Reload document on application:openFile:

[sveinbjornt]

I often use MacDown to view Markdown documents that I edit using XCode, by selecting "Open with External Editor" from within XCode. However, the Markdown document is not reloaded when reopened with Macdown.

It would be great if Macdown reloaded the Markdown document when it receives an application:openFile: event. Just a suggestion from a casual user.

[joelwross]

+1. Running external tools to modify the file (e.g., doctoc) it would be useful if the source window would update on changes, or if there was a way to "reload" the source without opening and closing the document.

[FranklinYu]

I tried these steps but didn't reproduce the issue:

1. open foo.md with MacDown;
2. close the window of foo.md;
3. edit foo.md in another editor;
4. open foo.md with MacDown, again;

I saw an updated foo.md. Did I miss anything?

[klonos]

Did I miss anything?

Yep, step 2: IIUTC you should not close the document from MacDown. If the file is edited with another editor and then saved while still open in MacDown, then the document should be reloaded in MacDown (so that the changes from the other editor are loaded).

[sveinbjornt]

The best logic for this is:

if unchanged document open and it is changed by another program:
    update document with changes from the other program
else if changed document open and it is changed by another program:
    ask user if he wants to overwrite his changes or keep own edits

[uranusjr]

[…] when it receives an application:openFile: event.

Would this work? I thought this is called only when you open a file. It would be the way to go if this is also called when an open document becomes active.

Note: I did try using presentedItemDidChange to detect external modification (#651), but that doesn’t work.

[sveinbjornt]

I've used VDKQueue for this kind of thing in my own projects.

[FranklinYu]

Then this is a duplicate of #48. How does application:openFile: help here? Will that be automatically called by the system when the file is updated?

[FranklinYu]

Yes @uranusjr mentioned VDKQueue in #564 (comment).

[sveinbjornt]

applicationShouldHandleReopen is what I had in mind initially:

https://developer.apple.com/reference/appkit/nsapplicationdelegate/1428638-applicationshouldhandlereopen?language=objc

But VDKQueue is the way to go. That way, the file is automatically updated without MacDown needing an apple event to trigger it.

[uranusjr]

The problem about VDKQueue is I can’t find any documentation nor discussion about it. And I make sure it does not have any quirks before using it.

[sveinbjornt]

I've used it in my projects for years without trouble, but YMMV.

[uranusjr]

It seems like Transmission also uses it… I guess that’s good enough.

[FranklinYu]

Note that

you'll want to modify the code to make it Arc-compliant if you use it in that environment.

according to bdkjones/VDKQueue#8. We can use the fork that fixed that; I scanned the network and this fork seems to merged everything (which also brings risks of course).

[getaaron]

Doesn't NSDocument handle this by calling readFromData: ofType: error:? And in this method we call [self reloadFromLoadedString].

Is there a bug in this implementation? Not sure why we need VDKQueue if NSDocument handles the file changes for us.