iOS: add BrowserComponent.interfaceStyle property to pin web-view appearance (#5203)

WKWebView feeds the device's light/dark trait into the page's
prefers-color-scheme media query and the UA rendering of default
backgrounds and form controls. Since #4786 enabled the UIScene lifecycle
by default, the window is created programmatically and the
UIUserInterfaceStyle Info.plist key is no longer reliably applied to it,
so embedded web views started following the device dark mode with no way
to override it per component.

Add a BrowserComponent.BROWSER_PROPERTY_INTERFACE_STYLE property
("light"/"dark"/"auto") routed through setBrowserProperty to the native
widget, where it sets the web view's overrideUserInterfaceStyle. This is
the natural per-component vertical rather than an app-wide window hack.
overrideUserInterfaceStyle is a UIView property so the single cast covers
both WKWebView and the legacy UIWebView. Other platforms ignore the
unknown property as usual.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: shai-almog

CodenameOne/src/com/codename1/ui/BrowserComponent.java

@@ -91,6 +91,14 @@ public class BrowserComponent extends Container {
     /// Browser property key to control whether links with `target="_blank"` or `target="_new"`
     /// should be followed in the current browser view. Defaults to `true`.
     public static final String BROWSER_PROPERTY_FOLLOW_TARGET_BLANK = "BrowserComponent.followTargetBlank";
+    /// Browser property key to pin the appearance (light/dark) of the native web widget regardless
+    /// of the device-wide setting. This drives the `prefers-color-scheme` CSS media query and the
+    /// user-agent rendering of form controls and default backgrounds inside the page. Accepted
+    /// values are `"light"`, `"dark"` and `"auto"` (follow the device, the default). Use it via
+    /// `browser.setProperty(BrowserComponent.BROWSER_PROPERTY_INTERFACE_STYLE, "light")`.
+    /// Currently honored on iOS (WKWebView); platforms that do not support pinning the web-view
+    /// appearance ignore it.
+    public static final String BROWSER_PROPERTY_INTERFACE_STYLE = "BrowserComponent.interfaceStyle";
     /// String constant for web event listener `com.codename1.ui.events.ActionListener)`
     public static final String onStart = "onStart";
     /// String constant for web event listener `com.codename1.ui.events.ActionListener)`

Ports/iOSPort/nativeSources/IOSNative.m

@@ -3079,6 +3079,29 @@ void com_codename1_impl_ios_IOSNative_setBrowserFollowTargetBlank___long_boolean
     });
 }
 
+// Pin the appearance of the native web widget independently of the device-wide
+// setting. style: 0 = unspecified/auto (follow device), 1 = light, 2 = dark.
+// Setting overrideUserInterfaceStyle on the WKWebView feeds the trait collection
+// that drives the page's prefers-color-scheme media query and the UA rendering of
+// default backgrounds / form controls, so a page that adapts to dark mode can be
+// kept light (or dark) regardless of the user's system appearance.
+void com_codename1_impl_ios_IOSNative_setBrowserInterfaceStyle___long_int(CN1_THREAD_STATE_MULTI_ARG JAVA_OBJECT instanceObject, JAVA_LONG peer, JAVA_INT style) {
+    dispatch_sync(dispatch_get_main_queue(), ^{
+        POOL_BEGIN();
+        if (@available(iOS 13.0, *)) {
+            UIView* w = (BRIDGE_CAST UIView*)((void *)peer);
+            UIUserInterfaceStyle uiStyle = UIUserInterfaceStyleUnspecified;
+            if (style == 1) {
+                uiStyle = UIUserInterfaceStyleLight;
+            } else if (style == 2) {
+                uiStyle = UIUserInterfaceStyleDark;
+            }
+            w.overrideUserInterfaceStyle = uiStyle;
+        }
+        POOL_END();
+    });
+}
+
 
 void com_codename1_impl_ios_IOSNative_setPinchToZoomEnabled___long_boolean(CN1_THREAD_STATE_MULTI_ARG JAVA_OBJECT instanceObject, JAVA_LONG peer, JAVA_BOOLEAN enabled) {
     dispatch_sync(dispatch_get_main_queue(), ^{

Ports/iOSPort/src/com/codename1/impl/ios/IOSImplementation.java

@@ -7928,6 +7928,19 @@ public void setBrowserProperty(PeerComponent browserPeer, String key, Object val
         if (BrowserComponent.BROWSER_PROPERTY_FOLLOW_TARGET_BLANK.equals(key)) {
             nativeInstance.setBrowserFollowTargetBlank(get(browserPeer), Boolean.TRUE.equals(value));
         }
+        if (BrowserComponent.BROWSER_PROPERTY_INTERFACE_STYLE.equals(key)) {
+            // Maps to UIUserInterfaceStyle: 0 = unspecified/auto, 1 = light, 2 = dark.
+            int style = 0;
+            if (value != null) {
+                String v = value.toString();
+                if ("light".equalsIgnoreCase(v)) {
+                    style = 1;
+                } else if ("dark".equalsIgnoreCase(v)) {
+                    style = 2;
+                }
+            }
+            nativeInstance.setBrowserInterfaceStyle(get(browserPeer), style);
+        }
     }
 
     /**

Ports/iOSPort/src/com/codename1/impl/ios/IOSNative.java

@@ -253,6 +253,8 @@ native void fillGradient(int kind, int stopCount, float[] positions, float[] pre
 
     native void setBrowserUserAgent(long browserPeer, String ua);
     native void setBrowserFollowTargetBlank(long browserPeer, boolean follow);
+    // style: 0 = unspecified/auto (follow device), 1 = light, 2 = dark
+    native void setBrowserInterfaceStyle(long browserPeer, int style);
 
     native void browserBack(long browserPeer);
     native void browserStop(long browserPeer);