sdl2-ttf

The sdl2-ttf egg provides bindings to SDL_ttf version 2. SDL_ttf is a library for rendering text using TTF, OTF, and FON fonts. It is compatible with Simple DirectMedia Layer version 2 (SDL2), a popular library used in games and other software.

The sdl2-ttf egg is designed to be compatible with the sdl2 egg, which provides bindings to SDL 2.

Project / Source Code Repository: https://gitlab.com/chicken-sdl2/chicken-sdl2-ttf
Issue Tracker: https://gitlab.com/chicken-sdl2/chicken-sdl2-ttf/issues
Maintainer: John Croisant (john+chicken at croisant dot net)
License: BSD 2-Clause

Table of Contents:

Requirements

The sdl2-ttf egg requires the sdl2 egg, Simple DirectMedia Layer 2.0.0 or higher, and SDL_ttf 2.0 or higher. It will not work with older versions of SDL or SDL_ttf.

This egg requires CHICKEN Scheme 4.8 or higher. As of version 0.2.0, this egg is compatible with both CHICKEN 4 and CHICKEN 5.

Installation

In most cases, you can install the sdl2-ttf egg in the usual way:

chicken-install sdl2-ttf

The installer will try to automatically determine the SDL2 compiler and linker flags using the sdl2-config command.

In special cases, you may need to set the SDL2_CFLAGS, SDL2_LDFLAGS, SDL2_TTF_CFLAGS, and/or SDL2_TTF_LDFLAGS environment variables to provide the compiler and linker flags, then try again. (The SDL2_TTF_* flags are used in addition to the SDL2_* flags.)

For example:

export SDL2_CFLAGS="-I/usr/local/include/SDL2"
export SDL2_LDFLAGS="-L/usr/local/lib -lSDL2"
export SDL2_TTF_LDFLAGS="-lSDL2_ttf"
chicken-install sdl2-ttf

These environment variables are needed only when installing the egg itself. They are not needed when compiling or running programs that use the egg.

Installing on macOS

On macOS, the sdl2-ttf egg can be compiled using either UNIX-style libraries (e.g. compiled from source or installed via Homebrew) or Mac-style frameworks (e.g. downloaded from the SDL website).

When automatically determining compiler and linker flags on macOS, the installer will first check to see if sdl2-config is available. If it is available, the installer will use it to determine the flags.

If sdl2-config is not available, the installer will check to see if SDL2.framework and SDL2_ttf.framework are available in either the /Library/Frameworks or /System/Library/Frameworks directories. If so, the installer will use the frameworks.

If the frameworks are installed in some other directory, or if you want to force using the framework even when sdl2-config is available, set the SDL2_CFLAGS, SDL2_LDFLAGS, SDL2_TTF_CFLAGS, and/or SDL2_TTF_LDFLAGS enviroment variables to tell the compiler where to find the frameworks:

export SDL2_CFLAGS="-F/path/to/your/frameworks"
export SDL2_LDFLAGS="-F/path/to/your/frameworks -framework SDL2"
export SDL2_TTF_LDFLAGS="-framework SDL2_ttf"
chicken-install sdl2-ttf

Usage and Examples

To avoid procedure name collisions, it is recommended that you import the sdl2-ttf module using a prefix such as "ttf:", like so:

(cond-expand
  (chicken-4 (use (prefix sdl2 "sdl2:")
                  (prefix sdl2-ttf "ttf:")))
  (chicken-5 (import (prefix sdl2 "sdl2:")
                     (prefix sdl2-ttf "ttf:"))))

(sdl2:set-main-ready!)
(sdl2:init!)
(ttf:init!)

(define font (ttf:open-font "ComicNeue-Regular.otf" 40))
(define text "Hello, World!")
(define-values (w h) (ttf:size-utf8 font text))
(define window (sdl2:create-window! text 'centered 'centered w h))

(let ((text-surf (ttf:render-utf8-shaded
                  font text
                  (sdl2:make-color 0   0   0)
                  (sdl2:make-color 255 255 255))))
  (sdl2:blit-surface! text-surf #f
                      (sdl2:window-surface window) #f))

(sdl2:update-window-surface! window)
(sdl2:delay! 5000)
(sdl2:quit!)

The demos directory contains small programs demonstrating how to use various features of sdl2-ttf.

The chicken-sdl2-examples repository contains complete example games and programs, some of which may use the sdl2-ttf egg.

