Slider (`gsp_slider`)

Draggable horizontal or vertical ranged-value control.

When to use

Use it for a value with a clear minimum and maximum.

Local interactive preview

First set up the commands from the compatibility guide, then run from an unpacked component or public repository root with gspc and gsp_sim_host:

slider-preview.sh

mkdir -p gsp-out/widget-preview
gspc pack \
  examples/usage/widgets/slider/slider.json \
  --deployable -o gsp-out/widget-preview/slider.gspb
gsp_sim_host \
  --bundle gsp-out/widget-preview/slider.gspb --frames 0

These commands compile the example and open it in the ESP-GSP simulator browser preview.

Runtime behavior

Clicking or dragging updates the retained value. Application code can update the same value through the generated setter.

If application code must read or update an object, give it a stable name. GSPC then generates the typed functions listed below.

Example scene

slider.json

{
  "screen": "widget_slider",
  "w": 480,
  "h": 320,
  "screen_bg": "#101827",
  "font": "../../../common/fonts/DejaVuSans.ttf",
  "default_font_size": 18,
  "objects": [
    {"type":"label","parent":-1,"x":32,"y":28,"w":416,"h":30,"text":"Slider","font_size":26,"fg_color":"#F8FAFC"},
    {"type":"label","parent":-1,"x":32,"y":68,"w":416,"h":24,"text":"Drag the handle to change the value.","fg_color":"#A9B8CC"},
    {"type":"slider","parent":-1,"name":"volume","x":32,"y":118,"w":320,"h":32,"min":0,"max":100,"value":68,"track_size":10,"radius":16,"bg_color":"#334155","fg_color":"#38BDF8","knob_color":"#F8FAFC"},
    {"type":"slider","parent":-1,"name":"temperature","x":32,"y":190,"w":320,"h":32,"min":16,"max":30,"value":23,"track_size":8,"radius":16,"bg_color":"#334155","fg_color":"#F59E0B","knob_color":"#FEF3C7"},
    {"type":"slider","parent":-1,"name":"vertical_level","x":398,"y":106,"w":28,"h":152,"vertical":true,"value":44,"track_size":9,"radius":14,"bg_color":"#334155","fg_color":"#A78BFA","knob_color":"#F5F3FF"}
  ]
}

The canonical example is examples/usage/widgets/slider/slider.json. Copy any relative assets referenced by the scene with it.

Generated C API

const gsp_component_directory_t *const * gsp_slider_docs_component_directories(uint16_t *out_count)
esp_err_t gsp_widget_slider_temperature_get_effective_visible(esp_gsp_handle_t gsp, bool *out_visible)
esp_err_t gsp_widget_slider_temperature_get_info(esp_gsp_handle_t gsp, esp_gsp_component_info_t *out_info)
esp_err_t gsp_widget_slider_temperature_get_value(esp_gsp_handle_t gsp, int32_t *out_value)
esp_err_t gsp_widget_slider_temperature_set_value(esp_gsp_handle_t gsp, int32_t value)
esp_err_t gsp_widget_slider_vertical_level_get_effective_visible(esp_gsp_handle_t gsp, bool *out_visible)
esp_err_t gsp_widget_slider_vertical_level_get_info(esp_gsp_handle_t gsp, esp_gsp_component_info_t *out_info)
esp_err_t gsp_widget_slider_vertical_level_get_value(esp_gsp_handle_t gsp, int32_t *out_value)
esp_err_t gsp_widget_slider_vertical_level_set_value(esp_gsp_handle_t gsp, int32_t value)
esp_err_t gsp_widget_slider_volume_get_effective_visible(esp_gsp_handle_t gsp, bool *out_visible)
esp_err_t gsp_widget_slider_volume_get_info(esp_gsp_handle_t gsp, esp_gsp_component_info_t *out_info)
esp_err_t gsp_widget_slider_volume_get_value(esp_gsp_handle_t gsp, int32_t *out_value)
esp_err_t gsp_widget_slider_volume_set_value(esp_gsp_handle_t gsp, int32_t value)
esp_gsp_config_t gsp_slider_docs_config(void)
size_t gsp_slider_docs_dynamic_image_slots(void)

These signatures come from the actual compiler output for this JSON.

