define types

packages/roosterjs-content-model-types/lib/index.ts

@@ -445,6 +445,7 @@ export {
     ModelToTextCallbacks,
     ModelToTextChecker,
 } from './parameter/ModelToTextCallbacks';
+export { MergeFormatValueCallback, MergeFormatValueCallbacks } from './parameter/MergeFormatValueCallbacks';
 
 export { BasePluginEvent, BasePluginDomEvent } from './event/BasePluginEvent';
 export { BeforeCutCopyEvent } from './event/BeforeCutCopyEvent';

packages/roosterjs-content-model-types/lib/parameter/MergeFormatValueCallback.ts

@@ -0,0 +1,20 @@
+import type { ContentModelFormatState } from './ContentModelFormatState';
+
+/**
+ * Callback function type to merge the values of a specific format key
+ * @param format The current retrieved format state
+ * @param newValue The new format value to merge
+ */
+export type MergeFormatValueCallback = <K extends keyof ContentModelFormatState>(
+    format: ContentModelFormatState,
+    newValue: ContentModelFormatState[K] | undefined
+) => void;
+
+/**
+ * Callbacks to customize the behavior of merging different format values from selected content
+ * @param format The current retrieved format state
+ * @param newValue The new format value to merge
+ */
+export type MergeFormatValueCallbacks = {
+    [K in keyof ContentModelFormatState]?: MergeFormatValueCallback;
+};