Add solid-color rendering to swaybg

11 files changed, 550 insertions, 39 deletions

diff --git a/client/buffer-pool.c b/client/buffer-pool.c
new file mode 100644
index 00000000..26d0f7e5
--- /dev/null
+++ b/client/buffer-pool.c
@@ -0,0 +1,123 @@
+#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;
+}
diff --git a/client/meson.build b/client/meson.build
new file mode 100644
index 00000000..597899ce
--- /dev/null
+++ b/client/meson.build
@@ -0,0 +1,21 @@
+deps = [
+	cairo,
+	pango,
+	pangocairo,
+	wlroots,
+	wayland_client,
+]
+
+if gdk_pixbuf.found()
+	deps += [gdk_pixbuf]
+endif
+
+lib_sway_client = static_library(
+	'sway-client',
+	files(
+		'buffer-pool.c',
+	),
+	dependencies: deps,
+	link_with: [lib_sway_common],
+	include_directories: sway_inc
+)
diff --git a/common/cairo.c b/common/cairo.c
new file mode 100644
index 00000000..c6bd0da9
--- /dev/null
+++ b/common/cairo.c
@@ -0,0 +1,127 @@
+#include <stdint.h>
+#include <cairo/cairo.h>
+#include "cairo.h"
+#ifdef WITH_GDK_PIXBUF
+#include <gdk-pixbuf/gdk-pixbuf.h>
+#endif
+
+void cairo_set_source_u32(cairo_t *cairo, uint32_t color) {
+	cairo_set_source_rgba(cairo,
+			(color >> (3*8) & 0xFF) / 255.0,
+			(color >> (2*8) & 0xFF) / 255.0,
+			(color >> (1*8) & 0xFF) / 255.0,
+			(color >> (0*8) & 0xFF) / 255.0);
+}
+
+cairo_surface_t *cairo_image_surface_scale(cairo_surface_t *image,
+		int width, int height) {
+	int image_width = cairo_image_surface_get_width(image);
+	int image_height = cairo_image_surface_get_height(image);
+
+	cairo_surface_t *new =
+		cairo_image_surface_create(CAIRO_FORMAT_ARGB32, width, height);
+	cairo_t *cairo = cairo_create(new);
+	cairo_scale(cairo, (double)width / image_width,
+			(double)height / image_height);
+	cairo_set_source_surface(cairo, image, 0, 0);
+
+	cairo_paint(cairo);
+	cairo_destroy(cairo);
+	return new;
+}
+
+#ifdef WITH_GDK_PIXBUF
+cairo_surface_t* gdk_cairo_image_surface_create_from_pixbuf(const GdkPixbuf *gdkbuf) {
+	int chan = gdk_pixbuf_get_n_channels(gdkbuf);
+	if (chan < 3) {
+		return NULL;
+	}
+
+	const guint8* gdkpix = gdk_pixbuf_read_pixels(gdkbuf);
+	if (!gdkpix) {
+		return NULL;
+	}
+	gint w = gdk_pixbuf_get_width(gdkbuf);
+	gint h = gdk_pixbuf_get_height(gdkbuf);
+	int stride = gdk_pixbuf_get_rowstride(gdkbuf);
+
+	cairo_format_t fmt = (chan == 3) ? CAIRO_FORMAT_RGB24 : CAIRO_FORMAT_ARGB32;
+	cairo_surface_t * cs = cairo_image_surface_create (fmt, w, h);
+	cairo_surface_flush (cs);
+	if ( !cs || cairo_surface_status(cs) != CAIRO_STATUS_SUCCESS) {
+		return NULL;
+	}
+
+	int cstride = cairo_image_surface_get_stride(cs);
+	unsigned char * cpix = cairo_image_surface_get_data(cs);
+
+	if (chan == 3) {
+		int i;
+		for (i = h; i; --i) {
+			const guint8 *gp = gdkpix;
+			unsigned char *cp = cpix;
+			const guint8* end = gp + 3*w;
+			while (gp < end) {
+#if G_BYTE_ORDER == G_LITTLE_ENDIAN
+				cp[0] = gp[2];
+				cp[1] = gp[1];
+				cp[2] = gp[0];
+#else
+				cp[1] = gp[0];
+				cp[2] = gp[1];
+				cp[3] = gp[2];
+#endif
+				gp += 3;
+				cp += 4;
+			}
+			gdkpix += stride;
+			cpix += cstride;
+		}
+	} else {
+		/* premul-color = alpha/255 * color/255 * 255 = (alpha*color)/255
+		 * (z/255) = z/256 * 256/255     = z/256 (1 + 1/255)
+		 *         = z/256 + (z/256)/255 = (z + z/255)/256
+		 *         # recurse once
+		 *         = (z + (z + z/255)/256)/256
+		 *         = (z + z/256 + z/256/255) / 256
+		 *         # only use 16bit uint operations, loose some precision,
+		 *         # result is floored.
+		 *       ->  (z + z>>8)>>8
+		 *         # add 0x80/255 = 0.5 to convert floor to round
