Add count parameter to sfVulkan_getGraphicsRequiredInstanceExtensions

Based on `sfSoundRecorder_getAvailableDevices()`

Fixes #227

Co-authored-by: kimci86 <kimci86@hotmail.fr>

include/SFML/Window/Vulkan.h

@@ -26,6 +26,7 @@
 // Headers
 ////////////////////////////////////////////////////////////
 #include <SFML/Window/Export.h>
+#include <stddef.h>
 
 
 typedef struct VkInstance_T* VkInstance;
@@ -76,7 +77,9 @@ CSFML_WINDOW_API sfVulkanFunctionPointer sfVulkan_getFunction(const char* name);
 ////////////////////////////////////////////////////////////
 /// \brief Get Vulkan instance extensions required for graphics
 ///
+/// \param count Pointer to a variable that will be filled with the number of instance extensions in the array
+///
 /// \return Vulkan instance extensions required for graphics
 ///
 ////////////////////////////////////////////////////////////
-CSFML_WINDOW_API const char* const* sfVulkan_getGraphicsRequiredInstanceExtensions(void);
+CSFML_WINDOW_API const char* const* sfVulkan_getGraphicsRequiredInstanceExtensions(size_t* count);

src/SFML/Window/Vulkan.cpp

@@ -48,7 +48,12 @@ sfVulkanFunctionPointer sfVulkan_getFunction(const char* name)
 
 
 ////////////////////////////////////////////////////////////
-const char* const* sfVulkan_getGraphicsRequiredInstanceExtensions()
+const char* const* sfVulkan_getGraphicsRequiredInstanceExtensions(size_t* count)
 {
-    return &sf::Vulkan::getGraphicsRequiredInstanceExtensions()[0];
+    static std::vector<const char*> extensions = sf::Vulkan::getGraphicsRequiredInstanceExtensions();
+
+    if (count)
+        *count = extensions.size();
+
+    return !extensions.empty() ? &extensions[0] : NULL;
 }