More robust transfer queue fallback system

Author: artdeell

src/main/java/net/vulkanmod/vulkan/queue/Queue.java

@@ -86,6 +86,14 @@ public static QueueFamilyIndices getQueueFamilies() {
         return queueFamilyIndices;
     }
 
+    private static int findFirstQueueIndex(VkQueueFamilyProperties.Buffer queueFamilies, int flags) {
+        for (int i = 0; i < queueFamilies.capacity(); i++) {
+            int queueFlags = queueFamilies.get(i).queueFlags();
+            if((queueFlags & flags) != 0) return i;
+        }
+        return -1;
+    }
+
     public static QueueFamilyIndices findQueueFamilies(VkPhysicalDevice device) {
         QueueFamilyIndices indices = new QueueFamilyIndices();
 
@@ -141,40 +149,22 @@ public static QueueFamilyIndices findQueueFamilies(VkPhysicalDevice device) {
             }
 
             if (indices.transferFamily == -1) {
-
-                int fallback = -1;
-                for (int i = 0; i < queueFamilies.capacity(); i++) {
-                    int queueFlags = queueFamilies.get(i).queueFlags();
-
-                    if ((queueFlags & VK_QUEUE_TRANSFER_BIT) != 0) {
-                        if (fallback == -1)
-                            fallback = i;
-
-                        if ((queueFlags & (VK_QUEUE_GRAPHICS_BIT)) == 0) {
-                            indices.transferFamily = i;
-
-                            if (i != indices.computeFamily)
-                                break;
-                            fallback = i;
-                        }
-                    }
-
-                    if (fallback == -1)
-                        throw new RuntimeException("Failed to find queue family with transfer support");
-
-                    indices.transferFamily = fallback;
+                // Some driversmay not have a transfer-only queue (for example iGPUs, when there's usually no need for DMA)
+                int fallback = findFirstQueueIndex(queueFamilies, VK_QUEUE_TRANSFER_BIT);
+                if(fallback == -1) {
+                    // the Adreno driver takes this further: it straight up has no queues with the transfer bit.
+                    // Rely on a compute or graphics queue in this case.
+                    Initializer.LOGGER.warn("No transfer queues found, will try compute-graphics queue");
+                    fallback = findFirstQueueIndex(queueFamilies, VK_QUEUE_GRAPHICS_BIT | VK_QUEUE_COMPUTE_BIT);
                 }
+                if(fallback == -1)
+                    throw new RuntimeException("Failed to a suitable transfer queue fallback");
+                else
+                    indices.transferFamily = fallback;
             }
 
             if (indices.computeFamily == -1) {
-                for (int i = 0; i < queueFamilies.capacity(); i++) {
-                    int queueFlags = queueFamilies.get(i).queueFlags();
-
-                    if ((queueFlags & VK_QUEUE_COMPUTE_BIT) != 0) {
-                        indices.computeFamily = i;
-                        break;
-                    }
-                }
+                indices.computeFamily = findFirstQueueIndex(queueFamilies, VK_QUEUE_COMPUTE_BIT);
             }
 
             if (indices.graphicsFamily == VK_QUEUE_FAMILY_IGNORED)