feat: canvas background selector — grid, dot, or blank preference

Add user-selectable canvas background style via data-canvas-bg attribute
and CSS custom properties (--rs-canvas-bg-image, --rs-canvas-bg-size).
Three options: grid (default), dot, blank — persisted in localStorage.

- theme.css: new tokens + [data-canvas-bg] selectors
- rstack-identity.ts: Grid/Dot/Blank selector in user dropdown
- canvas.html: CSS vars, zoom-aware scaling, canvas-bg-change listener
- flows.css: use shared bg-image/bg-size vars (fixes rFlows theme bug)
- FOUC prevention in all entry points (shell.ts, create-space.html)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

modules/rflows/components/flows.css

@@ -241,8 +241,8 @@
 	width: 100%; height: 100%; display: block;
 	cursor: grab;
 	background-color: var(--rs-canvas-bg);
-	background-image: radial-gradient(circle, var(--rs-canvas-grid) 1px, transparent 1px);
-	background-size: 20px 20px;
+	background-image: var(--rs-canvas-bg-image);
+	background-size: var(--rs-canvas-bg-size);
 }
 .flows-canvas-svg.panning { cursor: grabbing; }
 .flows-canvas-svg.dragging { cursor: move; }

server/shell.ts

@@ -111,7 +111,7 @@ export function renderShell(opts: ShellOptions): string {
   <meta name="apple-mobile-web-app-capable" content="yes">
   <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
   <title>${escapeHtml(title)}</title>
-  <script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t)})()</script>
+  <script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t);var b=localStorage.getItem('canvas-bg')||'grid';document.documentElement.setAttribute('data-canvas-bg',b)})()</script>
   <link rel="stylesheet" href="/theme.css">
   <link rel="stylesheet" href="/shell.css">
   <style>
@@ -753,7 +753,7 @@ export function renderExternalAppShell(opts: ExternalAppShellOptions): string {
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <link rel="icon" type="image/png" href="/favicon.png">
   <title>${escapeHtml(title)}</title>
-  <script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t)})()</script>
+  <script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t);var b=localStorage.getItem('canvas-bg')||'grid';document.documentElement.setAttribute('data-canvas-bg',b)})()</script>
   <link rel="stylesheet" href="/theme.css">
   <link rel="stylesheet" href="/shell.css">
   <style>
@@ -1013,7 +1013,7 @@ export function renderModuleLanding(opts: ModuleLandingOptions): string {
   <meta name="apple-mobile-web-app-capable" content="yes">
   <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
   <title>${escapeHtml(mod.name)} — rSpace</title>
-  <script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t)})()</script>
+  <script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t);var b=localStorage.getItem('canvas-bg')||'grid';document.documentElement.setAttribute('data-canvas-bg',b)})()</script>
   <link rel="stylesheet" href="/theme.css">
   <link rel="stylesheet" href="/shell.css">
   ${cssBlock}
@@ -1355,7 +1355,7 @@ export function renderSubPageInfo(opts: SubPageInfoOptions): string {
   <meta name="apple-mobile-web-app-capable" content="yes">
   <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
   <title>${escapeHtml(subPage.title)} — ${escapeHtml(mod.name)} | rSpace</title>
-  <script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t)})()</script>
+  <script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t);var b=localStorage.getItem('canvas-bg')||'grid';document.documentElement.setAttribute('data-canvas-bg',b)})()</script>
   <link rel="stylesheet" href="/theme.css">
   <link rel="stylesheet" href="/shell.css">
   <style>${MODULE_LANDING_CSS}</style>

