Set initial crop handles to original page location

Treat the image tile set's 0 coordinate as the top and use pageSize to
compute the bottom of the original screenshot.

Bug: 179907401
Test: Verify potisitioning when scrolling from the top, bottom and
middle.

Change-Id: I44fca11474221b5d4249483bf22a88ede5e8104e

packages/SystemUI/src/com/android/systemui/screenshot/CropView.java

@@ -136,7 +136,7 @@ public class CropView extends View {
             case MotionEvent.ACTION_UP:
                 if (mCurrentDraggingBoundary != CropBoundary.NONE) {
                     // Commit the delta to the stored crop values.
-                    commitDeltas();
+                    commitDeltas(mCurrentDraggingBoundary);
                     updateListener(event);
                 }
         }
@@ -184,12 +184,12 @@ public class CropView extends View {
         animator.addListener(new AnimatorListenerAdapter() {
             @Override
             public void onAnimationEnd(Animator animation) {
-                commitDeltas();
+                commitDeltas(boundary);
             }
 
             @Override
             public void onAnimationCancel(Animator animation) {
-                commitDeltas();
+                commitDeltas(boundary);
             }
         });
         animator.setFloatValues(0f, 1f);
@@ -228,11 +228,14 @@ public class CropView extends View {
         mCropInteractionListener = listener;
     }
 
-    private void commitDeltas() {
-        mTopCrop += mTopDelta;
-        mBottomCrop += mBottomDelta;
-        mTopDelta = 0;
-        mBottomDelta = 0;
+    private void commitDeltas(CropBoundary boundary) {
+        if (boundary == CropBoundary.TOP) {
+            mTopCrop += mTopDelta;
+            mTopDelta = 0;
+        } else if (boundary == CropBoundary.BOTTOM) {
+            mBottomCrop += mBottomDelta;
+            mBottomDelta = 0;
+        }
     }
 
     private void updateListener(MotionEvent event) {

packages/SystemUI/src/com/android/systemui/screenshot/LongScreenshotActivity.java

@@ -339,14 +339,22 @@ public class LongScreenshotActivity extends Activity {
                     }
 
                     @Override
-                    public void onComplete(ImageTileSet imageTileSet) {
+                    public void onComplete(ImageTileSet imageTileSet, int pageSize) {
                         Log.i(TAG, "Got tiles " + imageTileSet.getWidth() + " x "
                                 + imageTileSet.getHeight());
                         mPreview.setImageDrawable(imageTileSet.getDrawable());
                         updateCropLocation();
                         mMagnifierView.setDrawable(imageTileSet.getDrawable(),
                                 imageTileSet.getWidth(), imageTileSet.getHeight());
-                        mCropView.animateBoundaryTo(CropView.CropBoundary.BOTTOM, 0.5f);
+                        // Original boundaries go from the image tile set's y=0 to y=pageSize, so
+                        // we animate to that as a starting crop position.
+                        float topFraction = Math.max(0,
+                                -imageTileSet.getTop() / (float) imageTileSet.getHeight());
+                        float bottomFraction = Math.min(1f,
+                                1 - (imageTileSet.getBottom() - pageSize)
+                                        / (float) imageTileSet.getHeight());
+                        mCropView.animateBoundaryTo(CropView.CropBoundary.TOP, topFraction);
+                        mCropView.animateBoundaryTo(CropView.CropBoundary.BOTTOM, bottomFraction);
                         mBackgroundExecutor.execute(() -> saveCacheBitmap(imageTileSet));
                     }
                 });

packages/SystemUI/src/com/android/systemui/screenshot/ScrollCaptureController.java

@@ -164,7 +164,7 @@ public class ScrollCaptureController {
         if (mImageTileSet.isEmpty()) {
             mCaptureCallback.onError();
         } else {
-            mCaptureCallback.onComplete(mImageTileSet);
+            mCaptureCallback.onComplete(mImageTileSet, session.getPageHeight());
         }
     }
 
@@ -172,7 +172,7 @@ public class ScrollCaptureController {
      * Callback for image capture completion or error.
      */
     public interface ScrollCaptureCallback {
-        void onComplete(ImageTileSet imageTileSet);
+        void onComplete(ImageTileSet imageTileSet, int pageHeight);
         void onError();
     }