Add engine version to svg file

Author: thomasp85

R/cpp11.R

@@ -15,3 +15,7 @@ svgstring_ <- function(env, bg, width, height, pointsize, standalone) {
 get_svg_content <- function(p) {
   .Call(`_vdiffr_get_svg_content`, p)
 }
+
+set_engine_version <- function(version) {
+  invisible(.Call(`_vdiffr_set_engine_version`, version))
+}

R/vdiffr.R

@@ -10,3 +10,7 @@ SVG_ENGINE_VER <- "2.0"
 svg_engine_ver <- function() {
   as.numeric_version(SVG_ENGINE_VER)
 }
+
+.onLoad <- function(lib, pkg) {
+  set_engine_version(SVG_ENGINE_VER)
+}

src/cpp11.cpp

@@ -32,19 +32,29 @@ extern "C" SEXP _vdiffr_get_svg_content(SEXP p) {
     return cpp11::as_sexp(get_svg_content(cpp11::as_cpp<cpp11::decay_t<cpp11::external_pointer<std::stringstream>>>(p)));
   END_CPP11
 }
+// engine_version.cpp
+void set_engine_version(cpp11::strings version);
+extern "C" SEXP _vdiffr_set_engine_version(SEXP version) {
+  BEGIN_CPP11
+    set_engine_version(cpp11::as_cpp<cpp11::decay_t<cpp11::strings>>(version));
+    return R_NilValue;
+  END_CPP11
+}
 
 extern "C" {
 /* .Call calls */
 extern SEXP _vdiffr_compare_files(SEXP, SEXP);
 extern SEXP _vdiffr_get_svg_content(SEXP);
+extern SEXP _vdiffr_set_engine_version(SEXP);
 extern SEXP _vdiffr_svglite_(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP, SEXP);
 extern SEXP _vdiffr_svgstring_(SEXP, SEXP, SEXP, SEXP, SEXP, SEXP);
 
 static const R_CallMethodDef CallEntries[] = {
-    {"_vdiffr_compare_files",   (DL_FUNC) &_vdiffr_compare_files,   2},
-    {"_vdiffr_get_svg_content", (DL_FUNC) &_vdiffr_get_svg_content, 1},
-    {"_vdiffr_svglite_",        (DL_FUNC) &_vdiffr_svglite_,        7},
-    {"_vdiffr_svgstring_",      (DL_FUNC) &_vdiffr_svgstring_,      6},
+    {"_vdiffr_compare_files",      (DL_FUNC) &_vdiffr_compare_files,      2},
+    {"_vdiffr_get_svg_content",    (DL_FUNC) &_vdiffr_get_svg_content,    1},
+    {"_vdiffr_set_engine_version", (DL_FUNC) &_vdiffr_set_engine_version, 1},
+    {"_vdiffr_svglite_",           (DL_FUNC) &_vdiffr_svglite_,           7},
+    {"_vdiffr_svgstring_",         (DL_FUNC) &_vdiffr_svgstring_,         6},
     {NULL, NULL, 0}
 };
 }

src/devSVG.cpp

@@ -39,6 +39,7 @@ extern "C" {
 #include "utils.h"
 #include "tinyformat.h"
 
+#include "engine_version.h"
 #include "glyph_dims.h"
 
 typedef std::shared_ptr<SvgStream> SvgStreamPtr;
@@ -465,11 +466,13 @@ void svg_new_page(const pGEcontext gc, pDevDesc dd) {
   }
 
   (*stream) << " class='svglite'";
+  
+  (*stream) << " data-engine-version='" << get_engine_version() << "'";
 
   (*stream) << " width='" << dd->right << "pt' height='" << dd->bottom << "pt'";
 
   (*stream) << " viewBox='0 0 " << dd->right << ' ' << dd->bottom << "'>\n";
-
+  
   // Setting default styles
   (*stream) << "<defs>\n";
   (*stream) << "  <style type='text/css'><![CDATA[\n";

src/engine_version.cpp

@@ -0,0 +1,13 @@
+#include "engine_version.h"
+#include <cpp11/strings.hpp>
+
+std::string ENGINE_VERSION = "";
+
+std::string get_engine_version() {
+  return ENGINE_VERSION;
+}
+
+[[cpp11::register]]
+void set_engine_version(cpp11::strings version) {
+  ENGINE_VERSION = cpp11::as_cpp<std::string>(version);
+}

src/engine_version.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#include <string>
+
+std::string get_engine_version();