backend/x11: switch to wlr_swapchain

3 files changed, 385 insertions, 33 deletions

diff --git a/backend/x11/backend.c b/backend/x11/backend.c
index f2b09a25..980bc14c 100644
--- a/backend/x11/backend.c
+++ b/backend/x11/backend.c
@@ -6,12 +6,16 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <time.h>
+#include <unistd.h>
 
 #include <wlr/config.h>
 
+#include <drm_fourcc.h>
 #include <X11/Xlib-xcb.h>
 #include <wayland-server-core.h>
 #include <xcb/xcb.h>
+#include <xcb/dri3.h>
+#include <xcb/present.h>
 #include <xcb/xfixes.h>
 #include <xcb/xinput.h>
 
@@ -25,8 +29,26 @@
 #include <wlr/util/log.h>
 
 #include "backend/x11.h"
+#include "render/drm_format_set.h"
+#include "render/gbm_allocator.h"
+#include "render/wlr_renderer.h"
 #include "util/signal.h"
 
+// See dri2_format_for_depth in mesa
+const struct wlr_x11_format formats[] = {
+	{ .drm = DRM_FORMAT_XRGB8888, .depth = 24, .bpp = 32 },
+	{ .drm = DRM_FORMAT_ARGB8888, .depth = 32, .bpp = 32 },
+};
+
+static const struct wlr_x11_format *x11_format_from_depth(uint8_t depth) {
+	for (size_t i = 0; i < sizeof(formats) / sizeof(formats[0]); i++) {
+		if (formats[i].depth == depth) {
+			return &formats[i];
+		}
+	}
+	return NULL;
+}
+
 struct wlr_x11_output *get_x11_output_from_window_id(
 		struct wlr_x11_backend *x11, xcb_window_t window) {
 	struct wlr_x11_output *output;
@@ -82,6 +104,8 @@ static void handle_x11_event(struct wlr_x11_backend *x11,
 		xcb_ge_generic_event_t *ev = (xcb_ge_generic_event_t *)event;
 		if (ev->extension == x11->xinput_opcode) {
 			handle_x11_xinput_event(x11, ev);
+		} else if (ev->extension == x11->present_opcode) {
+			handle_x11_present_event(x11, ev);
 		} else {
 			handle_x11_unknown_event(x11, event);
 		}
@@ -157,6 +181,7 @@ static void backend_destroy(struct wlr_backend *backend) {
 
 	wlr_renderer_destroy(x11->renderer);
 	wlr_egl_finish(&x11->egl);
+	free(x11->drm_format);
 
 #if WLR_HAS_XCB_ERRORS
 	xcb_errors_context_free(x11->errors_context);
@@ -190,6 +215,27 @@ static void handle_display_destroy(struct wl_listener *listener, void *data) {
 	backend_destroy(&x11->backend);
 }
 
+static xcb_depth_t *get_depth(xcb_screen_t *screen, uint8_t depth) {
+	xcb_depth_iterator_t iter = xcb_screen_allowed_depths_iterator(screen);
+	while (iter.rem > 0) {
+		if (iter.data->depth == depth) {
+			return iter.data;
+		}
+		xcb_depth_next(&iter);
+	}
+	return NULL;
+}
+
+static xcb_visualid_t pick_visualid(xcb_depth_t *depth) {
+	xcb_visualtype_t *visuals = xcb_depth_visuals(depth);
+	for (int i = 0; i < xcb_depth_visuals_length(depth); i++) {
+		if (visuals[i]._class == XCB_VISUAL_CLASS_TRUE_COLOR) {
+			return visuals[i].visual_id;
+		}
+	}
+	return 0;
+}
+
 struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 		const char *x11_display,
 		wlr_renderer_create_func_t create_renderer_func) {
@@ -247,6 +293,47 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 
 	const xcb_query_extension_reply_t *ext;
 
