[Bug] hsWindow:snapshot(true) gives error

[dasmurphy]

I made some tests with the webview and tried to save a screenshot to a file.

The Bug

When i try this it works.

webview:hswindow():snapshot():saveToFile('~/test.png',false,'png')

When i try this to save the transparency in the file, it gives an error.

webview:hswindow():snapshot(true):saveToFile('~/test.png',false,'png')

The error is:

[string "return webview:hswindow():snapshot(true):save..."]:1: ERROR: incorrect number of arguments. Expected 1, got 2
stack traceback:
	[C]: in method 'snapshot'
	[string "return webview:hswindow():snapshot(true):save..."]:1: in main chunk
	[C]: in function 'xpcall'
	...app/Contents/Resources/extensions/hs/_coresetup/init.lua:514: in function <...app/Contents/Resources/extensions/hs/_coresetup/init.lua:494>

The documentation states:

hs.window:snapshot([keepTransparency]) -> hs.image-object

keepTransparency is optional. In the current state it give an error.

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Code internals

I think this line is not correct
https://github.com/Hammerspoon/hammerspoon/blob/master/extensions/window/internal.m#L621

[skin checkArgs:LS_TUSERDATA, USERDATA_TAG, LS_TBREAK];

I think it must be something like

[skin checkArgs:LS_TUSERDATA, USERDATA_TAG, LS_TBOOLEAN|LS_TOPTIONAL, LS_TBREAK];

The second parameter check seemed to be wrong, but my Macos development skills are a little bit limited currently and i did not test it out.

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Workaround for others

After looking around i found a workaround, which works fine.

hs.window.snapshotForID(webview:hswindow():id(),true):saveToFile('~/test.png',false,'png')

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Question

Would it be possible to fix this? In theory you can't save any transparency currently. Look fairly easy to fix and release it.

[cmsj]

Thanks for the great bug report - you nailed it with where the mistake is. I'll fix it momentarily.

[luckman212]

@dasmurphy nice, I ran into this too and was going to report it- you nailed it 👍

[dasmurphy]

@cmsj Thanks for the fix!

@luckman212 Hope my workaround helped you a little bit.