Merge pull request #1069 from emersion/screencopy

Add wlr-screencopy-unstable-v1 support

backend/drm/drm.c

@@ -683,7 +683,7 @@ static bool drm_connector_set_cursor(struct wlr_output *output,
 		wlr_render_texture_with_matrix(rend, texture, matrix, 1.0);
 		wlr_renderer_end(rend);
 
-		wlr_renderer_read_pixels(rend, WL_SHM_FORMAT_ARGB8888, bo_stride,
+		wlr_renderer_read_pixels(rend, WL_SHM_FORMAT_ARGB8888, NULL, bo_stride,
 			plane->surf.width, plane->surf.height, 0, 0, 0, 0, bo_data);
 
 		swap_drm_surface_buffers(&plane->surf, NULL);

examples/meson.build

@@ -1,6 +1,8 @@
 threads = dependency('threads')
 wayland_cursor = dependency('wayland-cursor')
 
+libpng = dependency('libpng', required: false)
+
 # These versions correspond to ffmpeg 4.0
 libavutil = dependency('libavutil', version: '>=56.14.100', required: false)
 libavcodec = dependency('libavcodec', version: '>=58.18.100', required: false)
@@ -56,3 +58,11 @@ if libavutil.found() and libavcodec.found() and libavformat.found()
 				libavformat, wlroots, threads ]
 	)
 endif
+
+if libpng.found()
+	executable(
+		'screencopy',
+		'screencopy.c',
+		dependencies: [wayland_client, wlr_protos, wlroots, libpng]
+	)
+endif

