Restrict forced panning to known bad platforms

Let's not punish systems that implement overlay scrollbars in a
functional way. The only current example is Firefox on Windows 11 and on
Linux.

app/ui.js

@@ -8,7 +8,8 @@
 
 import * as Log from '../core/util/logging.js';
 import _, { l10n } from './localization.js';
-import { isTouchDevice, isSafari, hasScrollbarGutter, dragThreshold }
+import { isTouchDevice, isMac, isIOS, isAndroid, isChromeOS, isSafari,
+         hasScrollbarGutter, dragThreshold }
     from '../core/util/browser.js';
 import { setCapture, getPointerEvent } from '../core/util/events.js';
 import KeyTable from "../core/input/keysym.js";
@@ -1326,13 +1327,25 @@ const UI = {
 
         const scaling = UI.getSetting('resize') === 'scale';
 
+        // Some platforms have overlay scrollbars that are difficult
+        // to use in our case, which means we have to force panning
+        // FIXME: Working scrollbars can still be annoying to use with
+        //        touch, so we should ideally be able to have both
+        //        panning and scrollbars at the same time
+
+        let brokenScrollbars = false;
+
+        if (!hasScrollbarGutter) {
+            if (isIOS() || isAndroid() || isMac() || isChromeOS()) {
+                brokenScrollbars = true;
+            }
+        }
+
         if (scaling) {
             // Can't be clipping if viewport is scaled to fit
             UI.forceSetting('view_clip', false);
             UI.rfb.clipViewport  = false;
-        } else if (!hasScrollbarGutter) {
+        } else if (brokenScrollbars) {
-            // Some platforms have scrollbars that are difficult
-            // to use in our case, so we always use our own panning
             UI.forceSetting('view_clip', true);
             UI.rfb.clipViewport = true;
         } else {