fcft_from_name - Man Page

instantiate a new font

Synopsis

#include <fcft/fcft.h>

struct fcft_font *fcft_from_name(

size_t count, const char *names[static count], const char *attributes);

Description

fcft_from_name() instantiates a new fcft font object from the FontConfig formatted font names. The first element in names is the primary font, and the remaining elements (if any) are fallback fonts.

You must supply at least one font name.

All aspects of the font (size, DPI, variant etc) are configured through the font name, using colon separated attribute=value pairs (e.g. "Serif:size=26:slant=italic").

attributes is a convenient way to apply a set of attributes to all fonts in names. attributes may be NULL, in which case no extra attributes are appended to the strings in names.

The primary font will be instantiated immediately, and any failure to do so will result in an error. Fallback fonts are instantiated on demand, and any failure to do so will result in the that fallback font being ignored, and the next one in the list is tried instead.

Return Value

On success, fcft_from_name() returns a pointer to an allocated fcft_font object. On error, NULL is returned.

  struct fcft_font {
      int height;
      int descent;
      int ascent;

    struct {
        int x;
        int y;
    } max_advance;

    struct {
        int x;
        int y;
    } space_advance;

    struct {
        int position;
        int thickness;
    } underline;

    struct {
        int position;
        int thickness;
    } strikeout;
};

height is the line height, in pixels.

descent is the distance between the baseline and the font's lowest descending glyph, in pixels. In fcft's case, it is generally positive (a negative value means the descent stretches up from the baseline).

ascent is the distance between the baseline and the font's highest ascending glyph, in pixels. Generally a positive number (a negative value means the ascent stretches down below the baseline).

ascent + descent is often the same as height, but not necessarily. height may be larger, meaning the font intentionally adds extra (vertical) space between lines. Or it may be smaller, in which case lines overlap.

max_advance is the amount, in pixels, the font's widest glyph advances the pen position; x for a horizontal layout, and y for a vertical layout.

space_advance is the amount, in pixels, the glyph for space (0x20) advances the pen position; x for a horizontal layout, and y for a vertical layout.

underline describes how to render underlines. position is the distance, in pixels, from the baseline. A positive value means above the baseline, and a negative value means below the baseline. thickness is the line's thickness, in pixels.

strikeout describes how to render strikeouts. See underline for a description of its members.

Example

In this example, we instantiate Times New Roman at a point size of 8 as the primary font.

We also tell it to use Serif Bold (point size 10) as a fallback font (note that it is usually better to let FontConfig handle fallback to generic fonts like this).

Furthermore, both fonts will be Italic, and will be using DPI=140.

We then proceed to render the string hello world. You are assumed to know how to create and use a pixman image. This example only shows how one can use fcft to instantiate a font, rasterize glyphs and then blend them onto a target pixman image.

  #include <stdlib.h>
  #include <wchar.h>
  #include <fcft/fcft.h>

int
main(void)
{
    if (!fcft_set_scaling_filter(FCFT_SCALING_FILTER_LANCZOS3))
       return EXIT_FAILURE;

    struct fcft_font *font = fcft_from_name(
        2,
        (const char *[]){
            "Times New Roman:size=8",
            "Serif:size=10:weight=bold",
        },
        "slant=italic:dpi=140");

    if (font == NULL)
        return EXIT_FAILURE;

    /* Here you need to instantiate a 'target' pixman image, to blend
       with */
    pixman_image_t *canvas = ...;

    /* String to print */
    static const wchar_t *const hello = L"hello world";

    /*
     * Pen position in canvas. The numbers chosen here are more or less
     * random. Note however, that the composite calls below assume 'y'
     * is the font's baseline (and thus the glyphs will be rendered
     * above 'y')
     */
    struct {
        int x;
        int y;
    } pen = {.x = 25, .y = 50};

    /* Glyphs will be rendered in white */
    pixman_image_t *color = pixman_image_create_solid_fill(
        &(struct pixman_color_t){
            .red = 0xffff,
            .green = 0xffff,
            .blue = 0xffff,
            .alpha = 0xffff,
        });

    for (size_t i = 0; i < wcslen(hello); i++) {
        const struct fcft_glyph *glyph = fcft_glyph_rasterize(
            font, hello[i], FCFT_SUBPIXEL_DEFAULT);

        if (glyph == NULL)
            continue;

        /* Kerning */
        long x_kern = 0;
        if (i > 0) {
            fcft_kerning(font, hello[i - 1], hello[i], &x_kern, NULL);

        pen.x += x_kern;

        if (pixman_image_get_format(glyph->pix) == PIXMAN_a8r8g8b8) {
            /* Glyph is a pre-rendered image; typically a color emoji */
            pixman_image_composite32(
                PIXMAP_OP_OVER, glyph->pix, NULL, canvas, 0, 0, 0, 0,
                pen.x + glyph->x, pen.y + font->ascent - glyph->y,
                glyph->width, glyph->height);
        }

        else {
            /* Glyph is an alpha mask */
            pixman_image_composite32(
                PIXMAN_OP_OVER, color, glyph->pix, canvas, 0, 0, 0, 0,
                pen.x + glyph->x, pen.y + font->ascent - glyph->y,
                glyph->width, glyph->height);
        }

        /* Advance pen position */
        pen.x += glyph->advance.x;
    }

    pixman_image_unref(src);

    fcft_destroy(font);
    return EXIT_SUCCESS;
}

See Also

fcft_clone(3), fcft_destroy(3), fcft_glyph_rasterize(3), fcft_kerning(3), fcft_size_adjust(3)

Referenced By

fcft_clone(3), fcft_destroy(3), fcft_glyph_rasterize(3), fcft_kerning(3), fcft_set_scaling_filter(3), fcft_size_adjust(3).

2021-03-08 2.3.2 fcft