Objects with large icons on map can result in massive lag

[Valtosin]

If the map has objects with large icons, then when interacting (like SHIFT-Clicking or CTRL+SHIFT-Clicking) with objects, SDMM starts to work amazingly slow, until you release buttons.

Reproduction:

1. Find a repo with large icons (or try something with icon size above 128x128) on the map. Like our https://github.com/frosty-dev/white or yogs https://github.com/yogstation13/Yogstation
2. Load .dmm with a lot of objects with big icons.
3. Try to SHIFT-Clicking or CTRL+SHIFT-Clicking on anything.
4. Suffer.

Temporary solution for mappers:

Use filters to disable things with large icons or use RMB.

[itsmeow]

can't reproduce this. I put a few hundred Nar'Sie and it's just fine.