Respect sprite X and Y offsets

This makes menus display more correctly, and also fixes trees and other
objects on the main map, although it messes up bounds clipping (sigh).

doc/formats/mnu.md

@@ -183,3 +183,21 @@ values:
 | 405,0,0,{8, 16} | ? |
 | 405,22,22,{2, 4, 5, 6, 7, 8, 9, 10, 13, 16} | ? |
 | 405,30,-1,5 | ? |
+
+## Positioning
+
+The X-CORD and Y-CORD values would seem to be related, to this, but they are
+universally set to 0 or -1.
+
+Far more important are the XOffset and YOffset values for each sprite in the
+associated .obj files. Taking these into account is enough to draw `Options.mnu`
+successfully, for instance:
+
+![](img/Options.mnu.png)
+
+## Animation
+
+This seems to be done by choosing a different sprite to draw every N ticks. They
+are laid out sequentially, but I don't yet know how to animate them. It's likely
+to be the same approach as used for other obj files.
+

doc/formats/obj.md

@@ -202,15 +202,13 @@ in the CENTER position. Interesting.
 
 | Offset | Purpose |
 | ------ | ------- |
-| 0x0000 | ?
+| 0x0000 | x,y offset (16 bits each) |
 | 0x0004 | x,y size (16 bits each) |
 | 0x0008 | ? (blank in all cases so far)
 | 0x000c | Size of remaining pixeldata |
 | 0x0010 | Padding? |
 | 0x0014 | Padding? |
 
-We still don't know what the first 32 bits are all about.
-
 The volume represented by a cell is a little odd. We see three faces of a fake
 3D volume of size 64x64x32(ish). This is presented in an isomorphic fashion, so
 the height is 32px at the leftmost and rightmost extents and 96 in the centre.
@@ -222,8 +220,9 @@ for instance.
 
 Loading a constructed `palette.obj` containing 1x63 pixels, with 0x0000 for the
 first 32 bits, caused WH40K_TD.exe to render the pixels far to the left and above
-the cell the palette objects were being placed into. This suggests they
-represent an x,y offset to draw to. Need to experiment more. 
+the cell the palette objects were being placed into. Menus have a `.obj` file
+associated with them too, and the elements for `Main.mnu` draw in the correct
+places if we treat it as such.
 
 Considering sprites with a 1,1 x,y.