+	// DRI3 extension
+
+	ext = xcb_get_extension_data(x11->xcb, &xcb_dri3_id);
+	if (!ext || !ext->present) {
+		wlr_log(WLR_ERROR, "X11 does not support DRI3 extension");
+		goto error_display;
+	}
+
+	xcb_dri3_query_version_cookie_t dri3_cookie =
+		xcb_dri3_query_version(x11->xcb, 1, 2);
+	xcb_dri3_query_version_reply_t *dri3_reply =
+		xcb_dri3_query_version_reply(x11->xcb, dri3_cookie, NULL);
+	if (!dri3_reply || dri3_reply->major_version < 1 ||
+			dri3_reply->minor_version < 2) {
+		wlr_log(WLR_ERROR, "X11 does not support required DRI3 version");
+		goto error_display;
+	}
+	free(dri3_reply);
+
+	// Present extension
+
+	ext = xcb_get_extension_data(x11->xcb, &xcb_present_id);
+	if (!ext || !ext->present) {
+		wlr_log(WLR_ERROR, "X11 does not support Present extension");
+		goto error_display;
+	}
+	x11->present_opcode = ext->major_opcode;
+
+	xcb_present_query_version_cookie_t present_cookie =
+		xcb_present_query_version(x11->xcb, 1, 2);
+	xcb_present_query_version_reply_t *present_reply =
+		xcb_present_query_version_reply(x11->xcb, present_cookie, NULL);
+	if (!present_reply || present_reply->major_version < 1) {
+		wlr_log(WLR_ERROR, "X11 does not support required Present version");
+		free(present_reply);
+		goto error_display;
+	}
+	free(present_reply);
+
+	// Xfixes extension
+
 	ext = xcb_get_extension_data(x11->xcb, &xcb_xfixes_id);
 	if (!ext || !ext->present) {
 		wlr_log(WLR_ERROR, "X11 does not support Xfixes extension");
@@ -265,6 +352,8 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	}
 	free(fixes_reply);
 
+	// Xinput extension
+
 	ext = xcb_get_extension_data(x11->xcb, &xcb_input_id);
 	if (!ext || !ext->present) {
 		wlr_log(WLR_ERROR, "X11 does not support Xinput extension");
@@ -295,6 +384,32 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	wl_event_source_check(x11->event_source);
 
 	x11->screen = xcb_setup_roots_iterator(xcb_get_setup(x11->xcb)).data;
+	if (!x11->screen) {
+		wlr_log(WLR_ERROR, "Failed to get X11 screen");
+		goto error_display;
+	}
+
+	x11->depth = get_depth(x11->screen, 32);
+	if (!x11->depth) {
+		wlr_log(WLR_ERROR, "Failed to get 32-bit depth for X11 screen");
+		goto error_display;
+	}
+
+	x11->visualid = pick_visualid(x11->depth);
+	if (!x11->visualid) {
+		wlr_log(WLR_ERROR, "Failed to pick X11 visual");
+		goto error_display;
+	}
+
+	x11->x11_format = x11_format_from_depth(x11->depth->depth);
+	if (!x11->x11_format) {
+		wlr_log(WLR_ERROR, "Unsupported depth %"PRIu8, x11->depth->depth);
+		goto error_display;
+	}
+
+	x11->colormap = xcb_generate_id(x11->xcb);
+	xcb_create_colormap(x11->xcb, XCB_COLORMAP_ALLOC_NONE, x11->colormap,
+		x11->screen->root, x11->visualid);
 
 	if (!create_renderer_func) {
 		create_renderer_func = wlr_renderer_autocreate;
@@ -306,18 +421,53 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 		EGL_RED_SIZE, 1,
 		EGL_GREEN_SIZE, 1,
 		EGL_BLUE_SIZE, 1,
-		EGL_ALPHA_SIZE, 0,
+		EGL_ALPHA_SIZE, 1,
 		EGL_NONE,
 	};
 
 	x11->renderer = create_renderer_func(&x11->egl, EGL_PLATFORM_X11_KHR,
 		x11->xlib_conn, config_attribs, x11->screen->root_visual);
-
 	if (x11->renderer == NULL) {
 		wlr_log(WLR_ERROR, "Failed to create renderer");
 		goto error_event;
 	}
 
