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N_GUI_CTX Struct N_GUI_CUSTOM_DATA Struct N_GUI_DATAGRID_COL Struct N_GUI_DATAGRID_DATA Struct N_GUI_DROPMENU_DATA Struct N_GUI_DROPMENU_ENTRY Struct N_GUI_GRID_CALLBACKS Struct N_GUI_HEXVIEW_DATA Struct N_GUI_IMAGE_DATA Struct N_GUI_KVTABLE Struct N_GUI_KV_CONTENT Struct N_GUI_KV_ROW Struct N_GUI_LABEL_DATA Struct N_GUI_LISTBOX_DATA Struct N_GUI_LISTITEM Struct N_GUI_MARKDOWNVIEW_DATA Struct N_GUI_MD_FONTS Struct N_GUI_MD_STYLE Struct N_GUI_MEAS_ENTRY Struct N_GUI_MOUSE_EVENT Struct N_GUI_PENDING_GEOM Struct N_GUI_PENDING_WIDGET Struct N_GUI_POPUP Struct N_GUI_PROGRESSBAR_DATA Struct N_GUI_RADIOLIST_DATA Struct N_GUI_SB_TRACK Struct N_GUI_SCROLLBAR_DATA Struct N_GUI_SECTION Struct N_GUI_SECTIONLIST Struct N_GUI_SLIDER_DATA Struct N_GUI_SPLITPANE_DATA Struct N_GUI_STYLE Struct N_GUI_SUGGEST_SINK Struct N_GUI_SYNTAXVIEW_DATA Struct N_GUI_TAB_PANEL Struct N_GUI_TB_BUTTONS Struct N_GUI_TEXTAREA_DATA Struct N_GUI_TEXT_DIMS Struct N_GUI_THEME Struct N_GUI_TREE Struct N_GUI_TREE_NODE Struct N_GUI_TREE_STATE Struct N_GUI_WIDGET Struct N_GUI_WINDOW Struct N_H2_FRAME Struct N_H2_HEADER Struct N_H2_HPACK Struct N_H2_REQUEST Struct N_H2_SERVER Struct N_H2_SETTING Struct N_HTML_ATTR_ Struct N_HTML_FORM Struct N_HTML_TAG_ Struct N_HTTP3_RESPONSE Struct N_HTTP_FIELD Struct N_HTTP_FORM Struct N_HTTP_FORM_MULTIPART Struct N_HTTP_FORM_PART Struct N_HTTP_MULTIPART_PART Struct N_HTTP_REQUEST Struct N_HTTP_RESP Struct N_HTTP_RESPONSE Struct N_HTTP_SERVER Struct N_HTTP_SERVER_CONFIG Struct N_HTTP_SERVER_REQUEST Struct N_HTTP_SERVER_STATS Struct N_HTTP_SET_COOKIE Struct N_HTTP_STREAM Struct N_ISO_CAMERA Struct N_ISO_OBJECT Struct N_KAFKA Struct N_KAFKA_EVENT Struct N_MOCK_SERVER Struct N_MODULE Struct N_PARALLEL_SLICE Struct N_PARALLEL_TEAM Struct N_PARALLEL_WORKER Struct N_PCRE Struct N_PROXY_CFG Struct N_PTH Struct N_PTH_TENSOR Struct N_QUERY Struct N_ROUTE Struct N_ROUTER Struct N_ROUTE_MATCH Struct N_SHA256 Struct N_SOCKET Struct N_SPAWN_PIPE Struct N_SSE_CONN Struct N_SSE_EVENT Struct N_STR Struct N_TIFF Struct N_TIFF_ENTRY Struct N_TIME Struct N_URL Struct N_URL_PARAM Struct N_USER Struct N_USERLIST Struct N_WS_CONN Struct N_WS_FRAME Struct N_WS_MESSAGE Struct N_ZIP_MEMBER Struct OCTREE Struct OCTREE_NODE Struct PARSER Struct PARTICLE Struct PARTICLE_EMITTER Struct PARTICLE_SYSTEM Struct PEER Struct PHYSICS Struct PK_OBJ Struct PK_VM Struct POINT2D Struct POINT3D Struct PRETTY_OUT Struct QNODE Struct QUADTREE Struct QUADTREE_NODE Struct REC Struct RGB Struct SAMPLE Struct SEEN Struct SHARER Struct SRV Struct SRV_ARG Struct STACK Struct STACK_ITEM Struct SYNTAX_RUN Struct THREAD_POOL Struct THREAD_POOL_NODE Struct THREAD_WAITING_PROC Struct TRAJECTORY Struct TRAJECTORY_POINT Struct TREE Struct TREE_NODE Struct TS_LOG Struct WAYPOINT3D Struct WORKER_ARG Struct ZIP_SINK Struct _N_DC_ENTRY Struct _N_DC_GROUP_ENTRY Struct _N_GUI_COLORWHEEL Struct _N_GUI_COLORWHEEL_BLOCK Struct _N_GUI_COLORWHEEL_MOUSE Struct _N_GUI_CURVE Struct _N_GUI_CURVE_BLOCK Struct _N_GUI_CURVE_MOUSE Struct _N_GUI_GRID Struct _N_GUI_POPUP_ENTRY Struct _N_GUI_POPUP_LEVEL Struct _N_GUI_SB_SKIN Struct _N_GUI_TA_STEP Struct _N_GUI_THUMB Struct _N_GUI_WRAP_ACC Struct _compiled Struct _conn Struct _ip_slot Struct _mp_param Struct _n_civil Struct _seg Struct client Struct collector Struct date_vector Struct md_atom Struct md_cells Struct md_hit Struct md_line_ctx Struct mline Struct n_http_req_header Struct n_http_req_limits Struct n_http_request Struct n_markdown_block Struct n_markdown_doc Struct n_markdown_inline Struct n_markdown_span Struct n_reactor_stats Struct n_url_safe Struct n_url_safe_head Struct n_wrap_item Struct producer_state Struct rects Struct reply Struct runner Struct sink Struct tbuf Struct wrap_hit Struct wrap_span Structures Union COORD_VALUE Union HASH_DATA Union NODE_DATA_TYPES Union STACK_DATA dir_310dcdd4703e877a6b99d5dc3fc54d27 dir_68267d1309a1af8e8297ef4c3efbcdba dir_d28a4824dc47e487b107a5db32ef43c4 dir_d44c64559bbebec7f509842c48db8b23 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ex_base64_8c example ex_clock_sync_8c example ex_common_8c example ex_configfile_8c example ex_cookies_8c example ex_crypto_8c example ex_diff_8c example ex_digest_8c example ex_disk_cache_8c example ex_dns_8c example ex_ecc_8c example ex_entropy_8c example ex_exceptions_8c example ex_file_8c example ex_file_copy_8c example ex_fluid_8c example ex_fluid_config_8c example ex_fluid_config_8h example ex_git_8c example ex_gui_8c example ex_gui_bench_8c example ex_gui_button_keys_8c example ex_gui_checkbox_label_8c example ex_gui_checkbox_release_8c example ex_gui_color_picker_8c example ex_gui_colorwheel_8c example ex_gui_combobox_items_8c example ex_gui_combobox_wheel_8c example ex_gui_cursor_8c example ex_gui_curve_8c example ex_gui_custom_8c example ex_gui_custom_mouse_8c example ex_gui_datagrid_8c example ex_gui_datagrid_keys_8c example ex_gui_datagrid_sort_8c example ex_gui_detach_8c example ex_gui_dictionary_8c example ex_gui_display_fallback_8c example ex_gui_double_click_8c example ex_gui_dropmenu_8c example ex_gui_frameless_drag_8c example ex_gui_global_scroll_8c example ex_gui_glyph_8c example ex_gui_grid_8c example ex_gui_hexview_8c example ex_gui_hover_8c example ex_gui_isometric_8c example ex_gui_kvtable_8c example ex_gui_label_fits_8c example ex_gui_label_lines_8c example ex_gui_layout_persist_8c example ex_gui_listbox_8c example ex_gui_md_8c example ex_gui_multiwin_8c example ex_gui_network_8c example ex_gui_particles_8c example ex_gui_placeholder_8c example ex_gui_popup_8c example ex_gui_progressbar_8c example ex_gui_reentrant_8c example ex_gui_round_8c example ex_gui_sectionlist_8c example ex_gui_slider_default_8c example ex_gui_slider_handle_8c example ex_gui_slider_step_8c example ex_gui_splitpane_8c example ex_gui_suggest_8c example ex_gui_syntaxview_8c example ex_gui_text_shorten_8c example ex_gui_textarea_selection_8c example ex_gui_tooltip_8c example ex_gui_tree_lazy_8c example ex_gui_tree_order_8c example ex_gui_tree_state_8c example ex_gui_window_rect_8c example ex_gui_zorder_8c example