XnView Software

according to your reply , i suddenly realize the bug is based on when you center click the tab, the tab toolbar get the focus, but center click means to close the tab, so ... the focus lost.

Not exactly.
He's problem is re-sort tabs, and my problem is failed to switch to pre/next file with stroll button in the same tab, after we closed the inactive tabs with center button click when we had more than one tab .

well, you open the browser tab first, and you open 2 pictures in the browser. Now you have 3 tabs, right? I set the mouse scroll action to the pre/next file, which is working normally, but if you active the 3rd tab, and click the 2nd tab with center button, you'll see the 2nd tab is closeed(which is ...