another sometimes-works case for multiple widgets

notes.md

@@ -2,6 +2,7 @@
 
 ## `C` cosmetic, `F` functional, `P` performance, `B` bug fix
 
+* `B` client/worker cache invalidated by latest rotation work
 * `B` saved profile should be restored / defaulted when switching devices?
 * `B` normals possibly inverted on faces in 2D to 3D conversion
 * `B` normalize left, bottom, right pop menu time/click and value persistence
@@ -11,13 +12,12 @@
 * `P` allow selection to me decimated on demand (context menu?)
 * `P` improve decimation speed: omit point conversion or use wasm
 * `P` client/worker interface normalization
-* `P` explore widget vertex reloading / replacing
+* `P` explore widget vertex reloading / replacing (Onshape primarily)
 
 * `F` SVG import to 3D part like images
 
 # FDM
 
-* `B` client/worker cache invalidated by latest rotation work
 * `B` fix adaptive slicing with multi-extruder
 * `B` fix support projection/end with grouped parts
 * `B` multi-extruder rendering of raft fails to offset the rest of the print
@@ -51,10 +51,7 @@
 
 # FDM - BELT
 
-* `B` when resize causes a part to move off-bed, move it back on
-* `B` grouped widgets get placed off in space
-* `B` layer retract broken?
-* `B` infill / thin-fill is generating tons of small linear segments
+* `B` multiple parts with one angled against origin "floats" in preview
 * `B` finish supports for belt printing. add progress.
 
 # CAM

src/kiri/worker.js

@@ -100,12 +100,16 @@ KIRI.worker = {
             return { miny, maxy };
         }
 
-        for (let group of Object.values(wgroup)) {
+        function gmin(group) {
             let minv = {};
             for (let w of group) {
                 minv = mins(w.vertices, minv);
             }
-            let { miny, maxy } = minv;
+            return minv;
+        }
+
+        for (let group of Object.values(wgroup)) {
+            let { miny, maxy } = gmin(group);
 
             let widget = group[0];
             let track = widget.track;
@@ -113,8 +117,9 @@ KIRI.worker = {
             let ypos = settings.device.bedDepth / 2 + track.pos.y + miny;
             let rotation = (Math.PI / 180) * 45;
 
-            widget.belt = { xpos, ypos };
             widget.rotate(rotation,0,0,true);
+            let minr = gmin(group);
+            widget.belt = { xpos, ypos, yadd: minr.maxy - minr.miny };
             for (let others of group.slice(1)) {
                 others.belt = widget.belt;
             }

src/mode/fdm/prepare.js

@@ -295,7 +295,7 @@
                 let o = rotinfo.ypos * beltfact;
                 offset = {
                     x: rotinfo.xpos,
-                    y: o - belt.midy,// - belt.miny,
+                    y: o - belt.midy - belt.yadd/2,
                     z: o,
                 };
                 // offset = { x:0, y:0, z:0 };