+	// TODO: we can use DRI3Open instead
+	int drm_fd = wlr_renderer_get_drm_fd(x11->renderer);
+	if (fd < 0) {
+		wlr_log(WLR_ERROR, "Failed to get DRM device FD from renderer");
+		return false;
+	}
+
+	drm_fd = dup(drm_fd);
+	if (fd < 0) {
+		wlr_log_errno(WLR_ERROR, "dup failed");
+		return false;
+	}
+
+	struct wlr_gbm_allocator *alloc = wlr_gbm_allocator_create(drm_fd);
+	if (alloc == NULL) {
+		wlr_log(WLR_ERROR, "Failed to create GBM allocator");
+		return false;
+	}
+	x11->allocator = &alloc->base;
+
+	const struct wlr_drm_format_set *formats =
+		wlr_renderer_get_dmabuf_render_formats(x11->renderer);
+	if (formats == NULL) {
+		wlr_log(WLR_ERROR, "Failed to get available DMA-BUF formats from renderer");
+		return false;
+	}
+	const struct wlr_drm_format *format =
+		wlr_drm_format_set_get(formats, x11->x11_format->drm);
+	if (format == NULL) {
+		wlr_log(WLR_ERROR, "Renderer doesn't support DRM format 0x%"PRIX32,
+			x11->x11_format->drm);
+		return false;
+	}
+	// TODO intersect modifiers with DRI3GetSupportedModifiers
+	x11->drm_format = wlr_drm_format_dup(format);
+
 #if WLR_HAS_XCB_ERRORS
 	if (xcb_errors_context_new(x11->xcb, &x11->errors_context) != 0) {
 		wlr_log(WLR_ERROR, "Failed to create error context");
@@ -325,6 +475,8 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	}
 #endif
 
+	x11->present_event_id = xcb_generate_id(x11->xcb);
+
 	wlr_input_device_init(&x11->keyboard_dev, WLR_INPUT_DEVICE_KEYBOARD,
 		&input_device_impl, "X11 keyboard", 0, 0);
 	wlr_keyboard_init(&x11->keyboard, &keyboard_impl);
diff --git a/backend/x11/meson.build b/backend/x11/meson.build
index 40530bb0..51c6dd04 100644
--- a/backend/x11/meson.build
+++ b/backend/x11/meson.build
@@ -2,8 +2,10 @@ x11_libs = []
 x11_required = [
 	'x11-xcb',
 	'xcb',
-	'xcb-xinput',
+	'xcb-dri3',
+	'xcb-present',
 	'xcb-xfixes',
+	'xcb-xinput',
 ]
 
 msg = []
diff --git a/backend/x11/output.c b/backend/x11/output.c
index 07374b61..0e81179d 100644
--- a/backend/x11/output.c
+++ b/backend/x11/output.c
@@ -4,6 +4,9 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <drm_fourcc.h>
+#include <xcb/dri3.h>
+#include <xcb/present.h>
 #include <xcb/xcb.h>
 #include <xcb/xinput.h>
 
@@ -13,6 +16,8 @@
 #include <wlr/util/log.h>
 
 #include "backend/x11.h"
+#include "render/swapchain.h"
+#include "render/wlr_renderer.h"
 #include "util/signal.h"
 
 static int signal_frame(void *data) {
@@ -85,7 +90,8 @@ static void output_destroy(struct wlr_output *wlr_output) {
 
 	wl_list_remove(&output->link);
 	wl_event_source_remove(output->frame_timer);
-	wlr_egl_destroy_surface(&x11->egl, output->surf);
+	wlr_buffer_unlock(output->back_buffer);
+	wlr_swapchain_destroy(output->swapchain);
 	xcb_destroy_window(x11->xcb, output->win);
 	xcb_flush(x11->xcb);
 	free(output);
@@ -96,7 +102,20 @@ static bool output_attach_render(struct wlr_output *wlr_output,
 	struct wlr_x11_output *output = get_x11_output_from_output(wlr_output);
 	struct wlr_x11_backend *x11 = output->x11;
 
-	return wlr_egl_make_current(&x11->egl, output->surf, buffer_age);
+	wlr_buffer_unlock(output->back_buffer);
+	output->back_buffer = wlr_swapchain_acquire(output->swapchain, buffer_age);
+	if (!output->back_buffer) {
+		return false;
+	}
+
+	if (!wlr_egl_make_current(&x11->egl, EGL_NO_SURFACE, NULL)) {
+		return false;
+	}
+	if (!wlr_renderer_bind_buffer(x11->renderer, output->back_buffer)) {
+		return false;
+	}
+
+	return true;
 }
 
 static bool output_test(struct wlr_output *wlr_output) {
@@ -112,6 +131,125 @@ static bool output_test(struct wlr_output *wlr_output) {
 	return true;
 }
 
