Debug

LittleJS Debug System

  • Press Esc to toggle debug overlay with object picking
  • Number keys toggle debug visualizations (physics, particles, etc.) while the overlay is open
  • +/- keys control time scale for slow motion/fast forward while the overlay is open
  • setDebugKeysAlways lets those keys work with the overlay closed too
  • ASSERT and LOG macros for development (removed in release builds)
  • Debug primitive rendering (rectangles, circles, lines, points, text)
  • Screenshot and video capture support
  • FPS counter and performance watermark
  • Debug overlay shows mouse position and picked objects
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Members

(static, constant) debug :boolean

True if debug is enabled

Type:
  • boolean
Default Value
  • true
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(static) debugKey :string

Key code used to toggle debug mode, Esc by default

Type:
  • string
Default Value
  • Escape
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(static) debugKeysAlways :boolean

Let the debug keys work while the overlay is closed, the number keys and the +/- time keys, for a game that does not use them; off by default, so they only work while the overlay is open

Type:
  • boolean
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(static) debugOverlay :boolean

True if the debug overlay is active, always false in release builds

Type:
  • boolean
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(static, constant) debugPointSize :number

Size to render debug points by default

Type:
  • number
Default Value
  • 0.5
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(static) debugTweakables :boolean

True if the tweakables panel is shown, 9 toggles it while the overlay is open; set it to show the panel from the start, the panel is never shown in release builds

Type:
  • boolean
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(static) debugWatermark :boolean

True if watermark with FPS should be shown, false in release builds

Type:
  • boolean
Default Value
  • true
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Methods

(static) ASSERT(assert, …output)

Asserts if the expression is false, does nothing in release builds Halts execution if the assert fails and throws an error

Parameters:
NameTypeAttributesDescription
assert*

any value, the assert fails when it is falsy

outputObject<repeatable>

error message output

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(static) LOG(…output)

Log to console if debug is enabled, does nothing in release builds

Parameters:
NameTypeAttributesDescription
outputObject<repeatable>

message output

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(static) debugCircle(pos, sizeopt, coloropt, timeopt, fillopt, screenSpaceopt)

Draw a debug circle in world space, or on the screen with screenSpace

Parameters:
NameTypeAttributesDefaultDescription
posVector2
sizenumber<optional>
0

diameter

colorColor | string<optional>
timenumber<optional>
0
fillboolean<optional>
false
screenSpaceboolean<optional>
drawScreenSpace
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(static) debugClear()

Clear all debug primitives in the list

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(static) debugLine(posA, posB, coloropt, widthopt, timeopt, screenSpaceopt)

Draw a debug line in world space, or on the screen with screenSpace

Parameters:
NameTypeAttributesDefaultDescription
posAVector2
posBVector2
colorColor | string<optional>
widthnumber<optional>
0.1
timenumber<optional>
0
screenSpaceboolean<optional>
drawScreenSpace
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(static) debugOverlap(posA, sizeA, posB, sizeB, coloropt, timeopt, screenSpaceopt)

Draw a debug combined axis aligned bounding box in world space, or on the screen with screenSpace

Parameters:
NameTypeAttributesDefaultDescription
posAVector2
sizeAVector2
posBVector2
sizeBVector2
colorColor | string<optional>
timenumber<optional>
screenSpaceboolean<optional>
drawScreenSpace
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(static) debugPoint(pos, coloropt, timeopt, angleopt, screenSpaceopt)

Draw a debug point in world space, or on the screen with screenSpace

Parameters:
NameTypeAttributesDefaultDescription
posVector2
colorColor | string<optional>
timenumber<optional>
anglenumber<optional>
screenSpaceboolean<optional>
drawScreenSpace
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(static) debugPoly(pos, points, coloropt, timeopt, angleopt, fillopt, screenSpaceopt)

Draw a debug poly in world space, or on the screen with screenSpace

Parameters:
NameTypeAttributesDefaultDescription
posVector2
pointsArray.<Vector2>
colorColor | string<optional>
timenumber<optional>
0
anglenumber<optional>
0
fillboolean<optional>
false
screenSpaceboolean<optional>
drawScreenSpace
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(static) debugRect(pos, sizeopt, coloropt, timeopt, angleopt, fillopt, screenSpaceopt)

Draw a debug rectangle in world space, or on the screen with screenSpace

Parameters:
NameTypeAttributesDefaultDescription
posVector2
sizeVector2<optional>
vec2(0)
colorColor | string<optional>
timenumber<optional>
0
anglenumber<optional>
0
fillboolean<optional>
false
screenSpaceboolean<optional>
drawScreenSpace
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(static) debugScreenshot()

Trigger debug system to take a screenshot

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(static) debugShowErrors()

Breaks on all asserts/errors, hides the canvas, and shows message in plain text This is a good function to call at the start of your game to catch all errors In release builds this function has no effect

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(static) debugText(text, pos, sizeopt, coloropt, timeopt, angleopt, fontopt, screenSpaceopt)

Draw debug text in world space, or on the screen with screenSpace

Parameters:
NameTypeAttributesDefaultDescription
textstring | number
posVector2
sizenumber<optional>
1
colorColor | string<optional>
timenumber<optional>
0
anglenumber<optional>
0
fontstring<optional>
monospace
screenSpaceboolean<optional>
drawScreenSpace
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(static) debugVideoCaptureIsActive()

Check if video capture is active

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(static) debugVideoCaptureStart()

Start capturing video

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(static) debugVideoCaptureStop()

Stop capturing video and save to disk

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(static) setDebugKey(key)

Set key code used to toggle debug mode, Esc by default

Parameters:
NameTypeDescription
keystring
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(static) setDebugKeysAlways(enableopt)

Set if the debug keys work while the overlay is closed, the number keys and the +/- time keys

Parameters:
NameTypeAttributesDefaultDescription
enableboolean<optional>
true
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(static) setDebugOverlay(showopt)

Open or close the debug overlay from code, as the debug key does; does nothing in release builds

Parameters:
NameTypeAttributesDefaultDescription
showboolean<optional>
true
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(static) setDebugTweakables(showopt)

Set if the tweakables panel is shown, as 9 does while the debug overlay is open

Parameters:
NameTypeAttributesDefaultDescription
showboolean<optional>
true
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(static) setDebugWatermark(show)

Set if watermark with FPS should be shown

Parameters:
NameTypeDescription
showboolean
Source