FSlateDrawElement::MakeLines() add some extra vertices

Hi,

I try to display some shape in a custom widget UI using UWidget and SCompoundWidget.

i succed in displaying a quad using FSlateDrawElement::MakeLines()

My quad is correct when its size is big.

But when i display a smaller quad, it seems that extra vertices are added.

Here is my code:

int32 SSymbolViewerCompoundWidget::OnPaint(const FPaintArgs& Args, const FGeometry& AllottedGeometry, const FSlateRect& MyCullingRect,
FSlateWindowElementList& OutDrawElements, int32 LayerId, const FWidgetStyle& InWidgetStyle,
bool bParentEnabled) const
{
FVector2D pointTopLeft;
pointTopLeft.X = 0;
pointTopLeft.Y = 0;

FVector2D pointBottomRight;
pointBottomRight.X = 25;
pointBottomRight.Y = 25;

TArray< FVector2D > linePoints;
linePoints.AddUninitialized(5);
linePoints[0] = FVector2D(pointTopLeft.X, pointTopLeft.Y);
linePoints[1] = FVector2D(pointTopLeft.X, pointBottomRight.Y);
linePoints[2] = FVector2D(pointBottomRight.X, pointBottomRight.Y);
linePoints[3] = FVector2D(pointBottomRight.X, pointTopLeft.Y);
linePoints[4] = FVector2D(pointTopLeft.X, pointTopLeft.Y);

FSlateDrawElement::MakeLines(
OutDrawElements,
LayerId,
AllottedGeometry.ToPaintGeometry(),
linePoints,
//MyCullingRect,
ESlateDrawEffect::None,
FLinearColor(1.0f, 1.0f, 1.0f, 1.0f),
true,
2.0f
);

return LayerId;
}

My my quad is not displayed as a quad ?