+static struct wlr_x11_buffer *import_x11_buffer(struct wlr_x11_output *output,
+		struct wlr_buffer *wlr_buffer) {
+	struct wlr_x11_backend *x11 = output->x11;
+
+	struct wlr_dmabuf_attributes attrs = {0};
+	if (!wlr_buffer_get_dmabuf(wlr_buffer, &attrs)) {
+		return NULL;
+	}
+
+	if (attrs.format != x11->x11_format->drm) {
+		// The pixmap's depth must match the window's depth, otherwise Present
+		// will throw a Match error
+		return NULL;
+	}
+
+	// xcb closes the FDs after sending them, so we need to dup them here
+	struct wlr_dmabuf_attributes dup_attrs = {0};
+	if (!wlr_dmabuf_attributes_copy(&dup_attrs, &attrs)) {
+		return NULL;
+	}
+
+	const struct wlr_x11_format *x11_fmt = x11->x11_format;
+	xcb_pixmap_t pixmap = xcb_generate_id(x11->xcb);
+	xcb_dri3_pixmap_from_buffers(x11->xcb, pixmap, output->win,
+		attrs.n_planes, attrs.width, attrs.height, attrs.stride[0],
+		attrs.offset[0], attrs.stride[1], attrs.offset[1], attrs.stride[2],
+		attrs.offset[2], attrs.stride[3], attrs.offset[3], x11_fmt->depth,
+		x11_fmt->bpp, attrs.modifier, dup_attrs.fd);
+
+	struct wlr_x11_buffer *buffer = calloc(1, sizeof(struct wlr_x11_buffer));
+	if (!buffer) {
+		xcb_free_pixmap(x11->xcb, pixmap);
+		return NULL;
+	}
+	buffer->buffer = wlr_buffer_lock(wlr_buffer);
+	buffer->pixmap = pixmap;
+	buffer->x11 = x11;
+	wl_list_insert(&output->buffers, &buffer->link);
+	return buffer;
+}
+
+static void destroy_x11_buffer(struct wlr_x11_buffer *buffer) {
+	if (!buffer) {
+		return;
+	}
+	wl_list_remove(&buffer->link);
+	xcb_free_pixmap(buffer->x11->xcb, buffer->pixmap);
+	wlr_buffer_unlock(buffer->buffer);
+	free(buffer);
+}
+
+static bool output_commit_buffer(struct wlr_x11_output *output) {
+	struct wlr_x11_backend *x11 = output->x11;
+
+	assert(output->back_buffer != NULL);
+
+	wlr_renderer_bind_buffer(x11->renderer, NULL);
+	wlr_egl_unset_current(&x11->egl);
+
+	struct wlr_x11_buffer *x11_buffer =
+		import_x11_buffer(output, output->back_buffer);
+	if (!x11_buffer) {
+		goto error;
+	}
+
+	xcb_xfixes_region_t region = XCB_NONE;
+	if (output->wlr_output.pending.committed & WLR_OUTPUT_STATE_DAMAGE) {
+		pixman_region32_t *damage = &output->wlr_output.pending.damage;
+
+		int rects_len = 0;
+		pixman_box32_t *rects = pixman_region32_rectangles(damage, &rects_len);
+
+		xcb_rectangle_t *xcb_rects = calloc(rects_len, sizeof(xcb_rectangle_t));
+		if (!xcb_rects) {
+			goto error;
+		}
+
+		for (int i = 0; i < rects_len; i++) {
+			pixman_box32_t *box = &rects[i];
+			xcb_rects[i] = (struct xcb_rectangle_t){
+				.x = box->x1,
+				.y = box->y1,
+				.width = box->x2 - box->x1,
+				.height = box->y2 - box->y1,
+			};
+		}
+
+		xcb_xfixes_region_t region = xcb_generate_id(x11->xcb);
+		xcb_xfixes_create_region(x11->xcb, region, rects_len, xcb_rects);
+
+		free(xcb_rects);
+	}
+
+	uint32_t serial = output->wlr_output.commit_seq;
+	uint32_t options = 0;
+	xcb_present_pixmap(x11->xcb, output->win, x11_buffer->pixmap, serial,
+		0, region, 0, 0, XCB_NONE, XCB_NONE, XCB_NONE, options, 0, 0, 0,
+		0, NULL);
+
+	if (region != XCB_NONE) {
+		xcb_xfixes_destroy_region(x11->xcb, region);
+	}
+
+	wlr_buffer_unlock(output->back_buffer);
+	output->back_buffer = NULL;
+
+	wlr_swapchain_set_buffer_submitted(output->swapchain, x11_buffer->buffer);
+
+	wlr_output_send_present(&output->wlr_output, NULL);
+
+	return true;
+
+error:
+	destroy_x11_buffer(x11_buffer);
+	wlr_buffer_unlock(output->back_buffer);
+	output->back_buffer = NULL;
+	return false;
+}
+
 static bool output_commit(struct wlr_output *wlr_output) {
 	struct wlr_x11_output *output = get_x11_output_from_output(wlr_output);
 	struct wlr_x11_backend *x11 = output->x11;
@@ -145,24 +283,21 @@ static bool output_commit(struct wlr_output *wlr_output) {
 	}
 