examples/screencopy.c

@@ -0,0 +1,270 @@
+/*
+ * Copyright © 2008 Kristian Høgsberg
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#define _XOPEN_SOURCE 700
+#define _POSIX_C_SOURCE 199309L
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <png.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <wayland-client-protocol.h>
+#include "wlr-screencopy-unstable-v1-client-protocol.h"
+
+struct format {
+	enum wl_shm_format wl_format;
+	bool is_bgr;
+};
+
+static struct wl_shm *shm = NULL;
+static struct zwlr_screencopy_manager_v1 *screencopy_manager = NULL;
+static struct wl_output *output = NULL;
+
+static struct {
+	struct wl_buffer *wl_buffer;
+	void *data;
+	enum wl_shm_format format;
+	int width, height, stride;
+	bool y_invert;
+} buffer;
+bool buffer_copy_done = false;
+
+// wl_shm_format describes little-endian formats, libpng uses big-endian
+// formats (so Wayland's ABGR is libpng's RGBA).
+static const struct format formats[] = {
+	{WL_SHM_FORMAT_XRGB8888, true},
+	{WL_SHM_FORMAT_ARGB8888, true},
+	{WL_SHM_FORMAT_XBGR8888, false},
+	{WL_SHM_FORMAT_ABGR8888, false},
+};
+
+static int backingfile(off_t size) {
+	char template[] = "/tmp/wlroots-shared-XXXXXX";
+	int fd = mkstemp(template);
+	if (fd < 0) {
+		return -1;
+	}
+
+	int ret;
+	while ((ret = ftruncate(fd, size)) == EINTR) {
+		// No-op
+	}
+	if (ret < 0) {
+		close(fd);
+		return -1;
+	}
+
+	unlink(template);
+	return fd;
+}
+
+static struct wl_buffer *create_shm_buffer(enum wl_shm_format fmt,
+		int width, int height, int stride, void **data_out) {
+	int size = stride * height;
+
+	int fd = backingfile(size);
+	if (fd < 0) {
+		fprintf(stderr, "creating a buffer file for %d B failed: %m\n", size);
+		return NULL;
+	}
+
+	void *data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (data == MAP_FAILED) {
+		fprintf(stderr, "mmap failed: %m\n");
+		close(fd);
+		return NULL;
+	}
+
+	struct wl_shm_pool *pool = wl_shm_create_pool(shm, fd, size);
+	close(fd);
+	struct wl_buffer *buffer = wl_shm_pool_create_buffer(pool, 0, width, height,
+		stride, fmt);
+	wl_shm_pool_destroy(pool);
+
+	*data_out = data;
+	return buffer;
+}
+
+static void frame_handle_buffer(void *data,
+		struct zwlr_screencopy_frame_v1 *frame, uint32_t format,
+		uint32_t width, uint32_t height, uint32_t stride) {
+	buffer.format = format;
+	buffer.width = width;
+	buffer.height = height;
+	buffer.stride = stride;
+	buffer.wl_buffer =
+		create_shm_buffer(format, width, height, stride, &buffer.data);
+	if (buffer.wl_buffer == NULL) {
+		fprintf(stderr, "failed to create buffer\n");
+		exit(EXIT_FAILURE);
+	}
+
+	zwlr_screencopy_frame_v1_copy(frame, buffer.wl_buffer);
+}
+
+static void frame_handle_flags(void *data,
+		struct zwlr_screencopy_frame_v1 *frame, uint32_t flags) {
+	buffer.y_invert = flags & ZWLR_SCREENCOPY_FRAME_V1_FLAGS_Y_INVERT;
+}
+
+static void frame_handle_ready(void *data,
+		struct zwlr_screencopy_frame_v1 *frame, uint32_t tv_sec_hi,
+		uint32_t tv_sec_lo, uint32_t tv_nsec) {
+	buffer_copy_done = true;
+}
+
+static void frame_handle_failed(void *data,
+		struct zwlr_screencopy_frame_v1 *frame) {
+	fprintf(stderr, "failed to copy frame\n");
+	exit(EXIT_FAILURE);
+}
+
+static const struct zwlr_screencopy_frame_v1_listener frame_listener = {
+	.buffer = frame_handle_buffer,
+	.flags = frame_handle_flags,
+	.ready = frame_handle_ready,
+	.failed = frame_handle_failed,
+};
+
+static void handle_global(void *data, struct wl_registry *registry,
+		uint32_t name, const char *interface, uint32_t version) {
+	if (strcmp(interface, wl_output_interface.name) == 0 && output == NULL) {
+		output = wl_registry_bind(registry, name, &wl_output_interface, 1);
+	} else if (strcmp(interface, wl_shm_interface.name) == 0) {
+		shm = wl_registry_bind(registry, name, &wl_shm_interface, 1);
+	} else if (strcmp(interface,
+			zwlr_screencopy_manager_v1_interface.name) == 0) {
+		screencopy_manager = wl_registry_bind(registry, name,
+			&zwlr_screencopy_manager_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,
+};
+
+static void write_image(char *filename, enum wl_shm_format wl_fmt, int width,
+		int height, int stride, bool y_invert, png_bytep data) {
+	const struct format *fmt = NULL;
+	for (size_t i = 0; i < sizeof(formats) / sizeof(formats[0]); ++i) {
+		if (formats[i].wl_format == wl_fmt) {
+			fmt = &formats[i];
+			break;
+		}
+	}
+	if (fmt == NULL) {
+		fprintf(stderr, "unsupported format %"PRIu32"\n", wl_fmt);
+		exit(EXIT_FAILURE);
+	}
+
+	FILE *f = fopen(filename, "wb");
+	if (f == NULL) {
+		fprintf(stderr, "failed to open output file\n");
+		exit(EXIT_FAILURE);
+	}
+
+	png_structp png =
+		png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+	png_infop info = png_create_info_struct(png);
+
+	png_init_io(png, f);
+
+	png_set_IHDR(png, info, width, height, 8, PNG_COLOR_TYPE_RGBA,
+		PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_DEFAULT,
+		PNG_FILTER_TYPE_DEFAULT);
+
+	if (fmt->is_bgr) {
+		png_set_bgr(png);
+	}
+
+	png_write_info(png, info);
+
+	for (size_t i = 0; i < (size_t)height; ++i) {
+		png_bytep row;
+		if (y_invert) {
+			row = data + (height - i - 1) * stride;
+		} else {
+			row = data + i * stride;
+		}
+		png_write_row(png, row);
+	}
+
+	png_write_end(png, NULL);
+
+	png_destroy_write_struct(&png, &info);
+
+	fclose(f);
+}
+
+int main(int argc, char *argv[]) {
+	struct wl_display * display = wl_display_connect(NULL);
+	if (display == NULL) {
+		fprintf(stderr, "failed to create display: %m\n");
+		return EXIT_FAILURE;
+	}
+
+	struct wl_registry *registry = wl_display_get_registry(display);
+	wl_registry_add_listener(registry, &registry_listener, NULL);
+	wl_display_dispatch(display);
+	wl_display_roundtrip(display);
+
+	if (shm == NULL) {
+		fprintf(stderr, "compositor is missing wl_shm\n");
+		return EXIT_FAILURE;
+	}
+	if (screencopy_manager == NULL) {
+		fprintf(stderr, "compositor doesn't support wlr-screencopy-unstable-v1\n");
+		return EXIT_FAILURE;
+	}
+	if (output == NULL) {
+		fprintf(stderr, "no output available\n");
+		return EXIT_FAILURE;
+	}
+
+	struct zwlr_screencopy_frame_v1 *frame =
+		zwlr_screencopy_manager_v1_capture_output(screencopy_manager, 0, output);
+	zwlr_screencopy_frame_v1_add_listener(frame, &frame_listener, NULL);
+
+	while (!buffer_copy_done && wl_display_dispatch(display) != -1) {
+		// This space is intentionally left blank
+	}
+
+	write_image("wayland-screenshot.png", buffer.format, buffer.width,
+		buffer.height, buffer.stride, buffer.y_invert, buffer.data);
+	wl_buffer_destroy(buffer.wl_buffer);
+
+	return EXIT_SUCCESS;
+}