Fields in this example

Field	Type	Required	Default / range	Dynamic	Compiler definition
type	string	yes	—	—	widget type
parent	int	yes	default -1; -1…65534	—	parent object index (-1 = screen root)
x	int	yes	default 0; -32768…32767	scene: yes; template: —	x relative to parent
y	int	yes	default 0; -32768…32767	scene: yes; template: —	y relative to parent
w	int	yes	0…65535	scene: —; template: —	width in px
h	int	yes	0…65535	scene: —; template: —	height in px
name	identifier	—	—	—	stable component name; generates GSP_OBJ_KEY_<NAME>
fg_color	color	—	—	—	foreground color (text/knob/line/mark per type)
bg_color	color	—	—	yes	background/fill color (#RRGGBB or #RRGGBBAA)
radius	int	—	default 0; 0…65535	scene: —; template: —	corner radius in px
value	int	—	—	yes	initial value (in min..max units)
min	int	—	default 0; -2147483648…2147483647	—	value range lower bound
max	int	—	default 100; -2147483648…2147483647	—	value range upper bound
vertical	bool	—	default false	—	vertical orientation
knob_color	color	—	default #FFFFFF	—	slider/toggle knob color
track_size	int	—	default 0; 0…4096	—	track thickness

Show other fields supported by this Widget

Field	Type	Required	Default / range	Dynamic	Compiler definition
min_width	int	—	0…65535	—	compile-time minimum width in px
max_width	int	—	0…65535	—	compile-time maximum width in px
min_height	int	—	0…65535	—	compile-time minimum height in px
max_height	int	—	0…65535	—	compile-time maximum height in px
layout	enum	—	row, column, grid	—	child auto-layout: row/column/grid
layout_wrap	bool	—	default false	—	wrap row/column children into additional lines
grid_columns	int	—	1…65535	—	equal-width column count for grid layout
grid_column_span	int	—	default 1; 1…65535	—	column span in the parent grid layout
gap	int	—	default 0; 0…4096	—	auto-layout gap in px
padding	int	—	default 0; 0…4096	—	auto-layout padding in px
padding_left	int	—	0…4096	—	row layout: leading padding override
padding_right	int	—	0…4096	—	row layout: trailing padding override
padding_top	int	—	0…4096	—	column layout: leading padding override
padding_bottom	int	—	0…4096	—	column layout: trailing padding override
grow	int	—	default 0; 0…100	—	auto-layout grow weight
margin	int	—	default 0; 0…4096	—	auto-layout space on both child sides
margin_left	int	—	0…4096	—	auto-layout leading margin on the x axis
margin_right	int	—	0…4096	—	auto-layout trailing margin on the x axis
margin_top	int	—	0…4096	—	auto-layout leading margin on the y axis
margin_bottom	int	—	0…4096	—	auto-layout trailing margin on the y axis
align_main	enum	—	start, center, end, space_between	—	auto-layout main-axis placement
align_cross	enum	—	start, center, end, stretch	—	auto-layout cross-axis placement
hidden	bool	—	default false	yes	start hidden (show via actions or set_visible)
opacity	int	—	default 255; 0…255	scene: —; template: —	0-255 blend opacity
bg_gradient	color	—	—	—	second gradient stop (with bg_color)
gradient_dir	enum	—	default vertical; vertical, horizontal	—	gradient direction
shadow_color	color	—	—	—	static hard-shadow color
shadow_opacity	int	—	default 96; 0…255	—	static hard-shadow opacity
shadow_offset_x	int	—	-32768…32767	—	static hard-shadow x offset
shadow_offset_y	int	—	-32768…32767	—	static hard-shadow y offset
shadow_spread	int	—	0…4096	—	static hard-shadow spread in px
shadow_radius	int	—	0…65535	—	static hard-shadow corner radius
border_color	color	—	—	—	border stroke color
border_width	int	—	0…65535	—	border stroke width (needs border_color)
border_opacity	int	—	default 255; 0…255	—	border stroke opacity
outline_color	color	—	—	—	outside outline color
outline_width	int	—	default 0; 0…65535	—	outside outline width
outline_opacity	int	—	default 255; 0…255	—	outside outline opacity
outline_pad	int	—	default 0; 0…4096	—	gap between the element and its outline
