[Interest] QML: non scaled image strange issue under Linux

Fatih Uzunoğlu fuzun54 at outlook.com
Sat Jul 23 19:12:30 CEST 2022


In case OpenGL is used, this might be a bug in your OpenGL driver.

As far as I know; Qt uses `GL_NEAREST` when `smooth` is unset, and 
`GL_LINEAR` when `smooth` is set.

I doubt there is extra logic to check if the texture size is the same as 
`Image` size that it uses `GL_NEAREST` regardless of `smooth` property.

I think the docs should say something like "this is the expected 
behavior of the driver", about the `smooth` property.

You might consider using something like: `smooth: (paintedWidth !== 
width) || (paintedHeight !== height) `.

I think it would be better if Qt did not use `GL_LINEAR` in these cases 
by default:

- Texture size is the same as `Image` size.

- `Image` size is non-fractional upscaling of the texture size. (Integer 

That being said, I don't know how Qt RHI behaves. This is valid for 
direct OpenGL.

On 23/07/2022 03:40, Alexander Dyagilev wrote:
> Hello,
> I'm generating image (QR code) using QML image provider. Show it using 
> Image control using actual size (i.e. width height are not specified, 
> and I also set fill mode to Pad).
> Windows and macOS - works fine.
> Linux (Ubuntu) - it's shown blurred. If I set smooth property to false 
> - it's shown as expected.
> Is it a bug? In docs it's stated that smooth has no effect if image is 
> not scaled.
> Qt 5.12.12.
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