Prevent repaint overwrite of iOS screenshots

Author: shai-almog

CodenameOne/src/com/codename1/impl/CodenameOneImplementation.java

@@ -1214,6 +1214,20 @@ public void screenshot(SuccessCallback<Image> callback) {
         callback.onSucess(img);
     }
 
+    /**
+     * Indicates whether the Codename One implementation expects caller-side painting to run
+     * after a native screenshot has been captured. Implementations that composite peer
+     * components into the screenshot can override this to {@code false} so downstream code
+     * won't immediately repaint the captured image and accidentally hide native peers.
+     *
+     * @param screenshot the screenshot image produced by {@link #screenshot(SuccessCallback)}
+     * @return {@code true} if the caller should repaint Codename One components onto the
+     *         screenshot, {@code false} otherwise.
+     */
+    public boolean shouldPaintNativeScreenshot(Image screenshot) {
+        return true;
+    }
+
     /**
      * Returns true if the platform supports a native image cache.  The native image cache
      * is different than just {@link FileSystemStorage#hasCachesDir()}.  A native image cache

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

@@ -5013,6 +5013,20 @@ public void screenshot(SuccessCallback<Image> callback) {
         impl.screenshot(callback);
     }
 
+    /**
+     * Indicates whether callers should repaint Codename One components onto a screenshot image
+     * returned from {@link #screenshot(SuccessCallback)}. Platforms that already composite
+     * peer components into the native screenshot can return {@code false} to keep the captured
+     * pixels intact.
+     *
+     * @param screenshot the image returned from {@link #screenshot(SuccessCallback)}.
+     * @return {@code true} if the caller should repaint Codename One components onto the
+     *         screenshot, {@code false} otherwise.
+     */
+    public boolean shouldPaintNativeScreenshot(Image screenshot) {
+        return impl.shouldPaintNativeScreenshot(screenshot);
+    }
+
 
                            /**
      * Convenience method to schedule a task to run on the EDT after {@literal timeout}ms.

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

@@ -300,6 +300,7 @@ public void addCookie(Cookie c) {
     }
 
     private static SuccessCallback<Image> screenshotCallback;
+    private static volatile boolean lastScreenshotHasNativePeers;
 
     @Override
     public void screenshot(final SuccessCallback<Image> callback) {
@@ -337,6 +338,7 @@ static void onScreenshot(final byte[] imageData) {
         final SuccessCallback<Image> callback = screenshotCallback;
         screenshotCallback = null;
         if (callback == null) {
+            lastScreenshotHasNativePeers = false;
             return;
         }
 
@@ -366,6 +368,7 @@ public void run() {
                             }
 
                             if (image != null && image.getGraphics() != null) {
+                                lastScreenshotHasNativePeers = true;
                                 callback.onSucess(image);
                                 return;
                             }
@@ -374,11 +377,19 @@ public void run() {
                         Log.e(t);
                     }
                 }
+                lastScreenshotHasNativePeers = false;
                 callback.onSucess(null);
             }
         });
     }
 
+    @Override
+    public boolean shouldPaintNativeScreenshot(Image screenshot) {
+        boolean shouldPaint = !lastScreenshotHasNativePeers;
+        lastScreenshotHasNativePeers = false;
+        return shouldPaint;
+    }
+
     /**
      * Used to enable/disable native cookies from native code.
      * @param cookiesArray 

docs/demos/common/src/test/java/com/codenameone/developerguide/animations/AnimationDemosScreenshotTest.java

@@ -96,7 +96,9 @@ private void saveScreenshot(String storageKey, Image screenshot) throws IOExcept
 
     private Image capture(Form form) {
         Image screenshot = Image.createImage(form.getWidth(), form.getHeight());
-        form.paintComponent(screenshot.getGraphics(), true);
+        if (Display.getInstance().shouldPaintNativeScreenshot(screenshot)) {
+            form.paintComponent(screenshot.getGraphics(), true);
+        }
         return screenshot;
     }
 

scripts/device-runner-app/tests/Cn1ssDeviceRunnerHelper.java

@@ -62,7 +62,9 @@ static boolean emitCurrentFormScreenshot(String testName) {
             return false;
         }
         Image screenshot = img[0];
-        current.paintComponent(screenshot.getGraphics(), true);
+        if (Display.getInstance().shouldPaintNativeScreenshot(screenshot)) {
+            current.paintComponent(screenshot.getGraphics(), true);
+        }
         try {
             ImageIO io = ImageIO.getImageIO();
             if (io == null || !io.isFormatSupported(ImageIO.FORMAT_PNG)) {