text_line_space	int	—	default 0; 0…4096	—	extra spacing between static text rows in px
text_vertical_align	enum	—	default auto; auto, top, center, bottom	—	static text block placement; auto preserves single-line center and multiline top
text	string	—	—	yes	static text content (UTF-8)
text_align	enum	—	left, center, right	—	text alignment
overflow	enum	—	default clip; clip, ellipsis	—	single-line overflow
font	path	—	—	—	per-object TTF/OTF override
font_size	int	—	1…255	—	per-object font pixel size
font_charset	string	—	—	—	glyphs available to runtime-bound text; static text is added automatically
font_charset_file	path	—	—	—	UTF-8 character corpus relative to the scene; combined with font_charset and static text
font_link	enum	—	embedded, external, auto	—	font storage policy: embedded/external/auto
input	bool	—	default false	—	text field: attaches the caret/keyboard flow
animation_codec	enum	—	lossless, jpeg, hardware_jpeg	—	animation frame policy: lossless patches, JPEG full frames, or JPEG when the target has hardware decoding
svg_layout	enum	—	content, canvas	—	SVG part placement: cropped content or original canvas
morph_to	path	—	—	—	SVG end shape with matching paths and paints
morph	int	—	0…100	—	SVG shape interpolation progress (percent); generates a runtime setter
svg_element	string	—	—	—	SVG element id; imports its painted bounds as an independent image
tint	color	—	—	—	SVG silhouette color; generates a runtime color setter
image	path	—	—	yes	image file path (raster or compiled SVG)
codec	enum	—	raw, lossless, jpeg, auto, speed, size, store, qoi, rle16, rle16_a8, rle32, default, hardware_jpeg	—	image codec
quality	int	—	1…100	—	JPEG quality 1-100 (omitted = profile default)
jpeg_quality	int	—	1…100	—	legacy JPEG quality alias
compress	bool	—	—	—	image compression toggle (legacy; prefer codec)
cache_policy	enum	—	mmap_direct, mmap, decode_lru, lru, preload	—	image cache policy: mmap_direct, decode_lru or preload
store_scale	number	—	0.05…1.0	—	pre-scale factor applied when encoding
max_fps	int	—	0…120	—	GIF/animation frame-rate cap (0 = uncapped)
fit	enum	—	default stretch; stretch, fill, contain, cover	—	image fit mode
position_x	number	—	default 0.5; 0.0…1.0	—	image fit horizontal alignment
position_y	number	—	default 0.5; 0.0…1.0	—	image fit vertical alignment
rotation	int	—	default 0; -32768…32767	scene: image; template: —	clockwise image rotation around the bounding-box center; source alpha is supported; clipped to the box
scalable	bool	—	default false	—	enable runtime image scaling
scale	number	—	default 1.0; 0.0625…16.0	—	initial runtime image scale
min_scale	number	—	default 0.5; 0.0625…16.0	—	minimum runtime image scale
max_scale	number	—	default 4.0; 0.0625…16.0	—	maximum runtime image scale
knob	bool	—	default true	—	knob enabled
enabled	bool	—	—	—	initial interaction state; when present, exposes a runtime enabled property inherited by descendant controls
disabled_color	color	—	default #808080	—	disabled-state overlay color
disabled_opacity	int	—	default 112; 0…255	—	disabled-state overlay opacity
bind	identifier	—	—	—	public state name; generates GSP_BIND_<NAME>
bind_target	enum	—	visible, value, color, text, resource, data	—	explicit bind state family
callback	identifier	—	—	—	app callback name; generates scene-qualified event helpers
events	action_list	—	—	—	input bindings: [{event, action, ...}]
template	identifier	—	—	—	declare this subtree as a render template
max_instances	int	—	1…65535	—	maximum simultaneously live template instances; included in the automatic pool requirement
dynamic_color	bool	—	—	—	template member exposes a per-instance color slot
dynamic_image	bool	—	—	—	template image exposes a per-instance resource slot

Show fields shared by every Widget

Field	Type	Required	Default / range	Dynamic	Compiler definition
parent_name	string	—	—	—	parent by name instead of index