Merge pull request #4361 from salachi/TIMOB-13494-ImageViewScroll

TIMOB-13494-make sure that image doesn't scroll beyond it boundaries

android/modules/ui/src/java/ti/modules/titanium/ui/widget/TiImageView.java

@@ -102,15 +102,19 @@ public boolean onDown(MotionEvent e)
 			@Override
 			public boolean onScroll(MotionEvent e1, MotionEvent e2, float dx, float dy)
 			{
-				if (zoomControls.getVisibility() == View.VISIBLE) {
-					changeMatrix.postTranslate(-dx, -dy);
-					imageView.setImageMatrix(getViewMatrix());
-					requestLayout();
-					scheduleControlTimeout();
-					return true;
-				} else {
-					return false;
+				boolean retValue = false;
+				// Allow scrolling only if the image is zoomed in
+				if (zoomControls.getVisibility() == View.VISIBLE && scaleFactor > 1) {
+					// check if image scroll beyond its borders
+					if (!checkImageScrollBeyondBorders(dx, dy)) {
+						changeMatrix.postTranslate(-dx, -dy);
+						imageView.setImageMatrix(getViewMatrix());
+						requestLayout();
+						scheduleControlTimeout();
+						retValue = true;
+					}
 				}
+				return retValue;
 			}
 
 			@Override
@@ -445,4 +449,22 @@ public void setOrientation(int orientation)
 		this.orientation = orientation;
 		updateScaleType();
 	}
+
+	private boolean checkImageScrollBeyondBorders(float dx, float dy)
+	{
+		float[] matrixValues = new float[9];
+		Matrix m = new Matrix(changeMatrix);
+		// Apply the translation
+		m.postTranslate(-dx, -dy);
+		m.getValues(matrixValues);
+		// Image can move only the extra width or height that is available
+		// after scaling from the original width or height
+		float scaledAdditionalHeight = imageView.getHeight() * (matrixValues[4] - 1);
+		float scaledAdditionalWidth = imageView.getWidth() * (matrixValues[0] - 1);
+		if (matrixValues[5] > -scaledAdditionalHeight && matrixValues[5] < 0 && matrixValues[2] > -scaledAdditionalWidth
+			&& matrixValues[2] < 0) {
+			return false;
+		}
+		return true;
+	}
 }