Switch mode without restart

cameraview/src/main/java/com/otaliastudios/cameraview/engine/Camera1Engine.java

@@ -145,6 +145,36 @@ protected boolean collectCameraInfo(@NonNull Facing facing) {
         return false;
     }
 
+    @EngineThread
+    @Override
+    protected void prepareNewMode() {
+        if(previewAspectRatioEqualsForModes()) {
+            Camera.Parameters params = mCamera.getParameters();
+            setPictureSize(params);
+            applyDefaultFocus(params);
+            params.setRecordingHint(getMode() == Mode.VIDEO);
+            mCamera.setParameters(params);
+        } else {
+            restartBind();
+        }
+    }
+
+    private boolean previewAspectRatioEqualsForModes() {
+        if (mCaptureSize == null) {
+            return false;
+        }
+        Size prevModeSize = mCaptureSize;
+        mCaptureSize = computeCaptureSize();
+
+        boolean flip = getAngles().flip(Reference.SENSOR, Reference.VIEW);
+        AspectRatio prevModePreviewTargetRatio = AspectRatio.of(prevModeSize.getWidth(), prevModeSize.getHeight());
+        AspectRatio targetRatio = AspectRatio.of(mCaptureSize.getWidth(), mCaptureSize.getHeight());
+        if (flip) prevModePreviewTargetRatio = prevModePreviewTargetRatio.flip();
+        if (flip) targetRatio = targetRatio.flip();
+
+        return prevModePreviewTargetRatio.equals(targetRatio);
+    }
+
     //endregion
 
     //region Start
@@ -216,18 +246,7 @@ protected Task<Void> onStartPreview() {
         params.setPreviewFormat(ImageFormat.NV21);
         // setPreviewSize is not allowed during preview
         params.setPreviewSize(mPreviewStreamSize.getWidth(), mPreviewStreamSize.getHeight());
-        if (getMode() == Mode.PICTURE) {
-            // setPictureSize is allowed during preview
-            params.setPictureSize(mCaptureSize.getWidth(), mCaptureSize.getHeight());
-        } else {
-            // mCaptureSize in this case is a video size. The available video sizes are not
-            // necessarily a subset of the picture sizes, so we can't use the mCaptureSize value:
-            // it might crash. However, the setPictureSize() passed here is useless : we don't allow
-            // HQ pictures in video mode.
-            // While this might be lifted in the future, for now, just use a picture capture size.
-            Size pictureSize = computeCaptureSize(Mode.PICTURE);
-            params.setPictureSize(pictureSize.getWidth(), pictureSize.getHeight());
-        }
+        setPictureSize(params);
         mCamera.setParameters(params);
 
         mCamera.setPreviewCallbackWithBuffer(null); // Release anything left

cameraview/src/main/java/com/otaliastudios/cameraview/engine/Camera2Engine.java

@@ -389,6 +389,13 @@ protected final boolean collectCameraInfo(@NonNull Facing facing) {
         return false;
     }
 
+    @EngineThread
+    @Override
+    protected void prepareNewMode() {
+        LOG.w("prepareNewMode:", "can't prepare new mode without restart for Engine2");
+        restartBind();
+    }
+
     //endregion
 
     //region Start

cameraview/src/main/java/com/otaliastudios/cameraview/engine/CameraBaseEngine.java

@@ -2,6 +2,7 @@
 
 import android.graphics.PointF;
 import android.graphics.RectF;
+import android.hardware.Camera;
 import android.location.Location;
 
 import androidx.annotation.CallSuper;
@@ -390,12 +391,14 @@ public final void setMode(@NonNull Mode mode) {
                     new Runnable() {
                 @Override
                 public void run() {
-                    restart();
+                    prepareNewMode();
                 }
             });
         }
     }
 
+    protected abstract void prepareNewMode();
+
     @NonNull
     @Override
     public final Mode getMode() {
@@ -750,6 +753,21 @@ private Size getPreviewSurfaceSize(@NonNull Reference reference) {
                 : preview.getSurfaceSize();
     }
 
+    void setPictureSize(Camera.Parameters params) {
+        if (getMode() == Mode.PICTURE) {
+            // setPictureSize is allowed during preview
+            params.setPictureSize(mCaptureSize.getWidth(), mCaptureSize.getHeight());
+        } else {
+            // mCaptureSize in this case is a video size. The available video sizes are not
+            // necessarily a subset of the picture sizes, so we can't use the mCaptureSize value:
+            // it might crash. However, the setPictureSize() passed here is useless : we don't allow
+            // HQ pictures in video mode.
+            // While this might be lifted in the future, for now, just use a picture capture size.
+            Size pictureSize = computeCaptureSize(Mode.PICTURE);
+            params.setPictureSize(pictureSize.getWidth(), pictureSize.getHeight());
+        }
+    }
+
     /**
      * Returns the snapshot size, but not cropped with the view dimensions, which
      * is what we will do before creating the snapshot. However, cropping is done at various