Added rect draw api

Added some new maths types
Updated shaders to use new D_Rect structure
Added rect buffers to frames
Misc cleanup

code/vulkan/core.c

@@ -372,6 +372,16 @@ bool Vk_Setup(SDL_Window *window) {
 
 		vk.CreateDescriptorPool(vk.device, &descriptor_pool, 0, &frame->descriptors);
 
+		// rect buffer
+		//
+
+		Vk_Buffer *rbo = &frame->rbo;
+		rbo->usage        = VK_BUFFER_USAGE_STORAGE_BUFFER_BIT;
+		rbo->size         = D_MAX_RECTS * sizeof(D_Rect);
+		rbo->host_visible = true;
+
+		Vk_BufferCreate(rbo);
+
 		VkSemaphoreCreateInfo semaphore = { 0 };
 		semaphore.sType = VK_STRUCTURE_TYPE_SEMAPHORE_CREATE_INFO;
 
@@ -547,7 +557,7 @@ internal VkDeviceMemory Vk_Allocate(VkMemoryRequirements *mreq, VkMemoryProperty
 		}
 	}
 
-	if (type_index != -1) {
+	if (type_index != U32_MAX) {
 		VkMemoryAllocateInfo alloc_info = { 0 };
 		alloc_info.sType           = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_INFO;
 		alloc_info.allocationSize  = mreq->size;
@@ -556,6 +566,7 @@ internal VkDeviceMemory Vk_Allocate(VkMemoryRequirements *mreq, VkMemoryProperty
 		vk.AllocateMemory(vk.device, &alloc_info, 0, &result);
 	}
 
+	Assert(result != VK_NULL_HANDLE);
 	return result;
 }
 
@@ -566,6 +577,7 @@ void Vk_BufferCreate(Vk_Buffer *buffer) {
 	create_info.size  = buffer->size;
 
 	vk.CreateBuffer(vk.device, &create_info, 0, &buffer->handle);
+	Assert(buffer->handle != VK_NULL_HANDLE);
 
 	VkMemoryRequirements req;
 	vk.GetBufferMemoryRequirements(vk.device, buffer->handle, &req);
@@ -580,6 +592,7 @@ void Vk_BufferCreate(Vk_Buffer *buffer) {
 	if (buffer->host_visible) {
 		vk.MapMemory(vk.device, buffer->memory, 0, buffer->size, 0, &buffer->data);
 	}
+
 }
 
 void Vk_ImageCreate(Vk_Image *image) {