GlowEffectLib — Plan9Basic Documentation

GlowEffectLib — Outer Glow Effect

Creates a luminous aura around any visual control. GPU-accelerated outer glow that radiates outwards from the control’s edges. Wraps FireMonkey’s TGlowEffect. Perfect for neon UIs, selection highlighting, hover feedback, and sci-fi aesthetics. 17 functions.

Category	Count	Description
Error Handling	4	glow_error, errormsg$, strerror$, clearerror
Creation & Destruction	2	glow# (create), glow_free (destroy)
Properties	7	softness (2), color (3), opacity (2)
Effect Control	4	enabled, trigger (get/set)

ⓘ Color has 3 functions: glow_color# sets by string, glow_color$ gets as string, and glow_color gets as numeric ARGB value.

Outer Glow vs Inner Glow

Feature	GlowEffectLib (Outer)	InnerGlowEffectLib
Direction	Outward — radiates beyond edges	Inward — fills inside edges
Visual	Luminous halo/aura	Inner border glow
Best for	Neon buttons, selection, hover	Embossed panels, inset effects
Functions	17	16

Default Values

Property	Range	Default	Description
Softness	0.0–9.0	4.0	Glow spread/blur radius
GlowColor	Color name / hex	Yellow	Glow colour
Opacity	0.0–1.0	0.9	Glow intensity

Cross-Platform Support

Platform	Status	Notes
Windows	✅ Full Support	GPU-accelerated via Direct2D
Linux	✅ Full Support	Software rendering fallback
Android	✅ Full Support	GPU-accelerated

Error Handling

Function	Signature	Description
`glow_error()`	`glow_error@`	Returns last error code (0 = no error)
`glow_errormsg$()`	`glow_errormsg$@`	Returns last error message
`glow_strerror$(code)`	`glow_strerror$@n`	Converts error code to text
`glow_clearerror()`	`glow_clearerror@`	Clears error state

Error Codes

Code	Constant	Meaning
0	ERR_NONE	No error
1	ERR_NIL_EFFECT	Effect pointer is nil
2	ERR_INVALID_EFFECT	Not a valid TGlowEffect
3	ERR_INVALID_VALUE	Property value out of range
4	ERR_NIL_PARENT	Parent control is nil
5	ERR_INVALID_PARENT	Not a valid TFmxObject
6	ERR_INVALID_COLOR	Unrecognised colour name/hex

Creation & Destruction

Function	Signature	Description
`glow#(parent#)`	`glow#@#`	Creates outer glow on parent. Returns effect pointer. Defaults: softness 4.0, color Yellow, opacity 0.9
`glow_free(effect#)`	`glow_free@#`	Destroys effect, removes from parent

Softness

Controls glow spread/blur radius. Range 0.0–9.0.

Function	Signature	Description
`glow_softness#(effect#, value)`	`glow_softness#@#n`	Sets softness (0.0–9.0)
`glow_softness(effect#)`	`glow_softness@#`	Gets current softness

Range	Effect	Use Case
0.0–2.0	Tight glow, close to edge	Subtle highlight, thin border glow
2.0–5.0	Normal glow spread	General purpose, neon buttons
5.0–9.0	Wide, diffuse glow	Dramatic aura, ambient lighting

Color

Glow colour accepts named colours or hex strings. Three functions: set (string), get as string, get as number.

Function	Signature	Description
`glow_color#(effect#, color$)`	`glow_color#@#$`	Sets glow colour (name or hex string)
`glow_color$(effect#)`	`glow_color$@#`	Gets colour as string
`glow_color(effect#)`	`glow_color@#`	Gets colour as numeric ARGB value

Supported named colours: Black, White, Red, Green, Blue, Yellow, Cyan, Magenta, Gray, Grey, Silver, Maroon, Olive, Navy, Purple, Teal, Orange, Pink, Brown, Lime, Aqua, Fuchsia, Transparent, Null

Hex format: #RRGGBB or #AARRGGBB (e.g. "#00FFFF" for cyan, "#8000FF00" for 50% transparent green)

