[Upstream Bug, unfixable] Pixels on canvas are misaligned

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porg
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by porg »

One interesting observation:
• I zoom into the word "Goal" on a screenshot.
• The right lowercase L is a nice straight line to align with.
• Try to position my selection to include the whole "L".
• Zoom in via trackpad. The offset is ca 20% of a full pixel.
• Zoom further in or out via trackpad. With the same selection. The offset gets different: Next time maybe 60%, then 0%.
• Also if you unselect and make the selection again.
• The offset between selection border and letter L line differs each time.
porg
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by porg »

BUT: At the exact same zoomfactor (5000%) the offset is always the same. Also for each fresh selection you create with the same boundary line.

But inbetween the different zoomfactors that selection boundary offset changes quite dynamically and not consistently.

So some rounding error is going on.
porg
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by porg »

See my recently made observations in this ▶️ video (with sound! 🔈).
Note: In this video the rulers in the Detail Editor were set to hidden.
Last edited by porg on Tue Jun 07, 2022 5:43 pm, edited 3 times in total.
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by forum_adm »

What happens if you hide the rulers?
porg
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by porg »

1) In the previous video included in my previous post the rulers in the Editor window were set to hidden. I added a remark to the post that this is very clear for everyone reading this.

2) I now made ▶️ another video (with sound! 🔈) with the rulers in the Editor window being set to visible.

Learnings:
• The selection is always aligned with the pixel units of the rulers, both horizontal and vertical, at all zoom levels. At maximum it is off by 1 maybe 2 physical hardware pixels, but that offset remains stabily the same. So this is the minimum necessary rounding. And it is consistent.
• But with a given selection and zooming in/out via shortcuts at fixed zoom level steps OR when zooming smoothly via trackpad, the very same pixel on the canvas is once "a bit left" of the selection boundary, once "quite right", then again "strong off to the left", then again "minimally to the right", and so on. A rounding behavior which seems very random & chaotic for an outsider. And which makes it impossible to work, because you can not adapt to it "okay in reality it is alway a bit below". No it is once like this, once like that, another time again different. Completely chaotic. Impossible to adapt to it.
Last edited by porg on Tue Jun 07, 2022 5:43 pm, edited 1 time in total.
porg
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by porg »

So, have my new observations been of any help in your investigation of the bug?
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by forum_adm »

Not really. I checked onto three different machines and was not able to reproduce it.

Also, I found no code with any rounding issues. The selection frame is scaled by Apple Quartz for the display.

So, can you maybe try under a new user with the default prefs onto your machine?

Can you maybe try with the latest Monterey?
Fotokunst
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by Fotokunst »

Test, iMac 27inch 2019, macOS 12.4.
Is this OK?



Bildschirmfoto 2022-06-08 um 10.43.jpg
Bildschirmfoto 2022-06-08 um 10.43.jpg (27.15 KiB) Viewed 125 times
Zoom 5000%


Bildschirmfoto 2022-06-08 um 10.44.jpg
Bildschirmfoto 2022-06-08 um 10.44.jpg (22.71 KiB) Viewed 125 times
Zoom 5000%







I removed Bildschirmfoto 2022-06-08 um 10.45.jpg
That sreenshot was not usefull for testing.
You can ignore all comments of Pic 10.45.
Sorry for confusion.


Joerg
Last edited by Fotokunst on Thu Jun 09, 2022 7:10 pm, edited 4 times in total.
porg
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by porg »

@Joerg

I) ✅ Pics 10.43 and 10.44: Seem ok. But the pixel content makes it hard to judge with certainty, see III. At which zoom factor did you take these screenshots?

II) ❗️ Pic 10.45 (5000% zoom): Update: Situation unclear. @Joerg is still testing

III) Please try what I did in my previous two videos: Make a screenshot of text with antialiasing (simply from a TextEdit window). Turn rulers on. Zoom in. Make a selection. Then zoom in/out smoothly via trackpad or with CMD +/-. For me the selection was ALWAYS aligned with the rulers (at max 1 physical screen pixel off due to necessary rounding). What jumped around where the content pixels at the different zoom factors. Once the line was fully inside the selection ,then a little bit out, then much out, etc.
Last edited by porg on Thu Jun 09, 2022 10:27 pm, edited 4 times in total.
porg
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Re: [Blocker Bug] Selection border not aligned with pixel grid - Impossible to reliably tell which pixel selected

Post by porg »

@forum_adm

I) Joerg's testing on macOS 12.4 Monterrey and on iMac 27inch 2019, an OS and HW newer than mine, is still ongoing. Let's see what his findings will be.

II) I cannot update to Monterrey. My Retina MacBook Pro 15'' (Mid 2014) is only supported until including macOS 11 Big Sur.

III) But I did the test with a new user account and sadly I can reproduce the bug:
1) Created new user (normal user, no admin rights)
2) Made screenshot in TextEdit with macOS internal screenshot tool (⌘-4).
3) Opened PNG in GC.
- GC was uninitialized on that user account, hence gave me 2 successive dialogs:
- Detected Retina display. How shall I display? I choose "standard" (1 pixel).
- Detected alpha channel. How to proceed? I choose "Open and keep".
4) Rulers were off. Left them off.
5) Zoomed in. Made selection. 👉 ❌ Straight pixel lines NOT aligned with selection.
6) Turned on rulers:
- ✅ Selection frame always aligned with rulers. Also when resizing the selection it remains always aligned with the rulers. At all zoom factors.
- ❌ Pixels not aligned with rulers. Offset accumulates on each axis. Only every N-th pixel is aligned.
- ❌ Zooming in/out: The pixels dynamically jump in/out of the selection.
Last edited by porg on Thu Jun 09, 2022 10:28 pm, edited 1 time in total.