 	if (wlr_output->pending.committed & WLR_OUTPUT_STATE_BUFFER) {
-		pixman_region32_t *damage = NULL;
-		if (wlr_output->pending.committed & WLR_OUTPUT_STATE_DAMAGE) {
-			damage = &wlr_output->pending.damage;
-		}
-
-		if (!wlr_egl_swap_buffers(&x11->egl, output->surf, damage)) {
+		if (!output_commit_buffer(output)) {
 			return false;
 		}
-
-		wlr_output_send_present(wlr_output, NULL);
 	}
 
+	xcb_flush(x11->xcb);
+
 	return true;
 }
 
 static void output_rollback_render(struct wlr_output *wlr_output) {
 	struct wlr_x11_output *output = get_x11_output_from_output(wlr_output);
-	wlr_egl_unset_current(&output->x11->egl);
+	struct wlr_x11_backend *x11 = output->x11;
+	wlr_renderer_bind_buffer(x11->renderer, NULL);
+	wlr_egl_unset_current(&x11->egl);
 }
 
 static const struct wlr_output_impl output_impl = {
@@ -186,6 +321,7 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 		return NULL;
 	}
 	output->x11 = x11;
+	wl_list_init(&output->buffers);
 
 	struct wlr_output *wlr_output = &output->wlr_output;
 	wlr_output_init(wlr_output, &x11->backend, &output_impl, x11->wl_display);
@@ -193,6 +329,14 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 	wlr_output->width = 1024;
 	wlr_output->height = 768;
 
+	output->swapchain = wlr_swapchain_create(x11->allocator,
+		wlr_output->width, wlr_output->height, x11->drm_format);
+	if (!output->swapchain) {
+		wlr_log(WLR_ERROR, "Failed to create swapchain");
+		free(output);
+		return NULL;
+	}
+
 	output_set_refresh(&output->wlr_output, 0);
 
 	snprintf(wlr_output->name, sizeof(wlr_output->name), "X11-%zd",
@@ -204,14 +348,18 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 		"X11 output %zd", x11->last_output_num);
 	wlr_output_set_description(wlr_output, description);
 
-	uint32_t mask = XCB_CW_EVENT_MASK;
+	// The X11 protocol requires us to set a colormap and border pixel if the
+	// depth doesn't match the root window's
+	uint32_t mask = XCB_CW_BORDER_PIXEL | XCB_CW_EVENT_MASK | XCB_CW_COLORMAP;
 	uint32_t values[] = {
-		XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_STRUCTURE_NOTIFY
+		0,
+		XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_STRUCTURE_NOTIFY,
+		x11->colormap,
 	};
 	output->win = xcb_generate_id(x11->xcb);
-	xcb_create_window(x11->xcb, XCB_COPY_FROM_PARENT, output->win,
-		x11->screen->root, 0, 0, wlr_output->width, wlr_output->height, 1,
-		XCB_WINDOW_CLASS_INPUT_OUTPUT, x11->screen->root_visual, mask, values);
+	xcb_create_window(x11->xcb, x11->depth->depth, output->win,
+		x11->screen->root, 0, 0, wlr_output->width, wlr_output->height, 0,
+		XCB_WINDOW_CLASS_INPUT_OUTPUT, x11->visualid, mask, values);
 
 	struct {
 		xcb_input_event_mask_t head;
@@ -227,16 +375,14 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 			XCB_INPUT_XI_EVENT_MASK_LEAVE |
 			XCB_INPUT_XI_EVENT_MASK_TOUCH_BEGIN |
 			XCB_INPUT_XI_EVENT_MASK_TOUCH_END |
-			XCB_INPUT_XI_EVENT_MASK_TOUCH_UPDATE,
+			XCB_INPUT_XI_EVENT_MASK_TOUCH_UPDATE |
+			XCB_PRESENT_EVENT_MASK_IDLE_NOTIFY,
 	};
 	xcb_input_xi_select_events(x11->xcb, output->win, 1, &xinput_mask.head);
 