shared/components/rstack-identity.ts

@@ -362,6 +362,14 @@ export class RStackIdentity extends HTMLElement {
 							</label>
 							<span class="theme-icon">🌙</span>
 						</div>
+						<div class="dropdown-canvas-row">
+							<span class="canvas-label">Canvas</span>
+							<div class="canvas-options" id="canvas-bg-options">
+								<button class="canvas-opt${(localStorage.getItem("canvas-bg") || "grid") === "grid" ? " active" : ""}" data-bg="grid">Grid</button>
+								<button class="canvas-opt${localStorage.getItem("canvas-bg") === "dot" ? " active" : ""}" data-bg="dot">Dot</button>
+								<button class="canvas-opt${localStorage.getItem("canvas-bg") === "blank" ? " active" : ""}" data-bg="blank">Blank</button>
+							</div>
+						</div>
 						<div class="dropdown-divider"></div>
 						<button class="dropdown-item dropdown-item--danger" data-action="signout">🚪 Sign Out</button>
 					</div>
@@ -406,6 +414,22 @@ export class RStackIdentity extends HTMLElement {
 					this.dispatchEvent(new CustomEvent("theme-change", { bubbles: true, composed: true, detail: { theme: newTheme } }));
 				});
 			}
+
+			// Canvas background style selector
+			const canvasBgOptions = this.#shadow.getElementById("canvas-bg-options");
+			if (canvasBgOptions) {
+				canvasBgOptions.addEventListener("click", (e) => {
+					e.stopPropagation();
+					const btn = (e.target as HTMLElement).closest("[data-bg]") as HTMLElement | null;
+					if (!btn) return;
+					const bg = btn.dataset.bg!;
+					localStorage.setItem("canvas-bg", bg);
+					document.documentElement.setAttribute("data-canvas-bg", bg);
+					canvasBgOptions.querySelectorAll(".canvas-opt").forEach(b => b.classList.remove("active"));
+					btn.classList.add("active");
+					window.dispatchEvent(new Event("canvas-bg-change"));
+				});
+			}
 		} else {
 			this.#shadow.innerHTML = `
 				<style>${STYLES}</style>
@@ -1402,6 +1426,28 @@ const STYLES = `
 .theme-toggle input:checked + .theme-slider { background: #6366f1; }
 .theme-toggle input:checked + .theme-slider::before { transform: translateX(18px); }
 
+/* Canvas background selector in dropdown */
+.dropdown-canvas-row {
+  display: flex; align-items: center; justify-content: center;
+  gap: 8px; padding: 6px 16px;
+}
+.canvas-label {
+  font-size: 0.7rem; font-weight: 600; opacity: 0.5;
+  text-transform: uppercase; letter-spacing: 0.04em;
+}
+.canvas-options { display: flex; gap: 4px; }
+.canvas-opt {
+  font-size: 0.65rem; font-weight: 600; padding: 3px 8px;
+  border: 1px solid var(--rs-border); border-radius: 6px;
+  background: transparent; color: var(--rs-text-secondary);
+  cursor: pointer; transition: all 0.15s;
+}
+.canvas-opt:hover { background: var(--rs-bg-hover); }
+.canvas-opt.active {
+  background: var(--rs-accent); color: white;
+  border-color: var(--rs-accent);
+}
+
 /* Avatar wrapper + notification badge */
 .avatar-wrap { position: relative; }
 .notif-badge {

