Add BatchIndex node

Add "INT:batch_index" subtype
Add onInitBatch() callback for widgets

nodes.py

@@ -1034,6 +1034,22 @@ class ImagePadForOutpaint:
 
         return (new_image, mask)
 
+class BatchIndex:
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "batch_index": ("INT", {}),
+            },
+        }
+
+    RETURN_TYPES = ("INT", "FLOAT")
+    FUNCTION = "getBatchIndex"
+    CATEGORY = "utils"
+
+    def getBatchIndex(self, batch_index):
+        return (batch_index, batch_index)
+
 
 NODE_CLASS_MAPPINGS = {
     "KSampler": KSampler,
@@ -1076,6 +1092,7 @@ NODE_CLASS_MAPPINGS = {
     "TomePatchModel": TomePatchModel,
     "unCLIPCheckpointLoader": unCLIPCheckpointLoader,
     "CheckpointLoader": CheckpointLoader,
+    "BatchIndex": BatchIndex,
 }
 
 def load_custom_node(module_path):

web/scripts/app.js

@@ -946,7 +946,23 @@ class ComfyApp {
 				({ number, batchCount } = this.#queueItems.pop());
 
 				for (let i = 0; i < batchCount; i++) {
-					const p = await this.graphToPrompt();
+					let p = await this.graphToPrompt();
+
+					if (i == 0) {
+						for (const n of p.workflow.nodes) {
+							const node = graph.getNodeById(n.id);
+							if (node.widgets) {
+								for (const widget of node.widgets) {
+									// Allow widgets to run callbacks on firts iteration of a batch
+									// e.g. random seed after every gen
+									if (widget.onInitBatch) {
+										widget.onInitBatch();
+									}
+								}
+							}
+						}
+						p = await this.graphToPrompt();
+					}
 
 					try {
 						await api.queuePrompt(number, p);

web/scripts/widgets.js

@@ -43,6 +43,25 @@ function seedWidget(node, inputName, inputData) {
 	return { widget: seed, randomize };
 }
 
+export function batchIndexWidget(node, inputName, inputData) {
+
+	const { val, config } = getNumberDefaults(inputData, 1);
+	Object.assign(config, { precision: 0 });
+	const batchIndex = node.addWidget("number", inputName, val, () => {}, config)
+	batchIndex.forbidConvertToInput = true;
+	batchIndex.disabled = true;
+
+	batchIndex.onInitBatch = () => {
+		batchIndex.value = 0;
+	};
+
+	batchIndex.afterQueued = () => {
+		batchIndex.value += 1;
+	};
+
+	return batchIndex;
+}
+
 const MultilineSymbol = Symbol();
 const MultilineResizeSymbol = Symbol();
 
@@ -197,6 +216,7 @@ function addMultilineWidget(node, name, opts, app) {
 }
 
 export const ComfyWidgets = {
+	"INT:batch_index": batchIndexWidget,
 	"INT:seed": seedWidget,
 	"INT:noise_seed": seedWidget,
 	FLOAT(node, inputName, inputData) {