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Flutter-Requirements.md

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Flutter Application Requirements

Because desktop platforms are not supported Flutter targets, existing Flutter applications are likely to require slight modifications to run.

Target Platform Override

Most applications will need to override the target platform for the application to one of the supported values in order to avoid 'Unknown platform' exceptions. This should be done as early as possible.

In the simplest case, where the code will only run on desktop and the behavior should be consistent on all platforms, you can hard-code a single target:

import 'package:flutter/foundation.dart'
    show debugDefaultTargetPlatformOverride;
[...]

void main() {
  debugDefaultTargetPlatformOverride = TargetPlatform.fuchsia;
  [...]
}

If the code needs to run on both mobile and desktop, or you want different behavior on different desktop platforms, you can conditionalize on Platform. For example, the line in main() above could be replaced with a call to:

/// If the current platform is desktop, override the default platform to
/// a supported platform (iOS for macOS, Android for Linux and Windows).
/// Otherwise, do nothing.
void _setTargetPlatformForDesktop() {
  TargetPlatform targetPlatform;
  if (Platform.isMacOS) {
    targetPlatform = TargetPlatform.iOS;
  } else if (Platform.isLinux || Platform.isWindows) {
    targetPlatform = TargetPlatform.android;
  }
  if (targetPlatform != null) {
    debugDefaultTargetPlatformOverride = targetPlatform;
  }
}

Note that the target platform you use will affect not only the behavior and appearance of the widgets, but also the expectations Flutter will have for what is available on the platform, such as fonts.

Fonts

Flutter applications may default to fonts that are standard for the target platform, but unavailable on desktop. For instance, if the target platform is TargetPlatform.iOS the Material library will default to San Francisco, which is available on macOS but not Linux or Windows.

Most applications will need to set the font (e.g., via ThemeData) based on the host platform, or set a specific font that is bundled with the application. The example application demonstrates using and bundling Roboto on all platforms.

Symptoms of missing fonts can include text failing to display, console logging about failure to load fonts, or in some cases crashes.