website/canvas.html

@@ -11,7 +11,7 @@
 		<meta name="apple-mobile-web-app-capable" content="yes">
 		<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
 		<title>rSpace Canvas</title>
-		<script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t)})()</script>
+		<script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t);var b=localStorage.getItem('canvas-bg')||'grid';document.documentElement.setAttribute('data-canvas-bg',b)})()</script>
 		<link rel="stylesheet" href="/theme.css?v=1" />
 		<style>
 			/* When loaded inside an iframe, hide shell chrome */
@@ -972,10 +972,8 @@
 				width: 100%;
 				height: 100%;
 				background-color: var(--rs-canvas-bg);
-				background-image:
-					linear-gradient(var(--rs-canvas-grid) 1px, transparent 1px),
-					linear-gradient(90deg, var(--rs-canvas-grid) 1px, transparent 1px);
-				background-size: 20px 20px;
+				background-image: var(--rs-canvas-bg-image);
+				background-size: var(--rs-canvas-bg-size);
 				background-position: -1px -1px;
 				position: relative;
 				touch-action: none; /* Prevent browser gestures, handle manually */
@@ -5414,9 +5412,12 @@
 			function updateCanvasTransform() {
 				// Transform only the content layer — canvas viewport stays fixed
 				canvasContent.style.transform = `translate(${panX}px, ${panY}px) scale(${scale})`;
-				// Adjust grid to track pan/zoom so it appears infinite
-				const gridSize = 20 * scale;
-				canvas.style.backgroundSize = `${gridSize}px ${gridSize}px`;
+				// Adjust grid/dot pattern to track pan/zoom (skip for blank)
+				const bgStyle = document.documentElement.getAttribute('data-canvas-bg') || 'grid';
+				if (bgStyle !== 'blank') {
+					const gridSize = 20 * scale;
+					canvas.style.backgroundSize = `${gridSize}px ${gridSize}px`;
+				}
 				canvas.style.backgroundPosition = `${panX - 1}px ${panY - 1}px`;
 				// Keep MI bridge in sync
 				__miCanvasBridge.setViewport(panX, panY, scale);
@@ -5430,6 +5431,9 @@
 				presence.setCamera(panX, panY, scale);
 			}
 
+			// Re-render canvas background when user changes preference
+			window.addEventListener("canvas-bg-change", () => updateCanvasTransform());
+
 			document.getElementById("zoom-in").addEventListener("click", () => {
 				scale = Math.min(scale * 1.1, maxScale);
 				updateCanvasTransform();

website/create-space.html

@@ -11,7 +11,7 @@
 		<meta name="apple-mobile-web-app-capable" content="yes">
 		<meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
 		<title>Create a Space — rSpace</title>
-		<script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t)})()</script>
+		<script>(function(){var t=localStorage.getItem('canvas-theme');if(!t)t=matchMedia('(prefers-color-scheme:light)').matches?'light':'dark';document.documentElement.setAttribute('data-theme',t);var b=localStorage.getItem('canvas-bg')||'grid';document.documentElement.setAttribute('data-canvas-bg',b)})()</script>
 		<link rel="stylesheet" href="/theme.css">
 		<link rel="stylesheet" href="/shell.css">
 		<style>

website/public/theme.css

@@ -69,6 +69,10 @@
   /* Canvas */
   --rs-canvas-bg:          #0f172a;
   --rs-canvas-grid:        rgba(255, 255, 255, 0.04);
+  --rs-canvas-dot:         rgba(255, 255, 255, 0.06);
+  --rs-canvas-bg-image: linear-gradient(var(--rs-canvas-grid) 1px, transparent 1px),
+                        linear-gradient(90deg, var(--rs-canvas-grid) 1px, transparent 1px);
+  --rs-canvas-bg-size:  20px 20px;
 
   /* Toolbar */
   --rs-toolbar-bg:         #1e293b;
@@ -128,6 +132,7 @@
   /* Canvas */
   --rs-canvas-bg:          #fafaf7;
   --rs-canvas-grid:        #f1f5f9;
+  --rs-canvas-dot:         #e2e8f0;
 
   /* Toolbar */
   --rs-toolbar-bg:         #fafaf7;
@@ -181,6 +186,7 @@
 
     --rs-canvas-bg:          #fafaf7;
     --rs-canvas-grid:        #f1f5f9;
+    --rs-canvas-dot:         #e2e8f0;
 
     --rs-toolbar-bg:         #fafaf7;
     --rs-toolbar-btn-bg:     #f0efe9;
@@ -191,3 +197,13 @@
     --rs-toolbar-panel-border: #e2e8f0;
   }
 }
+
+/* ── Canvas background style overrides ── */
+[data-canvas-bg="dot"] {
+  --rs-canvas-bg-image: radial-gradient(circle, var(--rs-canvas-dot) 1px, transparent 1px);
+  --rs-canvas-bg-size:  20px 20px;
+}
+[data-canvas-bg="blank"] {
+  --rs-canvas-bg-image: none;
+  --rs-canvas-bg-size:  auto;
+}