Better grid resizing behavior.

inventory/templates/testing.html

@@ -2,24 +2,21 @@
 {% set dot_size = [grid_size * 1.25, 32]|max|int %}
 
 {% block style %}
-:root {
-    --grid: {{ grid_size }}px;
+
+#gridWrap {
+    width: 100%;
+    height: 80vh;
+    position: relative;
 }
 
 #grid {
+    position: relative;
     cursor: crosshair;
-    height: 80vh;
     width: 100%;
+    height: 100%;
     touch-action: none;
 }
 
-@supports (height: calc(round(nearest, 80vh, {{ grid_size }}px))) {
-    #grid {
-        height: calc(round(nearest, 80vh, var(--grid)) + 1px);
-        width: calc(round(nearest, 100%, var(--grid)) + 1px);
-    }
-}
-
 #toolBar {
     top: 10px;
     transform: translateX(-50%);
@@ -46,6 +43,7 @@
 
 {% block main %}
 <div class="container">
+    <div id="gridWrap">
         <div id="grid" class="position-relative overflow-hidden">
             <div id="toolBar"
                 class="btn-toolbar bg-light position-absolute border border-secondary-subtle rounded start-50 p-1 align-items-center flex-nowrap overflow-auto">
@@ -184,6 +182,7 @@
                 class="border border-black position-absolute d-none bg-warning-subtle px-1 py-0 user-select-none"></div>
             <canvas id="overlay" class="position-absolute w-100 h-100"></canvas>
         </div>
+    </div>
 </div>
 {% endblock %}
 
@@ -199,6 +198,7 @@ const gridEl = document.getElementById('grid');
 const importButtonEl = document.getElementById('importButton');
 const importEl = document.getElementById('import');
 const gridSizeEl = document.getElementById('gridSize');
+const gridWrapEl = document.getElementById('gridWrap');
 
 let gridSize = Number(gridSizeEl.value) || {{ grid_size }};
 let dotSize = Math.floor(Math.max(gridSize * 1.25, 32));
@@ -210,8 +210,11 @@ let selectedColor;
 let currentShape = null;
 let shapes = loadShapes();
 
-const ro = new ResizeObserver(() => resizeAndSetupCanvas());
-ro.observe(gridEl);
+let sizingRAF = 0;
+let lastApplied = { w: 0, h: 0 };
+
+const ro = new ResizeObserver(scheduleSnappedGridSize);
+ro.observe(gridWrapEl);
 
 const savedTool = localStorage.getItem('gridTool');
 if (savedTool) {
@@ -228,12 +231,43 @@ window.addEventListener('resize', resizeAndSetupCanvas);
 
 setGrid();
 
+function snapDown(n, step) {
+    return Math.floor(n / step) * step;
+}
+
+function applySnappedGridSize() {
+    sizingRAF = 0;
+
+    const grid = gridSize;
+    if (!Number.isFinite(grid) || grid < 1) return;
+
+    const w = gridWrapEl.clientWidth;
+    const h = gridWrapEl.clientHeight;
+
+    const snappedW = snapDown(w, grid);
+    const snappedH = snapDown(h, grid);
+
+    if (snappedW === lastApplied.w && snappedH === lastApplied.h) return;
+
+    lastApplied = { w: snappedW, h: snappedH };
+
+    gridEl.style.width = `${snappedW}px`;
+    gridEl.style.height = `${snappedH}px`;
+
+    resizeAndSetupCanvas();
+}
+
+function scheduleSnappedGridSize() {
+    if (sizingRAF) return;
+    sizingRAF = requestAnimationFrame(applySnappedGridSize);
+}
+
 function applyGridSize(newSize) {
     const n = Number(newSize);
     if (!Number.isFinite(n) || n < 1) return;
 
     gridSize = n;
-    document.documentElement.style.setProperty('--grid', `${gridSize}px`);
+    snapSizeToGrid();
 
     dotSize = Math.floor(Math.max(gridSize * 1.25, 32));
 
@@ -241,7 +275,7 @@ function applyGridSize(newSize) {
     dotSVGEl.setAttribute('height', dotSize);
 
     setGrid();
-    resizeAndSetupCanvas();
+    scheduleSnappedGridSize();
 }
 
 function pxToGrid(v) {
@@ -274,7 +308,29 @@ function setActiveType(typeId) {
     }
 }
 
+function snapSizeToGrid() {
+    const grid = gridSize;
+    const rect = gridEl.getBoundingClientRect();
+
+    const targetW = rect.width;
+    const targetH = rect.height;
+
+    const snappedW = Math.floor(targetW / grid) * grid + 1;
+    const snappedH = Math.floor(targetH / grid) * grid + 1;
+
+    gridEl.style.width = `${snappedW}px`;
+    gridEl.style.height = `${snappedH}px`;
+}
+
 function snapToGrid(x, y) {
+    /*
+        For portability, we do not allow pixel coordinates in the data model
+        and only use pixels for rendering. We display both spaces on the screen
+        to ensure no matter the mode, the user is reasoning in the same two
+        coordinate spaces as they need. Thus, snapping will happen even if
+        the tool doesn't use it.
+    */
+
     const rect = gridEl.getBoundingClientRect();
     const clampedX = Math.min(Math.max(x, rect.left), rect.right);
     const clampedY = Math.min(Math.max(y, rect.top), rect.bottom);
@@ -344,6 +400,7 @@ function normalizeLine(shape) {
 }
 
 function resizeAndSetupCanvas() {
+    snapSizeToGrid();
     dpr = window.devicePixelRatio || 1;
     const rect = canvasEl.getBoundingClientRect();
 
@@ -581,9 +638,6 @@ document.addEventListener('keydown', (e) => {
 });
 
 gridEl.addEventListener('pointermove', (e) => {
-    // Note to certain minds that keep thinking we want to mix grid and pixel coordinates.
-    // No. No we do not. Pixels are not portable. Stop it.
-
     if (!ctx) return;
 
     const { ix, iy, x: snapX, y: snapY } = snapToGrid(e.clientX, e.clientY);