Version History

0.2.0 (2019-02-13): Ported to be compatible with both CHICKEN 4 and CHICKEN 5. More user-friendly installation process.
0.1.0 (2015-12-25): Initial release.

For more information about what changed in each version, see the CHANGELOG.

API

About the API

API Stability

The sdl2-ttf egg follows "semantic versioning". Until version 1.0.0 is released, the API is not guaranteed to be "stable". That means the maintainer reserves the right to change the API if needed, possibly in ways that break backwards compatibility with previous versions. Large backwards-incompatible changes are unlikely, but there may be small tweaks and fixes to the API if problems are discovered.

After version 1.0.0 is released, the API is guaranteed to remain stable (no backwards-incompatible changes) until the next new major version (e.g. going from version 1.x to 2.0.0, or 2.x to 3.0.0).

Conventions

Procedures names, including function bindings, are Scheme style.
- All procedure names are lower case and hyphenated, with no "TTF_" prefix.
- Procedures that ask a "true or false" question (aka predicates) are suffixed with "?". Usually words such as "has" or "is" are removed from predicate names.
- Procedures that cause a mutation or side effect are suffixed with "!".
- Procedures that set the value of a field are named like TYPE-FIELD-set!, e.g. font-style-set!. For setters that have a corresponding getter, it is also possible to use (set! ...) to set the value, e.g. (set! (font-style my-font) '(bold)). Both forms are equivalent.
Some procedures signal an exception of kind (exn sdl2) if an error occurs or the operation fails. This is instead of returning an integer error code or null pointer.
Some procedures have two versions: one that returns a managed object, and one that returns an unmanaged object. See Struct Memory Management in the sdl2 egg docs.
Some procedures return multiple values. For example, size-text returns two values, the width and height. You can use receive, let-values, etc. to capture all the return values.

General

[procedure] (init!)

See TTF_Init.

Signals an exception of kind (exn sdl2) if initialization fails.

[procedure] (was-init?) → boolean

See TTF_WasInit.

[procedure] (quit!)

See TTF_Quit.

[procedure] (compiled-version) → list of integers
[procedure] (current-version) → list of integers

Returns a list of three nonnegative integers, indicating a version number of SDL_ttf. For example, the list (2 0 0) indicates SDL_ttf 2.0.0.

compiled-version returns the version of SDL_ttf that the sdl2-ttf egg was compiled with.
current-version returns the version of SDL_ttf that the sdl2-ttf egg is currently using.

For example, the user may have compiled the sdl2-ttf egg with SDL_ttf 2.0.0, then later upgraded SDL_ttf to 2.1.0, but not yet recompiled the sdl2-ttf egg with the new version. In such a case, compiled-version would return (2 0 0), and current-version would return (2 1 0). But, features from the new version would not be available until the user recompiles the sdl2-ttf egg.

See SDL_TTF_VERSION and TTF_Linked_Version.

Font

Font Loading

[procedure] (open-font filepath ptsize #!optional index) → ttf:font
[procedure] (open-font* filepath ptsize #!optional index) → ttf:font

Attempts to load the TTF or FON font file at the given filepath (a string). See TTF_OpenFontIndex.

ptsize is the point size (based on 72DPI) to load the font as. This basically translates to pixel height.

index allows you to choose a font face from a file containing multiple font faces. It defaults to 0, the first face.

Returns a ttf:font with the font data. Signals an exception of kind (exn sdl2) if the font could not be loaded.

open-font returns a managed ttf:font.
open-font* returns an unmanaged ttf:font, which must be closed with close-font! when you are done with it.

[procedure] (open-font-rw rwops close? ptsize #!optional index) → ttf:font
[procedure] (open-font-rw* rwops close? ptsize #!optional index) → ttf:font

Attempts a TTF or FON font from an sdl2:rwops. This procedure allows you to load a font from a variety of sources, such as a blob, string, memory pointer, or file. See TTF_OpenFontIndexRW.

If close? is #t, the sdl2:rwops will be automatically closed after the font is loaded. See rw-close! in the sdl2 egg. If close? is #f (the default), the sdl2:rwops will not be closed.

ptsize is the point size (based on 72DPI) to load the font as. This basically translates to pixel height.

index allows you to choose a font face from a file containing multiple font faces. It defaults to 0, the first face.

Returns a ttf:font with the font data. Signals an exception of kind (exn sdl2) if the font could not be loaded.

open-font-rw returns a managed ttf:font.
open-font-rw* returns an unmanaged ttf:font, which must be closed with close-font! when you are done with it.

ttf:font

ttf:font is a record type that wraps a pointer to a TTF_Font struct.

