扫描结束时判定为保留双张，则继续扫描，否则停止扫描

sane/scanner.cpp

@@ -553,6 +553,10 @@ scanner::~scanner()
 		thread_starting_->join();
 	thread_starting_.reset();
 
+	if (start_after_keep_.get() && start_after_keep_->joinable())
+		start_after_keep_->join();
+	start_after_keep_.reset();
+
 	if (cfg_)
 	{
 		cfg_->remove_all_schemes();  // schemes would add_ref on cfg_, so we clear them first. NOTE: do not call save after this !!!
@@ -1663,6 +1667,12 @@ int scanner::thread_start(void)
 	return ret;
 }
 
+int scanner::thread_start_after_keep()
+{
+	int ret = hg_sane_middleware::instance()->start(handle_, NULL);
+	return ret;
+}
+
 scanner::EXAPIPOS scanner::find_ex_api(int op_id)
 {
 	return std::find(ex_opts_.begin(), ex_opts_.end(), op_id);
@@ -3621,6 +3631,10 @@ int scanner::handle_device_event(int ev_code, void* data, unsigned int* len)
 			if (double_handle_ == DOUBLE_FEED_DISCARD)
 				return 0;
 		}
+		else
+		{
+			double_handle_ = DOUBLE_FEED_NEED_UI;
+		}
 
 		swprintf_s(name, _countof(name) - 1, L"img_%05u.bmp", ++img_ind_);
 		img = new scanned_img(handle_, simg->header, simg->data, simg->bytes, simg->flag.dpi, (tmp_path_ + name).c_str(), xfer_, &img_fmt_);
@@ -3673,11 +3687,25 @@ int scanner::handle_device_event(int ev_code, void* data, unsigned int* len)
 		//	ui_notify(ev_code, data, 0);
 	}
 	else if (ev_code == SANE_EVENT_SCAN_FINISHED)
+	{
+		if (double_handle_ == DOUBLE_FEED_KEEP)
+		{
+			if (start_after_keep_.get() && start_after_keep_->joinable())
+				start_after_keep_->join();
+			start_after_keep_.reset(new std::thread(&scanner::thread_start_after_keep, this));
+		}
+		else
 		{
 			err_ = *len;
 			scan_over_ = true;
 			scan_msg_ = data ? (char*)data : "OK";
 
+			if (double_handle_ == DOUBLE_FEED_DISCARD)
+			{
+				scan_msg_ = "OK";
+				err_ = 0;
+			}
+				
 			if (done_.get() && done_->joinable())
 				done_->join();
 			done_.reset(new std::thread(&scanner::scan_done, this));
@@ -3689,6 +3717,7 @@ int scanner::handle_device_event(int ev_code, void* data, unsigned int* len)
 				log_info(msg, 1);
 			}
 		}
+	}
 	//else if (ev_code == SANE_EVENT_ERROR)			// 閻忕偛绻楅弬鈧柨娑樿嫰濠€顏堝磻濠婂嫷鍓鹃柟娈垮亝瀵潡寮捄铏规綌缂佲偓鏉為绻嗛柟?- 2023-05-30
 	//{
 	//	if (callback::show_messagebox_ui && *len)

sane/scanner.h

@@ -1,4 +1,4 @@
-#pragma once
+#pragma once
 
 #include "scanned_img.h"
 #include <vector>
@@ -116,7 +116,9 @@ class scanner : public ISaneInvoker, virtual public refer
 	int set_is_multiout(bool enable);
 
 	int thread_start(void);
+	int thread_start_after_keep();
 	std::unique_ptr<std::thread>	thread_starting_;
+	std::unique_ptr<std::thread>	start_after_keep_;
 
 	typedef struct _ex_api
 	{