Gate the titlebar inset on a windowChrome capability instead of osType (#570)

packages/platform/src/tauri/index.ts

@@ -58,6 +58,7 @@ const ALL_CAPABILITIES: PlatformCapabilities = {
   localFiles: true,
   timeline: true,
   multiWindow: true,
+  windowChrome: true,
   plugins: true,
   encryption: true,
   updater: true,

packages/platform/src/types.ts

@@ -255,6 +255,13 @@ export interface PlatformCapabilities {
   timeline: boolean;
   /** More than one window or tab on the same data. */
   multiWindow: boolean;
+  /**
+   * The page is the window's titlebar: it draws the drag region and window
+   * controls, and leaves room for macOS traffic lights. False when something
+   * else owns the frame around the page (a browser tab), so none of that
+   * chrome should be reserved or drawn.
+   */
+  windowChrome: boolean;
   /** The plugin runtime. */
   plugins: boolean;
   /** Workspace encryption backed by a key the host keeps. */

packages/platform/src/web/README.md

@@ -129,13 +129,16 @@ Reported honestly, so callers gate on the question rather than on the host:
 
 | True | False |
 | --- | --- |
-| `cookieJar` (the jar stores and edits here; only filling it needs the sender) | `grpc`, `websocket`, `git`, `sync`, `tlsOptions`, `localFiles`, `timeline`, `multiWindow`, `plugins`, `encryption`, `updater`, `clipboardRead`, `systemFonts`, `license` |
+| `cookieJar` (the jar stores and edits here; only filling it needs the sender) | `grpc`, `websocket`, `git`, `sync`, `tlsOptions`, `localFiles`, `timeline`, `multiWindow`, `windowChrome`, `plugins`, `encryption`, `updater`, `clipboardRead`, `systemFonts`, `license` |
 
 `multiWindow: false` means the host cannot open a *second window* on demand —
 what `cmd_new_child_window` does for Settings and workspace switching. It is not
 a claim that nothing else is looking: other tabs may well be open on the same
 worker, and it pushes every write to all of them regardless.
 
+`windowChrome: false` means the browser owns the frame around the page, so the
+header draws no window controls and reserves no room for macOS traffic lights.
+
 ## Multiple tabs
 
 Each tab mints a label at load (`tab_xxxxxxxx`) and sends it with every command;

packages/platform/src/web/index.ts

@@ -49,6 +49,9 @@ function capabilitiesFor(): PlatformCapabilities {
     // else is looking: other tabs may well be open on the same worker, and it
     // pushes every write to all of them regardless of this flag.
     multiWindow: false,
+    // The browser draws the frame around the page. There are no traffic lights
+    // to leave room for and no window controls to draw.
+    windowChrome: false,
     plugins: false,
     encryption: false,
     updater: false,