[BUG] Horizontal Autoscale + Exclude Sidebar does not work scale correctly

[GSBicalho]

Setup

• OS: Windows 10
• Browser: Chrome, Foundry App
• Module version: 2.0.2
• Foundry version: 13.351
• Gaming system & version: Gumshoe 9.10
• Any other modules enabled: yes (libwrapper)

Describe the bug
Horizontal Fit and Automatic Fit (Outside) when the horizontal dimension is larger, both make the scene too big when Exclude Sidebar is set to true, hiding part of the scene behind the sidebar

To replicate, as Gamemaster:

• On User Configuration, check "Enable", "Viewbox" and "Control" for Gamemaster
• Create a scene with width large enough that it does not fit on your screen by more than the height (such that Automatic Fit (Outside) would leave it with empty space above and below). My monitor is 3840x2160, so I used 4000x2000 to demonstrate the issue, though increasing the width even further would make it more obvious
• In the Lockview configurations of the scene, set:
• Sidebar > On Scene Load > Expand
• Sidebar > Exclude Sidebar > Checked
• Autoscale > Horizontal Fit
• Force Initial View > Checked
• Save Changes

You should see that some of the scene is hidden behind the sidebar, as shown below.

Screenshots
With Horizontal Fit

With AutomaticFit (Outside)

Note how the scene expands below the sidebar

Additional context
This is caused not by Lockview itself, but by the fact that Foundry canvas.pan function has a constraint on how zoomed out a scene can be (defined in canvas.dimensions.scale.min). In order to have a scene that fills the screen horizontally and has space for the sidebar, Lockview tells foundry to scale it to the correct amount, but that is smaller than that minimum value, so it gets overridden. Setting canvas.dimensions.scale.min to 0 does appear to solve the issue:

getAutoscale(mode, scene = canvas.scene) {
        canvas.dimensions.scale.min = 0.0;

        let windowWidth = window.innerWidth;
        ...
    }

After making this change it scales correctly, except that then on first load the scene is slightly offset to the right:

Though for some reason then changing between autoscale options shifts it to the correct offset (at least until scene reload), which is where I stopped investigating the issue.

In something only tangentially related I discovered when trying to understand the bug (and which I thought was originally the source of the issue), the getAutoscale function calculates the horizontal scale for 'horizontal' and the autos differently, using window.innerWidth instead of windowWidth, which I believe is incorrect, so the behavior between them differs slightly.

[MaterialFoundry]

Before I look into this any further, let's make sure this issue isn't due to a misunderstanding of how it should work.

The autoscaling is applied to the background image of the scene (or the scene dimensions), not the entire canvas (which is the scene dimensions + padding). In the image below you can see that there's a big difference between the two: The scene dimensions are equal to the background image, the padding is the part of the canvas around background image where the grid is still visible.

Here's what happens when I set autoscaling to horizontal fit:

As you can see it fits to the background image, with the padding still visible behind the sidebar. This is the intended behavior. The only issue I can see is that there's a small gap on the right between the image and the sidebar.

If this is not the problem, then please let me know. It would be helpful to post screenshots of scenes with background image, otherwise it's not possible to see where the scene ends and the padding begins.

[GSBicalho]

Ah, right, I set it to 0 padding in my first examples, which is what I usually use in my setup, so the entire gridded area is the background image area.

I just ran it wit 0.25 padding and, as you mentioned, the scale is set correctly but ends up being shifted to the right. What I think is happening is that the minimum scale limit still exists, but I think the increased size caused by the padding affects the minimum scale for the scene foundry calculates, so it doesn't hit the minimum threshold, but you can see the effect with either padding 0 or padding 0.05.

Here's how a 8000x4000 scene loads with padding 0.05:

Shifted, as you mentioned. But if we move the canvas so the border of background image area is touching the edge of the screen, we can see that the background image area is still slightly too big, as it crosses over into the chat area, and that's the buggy behavior.

Here's how it looks with 0 padding (in lower resolution because I think github isn't fond of me uploading several large pictures in the same post):

Note that with 0 padding the effect is so severe it cuts off part of the background on the left. Here's how it looks when I move the background so the beginning of the background is lined up with the left side of the screen:

Let me know if this clears it up

[MaterialFoundry]

Thanks for the clarification. I can reproduce this now.
Your proposed solution appears to work, but I'm going to have to check if this has unintended consequences.
The minimum scale is not a static value, btw. It changes based on the window size (and maybe some other things), and there's probably a reason for it. It might be worthwhile to investigate it a bit further before setting the minimum scale to 0.