+		 *       =>  (z+0x80 + (z+0x80)>>8 ) >> 8
+		 * ------
+		 * tested as equal to lround(z/255.0) for uint z in [0..0xfe02]
+		 */
+#define PREMUL_ALPHA(x,a,b,z) \
+		G_STMT_START { z = a * b + 0x80; x = (z + (z >> 8)) >> 8; } \
+		G_STMT_END
+		int i;
+		for (i = h; i; --i) {
+			const guint8 *gp = gdkpix;
+			unsigned char *cp = cpix;
+			const guint8* end = gp + 4*w;
+			guint z1, z2, z3;
+			while (gp < end) {
+#if G_BYTE_ORDER == G_LITTLE_ENDIAN
+				PREMUL_ALPHA(cp[0], gp[2], gp[3], z1);
+				PREMUL_ALPHA(cp[1], gp[1], gp[3], z2);
+				PREMUL_ALPHA(cp[2], gp[0], gp[3], z3);
+				cp[3] = gp[3];
+#else
+				PREMUL_ALPHA(cp[1], gp[0], gp[3], z1);
+				PREMUL_ALPHA(cp[2], gp[1], gp[3], z2);
+				PREMUL_ALPHA(cp[3], gp[2], gp[3], z3);
+				cp[0] = gp[3];
+#endif
+				gp += 4;
+				cp += 4;
+			}
+			gdkpix += stride;
+			cpix += cstride;
+		}
+#undef PREMUL_ALPHA
+	}
+	cairo_surface_mark_dirty(cs);
+	return cs;
+}
+#endif //WITH_GDK_PIXBUF
diff --git a/common/meson.build b/common/meson.build
index abe0cdcf..01736ca6 100644
--- a/common/meson.build
+++ b/common/meson.build
@@ -1,12 +1,23 @@
-lib_sway_common = static_library('sway-common',
+deps = [
+	cairo,
+	wlroots
+]
+
+if gdk_pixbuf.found()
+	deps += [gdk_pixbuf]
+endif
+
+lib_sway_common = static_library(
+	'sway-common',
 	files(
+		'cairo.c',
+		'ipc-client.c',
 		'log.c',
 		'list.c',
-		'util.c',
-		'stringop.c',
 		'readline.c',
-		'ipc-client.c'
+		'stringop.c',
+		'util.c'
 	),
-	dependencies: [ wlroots ],
+	dependencies: deps,
 	include_directories: sway_inc
 )
diff --git a/include/buffer_pool.h b/include/buffer_pool.h
new file mode 100644
index 00000000..cdebd64d
--- /dev/null
+++ b/include/buffer_pool.h
@@ -0,0 +1,21 @@
+#ifndef _SWAY_BUFFERS_H
+#define _SWAY_BUFFERS_H
+#include <cairo/cairo.h>
+#include <pango/pangocairo.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <wayland-client.h>
+
+struct pool_buffer {
+	struct wl_buffer *buffer;
+	cairo_surface_t *surface;
+	cairo_t *cairo;
+	PangoContext *pango;
+	uint32_t width, height;
+	bool busy;
+};
+
+struct pool_buffer *get_next_buffer(struct wl_shm *shm,
+		struct pool_buffer pool[static 2], uint32_t width, uint32_t height);
+
+#endif
diff --git a/include/cairo.h b/include/cairo.h
new file mode 100644
index 00000000..f5f474d7
--- /dev/null
+++ b/include/cairo.h
@@ -0,0 +1,18 @@
+#ifndef _SWAY_CAIRO_H
+#define _SWAY_CAIRO_H
+#include <stdint.h>
+#include <cairo/cairo.h>
+
+void cairo_set_source_u32(cairo_t *cairo, uint32_t color);
+
+cairo_surface_t *cairo_image_surface_scale(cairo_surface_t *image,
+		int width, int height);
+
+#ifdef WITH_GDK_PIXBUF
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+cairo_surface_t* gdk_cairo_image_surface_create_from_pixbuf(
+		const GdkPixbuf *gdkbuf);
+#endif //WITH_GDK_PIXBUF
+
+#endif
diff --git a/meson.build b/meson.build
index 622769a3..0c35b0e5 100644
--- a/meson.build
+++ b/meson.build
@@ -27,7 +27,10 @@ wayland_client = dependency('wayland-client')
 wayland_egl    = dependency('wayland-egl')
 wayland_protos = dependency('wayland-protocols')
 xkbcommon      = dependency('xkbcommon')
+cairo          = dependency('cairo')
 pango          = dependency('pango')
+pangocairo     = dependency('pangocairo')
+gdk_pixbuf     = dependency('gdk-pixbuf-2.0', required: false)
 pixman         = dependency('pixman-1')
 libcap         = dependency('libcap')
 libinput       = dependency('libinput')
@@ -35,6 +38,10 @@ math           = cc.find_library('m')
 git = find_program('git', required: false)
 a2x = find_program('a2x', required: false)
 
