fix side data interpretation

MarathonData.md

@@ -633,7 +633,7 @@ Side is 64 bytes.
 | Point   | Collision top-right                               | ExTRight      |
 | Point   | Collision bottom-left                             | ExBLeft       |
 | Point   | Collision bottom-right                            | ExBRight      |
-| u16     | Control Panel Type                                | PanelType     |
+| u16     | Control panel preset number                       | PanelType     |
 | i16     | Control panel permutation                         | PanelPerm     |
 | u16     | First texture transfer mode                       | XferPri       |
 | u16     | Second texture transfer mode                      | XferSec       |
@@ -1041,6 +1041,9 @@ exit upon reading them.
 
 ### Control Panel Type ###
 
+This is used internally for each control panel preset and determines the
+permutation each one uses.
+
 | Value | Description                           | Permutation | Name          |
 | ----- | -----------                           | ----------- | ----          |
 | 0     | Oxygen refuel                         | None        | Oxygen        |

src/marathon/map.rs

@@ -55,6 +55,7 @@ fn read_side_tex(b: &[u8]) -> ResultS<SideTex>
 {
    let   offs = Point::read(&b[0..4])?;
    let tex_id = b.c_u16b(4)?;
+   let tex_id = if tex_id == 65535 {None} else {Some(tex_id)};
    Ok(SideTex{offs, tex_id})
 }
 
@@ -80,13 +81,7 @@ impl Chunked<Side> for Side
       let xfer_tra = b.c_u16b(46)?;
       let    shade = b.c_u32b(48)?;
       let    flags = SideFlags::from_bits_truncate(flags);
-      let paneltyp =
-         if flags.contains(SideFlags::Panel) {
-            Some(PanelType::from_repr(paneltyp)?)
-         } else {
-            None
-         };
-      let shade = Fx32::from_bits(shade);
+      let    shade = Fx32::from_bits(shade);
       Ok(Side{stype, flags, tex_pri, tex_sec, tex_tra, ex_tleft, ex_trigh,
               ex_bleft, ex_brigh, paneltyp, paneldat, xfer_pri, xfer_sec,
               xfer_tra, shade})
@@ -148,7 +143,7 @@ pub struct Line
 pub struct SideTex
 {
      offs: Point,
-   tex_id: u16,
+   tex_id: Option<u16>,
 }
 
 #[derive(Debug)]
@@ -163,7 +158,7 @@ pub struct Side
    ex_trigh: Point,
    ex_bleft: Point,
    ex_brigh: Point,
-   paneltyp: Option<PanelType>,
+   paneltyp: u16,
    paneldat: i16,
    xfer_pri: u16,
    xfer_sec: u16,
@@ -262,22 +257,6 @@ bitflags! {
    }
 }
 
-c_enum! {
-   #[derive(Debug)]
-   pub enum PanelType: u16
-   {
-      0 => Oxygen,
-      1 => Shield,
-      2 => Shield2x,
-      3 => Shield3x,
-      4 => Light,
-      5 => Platform,
-      6 => Tag,
-      7 => PatternBuf,
-      8 => Terminal,
-   }
-}
-
 impl fmt::Debug for Point
 {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result