labwc/src/common/font.c

// SPDX-License-Identifier: GPL-2.0-only
#include "common/font.h"
#include <cairo.h>
#include <pango/pangocairo.h>
#include <wlr/util/log.h>
#include "common/graphic-helpers.h"
#include "common/string-helpers.h"
#include "buffer.h"

PangoFontDescription *
font_to_pango_desc(struct font *font)
{
	PangoFontDescription *desc = pango_font_description_new();
	pango_font_description_set_family(desc, font->name);
	pango_font_description_set_size(desc, font->size * PANGO_SCALE);
	pango_font_description_set_style(desc, font->slant);
	pango_font_description_set_weight(desc, font->weight);
	return desc;
}

static PangoRectangle
font_extents(struct font *font, const char *string)
{
	PangoRectangle rect = { 0 };
	if (!string) {
		return rect;
	}
	cairo_surface_t *surface;
	cairo_t *c;
	PangoLayout *layout;

	surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 1, 1);
	c = cairo_create(surface);
	layout = pango_cairo_create_layout(c);
	pango_context_set_round_glyph_positions(pango_layout_get_context(layout), false);
	PangoFontDescription *desc = font_to_pango_desc(font);

	pango_layout_set_font_description(layout, desc);
	pango_layout_set_text(layout, string, -1);
	pango_layout_set_single_paragraph_mode(layout, TRUE);
	pango_layout_set_width(layout, -1);
	pango_layout_set_ellipsize(layout, PANGO_ELLIPSIZE_MIDDLE);
	pango_layout_get_extents(layout, NULL, &rect);
	pango_extents_to_pixels(&rect, NULL);

	/* we put a 2 px edge on each side - because Openbox does it :) */
	/* TODO: remove the 4 pixel addition and always do the padding by the caller */
	rect.width += 4;

	cairo_destroy(c);
	cairo_surface_destroy(surface);
	pango_font_description_free(desc);
	g_object_unref(layout);
	return rect;
}

int
font_height(struct font *font)
{
	PangoRectangle rectangle = font_extents(font, "abcdefg");
	return rectangle.height;
}

int
font_width(struct font *font, const char *string)
{
	PangoRectangle rectangle = font_extents(font, string);
	return rectangle.width;
}

void
font_get_buffer_size(int max_width, const char *text, struct font *font,
	int *width, int *height)
{
	PangoRectangle text_extents = font_extents(font, text);
	if (max_width > 0 && text_extents.width > max_width) {
		text_extents.width = max_width;
	}
	*width = text_extents.width;
	*height = text_extents.height;
}

void
font_buffer_create(struct lab_data_buffer **buffer, int max_width,
	int height, const char *text, struct font *font, const float *color,
	cairo_pattern_t *bg_pattern, double scale)
{
	if (string_null_or_empty(text)) {
		return;
	}

	int width, computed_height;
	font_get_buffer_size(max_width, text, font, &width, &computed_height);
	if (height <= 0) {
		height = computed_height;
	}

	*buffer = buffer_create_cairo(width, height, scale);
	if (!*buffer) {
		wlr_log(WLR_ERROR, "Failed to create font buffer");
		return;
	}

	cairo_surface_t *surf = (*buffer)->surface;
	cairo_t *cairo = cairo_create(surf);

	/*
	 * Fill with the background color first IF the background color
	 * is opaque. This is necessary for subpixel rendering to work
	 * properly (it does not work on top of transparency).
	 *
	 * However, if the background color is not opaque, leave the
	 * buffer unfilled (completely transparent) since the background
	 * is already rendered by the scene element underneath. In this
	 * case we have to disable subpixel rendering.
	 */
	bool opaque_bg = is_pattern_opaque(bg_pattern);
	if (opaque_bg) {
		cairo_set_source(cairo, bg_pattern);
		cairo_paint(cairo);
	}

	set_cairo_color(cairo, color);
	/* center vertically if height was explicitly specified */
	cairo_move_to(cairo, 0, (height - computed_height) / 2);

	PangoLayout *layout = pango_cairo_create_layout(cairo);
	pango_context_set_round_glyph_positions(pango_layout_get_context(layout), false);
	pango_layout_set_width(layout, width * PANGO_SCALE);
	pango_layout_set_text(layout, text, -1);
	pango_layout_set_ellipsize(layout, PANGO_ELLIPSIZE_END);

	if (!opaque_bg) {
		/* disable subpixel rendering */
		cairo_font_options_t *opts = cairo_font_options_create();
		cairo_font_options_set_antialias(opts, CAIRO_ANTIALIAS_GRAY);
		PangoContext *ctx = pango_layout_get_context(layout);
		pango_cairo_context_set_font_options(ctx, opts);
		cairo_font_options_destroy(opts);
	}

	PangoFontDescription *desc = font_to_pango_desc(font);
	pango_layout_set_font_description(layout, desc);
	pango_font_description_free(desc);
	pango_cairo_update_layout(cairo, layout);
	pango_cairo_show_layout(cairo, layout);

	g_object_unref(layout);

	cairo_surface_flush(surf);
	cairo_destroy(cairo);
}

void
font_finish(void)
{
	pango_cairo_font_map_set_default(NULL);
}