+if gdk_pixbuf.found()
+	add_project_arguments('-DWITH_GDK_PIXBUF', language : 'c')
+endif
+
 if a2x.found()
 	mandir = get_option('mandir')
 	man_files = [
@@ -89,6 +96,7 @@ subdir('protocols')
 subdir('common')
 subdir('sway')
 subdir('swaymsg')
+subdir('client')
 subdir('swaybg')
 
 config = configuration_data()
diff --git a/protocols/meson.build b/protocols/meson.build
index 73a6fda5..1fda600e 100644
--- a/protocols/meson.build
+++ b/protocols/meson.build
@@ -2,12 +2,6 @@ wl_protocol_dir = wayland_protos.get_pkgconfig_variable('pkgdatadir')
 
 wayland_scanner = find_program('wayland-scanner')
 
-wayland_scanner_server = generator(
-	wayland_scanner,
-	output: '@BASENAME@-protocol.h',
-	arguments: ['server-header', '@INPUT@', '@OUTPUT@'],
-)
-
 wayland_scanner_code = generator(
 	wayland_scanner,
 	output: '@BASENAME@-protocol.c',
@@ -20,10 +14,9 @@ wayland_scanner_client = generator(
 	arguments: ['client-header', '@INPUT@', '@OUTPUT@'],
 )
 