ex_hash_8c example ex_hex_8c example ex_html_8c example ex_http2_8c example ex_http2_server_8c example ex_http_cookie_8c example ex_http_form_8c example ex_http_mime_8c example ex_http_req_8c example ex_http_response_8c example ex_http_router_8c example ex_http_server_8c example ex_icc_8c example ex_iso_astar_8c example ex_json_8c example ex_kafka_8c example ex_linalg_8c example ex_list_8c example ex_log_8c example ex_markdown_8c example ex_module_8c example ex_monolith_8c example ex_network_8c example ex_network_8h example ex_network_accept_8c example ex_network_alpn_8c example ex_network_connect_abort_8c example ex_network_mock_8c example ex_network_proxy_8c example ex_network_reactor_8c example ex_network_sni_8c example ex_network_sse_8c example ex_network_ssl_8c example ex_network_ssl_hardened_8c example ex_network_ssl_hostname_8c example ex_network_ssl_nonblock_8c example ex_network_tls_defaults_8c example ex_network_ws_8c example ex_network_ws_limits_8c example ex_nstr_8c example ex_parallel_for_8c example ex_parallel_team_8c example ex_pcre_8c example ex_pretty_8c example ex_pth_8c example ex_query_8c example ex_random_8c example ex_sha256_8c example ex_signals_8c example ex_spawn_8c example ex_ssrf_8c example ex_stack_8c example ex_threads_8c example ex_tiff_8c example ex_time_formats_8c example ex_trajectory_8c example ex_trees_8c example ex_url_8c example ex_url_safe_8c example ex_wrap_8c example ex_x509_8c example ex_zip_8c example ex_zlib_8c example mainpage_8dox n__3d_8c n__3d_8h n__aabb_8c n__aabb_8h n__allegro5_8c n__allegro5_8h n__allegro__4_8c n__allegro__4_8h n__anim_8c n__anim_8h n__astar_8c n__astar_8h n__atlas_8c n__atlas_8h n__avro_8c n__avro_8h n__base64_8c n__base64_8h n__clipboard_8c n__clipboard_8h n__clock__sync_8c n__clock__sync_8h n__common_8c n__common_8h n__config__file_8c n__config__file_8h n__cookies_8c n__cookies_8h n__crypto_8c n__crypto_8h n__dead__reckoning_8c 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n__iso__engine_8h n__json_8c n__json_8h n__kafka_8c n__kafka_8h n__linalg_8c n__linalg_8h n__list_8c n__list_8h n__log_8c n__log_8h n__lz4_8c n__lz4_8h n__markdown_8c n__markdown_8h n__module_8c n__module_8h n__network_8c n__network_8h n__network__accept__pool_8c n__network__accept__pool_8h n__network__msg_8c n__network__msg_8h n__nodup__log_8c n__nodup__log_8h n__openssl__compat_8h n__particles_8c n__particles_8h n__pcre_8c n__pcre_8h n__pretty_8c n__pretty_8h n__pth_8c n__pth_8h n__query_8c n__query_8h n__random_8c n__random_8h n__reactor_8c n__reactor_8h n__sha256_8c n__sha256_8h n__signals_8c n__signals_8h n__ssrf_8c n__ssrf_8h n__stack_8c n__stack_8h n__str_8c n__str_8h n__thread__pool_8c n__thread__pool_8h n__tiff_8c n__tiff_8h n__time_8c n__time_8h n__trajectory_8c n__trajectory_8h n__trees_8c n__trees_8h n__url__safe_8c n__url__safe_8h n__user_8c n__user_8h n__windows_8h n__wrap_8c n__wrap_8h n__x509_8c n__x509_8h n__zip_8c n__zip_8h n__zlib_8c n__zlib_8h nilorea_8h
5 Module N_GUI_COLOR
gullradriel edited this page 2026-10-09 00:55:18 +02:00
Table of Contents