Opacity

Function	Signature	Description
`glow_opacity#(effect#, value)`	`glow_opacity#@#n`	Sets opacity (0.0–1.0)
`glow_opacity(effect#)`	`glow_opacity@#`	Gets current opacity

Range	Effect
0.0	Invisible (glow hidden)
0.3–0.5	Subtle, understated glow
0.6–0.8	Normal glow intensity
0.9–1.0	Intense, vivid glow

Effect Control

Function	Signature	Description
`glow_enabled#(effect#, value)`	`glow_enabled#@#n`	Enables (1) or disables (0)
`glow_enabled(effect#)`	`glow_enabled@#`	Gets enabled state
`glow_trigger#(effect#, trigger$)`	`glow_trigger#@#$`	Sets trigger (e.g. `"IsMouseOver=true"`)
`glow_trigger$(effect#)`	`glow_trigger$@#`	Gets trigger string

Complete Examples

Neon Button

╯ glow-neon.bas─◻✕
let frm# = form#("Neon Button", 400, 250)

' Dark background
let bg# = rectangle#(frm#)
rectangle_bounds#(bg#, 0, 0, 400, 250)
rectangle_fill#(bg#, "#1a1a2e")

' Neon button
let btn# = rectangle#(bg#)
rectangle_bounds#(btn#, 125, 90, 150, 50)
rectangle_fill#(btn#, "#1a1a2e")
rectangle_stroke#(btn#, "Cyan")
rectangle_strokethickness#(btn#, 2)
rectangle_corners#(btn#, 8, 8)

let lbl# = label#(btn#, "NEON", 55, 15)
label_fontcolor#(lbl#, "White")

' Cyan glow
let glow# = glow#(btn#)
glow_color#(glow#, "Cyan")
glow_softness#(glow#, 5.0)
glow_opacity#(glow#, 0.9)

form_show(frm#)

Neon Button Gallery

╯ glow-gallery.bas─◻✕
let frm# = form#("Neon Gallery", 500, 200)

let bg# = rectangle#(frm#)
rectangle_bounds#(bg#, 0, 0, 500, 200)
rectangle_fill#(bg#, "#0d0d0d")

CreateNeonBtn(bg#, 30, 70, "PLAY", "Lime")
CreateNeonBtn(bg#, 140, 70, "STOP", "Red")
CreateNeonBtn(bg#, 250, 70, "INFO", "Cyan")
CreateNeonBtn(bg#, 360, 70, "WARN", "Orange")

form_show(frm#)

function CreateNeonBtn(parent#, x, y, text$, color$) local btn#, lbl#, glow#
  btn# = rectangle#(parent#)
  rectangle_bounds#(btn#, x, y, 90, 40)
  rectangle_fill#(btn#, "#0d0d0d")
  rectangle_stroke#(btn#, color$)
  rectangle_strokethickness#(btn#, 2)
  rectangle_corners#(btn#, 5, 5)

  lbl# = label#(btn#, text$, 25, 10)
  label_fontcolor#(lbl#, "White")

  glow# = glow#(btn#)
  glow_color#(glow#, color$)
  glow_softness#(glow#, 4.0)
  glow_opacity#(glow#, 0.8)
endfunction

Hover Glow Cards

╯ glow-hover.bas─◻✕
let frm# = Pointer#(0)
let card1# = Pointer#(0)
let card2# = Pointer#(0)
let glow1# = Pointer#(0)
let glow2# = Pointer#(0)

frm# = form#("Hover Glow Cards", 450, 250)

let info# = label#(frm#, "Hover over the cards:", 30, 20)

' Card 1
card1# = rectangle#(frm#)
rectangle_bounds#(card1#, 50, 70, 150, 100)
rectangle_fill#(card1#, "White")
rectangle_corners#(card1#, 8, 8)

glow1# = glow#(card1#)
glow_color#(glow1#, "DodgerBlue")
glow_softness#(glow1#, 5.0)
glow_enabled#(glow1#, 0)

rectangle_onmouseenter#(card1#, "Card1Enter")
rectangle_onmouseleave#(card1#, "Card1Leave")
let lbl1# = label#(card1#, "Card 1", 50, 40)
label_hittest#(lbl1#, 0)