include/rootston/desktop.h

@@ -22,6 +22,7 @@
 #include <wlr/types/wlr_list.h>
 #include <wlr/types/wlr_idle.h>
 #include <wlr/types/wlr_idle_inhibit_v1.h>
+#include <wlr/types/wlr_screencopy_v1.h>
 #include "rootston/view.h"
 #include "rootston/config.h"
 #include "rootston/output.h"
@@ -54,6 +55,7 @@ struct roots_desktop {
 	struct wlr_linux_dmabuf *linux_dmabuf;
 	struct wlr_layer_shell *layer_shell;
 	struct wlr_virtual_keyboard_manager_v1 *virtual_keyboard;
+	struct wlr_screencopy_manager_v1 *screencopy;
 
 	struct wl_listener new_output;
 	struct wl_listener layout_change;

include/wlr/render/interface.h

@@ -34,7 +34,7 @@ struct wlr_renderer_impl {
 	int (*get_dmabuf_modifiers)(struct wlr_renderer *renderer, int format,
 		uint64_t **modifiers);
 	bool (*read_pixels)(struct wlr_renderer *renderer, enum wl_shm_format fmt,
-		uint32_t stride, uint32_t width, uint32_t height,
+		uint32_t *flags, uint32_t stride, uint32_t width, uint32_t height,
 		uint32_t src_x, uint32_t src_y, uint32_t dst_x, uint32_t dst_y,
 		void *data);
 	bool (*format_supported)(struct wlr_renderer *renderer,

include/wlr/render/wlr_renderer.h

@@ -7,6 +7,10 @@
 #include <wlr/render/wlr_texture.h>
 #include <wlr/types/wlr_box.h>
 
+enum wlr_renderer_read_pixels_flags {
+	WLR_RENDERER_READ_PIXELS_Y_INVERT = 1,
+};
+
 struct wlr_renderer_impl;
 
 struct wlr_renderer {
@@ -87,9 +91,12 @@ int wlr_renderer_get_dmabuf_modifiers(struct wlr_renderer *renderer, int format,
 /**
  * Reads out of pixels of the currently bound surface into data. `stride` is in
  * bytes.
+ *
+ * If `flags` is not NULl, the caller indicates that it accepts frame flags
+ * defined in `enum wlr_renderer_read_pixels_flags`.
  */
 bool wlr_renderer_read_pixels(struct wlr_renderer *r, enum wl_shm_format fmt,
-	uint32_t stride, uint32_t width, uint32_t height,
+	uint32_t *flags, uint32_t stride, uint32_t width, uint32_t height,
 	uint32_t src_x, uint32_t src_y, uint32_t dst_x, uint32_t dst_y, void *data);
 /**
  * Checks if a format is supported.

include/wlr/types/wlr_screencopy_v1.h

@@ -0,0 +1,39 @@
+#ifndef WLR_TYPES_WLR_SCREENCOPY_V1_H
+#define WLR_TYPES_WLR_SCREENCOPY_V1_H
+
+#include <wayland-server.h>
+
+struct wlr_screencopy_manager_v1 {
+	struct wl_global *global;
+	struct wl_list resources; // wl_resource
+	struct wl_list frames; // wlr_screencopy_frame_v1::link
+
+	struct wl_listener display_destroy;
+
+	void *data;
+};
+
+struct wlr_screencopy_frame_v1 {
+	struct wl_resource *resource;
+	struct wlr_screencopy_manager_v1 *manager;
+	struct wl_list link;
+
+	enum wl_shm_format format;
+	struct wlr_box box;
+	int stride;
+
+	struct wl_shm_buffer *buffer;
+	struct wl_listener buffer_destroy;
+
+	struct wlr_output *output;
+	struct wl_listener output_swap_buffers;
+
+	void *data;
+};
+
+struct wlr_screencopy_manager_v1 *wlr_screencopy_manager_v1_create(
+	struct wl_display *display);
+void wlr_screencopy_manager_v1_destroy(
+	struct wlr_screencopy_manager_v1 *screencopy);
+
+#endif

protocol/meson.build

@@ -42,6 +42,7 @@ protocols = [
 	'wlr-export-dmabuf-unstable-v1.xml',
 	'wlr-input-inhibitor-unstable-v1.xml',
 	'wlr-layer-shell-unstable-v1.xml',
+	'wlr-screencopy-unstable-v1.xml',
 ]
 
 client_protocols = [
@@ -51,8 +52,9 @@ client_protocols = [
 	'idle.xml',
 	'screenshooter.xml',
 	'wlr-export-dmabuf-unstable-v1.xml',
-	'wlr-layer-shell-unstable-v1.xml',
 	'wlr-input-inhibitor-unstable-v1.xml',
+	'wlr-layer-shell-unstable-v1.xml',
+	'wlr-screencopy-unstable-v1.xml',
 ]
 
 wl_protos_src = []

