DWC Debugging

This chapter covers debugging techniques specific to the Dynamic Web Client.

Overview

When a BBj program encounters an untrapped error, it drops to a minimal debug console where the developer can debug the problem and either restart or terminate the program. As of BBj 22, a basic console is available for debugging in DWC.

note

Like the BUI mini console, this debug console is not intended for production deployment.

The DWC Debug Console

The DWC debug console provides a way to:

• View variable values
• Execute BBj commands
• Step through code
• Restart or terminate the program

Triggering the Console

You can programmatically trigger the debug console using the ESCAPE statement:

console:
    escape
return

Example Program with Console Access

This example adds a button that triggers the debug console:

rem ' hello.txt
sysgui = unt
open (sysgui)"X0"
bbjapi! = bbjapi()
sysgui! = bbjapi!.getSysGui()
window! = sysgui!.addWindow(25,25,275,125,"Hello",$00090083$,$$)
window!.setCallback(bbjapi!.ON_CLOSE,"eoj")

hello! = window!.addButton(1,25,25,100,25,"Hello!")
hello!.focus()
hello!.setCallback(bbjapi!.ON_BUTTON_PUSH,"msgbox")

goodbye! = window!.addButton(2,150,25,100,25,"Goodbye!")
goodbye!.setCallback(bbjapi!.ON_BUTTON_PUSH,"eoj")

console! = window!.addButton(3,25,75,100,25,"Console")
console!.setCallback(bbjapi!.ON_BUTTON_PUSH,"console")

process_events

eoj:
release

msgbox:
  i = msgbox(info(1,4),64,fnmode$(info(3,6)))
  hello!.focus()
return

def fnmode$(mode$)
  if mode$="0" then return "Fat Client"
  if mode$="1" then return "Thin Client"
  if mode$="2" then return "Java Applet"
  if mode$="3" then return "Java Web Start"
  if mode$="4" then return "JavaBBjBridge"
  if mode$="5" then return "BUI (Browser)"
  if mode$="6" then return "DWC (Browser)"
  return mode$
fnend

console:
    escape
return

Using Browser Developer Tools

In addition to the DWC debug console, you can use the browser's built-in developer tools (covered in Chapter 02) for:

• Console tab - View JavaScript errors and print statement output
• Network tab - Monitor communication between client and server
• Elements tab - Inspect the DOM structure of DWC controls

Printing Debug Output

Use print statements to output debug information to the DWC mini console:

print "Variable value: ", myVar$
print "Object: ", myObject!

Comparison: BUI vs DWC Debugging

Feature	BUI	DWC
Mini console	Full-featured	Basic (as of BBj 22)
Browser DevTools	Yes	Yes
Print output	Mini console	Mini console
Escape to debug	Yes	Yes

Best Practices

1. Use print statements liberally during development - They help track program flow
2. Check the browser console - JavaScript errors appear there
3. Use Network tab - To diagnose communication issues
4. Remove debug code before production - Don't leave console triggers in production code