twainui增加接口防止界面阻塞

build2/qt/HGTwainUI/HGTwainUI.def

@@ -13,3 +13,4 @@ show_messagebox_ui
 show_twain_srclist_ui
 show_srclist_ui
 close_ui
+pump_ui_message

modules/twainui/twainui.cpp

@@ -326,3 +326,8 @@ int close_ui(int which)
 
     return 0;
 }
+
+void pump_ui_message(void* reserved)
+{
+    QApplication::processEvents();
+}

modules/twainui/twainui.h

@@ -126,3 +126,5 @@ enum which_ui
     UI_UNLOAD_MODULE = -1,  // this command is used to notify the module will be unloaded
 };
 HGEXPORT int close_ui(int which);
+
+HGEXPORT void pump_ui_message(void* reserved);