[procedure] (font? obj) → boolean

Returns #t if obj is a ttf:font.

[procedure] (close-font! font)

See TTF_CloseFont.

Close and free the memory of the ttf:font's underlying struct. font's pointer will be set to null (see struct-null? in the sdl2 egg). It is safe to call this procedure with managed or unmanaged ttf:fonts. It is safe (but has no effect) to free a struct record multiple times.

Font Attributes

[procedure] (font-style font) → list of symbols
[setter] (set! (font-style font) style)
[setter] (font-style-set! font style)

Get or set the ttf:font's style, as a list of zero or more of the following symbols:

bold
italic
underline
strikethrough

Returns an empty list if the font has no style. See TTF_FontGetStyle and TTF_FontSetStyle.

The setters accept either a list of symbols or an integer, representing bitwise-or'd integer constants.

NOTE: Bold and italic styles perform automatic adjustment of the font. The results sometimes do not look very good. For better-looking results, you should instead load the bold or italic versions of your font as a separate ttf:font.

[procedure] (font-outline font) → integer
[setter] (set! (font-outline font) outline)
[setter] (font-outline-set! font outline)

Get or set the ttf:font's outline, as a nonnegative integer number of pixels. See TTF_GetFontOutline and TTF_SetFontOutline.

[procedure] (font-hinting font) → symbol
[setter] (set! (font-hinting font) hinting)
[setter] (font-hinting-set! font hinting)

Get or set the ttf:font's hinting, as one of the following symbols:

normal
light
mono
none

See TTF_GetFontHinting and TTF_SetFontHinting.

[procedure] (font-kerning? font) → boolean
[setter] (set! (font-kerning? font) kerning)
[setter] (font-kerning-set! font kerning)

Get or set the ttf:font's kerning, as a boolean. #t means kerning is enabled, #f means kerning is disabled.

See TTF_GetFontKerning and TTF_SetFontKerning.

Font Metrics

[procedure] (font-height font) → integer
[procedure] (font-ascent font) → integer
[procedure] (font-descent font) → integer
[procedure] (font-line-skip font) → integer

Return various measurements of the ttf:font.

See TTF_FontHeight, TTF_FontAscent, TTF_FontDescent, TTF_FontLineSkip.

Font Faces

[procedure] (font-faces font) → integer

Returns the number of faces ("sub-fonts") available in the ttf:font. See TTF_FontFaces.

[procedure] (font-face-fixed-width? font) → boolean

Returns #t if the current face of the given ttf:font is a fixed width font (i.e. every glyph is the same width). See TTF_FontFaceIsFixedWidth.

[procedure] (font-face-family-name font) → string

Returns the current font face family name for the given ttf:font. See TTF_FontFaceFamilyName.

[procedure] (font-face-style-name font) → string

Returns the current font face style name for the given ttf:font. See TTF_FontFaceStyleName.

Glyph Metrics

[procedure] (glyph-provided font glyph) → integer or #f

If the glyph is provided by the font, this procedure returns a positive integer, indicating the glyph's index position in the font. If the glyph is not provided by the font, this procedure returns #f. See TTF_GlyphIsProvided.

glyph may be an integer (representing a 16-bit Unicode character) or a Scheme character in the ASCII range. Results may be incorrect if given a Scheme character outside the ASCII range.

[procedure] (glyph-metrics font glyph) → [min-x max-x min-y max-y advance]

Return various metrics about the given glyph. This procedure returns multiple values:

min-x: the glyph's minimum X offset
max-x: the glyph's maximum X offset
min-y: the glyph's minimum Y offset
max-y: the glyph's maximum Y offset
advance: the glyph's advance offset

See TTF_GlyphMetrics. There is a diagram which shows what these metrics mean.

glyph may be an integer (representing a 16-bit Unicode character) or a Scheme character in the ASCII range. Results may be incorrect if given a Scheme character outside the ASCII range.

Signals an exception of kind (exn sdl2) if an error occurs.

Rendering

Rendering Latin-1 (ISO 8859-1) Text

[procedure] (size-text font text) → [w h]

Calculate the size of the surface that would be created if you rendered the given Latin-1 (ISO 8859-1) text using the ttf:font. See TTF_SizeText.

Returns two values, the calculated width and the height, as integers.

This is much faster than actually rendering the text, so you can use this to quickly predict how much space would be needed. This is useful for calculating word wrapping, alignment, truncation, etc.

