The Problem:
You’re experiencing an issue where JavaScript files included locally in an HTML file using <script src="myScript.js"></script> do not execute within the TEdgeBrowser component in your Delphi 10.4.2 project, despite working correctly in other browsers like Chrome and Edge. The JavaScript files themselves are valid, and there are no apparent errors in the browser’s DevTools. External JavaScript files load correctly, suggesting the issue is specifically related to local file access.
Understanding the “Why” (The Root Cause):
The TEdgeBrowser component in Delphi uses WebView2, which employs strict security policies to prevent malicious scripts from running. By default, WebView2 restricts access to local files to prevent vulnerabilities. This is why your local JavaScript files aren’t executing while external ones are—external scripts are sourced from different domains and aren’t subject to the same local file access restrictions. Simply running Delphi as administrator doesn’t override these built-in security measures.
Step-by-Step Guide:
Step 1: Add Browser Arguments to Allow Local File Access:
This is the most straightforward solution. Before navigating to your HTML file in TEdgeBrowser, you need to add specific browser arguments that explicitly grant permission to access local files. This is done by setting the additionalBrowserArguments property of your TEdgeBrowser component. Add the following arguments:
additionalBrowserArguments := '--allow-file-access-from-files --disable-web-security';
Important Note: --disable-web-security should be used cautiously, especially in production environments. It significantly weakens security, making your application vulnerable to exploits. This should be considered primarily for development and testing purposes only. For production, explore alternative solutions like using a local web server or a different approach, such as embedding the JS directly in your HTML.
Step 2: Verify TEdgeBrowser Initialization:
Ensure that your TEdgeBrowser component is correctly initialized and that the Navigate method is called after setting the additionalBrowserArguments. Incorrect order can prevent the arguments from taking effect. A typical sequence might look like this (replace 'file:///path/to/your/html/file.html' with your actual file path):
procedure TForm1.Button1Click(Sender: TObject);
begin
EdgeBrowser1.AdditionalBrowserArguments := '--allow-file-access-from-files --disable-web-security';
EdgeBrowser1.Navigate('file:///path/to/your/html/file.html');
end;
Step 3 (If Step 1 and 2 Fail): Consider Alternative Solutions:
If adding browser arguments doesn’t solve the problem, you might need to consider more robust but less convenient solutions: Serving your HTML and JavaScript files via a local HTTP server or embedding the JavaScript directly within your HTML page.
Common Pitfalls & What to Check Next:
- Incorrect File Path: Double-check the path to your HTML and JavaScript files. WebView2 is very sensitive to exact paths. Use absolute paths when testing.
- Typographical Errors: Carefully review the
additionalBrowserArguments string for typos. Any errors will render the argument invalid.
- Browser Version: Ensure you have a recent version of WebView2 installed. Outdated versions might not support these arguments.
- Delphi Update: Make sure your Delphi 10.4.2 is up-to-date to benefit from the latest fixes and updates.
Still running into issues? Share your (sanitized) config files, the exact command you ran, and any other relevant details. The community is here to help!