From 2c1e6d4871c7c474190c578214a21f83a945bdcf Mon Sep 17 00:00:00 2001
From: Magnus Jacobsson <Magnus.Jacobsson@berotec.se>
Date: Tue, 6 Jul 2021 22:13:07 +0200
Subject: [PATCH] add render method to GVLayout that returns a GVRenderData
 object

Towards https://gitlab.com/graphviz/graphviz/-/issues/2001.
---
 lib/gvc++/GVLayout.cpp | 18 ++++++++++++++++--
 lib/gvc++/GVLayout.h   |  8 ++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/lib/gvc++/GVLayout.cpp b/lib/gvc++/GVLayout.cpp
index 879fc9fc8..9c97d1822 100644
--- a/lib/gvc++/GVLayout.cpp
+++ b/lib/gvc++/GVLayout.cpp
@@ -7,8 +7,7 @@
 #include "GVLayout.h"
 #include "GVRenderData.h"
 #include <cgraph++/AGraph.h>
-#include <gvc++/GVContext.h>
-#include <gvc++/GVLayout.h>
+#include <gvc/gvc.h>
 
 namespace GVC {
 
@@ -34,4 +33,19 @@ GVLayout::~GVLayout() {
   gvFreeLayout(m_gvc->c_struct(), m_g->c_struct());
 }
 
+GVRenderData GVLayout::render(const std::string &format) const {
+  char *result = nullptr;
+  unsigned int length = 0;
+  const auto rc = gvRenderData(m_gvc->c_struct(), m_g->c_struct(),
+                               format.c_str(), &result, &length);
+  if (rc) {
+    if (result) {
+      gvFreeRenderData(result);
+    }
+    throw std::runtime_error("Rendering failed");
+  }
+
+  return GVRenderData(result, length);
+}
+
 } // namespace GVC
diff --git a/lib/gvc++/GVLayout.h b/lib/gvc++/GVLayout.h
index aa66535d0..1c1d43bf6 100644
--- a/lib/gvc++/GVLayout.h
+++ b/lib/gvc++/GVLayout.h
@@ -2,8 +2,9 @@
 
 #include <memory>
 
-#include "cgraph++/AGraph.h"
-#include "gvc++/GVContext.h"
+#include "GVContext.h"
+#include "GVRenderData.h"
+#include <cgraph++/AGraph.h>
 
 #ifdef _WIN32
 #if gvc___EXPORTS // CMake's substitution of gvc++_EXPORTS
@@ -35,6 +36,9 @@ public:
   GVLayout(GVLayout &&) = default;
   GVLayout &operator=(GVLayout &&) = default;
 
+  // render the layout in the specified format
+  GVRenderData render(const std::string &format) const;
+
 private:
   std::shared_ptr<GVContext> m_gvc;
   std::shared_ptr<CGraph::AGraph> m_g;
-- 
2.40.0