How to Prevent Flickering in Transparent NSWindow with ContentView Using blendMode in SwiftUI

Описание: Discover how to effectively eliminate flickering issues in your transparent NSWindow using blendMode with SwiftUI by implementing a timer-based solution.
---
This video is based on the question https://stackoverflow.com/q/71383841/ asked by the user 'hillmark' ( https://stackoverflow.com/u/792406/ ) and on the answer https://stackoverflow.com/a/71392894/ provided by the user 'hillmark' ( https://stackoverflow.com/u/792406/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Prevent transparent NSWindow with a ContentView using blendMode from flickering

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Prevent Flickering in Transparent NSWindow with ContentView Using blendMode in SwiftUI

When working with SwiftUI and NSWindow, many developers encounter issues, particularly when trying to create a transparent window that utilizes a blendMode effect. The flickering of the window when it becomes inactive or is dragged can be a frustrating problem. This issue manifests as the ContentView inconsistently switching between blended and non-blended states, leading to a less than ideal user experience.

In this post, we will explore both the problem of flickering in a transparent NSWindow and the solution that can stabilize the visual rendering.

Understanding the Problem

Background Context

When a transparent NSWindow is created with a ContentView that employs blendMode, the expectation is that everything behind the window would appear seamlessly blended through a color filter overlay. However, flickering occurs under certain conditions:

Window Inactivity: When the window is not the active window.

Dragging the Window: During window dragging operations.

Rendering Issues: The ContentView may show as partially rendered or “dirty” during these interactions.

This flickering does not happen when blendMode is not in use, indicating that the rendering process tied to blend operations introduces complications when the user interacts with the window.

Code Overview

Here’s a concise look at the initial code setup causing flickering:

[[See Video to Reveal this Text or Code Snippet]]

Implementing the Solution

The Timer Approach

While it may seem a bit unconventional, adding a Timer to the ContentView has proven to fully eliminate flickering. By refreshing the view at a consistent interval, we can force a complete redraw without the erratic behavior caused by window focus changes.

Updated Code

Here's how you can implement the solution:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Key Components

@ State Variable: The currentDate variable is used here to trigger a view update each time it is modified.

Timer: A timer is set to publish updates every 1/60th of a second, allowing for a smooth refresh rate.

ZStack: This component enables layering of views; the black rectangle remains as the primary layer while the transparent text layer facilitates the redraw.

Additional Tips

NSVisualEffectView: Adding a default NSVisualEffectView can also stabilize the window better during activity. However, for those looking to avoid unnecessary complexity, using a Timer might be a simpler solution to maintain the window's performance.

Conclusion

In conclusion, while it may feel a bit hackish to rely on a Timer, it serves as an effective workaround for flickering in a transparent NSWindow with a ContentView using blendMode. It enhances the user experience by ensuring smooth interactions without visual artifacts.

By integrating these simple changes, you can create attractive and functional applications with SwiftUI that dynamically respond to user interactions.

Happy coding, and may your windows remain flicker-free!