GUI COLOR: a colour picker dialog and a swatch

Types

Name
typedef void(*)(const float rgba[4], void *user_data) N_GUI_COLOR_FN
called each time the picked colour changes.

Functions

Name
ALLEGRO_MOUSE_CURSOR * n_gui_eyedropper_cursor(float scale)
Make a pipette mouse cursor, for a tool that picks a colour from an image.
void n_gui_draw_color_swatch(float x, float y, float w, float h, const float rgba[4])
Draw a colour as a swatch, over a checkerboard so its alpha shows, with a thin dark border.
void n_gui_color_to_hex(const float rgba[4], char * out, size_t len)
Write a colour as #RRGGBBAA, each channel clamped to 0..1 and rounded to the nearest of 255 steps.
int n_gui_color_picker_window(const N_GUI_COLOR_PICKER * picker)
The picker's window id, for a caller that walks its windows or sets their flags.
int n_gui_color_picker_slider(const N_GUI_COLOR_PICKER * picker, int channel)
The slider for one channel, for a caller or a test that drives it.
void n_gui_color_picker_open(N_GUI_COLOR_PICKER * picker, const char * what, const float rgba[4], N_GUI_COLOR_FN on_change, void * user_data)
Open the picker on a colour, centred on the display.
N_GUI_COLOR_PICKER * n_gui_color_picker_new(N_GUI_CTX * ctx, const char * title, float scale)
Build a colour picker window in ctx, closed.
int n_gui_color_picker_is_open(const N_GUI_COLOR_PICKER * picker)
Whether the picker is open.
int n_gui_color_picker_get(const N_GUI_COLOR_PICKER * picker, float rgba[4])
The colour the picker holds now.
void n_gui_color_picker_free(N_GUI_COLOR_PICKER ** picker)
Close the picker's window and free the handle.
void n_gui_color_picker_close(N_GUI_COLOR_PICKER * picker)
Close the picker.

Types Documentation

typedef N_GUI_COLOR_FN

typedef void(* N_GUI_COLOR_FN) (const float rgba[4], void *user_data);

called each time the picked colour changes.

Parameters:

Functions Documentation

function n_gui_eyedropper_cursor

ALLEGRO_MOUSE_CURSOR * n_gui_eyedropper_cursor(
    float scale
)

Make a pipette mouse cursor, for a tool that picks a colour from an image.

Parameters:

  • scale the interface scale; the cursor is 32 pixels at 1.0, and never under 16.

Return: the cursor, or NULL when Allegro could not make one.

Allegro's system cursors have no pipette, and a crosshair says "point at something" without saying "a colour will be taken from it". Drawn with primitives rather than read from a file, so there is nothing to ship: a pale glass tube with a dark rubber bulb, outlined in black and white so it shows on a dark photograph and on a light one. The hot spot is the tip, at the bottom left, which is the pixel the colour is read from.

Needs a display to exist, as al_create_mouse_cursor() does. Show it with n_gui_set_cursor(); release it with al_destroy_mouse_cursor(), after setting another cursor, never while it is showing.

function n_gui_draw_color_swatch

void n_gui_draw_color_swatch(
    float x,
    float y,
    float w,
    float h,
    const float rgba[4]
)

Draw a colour as a swatch, over a checkerboard so its alpha shows, with a thin dark border.

Parameters:

  • x left edge.
  • y top edge.
  • w width. Nothing is drawn when zero or less.
  • h height. Nothing is drawn when zero or less.
  • rgba the colour, straight alpha. Must not be NULL.

