Add workaround for zoomed images

This should allow moving around on zoomed images. Pagination will kick back in when you get close enough to an edge.

2 files changed, 91 insertions, 1 deletions

diff --git a/org.fox.ttrss/src/main/java/org/fox/ttrss/GalleryImageFragment.java b/org.fox.ttrss/src/main/java/org/fox/ttrss/GalleryImageFragment.java
index cae52798..873706e0 100755
--- a/org.fox.ttrss/src/main/java/org/fox/ttrss/GalleryImageFragment.java
+++ b/org.fox.ttrss/src/main/java/org/fox/ttrss/GalleryImageFragment.java
@@ -44,7 +44,7 @@ public class GalleryImageFragment extends GalleryBaseFragment {
         ImageView imgView = view.findViewById(R.id.flavor_image);
 
         // TODO: ImageMatrixTouchHandler doesn't like context menus
-        ImageMatrixTouchHandler touchHandler = new ImageMatrixTouchHandler(view.getContext());
+        ImageMatrixTouchHandler touchHandler = new PagerAwareImageMatrixTouchHandler(view.getContext());
 
         imgView.setOnTouchListener(touchHandler);
 
diff --git a/org.fox.ttrss/src/main/java/org/fox/ttrss/PagerAwareImageMatrixTouchHandler.java b/org.fox.ttrss/src/main/java/org/fox/ttrss/PagerAwareImageMatrixTouchHandler.java
new file mode 100644
index 00000000..46609f8f
--- /dev/null
+++ b/org.fox.ttrss/src/main/java/org/fox/ttrss/PagerAwareImageMatrixTouchHandler.java
@@ -0,0 +1,90 @@
+package org.fox.ttrss;
+
+import android.content.Context;
+import android.graphics.Matrix;
+import android.graphics.drawable.Drawable;
+import android.view.MotionEvent;
+import android.view.View;
+import android.widget.ImageView;
+
+import com.bogdwellers.pinchtozoom.ImageMatrixTouchHandler;
+
+// Based on https://github.com/martinwithaar/PinchToZoom/blob/master/pinchtozoom/src/main/java/com/bogdwellers/pinchtozoom/view/ImageViewPager.java
+// mLastMotionX is a simplified version of ViewPager's MotionEvent logic
+public class PagerAwareImageMatrixTouchHandler extends ImageMatrixTouchHandler {
+    /**
+     * NOT Thread safe! (But it all happens on the UI thread anyway)
+     */
+    private static final float[] VALUES = new float[9];
+
+    private static final float SCALE_THRESHOLD = 1.2f;
+
+    private float mLastMotionX;
+
+    public PagerAwareImageMatrixTouchHandler(Context context) {
+        super(context);
+    }
+
+    @Override
+    public boolean onTouch(View view, MotionEvent event) {
+        super.onTouch(view, event);
+
+        if (event.getPointerCount() > 1) {
+            view.getParent().requestDisallowInterceptTouchEvent(true);
+            return true;
+        }
+
+        if (event.getAction() != MotionEvent.ACTION_MOVE)
+        {
+            return true;
+        }
+
+        float x = event.getX(0);
+        float dx = x - mLastMotionX;
+        mLastMotionX = x;
+
+        ImageView iv = (ImageView) view;
+        Drawable drawable = iv.getDrawable();
+        if (drawable != null) {
+            float vw = iv.getWidth();
+            float vh = iv.getHeight();
+            float dw = drawable.getIntrinsicWidth();
+            float dh = drawable.getIntrinsicHeight();
+
+            Matrix matrix = iv.getImageMatrix();
+            matrix.getValues(VALUES);
+            float tx = VALUES[Matrix.MTRANS_X] + dx;
+            float sdw = dw * VALUES[Matrix.MSCALE_X];
+
+            boolean blockScroll = VALUES[Matrix.MSCALE_X] / centerInsideScale(vw, vh, dw, dh) > SCALE_THRESHOLD && !translationExceedsBoundary(tx, vw, sdw) && sdw > vw; // Assumes x-y scales are equal
+            view.getParent().requestDisallowInterceptTouchEvent(blockScroll);
+        }
+
+        return true;
+    }
+
+    /**
+     * <p>Returns the scale ratio between view and drawable for the longest side.</p>
+     *
+     * @param vw
+     * @param vh
+     * @param dw
+     * @param dh
+     * @return
+     */
+    public static final float centerInsideScale(float vw, float vh, float dw, float dh) {
+        return vw / vh <= dw / dh ? vw / dw : vh / dh;
+    }
+
+    /**
+     * <p>Determines whether a translation makes the view exceed the boundary of a drawable.</p>
+     *
+     * @param tx
+     * @param vw
+     * @param dw
+     * @return
+     */
+    public static final boolean translationExceedsBoundary(float tx, float vw, float dw) {
+        return dw >= vw && (tx > 0 || tx < vw - dw);
+    }
+}