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Bug 5050

Summary: SDL_RenderDrawLine draws extra pixels at start and end of line
Product: SDL Reporter: William Cleveland <william.quartz>
Component: renderAssignee: Ryan C. Gordon <icculus>
Status: ASSIGNED --- QA Contact: Sam Lantinga <slouken>
Severity: major    
Priority: P2 Keywords: target-2.0.16
Version: 2.0.10   
Hardware: x86_64   
OS: Linux   
Attachments: A simple demo of the issue.

Description William Cleveland 2020-03-21 21:36:57 UTC 
Created attachment 4274 [details]
A simple demo of the issue.

SDL_RenderDrawLine draws extra pixels at the end points when the line is drawn from the 2nd to 4th quadrants. A quadrant reference is as:

                |
           3    |   2
                |
       -------------------
                |
           4    |   1
                |

I think my issue is related to:

https://bugzilla.libsdl.org/show_bug.cgi?id=2796
https://bugzilla.libsdl.org/show_bug.cgi?id=2711

The pixels always appear towards the 3rd quadrant side of the line.

I have attached a simple program that shows the issue in real time. Just click and draw and you will see two white pixels appear whenever the line is being drawn from quadrants 2 to 4.

The program will show a yellow line that has the issue, and it is reproducible--live.

My system is:
Intel® Core™ i5-9600K CPU @ 3.70GHz × 6
Radeon 550 Series (POLARIS12, DRM 3.33.0, 5.3.0-7642-generic, LLVM 9.0.0)
GNOME 3.34.2