Fonts and Characters

This section covers GLCD fonts and characters.

GLCD Support for Fonts

GCBASIC includes a default fixed bitmap font (5 or 6 pixels wide, 7 or 8 pixels high, depending on the driver) that is always available and needs no setup. Two optional font systems can be selected instead, by adding a #define before #include <GLCD.h>:

  • #define GLCD_EXTENDEDFONTSET1 — swaps in an extended character table covering ASCII 31-254 instead of the default limited range. This costs additional program memory (around 1.3 KB) in exchange for full extended-ASCII coverage.
  • #define GLCD_OLED_FONT — switches to a font engine tuned for OLED-family controllers (SSD1306, SH1106, and similar), with two internal sizes selected via GLCDfntDefaultsize.

Only one of these should be selected at a time; if neither is defined, the compact default font is used.

GLCD Support for Characters

Characters are drawn using GLCDDrawChar (a single character) or GLCDDrawString/GLCDPrint (a full string), which look up each character’s bitmap in the currently selected font table and write it to the display buffer at the given position.

There is no GLCD equivalent of LCDCreateChar (the character-LCD command for defining custom characters) — the built-in GLCD fonts are fixed, compiled-in bitmap tables. Genuinely custom fonts or characters require the separate glcd_ImagesandFonts_addin3.h add-in, which loads font or image objects from external EEPROM, identified by an object ID and selected by setting GLCDfntDefault (the built-in font is object ID fntGCB, value 0).

For larger digit-only text, such as clock or counter displays, GLCDPrintLargeFont uses a separate dedicated large font (13 pixels high, digits and a limited symbol set only) rather than scaling the normal character font.

GLCD Character Table

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GLCD Controlling Constants

The GCBASIC constants for control of fonts and characters are shown in the table below. Exact values are set by the specific display driver you include and can vary between drivers.

Constants Controls Options

GLCDFontWidth

Width, in pixels, of one character in the current font.

Typically 5 or 6, depending on the driver and font selected.

GLCDfntDefaultheight

Height, in pixels, of one character in the current font.

Typically 7 or 8, depending on the driver.

GLCDfntDefaultsize

A scale multiplier applied to both the width and height when drawing a character.

1 (normal size) by default; some drivers default to 2. Also selects between the two internal GLCD_OLED_FONT sizes when that font is in use.

GLCDfntDefault

Selects which font/image object GLCDDrawChar/GLCDDrawString reads from.

0 (fntGCB, the built-in font) by default; set to a custom object ID only when using the glcd_ImagesandFonts_addin3.h add-in.

See Also:

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