as to say,GUI.depth works only among differnt OnGUI() function.
thus, if I wanted to display different GUI Controls in one OnGUI() function,I don’t know how
If you need two controls to overlap but only one of them to get clicks from the overlapping region, you need to use two separate scripts. Each script should have its own OnGUI function, and each should set the GUI.depth value differently. The control with priority should have the lower depth value, so for example, you might display all higher priority with a GUI depth of 0 and the rest with a depth of 1. In cases where no controls overlap, you can just display as many of them as you like in the same OnGUI function.