protocol/wlr-screencopy-unstable-v1.xml

@@ -0,0 +1,179 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<protocol name="wlr_screencopy_unstable_v1">
+  <copyright>
+    Copyright © 2018 Simon Ser
+
+    Permission is hereby granted, free of charge, to any person obtaining a
+    copy of this software and associated documentation files (the "Software"),
+    to deal in the Software without restriction, including without limitation
+    the rights to use, copy, modify, merge, publish, distribute, sublicense,
+    and/or sell copies of the Software, and to permit persons to whom the
+    Software is furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice (including the next
+    paragraph) shall be included in all copies or substantial portions of the
+    Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+    DEALINGS IN THE SOFTWARE.
+  </copyright>
+
+  <description summary="screen content capturing on client buffers">
+    This protocol allows clients to ask the compositor to copy part of the
+    screen content to a client buffer.
+
+    Warning! The protocol described in this file is experimental and
+    backward incompatible changes may be made. Backward compatible changes
+    may be added together with the corresponding interface version bump.
+    Backward incompatible changes are done by bumping the version number in
+    the protocol and interface names and resetting the interface version.
+    Once the protocol is to be declared stable, the 'z' prefix and the
+    version number in the protocol and interface names are removed and the
+    interface version number is reset.
+  </description>
+
+  <interface name="zwlr_screencopy_manager_v1" version="1">
+    <description summary="manager to inform clients and begin capturing">
+      This object is a manager which offers requests to start capturing from a
+      source.
+    </description>
+
+    <request name="capture_output">
+      <description summary="capture an output">
+        Capture the next frame of an entire output.
+      </description>
+      <arg name="frame" type="new_id" interface="zwlr_screencopy_frame_v1"/>
+      <arg name="overlay_cursor" type="int"
+        summary="composite cursor onto the frame"/>
+      <arg name="output" type="object" interface="wl_output"/>
+    </request>
+
+    <request name="capture_output_region">
+      <description summary="capture an output's region">
+        Capture the next frame of an output's region.
+
+        The region is given in output logical coordinates, see
+        xdg_output.logical_size. The region will be clipped to the output's
+        extents.
+      </description>
+      <arg name="frame" type="new_id" interface="zwlr_screencopy_frame_v1"/>
+      <arg name="overlay_cursor" type="int"
+        summary="composite cursor onto the frame"/>
+      <arg name="output" type="object" interface="wl_output"/>
+      <arg name="x" type="int"/>
+      <arg name="y" type="int"/>
+      <arg name="width" type="int"/>
+      <arg name="height" type="int"/>
+    </request>
+
+    <request name="destroy" type="destructor">
+      <description summary="destroy the manager">
+        All objects created by the manager will still remain valid, until their
+        appropriate destroy request has been called.
+      </description>
+    </request>
+  </interface>
+
+  <interface name="zwlr_screencopy_frame_v1" version="1">
+    <description summary="a frame ready for copy">
+      This object represents a single frame.
+
+      When created, a "buffer" event will be sent. The client will then be able
+      to send a "copy" request. If the capture is successful, the compositor
+      will send a "flags" followed by a "ready" event.
+
+      If the capture failed, the "failed" event is sent. This can happen anytime
+      before the "ready" event.
+
+      Once either a "ready" or a "failed" event is received, the client should
+      destroy the frame.
+    </description>
+
+    <event name="buffer">
+      <description summary="buffer information">
+        Provides information about the frame's buffer. This event is sent once
+        as soon as the frame is created.
+
+        The client should then create a buffer with the provided attributes, and
+        send a "copy" request.
+      </description>
+      <arg name="format" type="uint" summary="buffer format"/>
+      <arg name="width" type="uint" summary="buffer width"/>
+      <arg name="height" type="uint" summary="buffer height"/>
+      <arg name="stride" type="uint" summary="buffer stride"/>
+    </event>
+
+    <request name="copy">
+      <description summary="copy the frame">
+        Copy the frame to the supplied buffer. The buffer must have a the
+        correct size, see zwlr_screencopy_frame_v1.buffer. The buffer needs to
+        have a supported format.
+
+        If the frame is successfully copied, a "flags" and a "ready" events are
+        sent. Otherwise, a "failed" event is sent.
+      </description>
+      <arg name="buffer" type="object" interface="wl_buffer"/>
+    </request>
+
+    <enum name="error">
+      <entry name="already_used" value="0"
+        summary="the object has already been used to copy a wl_buffer"/>
+      <entry name="invalid_buffer" value="1"
+        summary="buffer attributes are invalid"/>
+    </enum>
+
+    <enum name="flags" bitfield="true">
+      <entry name="y_invert" value="1" summary="contents are y-inverted"/>
+    </enum>
+
+    <event name="flags">
+      <description summary="frame flags">
+        Provides flags about the frame. This event is sent once before the
+        "ready" event.
+      </description>
+      <arg name="flags" type="uint" enum="flags" summary="frame flags"/>
+    </event>
+
+    <event name="ready">
+      <description summary="indicates frame is available for reading">
+        Called as soon as the frame is copied, indicating it is available
+        for reading. This event includes the time at which presentation happened
+        at.
+
+        The timestamp is expressed as tv_sec_hi, tv_sec_lo, tv_nsec triples,
+        each component being an unsigned 32-bit value. Whole seconds are in
+        tv_sec which is a 64-bit value combined from tv_sec_hi and tv_sec_lo,
+        and the additional fractional part in tv_nsec as nanoseconds. Hence,
+        for valid timestamps tv_nsec must be in [0, 999999999]. The seconds part
+        may have an arbitrary offset at start.
+
+        After receiving this event, the client should destroy the object.
+      </description>
+      <arg name="tv_sec_hi" type="uint"
+           summary="high 32 bits of the seconds part of the timestamp"/>
+      <arg name="tv_sec_lo" type="uint"
+           summary="low 32 bits of the seconds part of the timestamp"/>
+      <arg name="tv_nsec" type="uint"
+           summary="nanoseconds part of the timestamp"/>
+    </event>
+
+    <event name="failed">
+      <description summary="frame copy failed">
+        This event indicates that the attempted frame copy has failed.
+
+        After receiving this event, the client should destroy the object.
+      </description>
+    </event>
+
+    <request name="destroy" type="destructor">
+      <description summary="delete this object, used or not">
+        Destroys the frame. This request can be sent at any time by the client.
+      </description>
+    </request>
+  </interface>
+</protocol>

