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Bug 5050 - SDL_RenderDrawLine draws extra pixels at start and end of line
Summary: SDL_RenderDrawLine draws extra pixels at start and end of line
Status: ASSIGNED
Alias: None
Product: SDL
Classification: Unclassified
Component: render (show other bugs)
Version: 2.0.10
Hardware: x86_64 Linux
: P2 major
Assignee: Ryan C. Gordon
QA Contact: Sam Lantinga
URL:
Keywords: target-2.0.16
Depends on:
Blocks:
 
Reported: 2020-03-21 21:36 UTC by William Cleveland
Modified: 2020-07-16 18:29 UTC (History)
0 users

See Also:

Attachments
A simple demo of the issue. (3.02 KB, text/x-c++src)
2020-03-21 21:36 UTC, William Cleveland 		Details
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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