With a modern, fast Xeon processor under the hood of my Mac, one would expect a simple thing such as box selecting some icons on the desktop to be quick. However, I recently found out that between the time I click and I finished the box selection, the initial click did not register. In other words, imagine clicking top right somewhere on your desktop and immediately dragging the mouse to the bottom right to complete a box selection. I found that I had no selection box!
Only if I clicked, waited about 4 seconds then dragged the mouse did it box select properly. What was going on here? My desktop was pretty clean... Only about one column of icons on a 4k display. Or was that true?
Turns out, I had 720 files on my Desktop, but they were all hidden from common sight via the nifty Apple feature called stacks - whereby files are grouped by kind and collapsed into stacks to clean up the Desktop. I absolutely love that feature as I use the Desktop as a working area, however I now realized the cost of doing so. Only 720 items on the desktop, yet it caused a 4 second delay in mouse click response when selecting things. I moved all those files out to a subfolder, and my response times for box selection is back to near instant. So keep an eye on the depth of your stacks - it will kill your performance if left unchecked.