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Documentation Index

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Text labels, buttons, and input fields are the foundational interactive elements of any LWXGL interface. Labels render a static or dynamic string using the global X11 font. Buttons provide clickable regions with three distinct visual states. Input fields capture keyboard entry when the mouse cursor is inside them, storing up to 128 characters that can be retrieved at any time with GetInput. All element IDs are application-defined integers. An ID must be unique across all element types — it serves as the index into LWXGL’s internal element slot array.

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CreateText

void CreateText(int id, int x, int y, const char* text, int color);
Creates a text label element that renders text at position (x, y) using the current global font (9x15 or 9x15bold). The string pointer is stored directly — it is not copied — so the memory it points to must remain valid for the entire lifetime of the element.
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id
int
required
Unique element ID. If a slot at this index already holds an element, behavior is undefined.
​
x
int
required
X coordinate of the text baseline origin in pixels, relative to the window’s top-left corner.
​
y
int
required
Y coordinate of the text baseline origin in pixels.
​
text
const char*
required
Null-terminated string to display. The pointer must remain valid until DeleteElement(id) is called. To use a temporary or stack-allocated string, use CreateCopiedText instead.
​
color
int
required
Palette index (0–15) or CLR_* constant for the text foreground color.

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CreateCopiedText

void CreateCopiedText(int id, int x, int y, const char* text, int color);
Identical to CreateText, except that text is duplicated internally with strdup. The caller can free or reuse the original pointer immediately after this call returns. The duplicated copy is freed automatically when DeleteElement(id) is called.
​
id
int
required
Unique element ID.
​
x
int
required
X coordinate of the text baseline origin in pixels.
​
y
int
required
Y coordinate of the text baseline origin in pixels.
​
text
const char*
required
Null-terminated string to display. The string is copied; the original pointer can be freed after this call.
​
color
int
required
Palette index (0–15) or CLR_* constant for the text foreground color.
Use CreateText with a long-lived const char* literal for static labels. Use CreateCopiedText when the string is built dynamically — for example from snprintf into a local buffer.

​
CreateButton

void CreateButton(int id, int x, int y, int w, int h,
                  int u, int hvr, int p,
                  const char* label, void (*onclick)(void));
Creates a rectangular button element with three background color states (unpressed, hover, pressed) and a centered text label. The onclick callback is invoked on a left mouse button release while the cursor is inside the button bounds.
​
id
int
required
Unique element ID.
​
x
int
required
X coordinate of the button’s top-left corner in pixels.
​
y
int
required
Y coordinate of the button’s top-left corner in pixels.
​
w
int
required
Width of the button in pixels.
​
h
int
required
Height of the button in pixels.
​
u
int
required
Unpressed (idle) background color — palette index (0–15) or CLR_* constant.
​
hvr
int
required
Hover background color — shown when the mouse cursor is inside the button but no button is held.
​
p
int
required
Pressed background color — shown while the left mouse button is held down inside the button.
​
label
const char*
required
Null-terminated label string rendered centered in the button. The pointer is stored directly (not copied) and must remain valid for the element’s lifetime.
​
onclick
void (*)(void)
required
Function called when the button is clicked. Pass NULL for a non-interactive button (visual-only).

​
CreateInput

void CreateInput(int id, int x, int y, int w, int h, int u, int hvr, int max);
Creates a single-line text input field. The element captures keyboard events when the mouse cursor is inside its bounds, writing typed characters into an internal 128-byte buffer. The input becomes active (focused) on mouse entry and inactive on mouse exit.
​
id
int
required
Unique element ID.
​
x
int
required
X coordinate of the input field’s top-left corner in pixels.
​
y
int
required
Y coordinate of the input field’s top-left corner in pixels.
​
w
int
required
Width of the input field in pixels. Pass -1 to auto-compute the width as (max + 1) * 9 + 10 pixels, which is exactly wide enough to display max characters in the 9x15 font with padding.
​
h
int
required
Height of the input field in pixels.
​
u
int
required
Inactive (unfocused) background color — palette index (0–15) or CLR_* constant.
​
hvr
int
required
Active/hover background color — shown when the cursor is inside the field.
​
max
int
required
Maximum number of characters the field will accept. Clamped internally to 127 regardless of the value passed. The internal buffer is always 128 bytes (127 characters + null terminator).

​
GetInput

char* GetInput(int id);
Returns a direct pointer to the input element’s internal character buffer. The buffer is null-terminated and at most 128 bytes (127 characters + '\0'). The pointer remains valid until DeleteElement(id) is called.
​
id
int
required
ID of an existing input element created with CreateInput.
Do not free() the returned pointer. The buffer is owned by the element and freed by DeleteElement.

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Example

#include "libLWXGL.h"
#include <string.h>

#define ID_LABEL   0
#define ID_INPUT   1
#define ID_BUTTON  2

static const char* greeting = "Enter your name and click Submit.";

static void on_submit(void) {
    char* name = GetInput(ID_INPUT);
    if (strlen(name) == 0) return;

    /* Update the label text — use CreateCopiedText to handle a dynamic string */
    DeleteElement(ID_LABEL);
    CreateCopiedText(ID_LABEL, 20, 20, name, CLR_LGREEN);
}

int main(void) {
    if (CreateWindow(400, 200, "Input Demo", CLR_BLACK) != 0) return 1;

    CreateText(ID_LABEL, 20, 20, greeting, CLR_WHITE);

    /* Auto-width input for up to 20 characters */
    CreateInput(ID_INPUT, 20, 60, -1, 24, CLR_GRAY, CLR_LGRAY, 20);

    CreateButton(ID_BUTTON, 20, 100, 100, 30,
                 CLR_BLUE, CLR_LBLUE, CLR_CYAN,
                 "Submit", on_submit);

    MainWindowLoop(60, NULL);
    TerminateWindow();
    return 0;
}

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