-protocols = []
-
-client_protocols = [
-	'wlr-layer-shell-unstable-v1.xml',
+protocols = [
+	[wl_protocol_dir, 'stable/xdg-shell/xdg-shell.xml'],
+	['wlr-layer-shell-unstable-v1.xml']
 ]
 
 wl_protos_src = []
@@ -32,11 +25,6 @@ wl_protos_headers = []
 foreach p : protocols
 	xml = join_paths(p)
 	wl_protos_src += wayland_scanner_code.process(xml)
-	wl_protos_headers += wayland_scanner_server.process(xml)
-endforeach
-
-foreach p : client_protocols
-	xml = join_paths(p)
 	wl_protos_headers += wayland_scanner_client.process(xml)
 endforeach
 
diff --git a/swaybg/main.c b/swaybg/main.c
index 94e98228..4473869b 100644
--- a/swaybg/main.c
+++ b/swaybg/main.c
@@ -6,6 +6,10 @@
 #include <time.h>
 #include <wayland-client.h>
 #include <wlr/util/log.h>
+#include "buffer_pool.h"
+#include "cairo.h"
+#include "util.h"
+#include "wlr-layer-shell-unstable-v1-client-protocol.h"
 
 enum scaling_mode {
 	SCALING_MODE_STRETCH,
@@ -13,6 +17,31 @@ enum scaling_mode {
 	SCALING_MODE_FIT,
 	SCALING_MODE_CENTER,
 	SCALING_MODE_TILE,
+	SCALING_MODE_SOLID_COLOR,
+};
+
+struct swaybg_args {
+	int output_idx;
+	const char *path;
+	enum scaling_mode mode;
+};
+
+struct swaybg_state {
+	const struct swaybg_args *args;
+
+	struct wl_display *display;
+	struct wl_compositor *compositor;
+	struct zwlr_layer_shell_v1 *layer_shell;
+	struct wl_shm *shm;
+
+	struct wl_output *output;
+	struct wl_surface *surface;
+	struct zwlr_layer_surface_v1 *layer_surface;
+
+	bool run_display;
+	uint32_t width, height;
+	struct pool_buffer buffers[2];
+	struct pool_buffer *current_buffer;
 };
 
 bool is_valid_color(const char *color) {
@@ -33,7 +62,165 @@ bool is_valid_color(const char *color) {
 	return true;
 }
 
