swayfx/client/buffer-pool.c

#define _XOPEN_SOURCE 500
#include <assert.h>
#include <cairo/cairo.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <pango/pangocairo.h>
#include <unistd.h>
#include <wayland-client.h>
#include "buffer_pool.h"

static int create_pool_file(size_t size, char **name) {
	static const char template[] = "sway-client-XXXXXX";
	const char *path = getenv("XDG_RUNTIME_DIR");
	if (!path) {
		return -1;
	}

	int ts = (path[strlen(path) - 1] == '/');

	*name = malloc(
		strlen(template) +
		strlen(path) +
		(ts ? 0 : 1) + 1);
	sprintf(*name, "%s%s%s", path, ts ? "" : "/", template);

	int fd = mkstemp(*name);

	if (fd < 0) {
		return -1;
	}

	if (ftruncate(fd, size) < 0) {
		close(fd);
		return -1;
	}

	return fd;
}

static void buffer_release(void *data, struct wl_buffer *wl_buffer) {
	struct pool_buffer *buffer = data;
	buffer->busy = false;
}

static const struct wl_buffer_listener buffer_listener = {
	.release = buffer_release
};

static struct pool_buffer *create_buffer(struct wl_shm *shm,
		struct pool_buffer *buf, int32_t width, int32_t height,
		uint32_t format) {
	uint32_t stride = width * 4;
	uint32_t size = stride * height;

	char *name;
	int fd = create_pool_file(size, &name);
	assert(fd);
	void *data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	struct wl_shm_pool *pool = wl_shm_create_pool(shm, fd, size);
	buf->buffer = wl_shm_pool_create_buffer(pool, 0,
			width, height, stride, format);
	wl_shm_pool_destroy(pool);
	close(fd);
	unlink(name);
	free(name);
	fd = -1;

	buf->width = width;
	buf->height = height;
	buf->surface = cairo_image_surface_create_for_data(data,
			CAIRO_FORMAT_ARGB32, width, height, stride);
	buf->cairo = cairo_create(buf->surface);
	buf->pango = pango_cairo_create_context(buf->cairo);

	wl_buffer_add_listener(buf->buffer, &buffer_listener, buf);
	return buf;
}

static void destroy_buffer(struct pool_buffer *buffer) {
	if (buffer->buffer) {
		wl_buffer_destroy(buffer->buffer);
	}
	if (buffer->cairo) {
		cairo_destroy(buffer->cairo);
	}
	if (buffer->surface) {
		cairo_surface_destroy(buffer->surface);
	}
	if (buffer->pango) {
		g_object_unref(buffer->pango);
	}
	memset(buffer, 0, sizeof(struct pool_buffer));
}

struct pool_buffer *get_next_buffer(struct wl_shm *shm,
		struct pool_buffer pool[static 2], uint32_t width, uint32_t height) {
	struct pool_buffer *buffer = NULL;

	for (size_t i = 0; i < 2; ++i) {
		if (pool[i].busy) {
			continue;
		}
		buffer = &pool[i];
	}

	if (!buffer) {
		return NULL;
	}

	if (buffer->width != width || buffer->height != height) {
		destroy_buffer(buffer);
	}

	if (!buffer->buffer) {
		if (!create_buffer(shm, buffer, width, height,
					WL_SHM_FORMAT_ARGB8888)) {
			return NULL;
		}
	}
	return buffer;
}