render/gles2/renderer.c

@@ -250,9 +250,10 @@ static int gles2_get_dmabuf_modifiers(struct wlr_renderer *wlr_renderer,
 }
 
 static bool gles2_read_pixels(struct wlr_renderer *wlr_renderer,
-		enum wl_shm_format wl_fmt, uint32_t stride, uint32_t width,
+		enum wl_shm_format wl_fmt, uint32_t *flags, uint32_t stride,
-		uint32_t height, uint32_t src_x, uint32_t src_y, uint32_t dst_x,
+		uint32_t width, uint32_t height, uint32_t src_x, uint32_t src_y,
-		uint32_t dst_y, void *data) {
+		uint32_t dst_x, uint32_t dst_y, void *data) {
+	struct wlr_gles2_renderer *renderer =
 		gles2_get_renderer_in_context(wlr_renderer);
 
 	const struct wlr_gles2_pixel_format *fmt = get_gles2_format_from_wl(wl_fmt);
@@ -266,17 +267,31 @@ static bool gles2_read_pixels(struct wlr_renderer *wlr_renderer,
 	// Make sure any pending drawing is finished before we try to read it
 	glFinish();
 
+	glGetError(); // Clear the error flag
+
+	unsigned char *p = data + dst_y * stride;
+	uint32_t pack_stride = width * fmt->bpp / 8;
+	if (pack_stride == stride && dst_x == 0 && flags != NULL) {
+		// Under these particular conditions, we can read the pixels with only
+		// one glReadPixels call
+		glReadPixels(src_x, renderer->viewport_height - height - src_y,
+			width, height, fmt->gl_format, fmt->gl_type, p);
+		*flags = WLR_RENDERER_READ_PIXELS_Y_INVERT;
+	} else {
 		// Unfortunately GLES2 doesn't support GL_PACK_*, so we have to read
 		// the lines out row by row
-	unsigned char *p = data + dst_y * stride;
 		for (size_t i = src_y; i < src_y + height; ++i) {
 			glReadPixels(src_x, src_y + height - i - 1, width, 1, fmt->gl_format,
 				fmt->gl_type, p + i * stride + dst_x * fmt->bpp / 8);
 		}
+		if (flags != NULL) {
+			*flags = 0;
+		}
+	}
 
 	POP_GLES2_DEBUG;
 
-	return true;
+	return glGetError() == GL_NO_ERROR;
 }
 
 static bool gles2_format_supported(struct wlr_renderer *wlr_renderer,

render/wlr_renderer.c

@@ -139,14 +139,14 @@ int wlr_renderer_get_dmabuf_modifiers(struct wlr_renderer *r, int format,
 }
 
 bool wlr_renderer_read_pixels(struct wlr_renderer *r, enum wl_shm_format fmt,
-		uint32_t stride, uint32_t width, uint32_t height,
+		uint32_t *flags, uint32_t stride, uint32_t width, uint32_t height,
 		uint32_t src_x, uint32_t src_y, uint32_t dst_x, uint32_t dst_y,
 		void *data) {
 	if (!r->impl->read_pixels) {
 		return false;
 	}
-	return r->impl->read_pixels(r, fmt, stride, width, height, src_x, src_y,
+	return r->impl->read_pixels(r, fmt, flags, stride, width, height,
-		dst_x, dst_y, data);
+		src_x, src_y, dst_x, dst_y, data);
 }
 
