Big step forward nodes UI translation:

*Add menu is now translated.
*Nodes' title is now translated.
*Nodes' sockets' labels are now translated.

However, about the last point, and unless I’m mistaking, we’ll have to add the "i18n tag" N_() to all sockets' names, in the input/ouput templates declaration, in all nodes' files, as those sockets are collections created at runtime, I think po-generating script has no way to access that from bpy.types... Quite a piece of (borring) work. :/

source/blender/blenkernel/intern/node.c

@@ -55,6 +55,8 @@
 #include "BLI_path_util.h"
 #include "BLI_utildefines.h"
 
+#include "BLF_translation.h"
+
 #include "BKE_animsys.h"
 #include "BKE_action.h"
 #include "BKE_fcurve.h"
@@ -66,8 +68,6 @@
 #include "BKE_utildefines.h"
 #include "BKE_utildefines.h"
 
-#include "BLI_listbase.h"
-
 #include "RNA_access.h"
 
 #include "NOD_socket.h"
@@ -1658,7 +1658,7 @@ const char* nodeLabel(bNode *node)
 	else if (node->typeinfo->labelfunc)
 		return node->typeinfo->labelfunc(node);
 	else
-		return node->typeinfo->name;
+		return IFACE_(node->typeinfo->name);
 }
 
 struct bNodeTree *nodeGroupEditGet(struct bNode *node)

source/blender/editors/space_node/node_draw.c

@@ -49,6 +49,8 @@
 #include "BLI_threads.h"
 #include "BLI_utildefines.h"
 
+#include "BLF_translation.h"
+
 #include "BKE_context.h"
 #include "BKE_depsgraph.h"
 #include "BKE_main.h"
@@ -717,14 +719,12 @@ static void node_draw_basis(const bContext *C, ARegion *ar, SpaceNode *snode, bN
 		node_socket_circle_draw(ntree, sock, NODE_SOCKSIZE);
 		
 		if (stype->buttonfunc)
-			stype->buttonfunc(C, node->block, ntree, node, sock, sock->name, sock->locx+NODE_DYS, sock->locy-NODE_DYS, node->width-NODE_DY);
+			stype->buttonfunc(C, node->block, ntree, node, sock, IFACE_(sock->name), sock->locx+NODE_DYS, sock->locy-NODE_DYS, node->width-NODE_DY);
 	}
 	
 	/* socket outputs */
 	for(sock= node->outputs.first; sock; sock= sock->next) {
 		PointerRNA sockptr;
-		float slen;
-		int ofs;
 		
 		RNA_pointer_create((ID*)ntree, &RNA_NodeSocket, sock, &sockptr);
 		
@@ -733,15 +733,19 @@ static void node_draw_basis(const bContext *C, ARegion *ar, SpaceNode *snode, bN
 		
 		node_socket_circle_draw(ntree, sock, NODE_SOCKSIZE);
 		
-		ofs= 0;
+		{
-		UI_ThemeColor(TH_TEXT);
+			const char *name = IFACE_(sock->name);
-		slen= snode->aspect*UI_GetStringWidth(sock->name);
+			float slen;
-		while(slen > node->width) {
+			int ofs = 0;
-			ofs++;
+			UI_ThemeColor(TH_TEXT);
-			slen= snode->aspect*UI_GetStringWidth(sock->name+ofs);
+			slen= snode->aspect*UI_GetStringWidth(name);
+			while(slen > node->width) {
+				ofs++;
+				slen= snode->aspect*UI_GetStringWidth(name+ofs);
+			}
+			uiDefBut(node->block, LABEL, 0, name+ofs, (short)(sock->locx-15.0f-slen), (short)(sock->locy-9.0f), 
+					 (short)(node->width-NODE_DY), NODE_DY,  NULL, 0, 0, 0, 0, "");
 		}
-		uiDefBut(node->block, LABEL, 0, sock->name+ofs, (short)(sock->locx-15.0f-slen), (short)(sock->locy-9.0f), 
-				 (short)(node->width-NODE_DY), NODE_DY,  NULL, 0, 0, 0, 0, "");
 	}
 	
 	/* preview */

source/blender/editors/space_node/node_header.c

@@ -214,11 +214,11 @@ static void node_add_menu(bContext *C, uiLayout *layout, void *arg_nodeclass)
 		
