Gizmo: add invoke_prepare callback

Allows gizmo groups to set values based on the gizmo about to be invoked.

source/blender/makesrna/intern/rna_wm_gizmo.c

@@ -719,6 +719,25 @@ static void rna_gizmogroup_draw_prepare_cb(const bContext *C, wmGizmoGroup *gzgr
 	RNA_parameter_list_free(&list);
 }
 
+static void rna_gizmogroup_invoke_prepare_cb(const bContext *C, wmGizmoGroup *gzgroup, wmGizmo *gz)
+{
+	extern FunctionRNA rna_GizmoGroup_invoke_prepare_func;
+
+	PointerRNA gzgroup_ptr;
+	ParameterList list;
+	FunctionRNA *func;
+
+	RNA_pointer_create(NULL, gzgroup->type->ext.srna, gzgroup, &gzgroup_ptr);
+	func = &rna_GizmoGroup_invoke_prepare_func; /* RNA_struct_find_function(&wgroupr, "invoke_prepare"); */
+
+	RNA_parameter_list_create(&list, &gzgroup_ptr, func);
+	RNA_parameter_set_lookup(&list, "context", &C);
+	RNA_parameter_set_lookup(&list, "gizmo", &gz);
+	gzgroup->type->ext.call((bContext *)C, &gzgroup_ptr, func, &list);
+
+	RNA_parameter_list_free(&list);
+}
+
 void BPY_RNA_gizmogroup_wrapper(wmGizmoGroupType *gzgt, void *userdata);
 static void rna_GizmoGroup_unregister(struct Main *bmain, StructRNA *type);
 
@@ -808,6 +827,7 @@ static StructRNA *rna_GizmoGroup_register(
 	dummywgt.setup =            (have_function[2]) ? rna_gizmogroup_setup_cb : NULL;
 	dummywgt.refresh =          (have_function[3]) ? rna_gizmogroup_refresh_cb : NULL;
 	dummywgt.draw_prepare =     (have_function[4]) ? rna_gizmogroup_draw_prepare_cb : NULL;
+	dummywgt.invoke_prepare =   (have_function[5]) ? rna_gizmogroup_invoke_prepare_cb : NULL;
 
 	wmGizmoGroupType *gzgt = WM_gizmogrouptype_append_ptr(
 	        BPY_RNA_gizmogroup_wrapper, (void *)&dummywgt);
@@ -1304,6 +1324,14 @@ static void rna_def_gizmogroup(BlenderRNA *brna)
 	parm = RNA_def_pointer(func, "context", "Context", "", "");
 	RNA_def_parameter_flags(parm, PROP_NEVER_NULL, PARM_REQUIRED);
 
+	func = RNA_def_function(srna, "invoke_prepare", NULL);
+	RNA_def_function_ui_description(func, "Run before invoke");
+	RNA_def_function_flag(func, FUNC_REGISTER_OPTIONAL);
+	parm = RNA_def_pointer(func, "context", "Context", "", "");
+	RNA_def_parameter_flags(parm, PROP_NEVER_NULL, PARM_REQUIRED);
+	parm = RNA_def_pointer(func, "gizmo", "Gizmo", "", "");
+	RNA_def_parameter_flags(parm, PROP_NEVER_NULL, PARM_REQUIRED);
+
 	/* -------------------------------------------------------------------- */
 	/* Instance Variables */
 

source/blender/windowmanager/gizmo/WM_gizmo_types.h

@@ -372,6 +372,8 @@ typedef struct wmGizmoGroupType {
 	wmGizmoGroupFnRefresh refresh;
 	/* refresh data for drawing, called before each redraw */
 	wmGizmoGroupFnDrawPrepare draw_prepare;
+	/* Initialize data for before invoke. */
+	wmGizmoGroupFnInvokePrepare invoke_prepare;
 
 	/* Keymap init callback for this gizmo-group (optional),
 	 * will fall back to default tweak keymap when left NULL. */

source/blender/windowmanager/gizmo/intern/wm_gizmo_group.c

@@ -381,6 +381,9 @@ static bool gizmo_tweak_start_and_finish(
 			}
 		}
 		else {
+			if (gz->parent_gzgroup->type->invoke_prepare) {
+				gz->parent_gzgroup->type->invoke_prepare(C, gz->parent_gzgroup, gz);
+			}
 			/* Allow for 'button' gizmos, single click to run an action. */
 			WM_operator_name_call_ptr(C, mpop->type, WM_OP_INVOKE_DEFAULT, &mpop->ptr);
 		}

source/blender/windowmanager/gizmo/intern/wm_gizmo_map.c

@@ -948,6 +948,9 @@ void wm_gizmomap_modal_set(
 		if (gz->type->invoke &&
 		    (gz->type->modal || gz->custom_modal))
 		{
+			if (gz->parent_gzgroup->type->invoke_prepare) {
+				gz->parent_gzgroup->type->invoke_prepare(C, gz->parent_gzgroup, gz);
+			}
 			const int retval = gz->type->invoke(C, gz, event);
 			if ((retval & OPERATOR_RUNNING_MODAL) == 0) {
 				return;

source/blender/windowmanager/gizmo/wm_gizmo_fn.h

@@ -39,6 +39,8 @@ typedef void (*wmGizmoGroupFnRefresh)(
         const struct bContext *, struct wmGizmoGroup *);
 typedef void (*wmGizmoGroupFnDrawPrepare)(
         const struct bContext *, struct wmGizmoGroup *);
+typedef void (*wmGizmoGroupFnInvokePrepare)(
+        const struct bContext *, struct wmGizmoGroup *, struct wmGizmo *);
 typedef struct wmKeyMap *(*wmGizmoGroupFnSetupKeymap)(
         const struct wmGizmoGroupType *, struct wmKeyConfig *)
         ATTR_WARN_UNUSED_RESULT;