Scrolling into view UMG widget without mouse only works downward

[anonymous_user_823992f1]

SETUP:

1. In Blueprints creating a Scrollbox in a size box. It containing a uniform grid.
2. The grid is populated with 9 simple custom widgets all in column 0.
3. The blueprint holding all of this listens for DPAD up or DPAD down which decrements and increments a variable used to select one of the 9 custom widgets.
4. After up or down is pressed and the index modified, ScrollWidgetIntoView() is called on the newly selected widget

WHAT HAPPENS:
Press down, when the next widget is cut off from the list, will properly scroll to the widget. Pressing up does not scroll.

EXPECTED:
Pressing up will scroll the selected widget into view in the same way it works when scrolling downward.

VARIATIONS:

• This happens whether called ScrollWidgetIntoView() is called from C++ or Blueprints.
• This happens whether “animation scroll” is true or false.
• This happens whether vertical or horizontal scrolling (and horizontal seems to introduce other issues.)

[CyberKatana]

I have the same result after updating to 4.17. Scroll from top to down direction works perfectly, at up direction do not works. When i try again scroll down scroll not work. I think problem in detection of state of widget(in render zone/ not in render zone)

[anonymous_user_823992f1]

If this affects you, please vote up for visibility.

[anonymous_user_3580a01d]

Seeing the exact same issue and my head hurts a bit looking at the code. Will have a look tomorrow and hopefully make a patch.

[anonymous_user_e729f54e]

Hello fxstronster,

I was able to reproduce this issue on our end. I have written up a report and I have submitted it to the developers for further consideration. I have provided a link to the public tracker. Please feel free to use the link provided for future updates.

Link: Unreal Engine Issues and Bug Tracker (UE-50084)

Make it a great day

[anonymous_user_3580a01d]

Someone at Epic made some unorthodox math, here is a patch.

The file you want to change is Engine\Source\Runtime\Slate\Private\Widgets\Layout\SScrollBox.cpp

@@ -433,8 +433,9 @@
 		}
 		else
 		{
-			const float WidgetStartPosition = GetScrollComponentFromVector(WidgetGeometry->Geometry.Position);
-			const float WidgetEndPosition = GetScrollComponentFromVector(WidgetGeometry->Geometry.Position + WidgetGeometry->Geometry.GetLocalSize());
+			const FVector2D WidgetLocalPosition = MyGeometry.AbsoluteToLocal(WidgetGeometry->Geometry.GetAbsolutePosition());
+			const float WidgetStartPosition = GetScrollComponentFromVector(WidgetLocalPosition);
+			const float WidgetEndPosition = GetScrollComponentFromVector(WidgetLocalPosition + WidgetGeometry->Geometry.GetLocalSize());
 			const float ViewStartPosition = InScrollPadding;
 			const float ViewEndPosition = GetScrollComponentFromVector(MyGeometry.GetLocalSize() - InScrollPadding);

This is in UNIX patch format: scroll to line 433, remove lines with - in front, add lines with +

Will make a PR on GitHub

Make it a great engine.