-	output->surf = wlr_egl_create_surface(&x11->egl, &output->win);
-	if (!output->surf) {
-		wlr_log(WLR_ERROR, "Failed to create EGL surface");
-		free(output);
-		return NULL;
-	}
+	uint32_t present_mask = XCB_PRESENT_EVENT_MASK_IDLE_NOTIFY;
+	xcb_present_select_input(x11->xcb, x11->present_event_id, output->win,
+		present_mask);
 
 	xcb_change_property(x11->xcb, XCB_PROP_MODE_REPLACE, output->win,
 		x11->atoms.wm_protocols, XCB_ATOM_ATOM, 32, 1,
@@ -278,17 +424,30 @@ struct wlr_output *wlr_x11_output_create(struct wlr_backend *backend) {
 void handle_x11_configure_notify(struct wlr_x11_output *output,
 		xcb_configure_notify_event_t *ev) {
 	// ignore events that set an invalid size:
-	if (ev->width > 0 && ev->height > 0) {
-		wlr_output_update_custom_mode(&output->wlr_output, ev->width,
-			ev->height, output->wlr_output.refresh);
-
-		// Move the pointer to its new location
-		update_x11_pointer_position(output, output->x11->time);
-	} else {
+	if (ev->width == 0 || ev->height == 0) {
 		wlr_log(WLR_DEBUG,
 			"Ignoring X11 configure event for height=%d, width=%d",
 			ev->width, ev->height);
+		return;
+	}
+
+	if (output->swapchain->width != ev->width ||
+			output->swapchain->height != ev->height) {
+		struct wlr_swapchain *swapchain = wlr_swapchain_create(
+			output->x11->allocator, ev->width, ev->height,
+			output->x11->drm_format);
+		if (!swapchain) {
+			return;
+		}
+		wlr_swapchain_destroy(output->swapchain);
+		output->swapchain = swapchain;
 	}
+
+	wlr_output_update_custom_mode(&output->wlr_output, ev->width,
+		ev->height, output->wlr_output.refresh);
+
+	// Move the pointer to its new location
+	update_x11_pointer_position(output, output->x11->time);
 }
 
 bool wlr_output_is_x11(struct wlr_output *wlr_output) {
@@ -310,3 +469,42 @@ void wlr_x11_output_set_title(struct wlr_output *output, const char *title) {
 		x11_output->x11->atoms.net_wm_name, x11_output->x11->atoms.utf8_string, 8,
 		strlen(title), title);
 }
+
+static struct wlr_x11_buffer *get_x11_buffer(struct wlr_x11_output *output,
+		xcb_pixmap_t pixmap) {
+	struct wlr_x11_buffer *buffer;
+	wl_list_for_each(buffer, &output->buffers, link) {
+		if (buffer->pixmap == pixmap) {
+			return buffer;
+		}
+	}
+	return NULL;
+}
+
+void handle_x11_present_event(struct wlr_x11_backend *x11,
+		xcb_ge_generic_event_t *event) {
+	switch (event->event_type) {
+	case XCB_PRESENT_EVENT_IDLE_NOTIFY:;
+		xcb_present_idle_notify_event_t *idle_notify =
+			(xcb_present_idle_notify_event_t *)event;
+
+		struct wlr_x11_output *output =
+			get_x11_output_from_window_id(x11, idle_notify->window);
+		if (!output) {
+			wlr_log(WLR_DEBUG, "Got PresentIdleNotify event for unknown window");
+			return;
+		}
+
+		struct wlr_x11_buffer *buffer =
+			get_x11_buffer(output, idle_notify->pixmap);
+		if (!buffer) {
+			wlr_log(WLR_DEBUG, "Got PresentIdleNotify event for unknown buffer");
+			return;
+		}
+
+		destroy_x11_buffer(buffer);
+		break;
+	default:
+		wlr_log(WLR_DEBUG, "Unhandled Present event %"PRIu16, event->event_type);
+	}
+}