initial backend selection implementation

include/Refresh.h

@@ -332,6 +332,14 @@ typedef enum Refresh_BorderColor
 	REFRESH_BORDERCOLOR_INT_OPAQUE_WHITE
 } Refresh_BorderColor;
 
+typedef enum Refresh_Backend
+{
+	REFRESH_BACKEND_DONTCARE,
+	REFRESH_BACKEND_VULKAN,
+	REFRESH_BACKEND_PS5,
+	REFRESH_BACKEND_INVALID
+} Refresh_Backend;
+
 /* Structures */
 
 typedef struct Refresh_DepthStencilValue
@@ -594,9 +602,24 @@ REFRESHAPI void Refresh_HookLogFunctions(
 	Refresh_LogFunc error
 );
 
+/* Backend selection */
+
+/* Select the graphics API backend that Refresh should use.
+ *
+ * Note that Refresh is not required to select your preferred backend
+ * if it detects an incompatibility.
+ *
+ * Returns the backend that will actually be used.
+ *
+ * preferredBackend: The preferred backend that Refresh should select.
+ * flags: A pointer to a bitflag value that will be filled in with required SDL_WindowFlags masks.
+ */
+REFRESHAPI Refresh_Backend Refresh_SelectBackend(Refresh_Backend preferredBackend, uint32_t *flags);
+
 /* Device */
 
 /* Create a rendering context for use on the calling thread.
+ * You MUST have called Refresh_SelectDriver prior to calling this function.
  *
  * presentationParameters: A window handle and presentation mode.
  * debugMode: Enable debug mode properties.

src/Refresh.c

@@ -33,7 +33,8 @@
 
 /* Drivers */
 
-static const Refresh_Driver *drivers[] = {
+static const Refresh_Driver *backends[] = {
+	NULL,
 #ifdef REFRESH_DRIVER_VULKAN
 	&VulkanDriver,
 #endif
@@ -129,18 +130,55 @@ uint32_t Refresh_LinkedVersion(void)
 
 /* Driver Functions */
 
-static int32_t selectedDriver = 0;
+static Refresh_Backend selectedBackend = REFRESH_BACKEND_INVALID;
+
+Refresh_Backend Refresh_SelectBackend(Refresh_Backend preferredBackend, uint32_t *flags)
+{
+	uint32_t backendIndex, i;
+
+	if (preferredBackend != REFRESH_BACKEND_DONTCARE)
+	{
+		/* Try to force it! */
+		backendIndex = preferredBackend;
+
+		if (backends[backendIndex]->PrepareDriver(flags))
+		{
+			selectedBackend = preferredBackend;
+			return selectedBackend;
+		}
+	}
+
+	/* Iterate until we find an appropriate backend. */
+
+	for (i = 1; backends[i] != NULL; i += 1)
+	{
+		if (backends[i]->PrepareDriver(flags))
+		{
+			selectedBackend = i;
+			return i;
+		}
+	}
+
+	if (backends[i] == NULL)
+	{
+		Refresh_LogError("No supported Refresh backend found!");
+	}
+
+	selectedBackend = REFRESH_BACKEND_INVALID;
+	return REFRESH_BACKEND_INVALID;
+}
 
 Refresh_Device* Refresh_CreateDevice(
 	Refresh_PresentationParameters *presentationParameters,
 	uint8_t debugMode
 ) {
-	if (selectedDriver < 0)
+	if (selectedBackend == REFRESH_BACKEND_INVALID)
 	{
+		Refresh_LogError("Invalid backend selection. Did you call Refresh_SelectBackend?");
 		return NULL;
 	}
 
-	return drivers[selectedDriver]->CreateDevice(
+	return backends[selectedBackend]->CreateDevice(
 		presentationParameters,
 		debugMode
 	);

src/Refresh_Driver.h

@@ -542,6 +542,7 @@ struct Refresh_Device
 typedef struct Refresh_Driver
 {
 	const char *Name;
+	uint8_t (*PrepareDriver)(uint32_t *flags);
 	Refresh_Device* (*CreateDevice)(
 		Refresh_PresentationParameters *presentationParameters,
 		uint8_t debugMode

src/Refresh_Driver_Vulkan.c

@@ -10285,9 +10285,7 @@ static void VULKAN_INTERNAL_GetPhysicalDeviceProperties(
 
 static uint8_t VULKAN_INTERNAL_DeterminePhysicalDevice(
 	VulkanRenderer *renderer,
-	VkSurfaceKHR surface,
+	VkSurfaceKHR surface
-	const char **deviceExtensionNames,
-	uint32_t deviceExtensionCount
 ) {
 	VkResult vulkanResult;
 	VkPhysicalDevice *physicalDevices;
@@ -10513,9 +10511,8 @@ static uint8_t VULKAN_INTERNAL_CreateLogicalDevice(
 	return 1;
 }
 
