Why does generating desktop.ini trigger CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS?

Question

Hi dears: A program for a cloud filter has been implemented according to the following URL. https://learn.microsoft.com/en-us/windows/win32/cfapi/build-a-cloud-file-sync-engine

and it is configured for on-demand loading: The PopulationPolicy of StorageProviderSyncRootInfo is set to StorageProviderPopulationPolicy::Full.

When creating a cloud folder, the SHGetSetFolderCustomSettings function is used to set a custom icon for the folder, which generates a desktop.ini file.

At this point, the callback method for CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS is triggered.

Why does this happen, and how can one avoid triggering the callback method for CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS?

Thanks

Best

Answer 1

Hello,

Welcome to Microsoft Q&A!

CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS callback is used to ask the sync provider to provide information about the contents of a placeholder directory to satisfy a directory query operation or an attempt to open a file underneath the directory.

According to the Doc: CF_OPERATION_TRANSFER_PLACEHOLDERS_FLAGS enumeration

If the provider no longer wants its CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS callback to be invoked, it should mark the placeholder directory fully populated by setting the CF_OPERATION_TRANSFER_PLACEHOLDERS_FLAG_DISABLE_ON_DEMAND_POPULATION flag in CF_OPERATION_TYPE_TRANSFER_PLACEHOLDERS`.

If you no longer want to trigger the callback method for CF_CALLBACK_TYPE_FETCH_PLACEHOLDERS. I suggest you could try to set the flag CF_OPERATION_TRANSFER_PLACEHOLDERS_FLAG_DISABLE_ON_DEMAND_POPULATION in the callback.

Thank you.

Jeanine

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