Bug 1704853 - Disable skeleton UI on non-default density r=emalysz

This is a little more than we need to disable it, but I figure we'll want to
support different UI densities in the skeleton UI long term.

Differential Revision: https://phabricator.services.mozilla.com/D111906

xpfe/appshell/AppWindow.cpp

@@ -38,6 +38,7 @@
 #include "nsIScreenManager.h"
 #include "nsIScreen.h"
 #include "nsIWindowWatcher.h"
+#include "nsIWindowsUIUtils.h"
 #include "nsIURI.h"
 #include "nsAppShellCID.h"
 #include "nsReadableUtils.h"
@@ -1916,6 +1917,37 @@ nsresult AppWindow::MaybeSaveEarlyWindowPersistentValues(
 
   settings.rtlEnabled = intl::LocaleService::GetInstance()->IsAppLocaleRTL();
 
+  bool isInTabletMode = false;
+  bool autoTouchModePref =
+      Preferences::GetBool("browser.touchmode.auto", false);
+  if (autoTouchModePref) {
+    nsCOMPtr<nsIWindowsUIUtils> uiUtils(
+        do_GetService("@mozilla.org/windows-ui-utils;1"));
+    if (!NS_WARN_IF(!uiUtils)) {
+      uiUtils->GetInTabletMode(&isInTabletMode);
+    }
+  }
+
+  if (isInTabletMode) {
+    settings.uiDensity = SkeletonUIDensity::Touch;
+  } else {
+    int uiDensityPref = Preferences::GetInt("browser.uidensity", 0);
+    switch (uiDensityPref) {
+      case 0: {
+        settings.uiDensity = SkeletonUIDensity::Default;
+        break;
+      }
+      case 1: {
+        settings.uiDensity = SkeletonUIDensity::Compact;
+        break;
+      }
+      case 2: {
+        settings.uiDensity = SkeletonUIDensity::Touch;
+        break;
+      }
+    }
+  }
+
   Unused << PersistPreXULSkeletonUIValues(settings);
 #endif