Any Alpha value set in a FLinearColor used to draw a line on a Canvas HUD is ignored when the line is drawn

If an Alpha value is set in a FLinearColor that is used to draw a line on a Canvas HUD, the Alpha value is ignored when the line is drawn.

A comment in BatchedElements.cpp indicates that some legacy code relies on the Alpha value being ignored, but this information is not communicated to the user.

1. Create a new code project using the first person template, no starter content.
2. Edit the default HUD .h file that is created for the project to add the following line: FLinearColor VisorColor;
3. Edit the constructor of the default HUD .cpp file to set VisorColor: VisorColor = FLinearColor(0.234335005f, 0.894999981f, 0.296303988f, 0.5f);
   • Note the Alpha has been set to 0.5.
4. Add the following lines of code to the DrawHUD() function:

   float CenterX = Canvas->ClipX / 2;
   float CenterY = Canvas->ClipY / 2;
   float X10 = Canvas->ClipX * 0.1f;
   float Y10 = Canvas->ClipY * 0.1f;
   Canvas->K2_DrawLine(FVector2D(CenterX - X10, CenterY - Y10), FVector2D(0 + (2 * X10), CenterY - Y10), 10.0f, VisorColor);
   

5. Build the project in Visual Studio.
6. Open the project in the Editor.
7. Click Play to start PIE mode.

RESULT:
A horizontal green line is drawn on the HUD, but it is fully opaque. The Alpha set in VisorColor is not applied.

EXPECTED:
The Alpha set in VisorColor is used.