' Card 2
card2# = rectangle#(frm#)
rectangle_bounds#(card2#, 250, 70, 150, 100)
rectangle_fill#(card2#, "White")
rectangle_corners#(card2#, 8, 8)

glow2# = glow#(card2#)
glow_color#(glow2#, "LimeGreen")
glow_softness#(glow2#, 5.0)
glow_enabled#(glow2#, 0)

rectangle_onmouseenter#(card2#, "Card2Enter")
rectangle_onmouseleave#(card2#, "Card2Leave")
let lbl2# = label#(card2#, "Card 2", 50, 40)
label_hittest#(lbl2#, 0)

form_show(frm#)

function Card1Enter(sender#)
  glow_enabled#(glow1#, 1)
endfunction
function Card1Leave(sender#)
  glow_enabled#(glow1#, 0)
endfunction
function Card2Enter(sender#)
  glow_enabled#(glow2#, 1)
endfunction
function Card2Leave(sender#)
  glow_enabled#(glow2#, 0)
endfunction

Animatable Properties

Both Softness and Opacity can be animated with FloatAnimationLib for pulsing glow effects:

╯ glow-pulse.bas─◻✕
' Pulsing glow on a circle
let ani# = floatani#(glow#)
floatani_propertyname#(ani#, "Softness")
floatani_startvalue#(ani#, 2.0)
floatani_stopvalue#(ani#, 8.0)
floatani_duration#(ani#, 0.8)
floatani_autoreverse#(ani#, 1)
floatani_loop#(ani#, 1)
floatani_interpolation#(ani#, "Sinusoidal")
floatani_animationtype#(ani#, "InOut")
floatani_start(ani#)

Best Practices

Practice	Why
Use dark backgrounds for neon	Glow stands out best on dark surfaces
Softness 4–5 for general use	Good balance of visible glow without heavy rendering
Softness >7 on mobile with caution	Very wide glow can impact performance on mobile GPUs
Use `glow_enabled#` for hover	Toggle via mouse events for interactive feedback
Match glow colour to border	Creates cohesive neon look when stroke and glow match
Animate with FloatAnimationLib	Sinusoidal pulse on Softness creates natural breathing effect
Use `label_hittest#(lbl#, 0)`	Prevents labels inside glowing controls from stealing mouse events

Quick Reference

Function	Signature	Description
ERROR HANDLING
`glow_error()`	`glow_error@`	Last error code
`glow_errormsg$()`	`glow_errormsg$@`	Last error message
`glow_strerror$(code)`	`glow_strerror$@n`	Error code to text
`glow_clearerror()`	`glow_clearerror@`	Clear error state
CREATION & DESTRUCTION
`glow#(parent#)`	`glow#@#`	Create outer glow on control
`glow_free(effect#)`	`glow_free@#`	Destroy effect
SOFTNESS
`glow_softness#(e#, val)`	`glow_softness#@#n`	Set spread (0–9)
`glow_softness(e#)`	`glow_softness@#`	Get spread
COLOR
`glow_color#(e#, color$)`	`glow_color#@#$`	Set colour (name/hex)
`glow_color$(e#)`	`glow_color$@#`	Get colour as string
`glow_color(e#)`	`glow_color@#`	Get colour as ARGB number
OPACITY
`glow_opacity#(e#, val)`	`glow_opacity#@#n`	Set opacity (0–1)
`glow_opacity(e#)`	`glow_opacity@#`	Get opacity
EFFECT CONTROL
`glow_enabled#(e#, val)`	`glow_enabled#@#n`	Enable (1) / disable (0)
`glow_enabled(e#)`	`glow_enabled@#`	Get enabled state
`glow_trigger#(e#, str$)`	`glow_trigger#@#$`	Set trigger string
`glow_trigger$(e#)`	`glow_trigger$@#`	Get trigger string

17 functions. Part of the Plan9Basic visual effects library system.