+static void render_frame(struct swaybg_state *state) {
+	if (!state->run_display) {
+		return;
+	}
+
+	state->current_buffer = get_next_buffer(state->shm,
+			state->buffers, state->width, state->height);
+	cairo_t *cairo = state->current_buffer->cairo;
+
+	switch (state->args->mode) {
+	case SCALING_MODE_SOLID_COLOR:
+		cairo_set_source_u32(cairo, parse_color(state->args->path));
+		cairo_paint(cairo);
+		break;
+	default:
+		exit(1);
+		break;
+	}
+
+	wl_surface_attach(state->surface, state->current_buffer->buffer, 0, 0);
+	wl_surface_damage(state->surface, 0, 0, state->width, state->height);
+	wl_surface_commit(state->surface);
+}
+
+static void layer_surface_configure(void *data,
+		struct zwlr_layer_surface_v1 *surface,
+		uint32_t serial, uint32_t width, uint32_t height) {
+	struct swaybg_state *state = data;
+	state->width = width;
+	state->height = height;
+	render_frame(state);
+	zwlr_layer_surface_v1_ack_configure(surface, serial);
+}
+
+static void layer_surface_closed(void *data,
+		struct zwlr_layer_surface_v1 *surface) {
+	struct swaybg_state *state = data;
+	zwlr_layer_surface_v1_destroy(state->layer_surface);
+	wl_surface_destroy(state->surface);
+	state->run_display = false;
+}
+
+struct zwlr_layer_surface_v1_listener layer_surface_listener = {
+	.configure = layer_surface_configure,
+	.closed = layer_surface_closed,
+};
+
+static void handle_global(void *data, struct wl_registry *registry,
+		uint32_t name, const char *interface, uint32_t version) {
+	struct swaybg_state *state = data;
+	if (strcmp(interface, wl_compositor_interface.name) == 0) {
+		state->compositor = wl_registry_bind(registry, name,
+				&wl_compositor_interface, 1);
+	} else if (strcmp(interface, wl_shm_interface.name) == 0) {
+		state->shm = wl_registry_bind(registry, name,
+				&wl_shm_interface, 1);
+	} else if (strcmp(interface, wl_output_interface.name) == 0) {
+		static int output_idx = 0;
+		if (output_idx == state->args->output_idx) {
+			state->output = wl_registry_bind(registry, name,
+					&wl_output_interface, 1);
+		}
+		output_idx++;
+	} else if (strcmp(interface, zwlr_layer_shell_v1_interface.name) == 0) {
+		state->layer_shell = wl_registry_bind(
+				registry, name, &zwlr_layer_shell_v1_interface, 1);
+	}
+}
+
+static void handle_global_remove(void *data, struct wl_registry *registry,
+		uint32_t name) {
+	// who cares
+}
+
+static const struct wl_registry_listener registry_listener = {
+	.global = handle_global,
+	.global_remove = handle_global_remove,
+};
+
 int main(int argc, const char **argv) {
+	struct swaybg_args args = {0};
+	struct swaybg_state state = {0};
+	state.args = &args;
 	wlr_log_init(L_DEBUG, NULL);
+
+	if (argc != 4) {
+		wlr_log(L_ERROR, "Do not run this program manually. "
+				"See man 5 sway and look for output options.");
+		return 1;
+	}
+	args.output_idx = atoi(argv[1]);
+	args.path = argv[2];
+	args.mode = atoi(argv[3]);
+
+	args.mode = SCALING_MODE_STRETCH;
+	if (strcmp(argv[3], "stretch") == 0) {
+		args.mode = SCALING_MODE_STRETCH;
+	} else if (strcmp(argv[3], "fill") == 0) {
+		args.mode = SCALING_MODE_FILL;
+	} else if (strcmp(argv[3], "fit") == 0) {
+		args.mode = SCALING_MODE_FIT;
+	} else if (strcmp(argv[3], "center") == 0) {
+		args.mode = SCALING_MODE_CENTER;
+	} else if (strcmp(argv[3], "tile") == 0) {
+		args.mode = SCALING_MODE_TILE;
+	} else if (strcmp(argv[3], "solid_color") == 0) {
+		args.mode = SCALING_MODE_SOLID_COLOR;
+	} else {
+		wlr_log(L_ERROR, "Unsupported scaling mode: %s", argv[3]);
+		return 1;
+	}
+
+	state.display = wl_display_connect(NULL);
+	if (!state.display) {
+		wlr_log(L_ERROR, "Failed to create display\n");
+		return 1;
+	}
+
+	struct wl_registry *registry = wl_display_get_registry(state.display);
+	wl_registry_add_listener(registry, &registry_listener, &state);
+	wl_display_roundtrip(state.display);
+
+	if (!state.compositor) {
+		wlr_log(L_DEBUG, "wl-compositor not available");
+		return 1;
+	}
+	if (!state.layer_shell) {
+		wlr_log(L_ERROR, "layer-shell not available");
+		return 1;
+	}
+
+	state.surface = wl_compositor_create_surface(state.compositor);
+	if (!state.surface) {
+		wlr_log(L_ERROR, "failed to create wl_surface");
+		return 1;
+	}
+
+	state.layer_surface = zwlr_layer_shell_v1_get_layer_surface(
+			state.layer_shell, state.surface, state.output,
+			ZWLR_LAYER_SHELL_V1_LAYER_BACKGROUND, "wallpaper");
+	if (!state.layer_surface) {
+		wlr_log(L_ERROR, "failed to create zwlr_layer_surface");
+		return 1;
+	}
+	zwlr_layer_surface_v1_set_size(state.layer_surface, 0, 0);
+	zwlr_layer_surface_v1_set_anchor(state.layer_surface,
+			ZWLR_LAYER_SURFACE_V1_ANCHOR_TOP |
+			ZWLR_LAYER_SURFACE_V1_ANCHOR_RIGHT |
+			ZWLR_LAYER_SURFACE_V1_ANCHOR_BOTTOM |
+			ZWLR_LAYER_SURFACE_V1_ANCHOR_LEFT);
+	zwlr_layer_surface_v1_add_listener(state.layer_surface,
+			&layer_surface_listener, &state);
+	wl_surface_commit(state.surface);
+	wl_display_roundtrip(state.display);
+
+	state.run_display = true;
+	render_frame(&state);
+	while (wl_display_dispatch(state.display) != -1 && state.run_display) {
+		// This space intentionally left blank
+	}
 	return 0;
 }
diff --git a/swaybg/meson.build b/swaybg/meson.build
index 47315023..7f5d6bd1 100644
--- a/swaybg/meson.build
+++ b/swaybg/meson.build
@@ -1,8 +1,22 @@
+deps = [
+	cairo,
+	jsonc,
+	math,
+	pango,
+	pangocairo,
+	sway_protos,
+	wayland_client,
+]
+
+if gdk_pixbuf.found()
+	deps += [gdk_pixbuf]
+endif
+
 executable(
     'swaybg',
     'main.c',
     include_directories: [sway_inc],
-    dependencies: [wayland_client, sway_protos, jsonc, wlroots],
-    link_with: [lib_sway_common],
+    dependencies: deps,
+    link_with: [lib_sway_common, lib_sway_client],
     install: true
 )
diff --git a/wayland/buffers.c b/wayland/buffers.c
index e9780997..3b809e6f 100644
--- a/wayland/buffers.c
+++ b/wayland/buffers.c
@@ -50,11 +50,8 @@ static const struct wl_buffer_listener buffer_listener = {
 	.release = buffer_release
 };
 