Draws on the current target with the current transform and blender, which is expected to be Allegro's default premultiplied one.

function n_gui_color_to_hex

void n_gui_color_to_hex(
    const float rgba[4],
    char * out,
    size_t len
)

Write a colour as #RRGGBBAA, each channel clamped to 0..1 and rounded to the nearest of 255 steps.

Parameters:

  • rgba the colour. NULL writes an empty string.
  • out receives the text. Must not be NULL.
  • len room in out; 10 bytes holds all of it. Zero writes nothing.

function n_gui_color_picker_window

int n_gui_color_picker_window(
    const N_GUI_COLOR_PICKER * picker
)

The picker's window id, for a caller that walks its windows or sets their flags.

Parameters:

  • picker the picker.

Return: the window id, or -1 for a NULL picker.

function n_gui_color_picker_slider

int n_gui_color_picker_slider(
    const N_GUI_COLOR_PICKER * picker,
    int channel
)

The slider for one channel, for a caller or a test that drives it.

Parameters:

  • picker the picker.
  • channel 0 red, 1 green, 2 blue, 3 alpha.

Return: the slider's widget id, or -1 for a NULL picker or a channel out of range.

function n_gui_color_picker_open

void n_gui_color_picker_open(
    N_GUI_COLOR_PICKER * picker,
    const char * what,
    const float rgba[4],
    N_GUI_COLOR_FN on_change,
    void * user_data
)

Open the picker on a colour, centred on the display.

Parameters:

  • picker the picker. Must not be NULL.
  • what what the colour is, shown over the swatch, such as "Watermark: Colour". May be NULL.
  • rgba the colour to start from, clamped to 0..1. Must not be NULL.
  • on_change called on every change. May be NULL.
  • user_data handed back to on_change.

Replaces whatever the picker was editing, and whom it told, with rgba and on_change. Setting the sliders to rgba does not call on_change: only the user's changes do.

function n_gui_color_picker_new

N_GUI_COLOR_PICKER * n_gui_color_picker_new(
    N_GUI_CTX * ctx,
    const char * title,
    float scale
)

Build a colour picker window in ctx, closed.

Parameters:

  • ctx GUI context. Must not be NULL.
  • title window title. NULL gives "Colour".
  • scale multiplies every size, for a caller that sizes its dialogs by a display scale. Zero or less is taken as 1.

Return: a new picker owned by the caller, to release with n_gui_color_picker_free() before n_gui_destroy_ctx(), or NULL when a widget could not be created.

The window is a popup (N_GUI_ZORDER_POPUP) with a close button in its title bar. Its widgets belong to ctx like any others; the returned handle only remembers their ids and the colour being edited.

function n_gui_color_picker_is_open

int n_gui_color_picker_is_open(
    const N_GUI_COLOR_PICKER * picker
)

Whether the picker is open.

Parameters:

  • picker the picker. NULL gives 0.

Return: 1 when its window is open, 0 otherwise.

function n_gui_color_picker_get

int n_gui_color_picker_get(
    const N_GUI_COLOR_PICKER * picker,
    float rgba[4]
)

The colour the picker holds now.

Parameters:

  • picker the picker. Must not be NULL.
  • rgba receives red, green, blue, alpha, 0 to 1. Must not be NULL.

Return: TRUE, or FALSE on a NULL argument.

function n_gui_color_picker_free

void n_gui_color_picker_free(
    N_GUI_COLOR_PICKER ** picker
)

Close the picker's window and free the handle.

Parameters:

  • picker address of the handle; set to NULL. NULL, or a pointer to NULL, is a no-op.

The window and its widgets stay in the context, closed, until n_gui_destroy_ctx(); nothing in them points at the handle once it is closed. Call it while the context is still alive.

function n_gui_color_picker_close

void n_gui_color_picker_close(
    N_GUI_COLOR_PICKER * picker
)

Close the picker.

Parameters:

  • picker the picker. NULL is a no-op.

The colour stays as it was last changed, and on_change is forgotten. The title bar's close button does the same.

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