Dynamic cairo symbol lookup

wip

Author: lazka

cairo/cairomodule.c

@@ -33,6 +33,7 @@
 #include <Python.h>
 
 #include "private.h"
+#include "dynamic.h"
 
 #ifdef CAIRO_HAS_PDF_SURFACE
 #include <cairo-pdf.h>
@@ -124,7 +125,9 @@ static Pycairo_CAPI_t CAPI = {
 
 static PyObject *
 pycairo_cairo_version (PyObject *self, PyObject *ignored) {
-  return PyLong_FromLong (cairo_version());
+  RETURN_NULL_IF_NOT_HAS_CAIRO_FUNC(cairo_version);
+
+  return PyLong_FromLong (PYCAIRO_GET_CAIRO_FUNC(cairo_version)());
 }
 
 static PyObject *

cairo/dynamic.c

@@ -0,0 +1,49 @@
+#include <stddef.h>
+#ifdef _WIN32
+    #include <windows.h>
+#else
+    #define _GNU_SOURCE
+    #include <dlfcn.h>
+#endif
+
+#include "dynamic.h"
+
+#define INIT_CAIRO_FUNC(field, symbol_name) \
+    .field = {symbol_name, NULL, 0}
+
+_Pycairo_cairo_funcs_t _Pycairo_cairo_funcs = {
+    INIT_CAIRO_FUNC(cairo_version, "cairo_version"),
+};
+
+void* _Pycairo_get_cairo_symbol(const char* symbol_name) {
+    static void* cairo_handle = NULL;
+    static int handle_initialized = 0;
+
+    if (!handle_initialized) {
+        handle_initialized = 1;
+#ifdef _WIN32
+        HMODULE handle;
+        if (GetModuleHandleExA(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
+                               GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
+                               (LPCSTR)cairo_create, &handle)) {
+            cairo_handle = handle;
+        }
+#else
+        Dl_info info;
+        if (dladdr((void*)cairo_create, &info) != 0) {
+            cairo_handle = dlopen(info.dli_fname, RTLD_LAZY | RTLD_NOLOAD);
+        }
+#endif
+    }
+
+    if (!cairo_handle)
+        return NULL;
+
+#ifdef _WIN32
+    return (void*)GetProcAddress((HMODULE)cairo_handle, symbol_name);
+#else
+    dlerror();
+    void* symbol = dlsym(cairo_handle, symbol_name);
+    return (dlerror() == NULL) ? symbol : NULL;
+#endif
+}

cairo/dynamic.h

@@ -0,0 +1,41 @@
+#ifndef _PYCAIRO_DYNAMIC_H_
+#define _PYCAIRO_DYNAMIC_H_
+
+#include <cairo.h>
+
+void* _Pycairo_get_cairo_symbol(const char* symbol_name);
+
+#define _PYCAIRO_DECLARE_CAIRO_FUNC(name, ret_type, params) \
+    struct { \
+        const char* symbol_name; \
+        ret_type (*ptr)params; \
+        int checked; \
+    } name
+
+typedef struct {
+    _PYCAIRO_DECLARE_CAIRO_FUNC(cairo_version, int, (void));
+} _Pycairo_cairo_funcs_t;
+
+extern _Pycairo_cairo_funcs_t _Pycairo_cairo_funcs;
+
+#define PYCAIRO_GET_CAIRO_FUNC(field) \
+    (_Pycairo_cairo_funcs.field.checked ? _Pycairo_cairo_funcs.field.ptr : \
+     (_Pycairo_cairo_funcs.field.checked = 1, \
+      _Pycairo_cairo_funcs.field.ptr = _Pycairo_get_cairo_symbol(_Pycairo_cairo_funcs.field.symbol_name)))
+
+#define PYCAIRO_HAS_CAIRO_FUNC(field) \
+    (PYCAIRO_GET_CAIRO_FUNC(field) != NULL)
+
+#define PYCAIRO_CAIRO_FUNC_NAME(field) \
+    (_Pycairo_cairo_funcs.field.symbol_name)
+
+#define RETURN_NULL_IF_NOT_HAS_CAIRO_FUNC(field) \
+    do { \
+        if (!PYCAIRO_GET_CAIRO_FUNC(field)) { \
+            PyErr_Format(PyExc_RuntimeError, "%s not available in this cairo build", \
+                         PYCAIRO_CAIRO_FUNC_NAME(field)); \
+            return NULL; \
+        } \
+    } while(0)
+
+#endif // _PYCAIRO_DYNAMIC_H_

cairo/meson.build

@@ -22,6 +22,7 @@ sources = [
   'surface.c',
   'textcluster.c',
   'textextents.c',
+  'dynamic.c',
 ]
 
 foreach python_file : python_sources