-static struct buffer *create_buffer(struct window *window, struct buffer *buf,
-		int32_t width, int32_t height, int32_t scale, uint32_t format) {
-
-	width *= scale;
-	height *= scale;
+static struct buffer *create_buffer(struct wl_shm *shm, struct buffer *buf,
+		int32_t width, int32_t height, uint32_t format) {
 	uint32_t stride = width * 4;
 	uint32_t size = stride * height;
 
@@ -65,7 +62,7 @@ static struct buffer *create_buffer(struct window *window, struct buffer *buf,
 		return NULL; // never reached
 	}
 	void *data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
-	struct wl_shm_pool *pool = wl_shm_create_pool(window->registry->shm, fd, size);
+	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);
@@ -101,34 +98,30 @@ static void destroy_buffer(struct buffer *buffer) {
 	memset(buffer, 0, sizeof(struct buffer));
 }
 
-struct buffer *get_next_buffer(struct window *window) {
+struct pool_buffer *get_next_buffer(struct wl_shm *shm,
+		struct pool_buffer pool[2], uint32_t width, uint32_t height) {
 	struct buffer *buffer = NULL;
 
-	int i;
-	for (i = 0; i < 2; ++i) {
-		if (window->buffers[i].busy) {
+	for (size_t i = 0; i < sizeof(pool) / sizeof(pool[0]); ++i) {
+		if (buffers[i].busy) {
 			continue;
 		}
-		buffer = &window->buffers[i];
+		buffer = &buffers[i];
 	}
 
 	if (!buffer) {
 		return NULL;
 	}
 
-	if (buffer->width != window->width || buffer->height != window->height) {
+	if (buffer->width != width || buffer->height != height) {
 		destroy_buffer(buffer);
 	}
 
 	if (!buffer->buffer) {
-		if (!create_buffer(window, buffer,
-					window->width, window->height, window->scale,
+		if (!create_buffer(shm, buffer, width, height,
 					WL_SHM_FORMAT_ARGB8888)) {
 			return NULL;
 		}
 	}
-
-	window->cairo = buffer->cairo;
-	window->buffer = buffer;
 	return buffer;
 }