From 6309948563cdb3e6842eddfe453a352952c7319a Mon Sep 17 00:00:00 2001
From: Gordon Smith <GordonJSmith@gmail.com>
Date: Mon, 20 Jan 2025 14:04:36 +0000
Subject: [PATCH] feat: add a simple standalone version of graphviz

Export "layout" and "lastError"

Signed-off-by: Gordon Smith <GordonJSmith@gmail.com>
---
 packages/graphviz/src-cpp/CMakeLists.txt      | 25 +++---
 packages/graphviz/src-cpp/main-standalone.cpp | 84 +++++++++++++++++++
 2 files changed, 97 insertions(+), 12 deletions(-)
 create mode 100644 packages/graphviz/src-cpp/main-standalone.cpp

diff --git a/packages/graphviz/src-cpp/CMakeLists.txt b/packages/graphviz/src-cpp/CMakeLists.txt
index a512527e..c1845c07 100644
--- a/packages/graphviz/src-cpp/CMakeLists.txt
+++ b/packages/graphviz/src-cpp/CMakeLists.txt
@@ -51,11 +51,21 @@ add_executable(graphvizlib
 set_target_properties(graphvizlib PROPERTIES COMPILE_FLAGS "${CPP_FLAGS}")
 set_target_properties(graphvizlib PROPERTIES LINK_FLAGS "${LINK_FLAGS}")
 
+add_executable(graphvizlib-standalone
+    main-standalone.cpp
+    util.hpp
+    util.cpp
+)
+
+set_target_properties(graphvizlib-standalone PROPERTIES COMPILE_FLAGS "")
+set_target_properties(graphvizlib-standalone PROPERTIES LINK_FLAGS "--no-entry -s STANDALONE_WASM -s EXPORTED_FUNCTIONS=\"['_free', '_malloc', '_layout', '_lastError']\"")
+
 # link libraries
 function(add_graphviz_library library)
     find_library(GRAPHVIZ_${library} NAMES ${library})
     if(GRAPHVIZ_${library})
         target_link_libraries(graphvizlib PRIVATE ${GRAPHVIZ_${library}})
+        target_link_libraries(graphvizlib-standalone PRIVATE ${GRAPHVIZ_${library}})
     else()
         message(FATAL_ERROR "Could not find library ${library}!")
     endif()
@@ -90,18 +100,9 @@ target_link_libraries(graphvizlib PRIVATE
     ${EXPAT_LIBRARIES}
 )
 
-# add_executable(graphvizlib-web
-#     ${SRCS}
-# )
-
-# set_target_properties(graphvizlib-web PROPERTIES LINK_FLAGS "${LINK_FLAGS} -s ENVIRONMENT=web")
-
-# target_link_libraries(graphvizlib-web PRIVATE
-#     gvplugin_core
-#     gvplugin_dot_layout
-#     gvplugin_neato_layout
-#     ortho
-# )
+target_link_libraries(graphvizlib-standalone PRIVATE
+    ${EXPAT_LIBRARIES}
+)
 
 # add_executable(graphvizlib-worker
 #     ${SRCS}
diff --git a/packages/graphviz/src-cpp/main-standalone.cpp b/packages/graphviz/src-cpp/main-standalone.cpp
new file mode 100644
index 00000000..e3851bd2
--- /dev/null
+++ b/packages/graphviz/src-cpp/main-standalone.cpp
@@ -0,0 +1,84 @@
+#include "util.hpp"
+
+#include <gvc.h>
+#include <gvplugin.h>
+#include <graphviz_version.h>
+
+#include <emscripten.h>
+
+extern gvplugin_library_t gvplugin_dot_layout_LTX_library;
+extern gvplugin_library_t gvplugin_neato_layout_LTX_library;
+#ifdef HAVE_LIBGD
+extern gvplugin_library_t gvplugin_gd_LTX_library;
+#endif
+#ifdef HAVE_PANGOCAIRO
+extern gvplugin_library_t gvplugin_pango_LTX_library;
+#ifdef HAVE_WEBP
+extern gvplugin_library_t gvplugin_webp_LTX_library;
+#endif
+#endif
+extern gvplugin_library_t gvplugin_core_LTX_library;
+
+lt_symlist_t lt_preloaded_symbols[] = {
+    {"gvplugin_dot_layout_LTX_library", &gvplugin_dot_layout_LTX_library},
+    {"gvplugin_neato_layout_LTX_library", &gvplugin_neato_layout_LTX_library},
+#ifdef HAVE_PANGOCAIRO
+    {"gvplugin_pango_LTX_library", &gvplugin_pango_LTX_library},
+#ifdef HAVE_WEBP
+    {"gvplugin_webp_LTX_library", &gvplugin_webp_LTX_library},
+#endif
+#endif
+#ifdef HAVE_LIBGD
+    {"gvplugin_gd_LTX_library", &gvplugin_gd_LTX_library},
+#endif
+    {"gvplugin_core_LTX_library", &gvplugin_core_LTX_library},
+    {0, 0}};
+
+StringBuffer lastErrorStr;
+
+int vizErrorf(char *buf)
+{
+    lastErrorStr = buf;
+    return 0;
+}
+
+extern int Y_invert;
+int origYInvert = Y_invert;
+extern int Nop;
+int origNop = Nop;
+
+StringBuffer layout_result;
+
+extern "C"
+{
+    const char *layout(const char *src, const char *format, const char *engine)
+    {
+        layout_result = "";
+
+        GVC_t *gvc = gvContextPlugins(lt_preloaded_symbols, true);
+
+        Agraph_t *graph = agmemread(src);
+        if (graph)
+        {
+            char *data = NULL;
+            unsigned int length;
+
+            gvLayout(gvc, graph, engine);
+            gvRenderData(gvc, graph, format, &data, &length);
+            layout_result = data;
+            gvFreeRenderData(data);
+            gvFreeLayout(gvc, graph);
+            agclose(graph);
+        }
+
+        gvFinalize(gvc);
+        gvFreeContext(gvc);
+
+        return layout_result;
+    }
+
+    const char *lastError()
+    {
+        return lastErrorStr;
+    }
+}