[procedure] (render-text-solid font text fg) → sdl2:surface
[procedure] (render-text-solid* font text fg) → sdl2:surface

Render the given Latin-1 (ISO 8859-1) encoded text using "solid" rendering mode. See TTF_RenderText_Solid.

font must be a ttf:font specifying the font to render with.
text must be a Latin-1 (ISO 8859-1) encoded string specifying the text to render.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-text-solid returns a managed sdl2:surface.
render-text-solid* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

[procedure] (render-text-shaded font text fg bg) → sdl2:surface
[procedure] (render-text-shaded* font text fg bg) → sdl2:surface

Render the given Latin-1-encoded text using "shaded" rendering mode. See TTF_RenderText_Shaded.

font must be a ttf:font specifying the font to render with.
text must be a Latin-1 (ISO 8859-1) encoded string specifying the text to render.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.
bg must be a sdl2:color specifying the background color.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-text-shaded returns a managed sdl2:surface.
render-text-shaded* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

[procedure] (render-text-blended font text fg) → sdl2:surface
[procedure] (render-text-blended* font text fg) → sdl2:surface

Render the given Latin-1 (ISO 8859-1) encoded text using "blended" rendering mode. See TTF_RenderText_Blended.

font must be a ttf:font specifying the font to render with.
text must be a Latin-1 (ISO 8859-1) encoded string specifying the text to render.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-text-blended returns a managed sdl2:surface.
render-text-blended* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

Rendering UTF8 Text

[procedure] (size-utf8 font text) → [w h]

Calculate the size of the surface that would be created if you rendered the given UTF8 text using the ttf:font. See TTF_SizeUTF8.

Returns two values, the calculated width and the height, as integers.

This is much faster than actually rendering the text, so you can use this to quickly predict how much space would be needed. This is useful for calculating word wrapping, alignment, truncation, etc.

[procedure] (render-utf8-solid font text fg) → sdl2:surface
[procedure] (render-utf8-solid* font text fg) → sdl2:surface

Render the given UTF8 encoded text using "solid" rendering mode. See TTF_RenderUTF8_Solid.

font must be a ttf:font specifying the font to render with.
text must be a UTF8 encoded string specifying the text to render.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-utf8-solid returns a managed sdl2:surface.
render-utf8-solid* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

[procedure] (render-utf8-shaded font text fg bg) → sdl2:surface
[procedure] (render-utf8-shaded* font text fg bg) → sdl2:surface

Render the given UTF8 encoded text using "shaded" rendering mode. See TTF_RenderUTF8_Shaded.

font must be a ttf:font specifying the font to render with.
text must be a UTF8 encoded string specifying the text to render.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.
bg must be a sdl2:color specifying the background color.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-utf8-shaded returns a managed sdl2:surface.
render-utf8-shaded* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

[procedure] (render-utf8-blended font text fg) → sdl2:surface
[procedure] (render-utf8-blended* font text fg) → sdl2:surface

Render the given UTF8 encoded text using "blended" rendering mode. See TTF_RenderUTF8_Blended.

font must be a ttf:font specifying the font to render with.
text must be a UTF8 encoded string specifying the text to render.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-utf8-blended returns a managed sdl2:surface.
render-utf8-blended* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

Rendering Unicode Text

[procedure] (byte-swapped-unicode-set! swapped?)
[constant] UNICODE_BOM_NATIVE
[constant] UNICODE_BOM_SWAPPED

byte-swapped-unicode-set! sets the default byte order of Unicode chars. If swapped? is #t, this sets the default byte order to swapped. If swapped? is #f, this sets the default byte order to native. See TTF_ByteSwappedUNICODE.

UNICODE_BOM_NATIVE and UNICODE_BOM_SWAPPED are special Unicode characters (unsigned 16-bit integers). When used in a Unicode string, they temporarily (for the remainder of the string) override whether the byte order of Unicode chars is native or swapped. See UNICODE_BOM_NATIVE and UNICODE_BOM_SWAPPED.

[procedure] (size-unicode font unicode) → [w h]

Calculate the size of the surface that would be created if you rendered the given 16-bit Unicode encoded text using the ttf:font. See TTF_SizeUNICODE.

unicode must be a pointer or locative to a null-terminated C array of 16-bit unsigned integers, representing Unicode text. (SRFI-4 u16vectors can be wrapped in a locative using make-locative.)

Returns two values, the calculated width and the height, as integers.

