Associate and use spawnable entity icons/traces

[oznogon]

This PR builds on #2494.

Associate icons with ShipSpawnInfo and ObjectSpawnInfo, then use them in the GM entity creation screen lists:

Also use them as the cursor state for entity creation on the GM screen:

Screencast_20250708_101832.webm

In the process, this sets an on_gm_click_cursor string in gameGlobalInfo to define the cursor used on the GM screen when on_gm_click is defined. This is not yet exposed to scripting.

[daid]

what with the mouse cursor when this "" case is hit?
And how does it interact with the onGMClick lua function?

[oznogon]

Added handling of an empty icon string to default to mouse_create.png, and added an icon parameter to onGMClick that defaults to mouse_create.png if not set.

[aBlueShadow]

While they are looking cool, the downside is that the placement is now less precise. Not sure how often that will be relevant

[daid]

While they are looking cool, the downside is that the placement is now less precise. Not sure how often that will be relevant

Don't think that's a huge issue. I was working on something yesterday, and I really liked that you have this clear indication that you are placing something. I think it's a huge UX improvement.

[aBlueShadow]

I was working on something yesterday, and I really liked that you have this clear indication that you are placing something. I think it's a huge UX improvement.

Well, you had that indication of placing something already with the crosshair in #2494. Granted, now there is also a hint of what to place. So compared to that crosshair you gain info/awareness at the cost of precise placement.

But I agree, compared to legacy, it is definitely a big improvement

[oznogon]

Cursor precision is generally a challenge because of the 32px cursor size. The default delta-shaped cursor is effectively only 16x16 px because the center of the 32px cursor image is the click point. The modal selection cursors were legible enough at 16x16 to put them next to the delta, but the ship traces less so.

In practice I didn't feel limited in precision since the cursor places the ship where the cursor appears, though it would be even better if the ship's size and rotation could also be reflected in the cursor to effectively make it a stamp. That would require extending the cursor drawing code further.

I had also considered drawing the ship icon next to the crosshair cursor to retain the precision, but it would require either compositing the radar trace and crosshair into one 32px texture at a loss of radar trace legibility (it would have to be smaller than 16px to fit), or more changes to the cursor rendering code to draw a larger cursor texture or multiple images at once.

[aBlueShadow]

Cursor precision is generally a challenge because of the 32px cursor size. The default delta-shaped cursor is effectively only 16x16 px because the center of the 32px cursor image is the click point.

Speaking of size, I think the main reason it feels less precise is that the cursor is twice the size of the Icon. But maybe I just have to get used to it.

I had also considered drawing the ship icon next to the crosshair cursor to retain the precision, but it would require either compositing the radar trace and crosshair into one 32px texture at a loss of radar trace legibility (it would have to be smaller than 16px to fit), or more changes to the cursor rendering code to draw a larger cursor texture or multiple images at once.

I wonder if using just the crosshair cursor while showing the icon right next to the cancel button would work?