index the room by x,y instead of index from the view

so it is easier to implement a focus-ring as a separate dom node

src/domain/session/RoomGridViewModel.js

@@ -25,15 +25,39 @@ export class RoomGridViewModel extends ViewModel {
         this._viewModels = [];
     }
 
-    roomViewModelAt(idx) {
-        return this._viewModels[idx]?.vm;
+    _posToIdx(x, y) {
+        return (y * this.width) + x;
     }
 
-    get focusedIndex() {
-        return this._selectedIndex;
+    _idxToX(idx) {
+        return idx % this.width;
     }
 
-    setFocusedIndex(idx) {
+    _idxToY(idx) {
+        return Math.floor(idx / this.width);
+    }
+
+    roomViewModelAt(x, y) {
+        return this._viewModels[this._posToIdx(x, y)]?.vm;
+    }
+
+    get focusX() {
+        return this._idxToX(this._selectedIndex);
+    }
+
+    get focusY() {
+        return this._idxToY(this._selectedIndex);
+    }
+
+    isFocusAt(x, y) {
+        return this._posToIdx(x, y) === this._selectedIndex;
+    }
+
+    setFocusAt(x, y) {
+        this._setFocusedIndex(this._posToIdx(x, y));
+    }
+
+    _setFocusedIndex(idx) {
         if (idx === this._selectedIndex) {
             return;
         }
@@ -72,8 +96,13 @@ export class RoomGridViewModel extends ViewModel {
     /**
      * @package
      */
-    roomIndex(roomId) {
-        return this._viewModels.findIndex(vms => vms?.vm._room.id === roomId);
+    tryFocusRoom(roomId) {
+        const index = this._viewModels.findIndex(vms => vms?.vm._room.id === roomId);
+        if (index >= 0) {
+            this._setFocusedIndex(index);
+            return true;
+        }
+        return false;
     }
     
     /**

src/domain/session/SessionViewModel.js

@@ -109,14 +109,8 @@ export class SessionViewModel extends ViewModel {
     }
 
     _openRoom(room, roomTileVM) {
-        // for now, we don't support having the same room opened more than once,
-        // so bail out if we already have the room open
-        if (this._gridViewModel) {
-            const roomIndex = this._gridViewModel.roomIndex(room.id);
-            if (roomIndex >= 0) {
-                this._gridViewModel.setFocusedIndex(roomIndex);
+        if (this._gridViewModel?.tryFocusRoom(room.id)) {
             return;
-            }
         } else if (this._currentRoomViewModel?._room.id === room.id) {
             return;
         }

src/ui/web/session/RoomGridView.js

@@ -20,24 +20,27 @@ import {TemplateView} from "../general/TemplateView.js";
 
 export class RoomGridView extends TemplateView {
     render(t, vm) {
-        const roomViews = [];
-        const len = vm.width * vm.height;
-        for (let i = 0; i < len; i+=1) {
-            roomViews[i] = t.div({
-                onClick: () => vm.setFocusedIndex(i),
-                onFocusin: () => vm.setFocusedIndex(i),
-                className: {focused: vm => vm.focusedIndex === i},
-            },t.mapView(vm => vm.roomViewModelAt(i), roomVM => {
+        const children = [];
+        for (let y = 0; y < vm.height; y+=1) {
+            for (let x = 0; x < vm.width; x+=1) {
+                children.push(t.div({
+                    onClick: () => vm.setFocusAt(x, y),
+                    onFocusin: () => vm.setFocusAt(x, y),
+                    className: "container",
+                    style: `--column: ${x + 1}; --row: ${y + 1}`
+                },t.mapView(vm => vm.roomViewModelAt(x, y), roomVM => {
                     if (roomVM) {
                         return new RoomView(roomVM);
                     } else {
                         return new RoomPlaceholderView();
                     }
-            }))
+                })));
             }
+        }
+        children.push(t.div({className: "focus-ring", style: vm => `--column: ${vm.focusX + 1}; --row: ${vm.focusY + 1}`}));
         return t.div({
             className: "RoomGridView",
             style: `--columns: ${vm.width}; --rows: ${vm.height}`
-        }, roomViews);
+        }, children);
     }
 }