Comment by pestophagous | Hacker News Reader

Comment by pestophagous | Hacker News Reader

Indeed, it's all rectangles, all the way down. (For the most part.)

I implement a lot of QML (with C++ viewModels to back it).

My UI designer actually issued a challenge to me, to see if I could get "Debug Rectangles" to toggle on-and-off without a rebuild. I'm so grateful for that challenge, because once the seed of the idea was planted, my thirst for this "nice-to-have" feature grew until I couldn't NOT solve it.

I now have:

``` DebugRectangle{} ```

https://github.com/219-design/qt-qml-project-template-with-c...

... which I place inside any item that needs a highlight. I then leave this code in place (nothing to comment-in/comment-out).

I hijack an environment variable for the toggle. The icing on the cake was seeing that this works both when running a compiled binary executable ("my Qt/QML app binary") and when viewing my QML with just qmlscene. https://github.com/219-design/qt-qml-project-template-with-c...

If it's a non-release build that seems fine, but do you have a way to disable this in release builds? Even if the object doesn't show, since QML may be loaded dynamically, having these scattered around could slow your app.

I still remember optimizing customer code bases that suffered from horrible startup performance because they instantiated thousands of debug rects unconditionally all the time...

Yeah and in QML you can wrap this in a loader but even if it's disabled I could see potential problems there.

This is so cool! I think this is going to be very useful for me. How did you find the magic env variable?

Glad you like it! Good question about how did I find that variable. It's been over a year and I tried to trace the history of that discovery and I cannot fully recall. This page: https://doc.qt.io/qt-5/qtquickcontrols2-material.html ... mentions the environment variables. I think it had been a lucky coincidence. I had been racking my brain trying to figure out how I would toggle these rectangles without a rebuild, and then I was working with the Material Style feature in QML and I think that when I came across the table on that page labeled "Environment Variables" it just clicked and I realize it could be the answer I was looking for.

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