IOS Dev Diary – accessibility quirk with “Bold Text”

I just worked around a surprisingly tricky bug. The “Bold Text” accessibility feature in IOS has some really surprising impacts – it changes the rendering of images, specifically toolbar images.

In the IOS app I’m working on, I have a toolbar icon that I made in vector format (PDF). In the back and forth of working on the app, I set the global tint of the storyboard to white. The toolbar button was set to only use the vector image, and its tint is set to black. When I ran the application, the toolbar button showed up just fine, and in the tint (black) I selected for the button.

When one of my testers ran the app, the toolbar button “disappeared”. It was still there, but rendering white on the white toolbar. It took a while to figure out that the difference between our environments: that Bold Text was enabled in accessibility. Then it took a while longer to find that it wasn’t respecting the local tint, but using the global tint when enabled.

That “Bold Text” being enabled effected the image rendering came as a surprise to me. Some friends indicated they’d seen significant performance issues with Bold Text as well (in cells in a tableview), so they knew that it impacted image rendering – I guess it does something to try and make an image “bolder”, even though it’s not text. (I’m unable to perceive the visual difference in rendering the vector image)

It turns out that Accessibility Inspector also doesn’t reflect this setting. To try it out in the simulator, you need to go to the settings in the simulator directly and enable it. Fortunately, it does reflect the changes once enabled. (radr://49752183) UPDATE: marked as a duplicate of radr://49301632

Once I found that it was using the global tint, it was easy to set that global tint to something more sane (black in my case), so the workaround was very easy once I found it. Fortunately, the sample code for the bug report was equally easy. (radr://49752053)

In the end, I came away with a new “launch ready” checklist item:

  • review all the tints in the storyboard and make sure they’re consistent.

Published by heckj

Joe has broad software engineering development and management experience, from startups to large companies. Joe works on projects ranging from mobile to multi-cloud distributed systems, has set up and led engineering teams and processes, as well as managing and running services. Joe also contributes and collaborates with a wide variety of open source projects, and writes online at

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