 		/* XXX hack: negative numbers used for empty group types */
 		if (node_tree_has_type(ntree->type, NODE_GROUP))
-			uiItemV(layout, "New Group", 0, -NODE_GROUP);
+			uiItemV(layout, IFACE_("New Group"), 0, -NODE_GROUP);
 		if (node_tree_has_type(ntree->type, NODE_FORLOOP))
-			uiItemV(layout, "New For Loop", 0, -NODE_FORLOOP);
+			uiItemV(layout, IFACE_("New For Loop"), 0, -NODE_FORLOOP);
 		if (node_tree_has_type(ntree->type, NODE_WHILELOOP))
-			uiItemV(layout, "New While Loop", 0, -NODE_WHILELOOP);
+			uiItemV(layout, IFACE_("New While Loop"), 0, -NODE_WHILELOOP);
 		uiItemS(layout);
 		
 		for(ngroup=bmain->nodetree.first, event=0; ngroup; ngroup= ngroup->id.next, ++event) {
@@ -239,7 +239,7 @@ static void node_add_menu(bContext *C, uiLayout *layout, void *arg_nodeclass)
 		for (ntype=ntreeGetType(ntree->type)->node_types.first; ntype; ntype=ntype->next) {
 			if (ntype->nclass==nodeclass && ntype->name)
 				if (!compatibility || (ntype->compatibility & compatibility))
-					uiItemV(layout, ntype->name, 0, ntype->type);
+					uiItemV(layout, IFACE_(ntype->name), 0, ntype->type);
 		}
 	}
 }
@@ -247,7 +247,7 @@ static void node_add_menu(bContext *C, uiLayout *layout, void *arg_nodeclass)
 static void node_menu_add_foreach_cb(void *calldata, int nclass, const char *name)
 {
 	uiLayout *layout= calldata;
-	uiItemMenuF(layout, name, 0, node_add_menu, SET_INT_IN_POINTER(nclass));
+	uiItemMenuF(layout, IFACE_(name), 0, node_add_menu, SET_INT_IN_POINTER(nclass));
 }
 
 static void node_menu_add(const bContext *C, Menu *menu)

source/blender/nodes/composite/nodes/node_composite_moviedistortion.c

@@ -30,6 +30,8 @@
  *  \ingroup cmpnodes
  */
 
+#include "BLF_translation.h"
+
 
 #include "node_composite_util.h"
 
@@ -105,9 +107,9 @@ static void exec(void *data, bNode *node, bNodeStack **in, bNodeStack **out)
 static const char *label(bNode *node)
 {
 	if(node->custom1==0)
-		return "Undistortion";
+		return IFACE_("Undistortion");
 	else
-		return "Distortion";
+		return IFACE_("Distortion");
 }
 
 static void storage_free(bNode *node)

source/blender/nodes/intern/node_common.c

@@ -40,6 +40,8 @@
 #include "BLI_string.h"
 #include "BLI_utildefines.h"
 
+#include "BLF_translation.h"
+
 #include "BKE_action.h"
 #include "BKE_animsys.h"
 #include "BKE_global.h"
@@ -487,7 +489,7 @@ void node_group_remove_socket(bNodeTree *ngroup, bNodeSocket *gsock, int in_out)
 /* groups display their internal tree name as label */
 const char *node_group_label(bNode *node)
 {
-	return (node->id)? node->id->name+2: "Missing Datablock";
+	return (node->id)? node->id->name+2: IFACE_("Missing Datablock");
 }
 
 int node_group_valid(bNodeTree *ntree, bNodeTemplate *ntemp)

source/blender/nodes/intern/node_util.c

@@ -36,6 +36,8 @@
 #include "BLI_listbase.h"
 #include "BLI_utildefines.h"
 
+#include "BLF_translation.h"
+
 #include "BKE_colortools.h"
 #include "BKE_node.h"
 
@@ -74,28 +76,28 @@ const char *node_blend_label(bNode *node)
 {
 	const char *name;
 	RNA_enum_name(ramp_blend_items, node->custom1, &name);
-	return name;
+	return IFACE_(name);
 }
 
 const char *node_math_label(bNode *node)
 {
 	const char *name;
 	RNA_enum_name(node_math_items, node->custom1, &name);
-	return name;
+	return IFACE_(name);
 }
 
 const char *node_vect_math_label(bNode *node)
 {
 	const char *name;
 	RNA_enum_name(node_vec_math_items, node->custom1, &name);
-	return name;
+	return IFACE_(name);
 }
 
 const char *node_filter_label(bNode *node)
 {
 	const char *name;
 	RNA_enum_name(node_filter_items, node->custom1, &name);
-	return name;
+	return IFACE_(name);
 }
 
 ListBase node_internal_connect_default(bNodeTree *ntree, bNode *node)