 bool wlr_renderer_format_supported(struct wlr_renderer *r,

rootston/desktop.c

@@ -875,6 +875,9 @@ struct roots_desktop *desktop_create(struct roots_server *server,
 	wl_signal_add(&desktop->virtual_keyboard->events.new_virtual_keyboard,
 		&desktop->virtual_keyboard_new);
 	desktop->virtual_keyboard_new.notify = handle_virtual_keyboard;
+
+	desktop->screencopy = wlr_screencopy_manager_v1_create(server->wl_display);
+
 	return desktop;
 }
 

types/meson.build

@@ -50,6 +50,7 @@ lib_wlr_types = static_library(
 		'wlr_wl_shell.c',
 		'wlr_xcursor_manager.c',
 		'wlr_xdg_output.c',
+		'wlr_screencopy_v1.c',
 	),
 	include_directories: wlr_inc,
 	dependencies: [pixman, xkbcommon, wayland_server, wlr_protos],

types/wlr_screencopy_v1.c

@@ -0,0 +1,318 @@
+#include <assert.h>
+#include <stdlib.h>
+#include <wlr/render/wlr_renderer.h>
+#include <wlr/types/wlr_output.h>
+#include <wlr/types/wlr_screencopy_v1.h>
+#include <wlr/backend.h>
+#include "wlr-screencopy-unstable-v1-protocol.h"
+
+#define SCREENCOPY_MANAGER_VERSION 1
+
+static const struct zwlr_screencopy_frame_v1_interface frame_impl;
+
+static struct wlr_screencopy_frame_v1 *frame_from_resource(
+		struct wl_resource *resource) {
+	assert(wl_resource_instance_of(resource,
+		&zwlr_screencopy_frame_v1_interface, &frame_impl));
+	return wl_resource_get_user_data(resource);
+}
+
+static void frame_destroy(struct wlr_screencopy_frame_v1 *frame) {
+	if (frame == NULL) {
+		return;
+	}
+	wl_list_remove(&frame->link);
+	wl_list_remove(&frame->output_swap_buffers.link);
+	wl_list_remove(&frame->buffer_destroy.link);
+	// Make the frame resource inert
+	wl_resource_set_user_data(frame->resource, NULL);
+	free(frame);
+}
+
+static void frame_handle_output_swap_buffers(struct wl_listener *listener,
+		void *_data) {
+	struct wlr_screencopy_frame_v1 *frame =
+		wl_container_of(listener, frame, output_swap_buffers);
+	struct wlr_output_event_swap_buffers *event = _data;
+	struct wlr_output *output = frame->output;
+	struct wlr_renderer *renderer = wlr_backend_get_renderer(output->backend);
+
+	wl_list_remove(&frame->output_swap_buffers.link);
+	wl_list_init(&frame->output_swap_buffers.link);
+
+	int x = frame->box.x;
+	int y = frame->box.y;
+
+	struct wl_shm_buffer *buffer = frame->buffer;
+	assert(buffer != NULL);
+
+	enum wl_shm_format fmt = wl_shm_buffer_get_format(buffer);
+	int32_t width = wl_shm_buffer_get_width(buffer);
+	int32_t height = wl_shm_buffer_get_height(buffer);
+	int32_t stride = wl_shm_buffer_get_stride(buffer);
+
+	wl_shm_buffer_begin_access(buffer);
+	void *data = wl_shm_buffer_get_data(buffer);
+	uint32_t flags = 0;
+	bool ok = wlr_renderer_read_pixels(renderer, fmt, &flags, stride,
+		width, height, x, y, 0, 0, data);
+	wl_shm_buffer_end_access(buffer);
+
+	if (!ok) {
+		zwlr_screencopy_frame_v1_send_failed(frame->resource);
+		frame_destroy(frame);
+		return;
+	}
+
+	zwlr_screencopy_frame_v1_send_flags(frame->resource, flags);
+
+	uint32_t tv_sec_hi = event->when->tv_sec >> 32;
+	uint32_t tv_sec_lo = event->when->tv_sec & 0xFFFFFFFF;
+	zwlr_screencopy_frame_v1_send_ready(frame->resource,
+		tv_sec_hi, tv_sec_lo, event->when->tv_nsec);
+
+	frame_destroy(frame);
+}
+
+static void frame_handle_buffer_destroy(struct wl_listener *listener,
+		void *data) {
+	struct wlr_screencopy_frame_v1 *frame =
+		wl_container_of(listener, frame, buffer_destroy);
+	zwlr_screencopy_frame_v1_send_failed(frame->resource);
+	frame_destroy(frame);
+}
+
+static void frame_handle_copy(struct wl_client *client,
+		struct wl_resource *frame_resource,
+		struct wl_resource *buffer_resource) {
+	struct wlr_screencopy_frame_v1 *frame = frame_from_resource(frame_resource);
+	if (frame == NULL) {
+		return;
+	}
+
+	struct wlr_output *output = frame->output;
+
+	struct wl_shm_buffer *buffer = wl_shm_buffer_get(buffer_resource);
+	if (buffer == NULL) {
+		wl_resource_post_error(frame->resource,
