLAG_USE_SELF) {
 		bpy_pydriver_namespace_update_self(anim_rna);
 	}
 	else {
 		bpy_pydriver_namespace_clear_self();
 	}
 
-	if (driver->expr_comp == NULL)
-		driver->flag |= DRIVER_FLAG_RECOMPILE;
+	if (driver_orig->expr_comp == NULL)
+		driver_orig->flag |= DRIVER_FLAG_RECOMPILE;
 
 	/* compile the expression first if it hasn't been compiled or needs to be rebuilt */
-	if (driver->flag & DRIVER_FLAG_RECOMPILE) {
-		Py_XDECREF(driver->expr_comp);
-		driver->expr_comp = PyTuple_New(2);
+	if (driver_orig->flag & DRIVER_FLAG_RECOMPILE) {
+		Py_XDECREF(driver_orig->expr_comp);
+		driver_orig->expr_comp = PyTuple_New(2);
 
 		expr_code = Py_CompileString(expr, "<bpy driver>", Py_eval_input);
-		PyTuple_SET_ITEM(((PyObject *)driver->expr_comp), 0, expr_code);
+		PyTuple_SET_ITEM(((PyObject *)driver_orig->expr_comp), 0, expr_code);
 
-		driver->flag &= ~DRIVER_FLAG_RECOMPILE;
-		driver->flag |= DRIVER_FLAG_RENAMEVAR; /* maybe this can be removed but for now best keep until were sure */
+		driver_orig->flag &= ~DRIVER_FLAG_RECOMPILE;
+		driver_orig->flag |= DRIVER_FLAG_RENAMEVAR; /* maybe this can be removed but for now best keep until were sure */
 	}
 	else {
-		expr_code = PyTuple_GET_ITEM(((PyObject *)driver->expr_comp), 0);
+		expr_code = PyTuple_GET_ITEM(((PyObject *)driver_orig->expr_comp), 0);
 	}
 
-	if (driver->flag & DRIVER_FLAG_RENAMEVAR) {
+	if (driver_orig->flag & DRIVER_FLAG_RENAMEVAR) {
 		/* may not be set */
-		expr_vars = PyTuple_GET_ITEM(((PyObject *)driver->expr_comp), 1);
+		expr_vars = PyTuple_GET_ITEM(((PyObject *)driver_orig->expr_comp), 1);
 		Py_XDECREF(expr_vars);
 
-		expr_vars = PyTuple_New(BLI_listbase_count(&driver->variables));
-		PyTuple_SET_ITEM(((PyObject *)driver->expr_comp), 1, expr_vars);
+		expr_vars = PyTuple_New(BLI_listbase_count(&driver_orig->variables));
+		PyTuple_SET_ITEM(((PyObject *)driver_orig->expr_comp), 1, expr_vars);
 
-		for (dvar = driver->variables.first, i = 0; dvar; dvar = dvar->next) {
+		for (dvar = driver_orig->variables.first, i = 0; dvar; dvar = dvar->next) {
 			PyTuple_SET_ITEM(expr_vars, i++, PyUnicode_FromString(dvar->name));
 		}
 
-		driver->flag &= ~DRIVER_FLAG_RENAMEVAR;
+		driver_orig->flag &= ~DRIVER_FLAG_RENAMEVAR;
 	}
 	else {
-		expr_vars = PyTuple_GET_ITEM(((PyObject *)driver->expr_comp), 1);
+		expr_vars = PyTuple_GET_ITEM(((PyObject *)driver_orig->expr_comp), 1);
 	}
 
 	/* add target values to a dict that will be used as '__locals__' dict */
diff --git a/source/blender/python/intern/bpy_driver.h b/source/blender/python/intern/bpy_driver.h
index 017a6fe89c5..971cbdf901f 100644
--- a/source/blender/python/intern/bpy_driver.h
+++ b/source/blender/python/intern/bpy_driver.h
@@ -27,14 +27,7 @@
 #ifndef __BPY_DRIVER_H__
 #define __BPY_DRIVER_H__
 
-struct ChannelDriver;
-struct PathResolvedRNA;
-
 int bpy_pydriver_create_dict(void);
 extern PyObject *bpy_pydriver_Dict;
 
-/* externals */
-float BPY_driver_exec(struct PathResolvedRNA *anim_rna, struct ChannelDriver *driver, const float evaltime);
-void BPY_driver_reset(void);
-
 #endif  /* __BPY_DRIVER_H__ */