HPLIP

ADF sources should report dynamic scan image height

Bug #1886762 reported by Timo Teräs on 2020-07-08

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	HPLIP	New	Undecided	Unassigned

Bug Description

The SANE API requires that sane_get_parameters() returns "params->lines = -1" when the scanned page has unknown/dynamic height.

Currently HPLIP returns always the maximum size there. However, programs get broken if the image size returned in sane_read() does not match what sane_get_parameters() reported. This currently happens with automatic document feeder (ADF) inputs in which the height is dynamic based on the real page height.

The attached patch shows one way to fix the issue. It is limited to ESCL mode scanners only, and similar fix would be needed in all scanner types.