This is much faster than actually rendering the text, so you can use this to quickly predict how much space would be needed. This is useful for calculating word wrapping, alignment, truncation, etc.

[procedure] (render-unicode-solid font unicode fg) → sdl2:surface
[procedure] (render-unicode-solid* font unicode fg) → sdl2:surface

Render the given 16-bit Unicode encoded text using "solid" rendering mode. See TTF_RenderUNICODE_Solid.

font must be a ttf:font specifying the font to render with.
unicode must be a pointer or locative to a null-terminated C array of 16-bit unsigned integers, representing Unicode text. (SRFI-4 u16vectors can be wrapped in a locative using make-locative.)
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-unicode-solid returns a managed sdl2:surface.
render-unicode-solid* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

[procedure] (render-unicode-shaded font unicode fg bg) → sdl2:surface
[procedure] (render-unicode-shaded* font unicode fg bg) → sdl2:surface

Render the given 16-bit Unicode encoded text using "shaded" rendering mode. See TTF_RenderUNICODE_Shaded.

font must be a ttf:font specifying the font to render with.
unicode must be a pointer or locative to a null-terminated C array of 16-bit unsigned integers, representing Unicode text. (SRFI-4 u16vectors can be wrapped in a locative using make-locative.)
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.
bg must be a sdl2:color specifying the background color.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-unicode-shaded returns a managed sdl2:surface.
render-unicode-shaded* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

[procedure] (render-unicode-blended font unicode fg) → sdl2:surface
[procedure] (render-unicode-blended* font unicode fg) → sdl2:surface

Render the given 16-bit Unicode encoded text using "blended" rendering mode. See TTF_RenderUNICODE_Blended.

font must be a ttf:font specifying the font to render with.
unicode must be a pointer or locative to a null-terminated C array of 16-bit unsigned integers, representing Unicode text. (SRFI-4 u16vectors can be wrapped in a locative using make-locative.)
fg must be a sdl2:color specifying the foreground color, i.e. the color of the text itself.

Returns a sdl2:surface containing the rendered text. Signals an exception of kind (exn sdl2) if an error occurred.

render-unicode-blended returns a managed sdl2:surface.
render-unicode-blended* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

Rendering Individual Glyphs

[procedure] (render-glyph-solid font glyph fg) → sdl2:surface
[procedure] (render-glyph-solid* font glyph fg) → sdl2:surface

Render the given glyph using "solid" rendering mode. See TTF_RenderGlyph_Solid.

font must be a ttf:font specifying the font to render with.
glyph must be an integer (representing a 16-bit Unicode character) or a Scheme character in the ASCII range. Results may be incorrect if given a Scheme character outside the ASCII range.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the glyph itself.

Returns a sdl2:surface containing the rendered glyph. Signals an exception of kind (exn sdl2) if an error occurred.

render-glyph-solid returns a managed sdl2:surface.
render-glyph-solid* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

[procedure] (render-glyph-shaded font glyph fg bg) → sdl2:surface
[procedure] (render-glyph-shaded* font glyph fg bg) → sdl2:surface

Render the given glyph using "shaded" rendering mode. See TTF_RenderGlyph_Shaded.

font must be a ttf:font specifying the font to render with.
glyph must be an integer (representing a 16-bit Unicode character) or a Scheme character in the ASCII range. Results may be incorrect if given a Scheme character outside the ASCII range.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the glyph itself.
bg must be a sdl2:color specifying the background color.

Returns a sdl2:surface containing the rendered glyph. Signals an exception of kind (exn sdl2) if an error occurred.

render-glyph-shaded returns a managed sdl2:surface.
render-glyph-shaded* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.

[procedure] (render-glyph-blended font glyph fg) → sdl2:surface
[procedure] (render-glyph-blended* font glyph fg) → sdl2:surface

Render the given glyph using "blended" rendering mode. See TTF_RenderGlyph_Blended.

font must be a ttf:font specifying the font to render with.
glyph must be an integer (representing a 16-bit Unicode character) or a Scheme character in the ASCII range. Results may be incorrect if given a Scheme character outside the ASCII range.
fg must be a sdl2:color specifying the foreground color, i.e. the color of the glyph itself.

Returns a sdl2:surface containing the rendered glyph. Signals an exception of kind (exn sdl2) if an error occurred.

render-glyph-blended returns a managed sdl2:surface.
render-glyph-blended* returns an unmanaged sdl2:surface, which must be freed with free-surface! (from the sdl2 egg) when you are done with it.