+			ZWLR_SCREENCOPY_FRAME_V1_ERROR_INVALID_BUFFER,
+			"unsupported buffer type");
+		return;
+	}
+
+	enum wl_shm_format fmt = wl_shm_buffer_get_format(buffer);
+	int32_t width = wl_shm_buffer_get_width(buffer);
+	int32_t height = wl_shm_buffer_get_height(buffer);
+	int32_t stride = wl_shm_buffer_get_stride(buffer);
+	if (fmt != frame->format || width != frame->box.width ||
+			height != frame->box.height || stride != frame->stride) {
+		wl_resource_post_error(frame->resource,
+			ZWLR_SCREENCOPY_FRAME_V1_ERROR_INVALID_BUFFER,
+			"invalid buffer attributes");
+		return;
+	}
+
+	if (!wl_list_empty(&frame->output_swap_buffers.link) ||
+			frame->buffer != NULL) {
+		wl_resource_post_error(frame->resource,
+			ZWLR_SCREENCOPY_FRAME_V1_ERROR_ALREADY_USED,
+			"frame already used");
+		return;
+	}
+
+	frame->buffer = buffer;
+
+	wl_signal_add(&output->events.swap_buffers, &frame->output_swap_buffers);
+	frame->output_swap_buffers.notify = frame_handle_output_swap_buffers;
+
+	wl_resource_add_destroy_listener(buffer_resource, &frame->buffer_destroy);
+	frame->buffer_destroy.notify = frame_handle_buffer_destroy;
+
+	// Schedule a buffer swap
+	output->needs_swap = true;
+	wlr_output_schedule_frame(output);
+}
+
+static void frame_handle_destroy(struct wl_client *client,
+		struct wl_resource *frame_resource) {
+	wl_resource_destroy(frame_resource);
+}
+
+static const struct zwlr_screencopy_frame_v1_interface frame_impl = {
+	.copy = frame_handle_copy,
+	.destroy = frame_handle_destroy,
+};
+
+static void frame_handle_resource_destroy(struct wl_resource *frame_resource) {
+	struct wlr_screencopy_frame_v1 *frame = frame_from_resource(frame_resource);
+	frame_destroy(frame);
+}
+
+
+static const struct zwlr_screencopy_manager_v1_interface manager_impl;
+
+static struct wlr_screencopy_manager_v1 *manager_from_resource(
+		struct wl_resource *resource) {
+	assert(wl_resource_instance_of(resource,
+		&zwlr_screencopy_manager_v1_interface, &manager_impl));
+	return wl_resource_get_user_data(resource);
+}
+
+static void capture_output(struct wl_client *client,
+		struct wlr_screencopy_manager_v1 *manager, uint32_t version, uint32_t id,
+		int32_t overlay_cursor, struct wlr_output *output,
+		const struct wlr_box *box) {
+	struct wlr_box buffer_box = {0};
+	if (box == NULL) {
+		buffer_box.width = output->width;
+		buffer_box.height = output->height;
+	} else {
+		int ow, oh;
+		wlr_output_effective_resolution(output, &ow, &oh);
+
+		buffer_box = *box;
+
+		wlr_box_transform(&buffer_box, output->transform, ow, oh, &buffer_box);
+		buffer_box.x *= output->scale;
+		buffer_box.y *= output->scale;
+		buffer_box.width *= output->scale;
+		buffer_box.height *= output->scale;
+	}
+
+	struct wlr_screencopy_frame_v1 *frame =
+		calloc(1, sizeof(struct wlr_screencopy_frame_v1));
+	if (frame == NULL) {
+		wl_client_post_no_memory(client);
+		return;
+	}
+	frame->manager = manager;
+	frame->output = output;
+
+	frame->resource = wl_resource_create(client,
+		&zwlr_screencopy_frame_v1_interface, version, id);
+	if (frame->resource == NULL) {
+		free(frame);
+		wl_client_post_no_memory(client);
+		return;
+	}
+	wl_resource_set_implementation(frame->resource, &frame_impl, frame,
+		frame_handle_resource_destroy);
+
+	wl_list_insert(&manager->frames, &frame->link);
+
+	wl_list_init(&frame->output_swap_buffers.link);
+
+	frame->format = WL_SHM_FORMAT_XRGB8888;
+	frame->box = buffer_box;
+	frame->stride = 4 * buffer_box.width;
+	zwlr_screencopy_frame_v1_send_buffer(frame->resource, frame->format,
+		buffer_box.width, buffer_box.height, frame->stride);
+}
+
+static void manager_handle_capture_output(struct wl_client *client,
+		struct wl_resource *manager_resource, uint32_t id,
+		int32_t overlay_cursor, struct wl_resource *output_resource) {
+	struct wlr_screencopy_manager_v1 *manager =
+		manager_from_resource(manager_resource);
+	uint32_t version = wl_resource_get_version(manager_resource);