-static void VULKAN_INTERNAL_LoadEntryPoints(
+static void VULKAN_INTERNAL_LoadEntryPoints()
-	VulkanRenderer *renderer
+{
-) {
 	/* Load Vulkan entry points */
 	if (SDL_Vulkan_LoadLibrary(NULL) < 0)
 	{
@@ -10546,6 +10543,83 @@ static void VULKAN_INTERNAL_LoadEntryPoints(
 	#include "Refresh_Driver_Vulkan_vkfuncs.h"
 }
 
+static uint8_t VULKAN_PrepareDriver(uint32_t *flags)
+{
+	SDL_Window *dummyWindowHandle;
+	VulkanRenderer *renderer;
+	VkSurfaceKHR surface;
+	uint8_t result;
+
+	VULKAN_INTERNAL_LoadEntryPoints();
+
+	/* Test if we can create a Vulkan device */
+
+	dummyWindowHandle = SDL_CreateWindow(
+		"Refresh Vulkan",
+		0, 0,
+		128, 128,
+		SDL_WINDOW_VULKAN | SDL_WINDOW_HIDDEN
+	);
+
+	if (dummyWindowHandle == NULL)
+	{
+		Refresh_LogWarn("Vulkan: Could not create dummy window");
+		return 0;
+	}
+
+	/* partially set up VulkanRenderer so we can fall back in case of device non-compliance */
+	renderer = (VulkanRenderer*) SDL_malloc(sizeof(VulkanRenderer));
+	SDL_memset(renderer, '\0', sizeof(VulkanRenderer));
+
+	if (!VULKAN_INTERNAL_CreateInstance(renderer, dummyWindowHandle))
+	{
+		SDL_DestroyWindow(dummyWindowHandle);
+		SDL_free(renderer);
+		Refresh_LogWarn("Vulkan: Could not create Vulkan instance");
+		return 0;
+	}
+
+	if (!SDL_Vulkan_CreateSurface(
+		(SDL_Window*) dummyWindowHandle,
+		renderer->instance,
+		&surface
+	)) {
+		SDL_DestroyWindow(dummyWindowHandle);
+		SDL_free(renderer);
+		Refresh_LogWarn(
+			"SDL_Vulkan_CreateSurface failed: %s",
+			SDL_GetError()
+		);
+		return 0;
+	}
+
+	#define VULKAN_INSTANCE_FUNCTION(ext, ret, func, params) \
+		renderer->func = (vkfntype_##func) vkGetInstanceProcAddr(renderer->instance, #func);
+	#include "Refresh_Driver_Vulkan_vkfuncs.h"
+
+	result = VULKAN_INTERNAL_DeterminePhysicalDevice(renderer, surface);
+
+	renderer->vkDestroySurfaceKHR(
+		renderer->instance,
+		surface,
+		NULL
+	);
+	renderer->vkDestroyInstance(renderer->instance, NULL);
+	SDL_DestroyWindow(dummyWindowHandle);
+	SDL_free(renderer);
+
+	if (!result)
+	{
+		Refresh_LogWarn("Vulkan: Failed to determine a suitable physical device");
+	}
+	else
+	{
+		*flags = SDL_WINDOW_VULKAN;
+	}
+
+	return result;
+}
+
 static Refresh_Device* VULKAN_CreateDevice(
 	Refresh_PresentationParameters *presentationParameters,
 	uint8_t debugMode
@@ -10622,9 +10696,7 @@ static Refresh_Device* VULKAN_CreateDevice(
 	}
 	if (!VULKAN_INTERNAL_DeterminePhysicalDevice(
 		renderer,
-		surface,
+		surface
-		deviceExtensionNames,
-		deviceExtensionCount
 	)) {
 		Refresh_LogError("Failed to determine a suitable physical device");
 		return NULL;
@@ -11124,6 +11196,7 @@ static Refresh_Device* VULKAN_CreateDevice(
 
 Refresh_Driver VulkanDriver = {
 	"Vulkan",
+	VULKAN_PrepareDriver,
 	VULKAN_CreateDevice
 };