Using Debian, Celeste has massive screen tearing, and screen flashing.  All inputs are consumed, leaving  me unable  to move past the start screen.  The native Linux binary is being used, and I get an error, EXT_swap_control_tear unsupported. Fall back to standard VSync.

This is an example of the kind of graphical distortion I get. Apologies for the pictures of the screen as opposed to a screenshot ; the window consumes all my inputs, and does nothing with them.

I'd typically say this is a GPU issue, but other games have no issues with my GPU driver ; and this looks to be more of an issue with interacting with the windowing system - GPU glitches don't result in half transparent windows across the screen, in my experience.

The position of the visible chunks also changes. I have "Triplebuffer" and "TearFree"  enabled in my Xorg.conf for my intel iGPU.

The transparency is due to my camera not being fast enough to catch individual tears in the window. I don't  have a  compositor enabled, so transparency wouldn't make sense.

Enabling a compositor causes the tearing to  stop, but the flashing remains. The compositor reports these errors while Celeste is running:

error 3: BadWindow (invalid Window parameter) request 2 minor 0 serial 87112

error 3: BadWindow (invalid Window parameter) request 20 minor 0 serial 87113

error 3: BadWindow (invalid Window parameter) request 2 minor 0 serial 87114

error 3: BadWindow (invalid Window parameter) request 20 minor 0 serial 87115

error 3: BadWindow (invalid Window parameter) request 2 minor 0 serial 206317

error 3: BadWindow (invalid Window parameter) request 20 minor 0 serial 206318

Picom gives more descriptive errors:

[ 04/12/21 14:38:19.265 x_create_picture_with_pictfmt_and_pixmap ERROR ] failed to create picture (X error 9 DRAWABLE request 138 minor 4 serial 2346)

[ 04/12/21 14:38:19.265 paint_one ERROR ] Window 0x00600014 is missing painting data.

[ 04/12/21 14:38:21.384 x_create_picture_with_pictfmt_and_pixmap ERROR ] failed to create picture (X error 9 DRAWABLE request 138 minor 4 serial 12077)

[ 04/12/21 14:38:21.385 paint_one ERROR ] Window 0x0060005d is missing painting data.

Other OpenGL apps, such as GLXGears, work fine.

Update: Using Mesa 20 on Debian SID, the VSync error disappears.

However, the flashing and tearing remains. The compositor reports a new error on top of the error 3:

error 9: BadDrawable (invalid Pixmap or Window parameter) request 142 minor 1 serial 20401

Resolved! Disabling full screen in the settings (Which are confusingly not located in the Celeste folder...) fixes the tearing, despite not making it a windowed window!