+	struct wlr_output *output = wlr_output_from_resource(output_resource);
+
+	capture_output(client, manager, version, id, overlay_cursor, output, NULL);
+}
+
+static void manager_handle_capture_output_region(struct wl_client *client,
+		struct wl_resource *manager_resource, uint32_t id,
+		int32_t overlay_cursor, struct wl_resource *output_resource,
+		int32_t x, int32_t y, int32_t width, int32_t height) {
+	struct wlr_screencopy_manager_v1 *manager =
+		manager_from_resource(manager_resource);
+	uint32_t version = wl_resource_get_version(manager_resource);
+	struct wlr_output *output = wlr_output_from_resource(output_resource);
+
+	struct wlr_box box = {
+		.x = x,
+		.y = y,
+		.width = width,
+		.height = height,
+	};
+	capture_output(client, manager, version, id, overlay_cursor, output, &box);
+}
+
+static void manager_handle_destroy(struct wl_client *client,
+		struct wl_resource *manager_resource) {
+	wl_resource_destroy(manager_resource);
+}
+
+static const struct zwlr_screencopy_manager_v1_interface manager_impl = {
+	.capture_output = manager_handle_capture_output,
+	.capture_output_region = manager_handle_capture_output_region,
+	.destroy = manager_handle_destroy,
+};
+
+void manager_handle_resource_destroy(struct wl_resource *resource) {
+	wl_list_remove(wl_resource_get_link(resource));
+}
+
+static void manager_bind(struct wl_client *client, void *data, uint32_t version,
+		uint32_t id) {
+	struct wlr_screencopy_manager_v1 *manager = data;
+
+	struct wl_resource *resource = wl_resource_create(client,
+		&zwlr_screencopy_manager_v1_interface, version, id);
+	if (resource == NULL) {
+		wl_client_post_no_memory(client);
+		return;
+	}
+	wl_resource_set_implementation(resource, &manager_impl, manager,
+		manager_handle_resource_destroy);
+
+	wl_list_insert(&manager->resources, wl_resource_get_link(resource));
+}
+
+static void handle_display_destroy(struct wl_listener *listener, void *data) {
+	struct wlr_screencopy_manager_v1 *manager =
+		wl_container_of(listener, manager, display_destroy);
+	wlr_screencopy_manager_v1_destroy(manager);
+}
+
+struct wlr_screencopy_manager_v1 *wlr_screencopy_manager_v1_create(
+		struct wl_display *display) {
+	struct wlr_screencopy_manager_v1 *manager =
+		calloc(1, sizeof(struct wlr_screencopy_manager_v1));
+	if (manager == NULL) {
+		return NULL;
+	}
+
+	manager->global = wl_global_create(display,
+		&zwlr_screencopy_manager_v1_interface, SCREENCOPY_MANAGER_VERSION,
+		manager, manager_bind);
+	if (manager->global == NULL) {
+		free(manager);
+		return NULL;
+	}
+	wl_list_init(&manager->resources);
+	wl_list_init(&manager->frames);
+
+	manager->display_destroy.notify = handle_display_destroy;
+	wl_display_add_destroy_listener(display, &manager->display_destroy);
+
+	return manager;
+}
+
+void wlr_screencopy_manager_v1_destroy(
+		struct wlr_screencopy_manager_v1 *manager) {
+	if (manager == NULL) {
+		return;
+	}
+	wl_list_remove(&manager->display_destroy.link);
+	struct wlr_screencopy_frame_v1 *frame, *tmp_frame;
+	wl_list_for_each_safe(frame, tmp_frame, &manager->frames, link) {
+		wl_resource_destroy(frame->resource);
+	}
+	struct wl_resource *resource, *tmp_resource;
+	wl_resource_for_each_safe(resource, tmp_resource, &manager->resources) {
+		wl_resource_destroy(resource);
+	}
+	wl_global_destroy(manager->global);
+	free(manager);
+}

types/wlr_screenshooter.c

@@ -50,8 +50,8 @@ static void output_handle_frame(struct wl_listener *listener, void *_data) {
 	int32_t stride = wl_shm_buffer_get_stride(shm_buffer);
 	wl_shm_buffer_begin_access(shm_buffer);
 	void *data = wl_shm_buffer_get_data(shm_buffer);
-	bool ok = wlr_renderer_read_pixels(renderer, format, stride, width, height,
+	bool ok = wlr_renderer_read_pixels(renderer, format, NULL, stride,
-		0, 0, 0, 0, data);
+		width, height, 0, 0, 0, 0, data);
 	wl_shm_buffer_end_access(shm_buffer);
 
 	if (!ok) {