FRect.clipline returns no values even when colliding with a line

[NOTMEE12]

Environment:

Platform:               Windows-11-10.0.26200-SP0
System:                 Windows
System Version:         10.0.26200
Processor:              Intel64 Family 6 Model 154 Stepping 3, GenuineIntel     SSE2: Yes       AVX2: Yes       NEON: No
Architecture:           Bits: 64bit     Linkage: WindowsPE

Python:                 CPython 3.13.2 (main, Mar 17 2025, 21:04:07) [MSC v.1943 64 bit (AMD64)]
GIL Enabled:            True
pygame version:         2.5.6
SDL versions:           Linked: 2.32.10 Compiled: 2.32.10
SDL Mixer versions:     Linked: 2.8.1   Compiled: 2.8.1
SDL Font versions:      Linked: 2.24.0  Compiled: 2.24.0
SDL Image versions:     Linked: 2.8.8   Compiled: 2.8.8
Freetype versions:      Linked: 2.11.1  Compiled: 2.11.1

Display Driver:         Display Not Initialized
Mixer Driver:           Mixer Not Initialized

Current behavior:

Collision using bool(FRect.clipline(line)) shows False even when rect collides line.

Expected behavior:

It should return points (of floats) (thus be a truthy list).

Test code

import pygame

win = pygame.display.set_mode((100, 100), pygame.SCALED)
clock = pygame.time.Clock()
rect = pygame.FRect((0, 0), (0, 0))
line = [(0, 0), (0, 0)]

running = True
while running:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.MOUSEBUTTONDOWN:
            if event.button == 1:
                rect.topleft = (event.pos[0] / 100, event.pos[1] / 100)
            if event.button == 3:
                line[0] = (event.pos[0] / 100, event.pos[1] / 100)

    if pygame.mouse.get_pressed()[0]:
        rect.size = (
            event.pos[0] / 100 - rect.left,
            event.pos[1] / 100 - rect.top,
        )
    if pygame.mouse.get_pressed()[2]:
        line[1] = (event.pos[0] / 100, event.pos[1] / 100)

    win.fill("black")

    color = "red" if not bool(rect.clipline(line)) else "green"

    pygame.draw.rect(
        win,
        color,
        (rect.left * 100, rect.top * 100, rect.width * 100, rect.height * 100),
        width=1,
    )
    pygame.draw.line(
        win,
        color,
        (line[0][0] * 100, line[0][1] * 100),
        (line[1][0] * 100, line[1][1] * 100),
    )

    pygame.display.flip()
    clock.tick(60)

The code above translates the window space to a "world" space (values between (0-1, 0-1)), performs collision check and then renders the rect and the line scaled to the window space.

[Etanla78lmx]

Hello, i'm computer science student and i need to contribute to an open-source project for one of my courses. I would like to work on this issue as my first contribution. Thank you!

[NOTMEE12]

Thanks. I'd love to see this fixed

[oddbookworm]

Before asserting that this is something that needs to be fixed, is this something even meaningful to fix? The point of a rect is that it represents a rectangular region, which isn't really the case when you've got a size-zero rect. SDL rect functions include the left and top boundaries, but not the bottom and right boundaries, so one can argue that this behaves exactly as expected

[NOTMEE12]

Sure when the rect has size-zero rect it shouldn't collide, but the issue here is that the collisions happens with rects that have size as floats. I was working on a game where I used pygame.Frect for the player collisions (which were in grid space, the player wasn't a square unit size) and it had issues (of sometimes not finding collisions) which I eventually pinpointed to this.

I might have not been clear of how to use the test code, you should press and hold LMB to create a Frect (which it then translates to world space). To create a line you should press and hold RMB.