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Browser Constraints

This chapter covers browser constraints and limitations when working with DWC applications.

Overview​

The browser environment has certain constraints that differ from traditional GUI applications. Understanding these constraints helps you design better DWC applications.

Handling Client Files​

The browser does not support direct access to client files. This section describes how to implement file uploads and downloads with DWC.

Client Files Handling

File Uploads​

rem Create a file chooser for uploads
fileChooser! = wnd!.addFileChooser()
fileChooser!.setCallback(BBjFileChooser.ON_FILE_SELECTED, "onFileSelected")

File Downloads​

rem Trigger a file download
web! = BBjAPI().getWebManager()
web!.download(serverFilePath$, clientFileName$)

Printing and Print Preview​

The browser does not offer direct access to printers. Modern webapp printing is typically done by:

  1. Displaying the printout in the client
  2. Using the browser's print selection

Printing Options​

MethodDescription
SYSPRINTServer-side printing
BBjPrinterBBj's printer interface
Jasper ReportsGenerate PDF reports for download
rem Generate a PDF for preview
rem Then download or display in browser
web!.download(pdfPath$, "report.pdf")

Security Constraints​

Browsers enforce security policies that affect DWC apps:

  • Same-Origin Policy - Restricts cross-domain requests
  • HTTPS Requirements - Some features require secure connections
  • Cookie Limitations - Third-party cookie restrictions

Local Storage​

For storing client-side data:

rem Store data in browser
web!.setSessionStorage("key", "value")

rem Retrieve data
value$ = web!.getSessionStorage("key")

Clipboard Access​

Clipboard operations require user interaction:

rem Copy to clipboard (requires user gesture)
web!.copyToClipboard(text$)

Best Practices​

  1. Design for the web - Don't expect desktop behaviors
  2. Handle offline scenarios - Consider network interruptions
  3. Use progressive enhancement - Basic functionality should work everywhere
  4. Test on multiple browsers - Chrome, Firefox, Edge, Safari