backend/x11: add support for shm buffers

README.md

@@ -62,6 +62,7 @@ If you choose to enable X11 support:
 * xcb-icccm
 * xcb-image
 * xcb-render
+* xcb-shm
 * xcb-errors (optional, for improved error reporting)
 
 Run these commands:

backend/x11/backend.c

@@ -17,6 +17,7 @@
 #include <xcb/dri3.h>
 #include <xcb/present.h>
 #include <xcb/render.h>
+#include <xcb/shm.h>
 #include <xcb/xcb_renderutil.h>
 #include <xcb/xfixes.h>
 #include <xcb/xinput.h>
@@ -32,6 +33,7 @@
 #include "backend/x11.h"
 #include "render/drm_format_set.h"
 #include "render/gbm_allocator.h"
+#include "render/shm_allocator.h"
 #include "render/wlr_renderer.h"
 #include "util/signal.h"
 
@@ -198,6 +200,7 @@ static void backend_destroy(struct wlr_backend *backend) {
 	wlr_renderer_destroy(x11->renderer);
 	wlr_allocator_destroy(x11->allocator);
 	wlr_drm_format_set_finish(&x11->dri3_formats);
+	wlr_drm_format_set_finish(&x11->shm_formats);
 	free(x11->drm_format);
 
 #if HAS_XCB_ERRORS
@@ -341,20 +344,26 @@ static bool query_dri3_modifiers(struct wlr_x11_backend *x11,
 	return true;
 }
 
-static bool query_dri3_formats(struct wlr_x11_backend *x11) {
+static bool query_formats(struct wlr_x11_backend *x11) {
 	xcb_depth_iterator_t iter = xcb_screen_allowed_depths_iterator(x11->screen);
 	while (iter.rem > 0) {
 		uint8_t depth = iter.data->depth;
 
 		const struct wlr_x11_format *format = x11_format_from_depth(depth);
 		if (format != NULL) {
+			if (x11->have_shm) {
+				wlr_drm_format_set_add(&x11->shm_formats, format->drm,
+					DRM_FORMAT_MOD_INVALID);
+			}
+
+			if (x11->have_dri3) {
 				wlr_drm_format_set_add(&x11->dri3_formats, format->drm,
 					DRM_FORMAT_MOD_INVALID);
-
 				if (!query_dri3_modifiers(x11, format)) {
 					return false;
 				}
 			}
+		}
 
 		xcb_depth_next(&iter);
 	}
@@ -438,24 +447,52 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	// 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;
-	}
-
+	if (ext && ext->present) {
 		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) {
-		wlr_log(WLR_ERROR, "X11 does not support required DRI3 version "
-			"(has %"PRIu32".%"PRIu32", want 1.0)",
-			dri3_reply->major_version, dri3_reply->minor_version);
-		goto error_display;
-	}
+		if (dri3_reply && dri3_reply->major_version >= 1) {
+			x11->have_dri3 = true;
 			x11->dri3_major_version = dri3_reply->major_version;
 			x11->dri3_minor_version = dri3_reply->minor_version;
+		} else {
+			wlr_log(WLR_INFO, "X11 does not support required DRI3 version "
+				"(has %"PRIu32".%"PRIu32", want 1.0)",
+				dri3_reply->major_version, dri3_reply->minor_version);
+		}
 		free(dri3_reply);
+	} else {
+		wlr_log(WLR_INFO, "X11 does not support DRI3 extension");
+	}
+
+	// SHM extension
+
+	ext = xcb_get_extension_data(x11->xcb, &xcb_shm_id);
+	if (ext && ext->present) {
+		xcb_shm_query_version_cookie_t shm_cookie =
+			xcb_shm_query_version(x11->xcb);
+		xcb_shm_query_version_reply_t *shm_reply =
+			xcb_shm_query_version_reply(x11->xcb, shm_cookie, NULL);
+		if (shm_reply) {
+			if (shm_reply->major_version >= 1 || shm_reply->minor_version >= 2) {
+				if (shm_reply->shared_pixmaps) {
+					x11->have_shm = true;
+				} else {
+					wlr_log(WLR_INFO, "X11 does not support shared pixmaps");
+				}
+			} else {
+				wlr_log(WLR_INFO, "X11 does not support required SHM version "
+					"(has %"PRIu32".%"PRIu32", want 1.2)",
+					shm_reply->major_version, shm_reply->minor_version);
+			}
+		} else {
+			wlr_log(WLR_INFO, "X11 does not support required SHM version");
+		}
+		free(shm_reply);
+	} else {
+		wlr_log(WLR_INFO, "X11 does not support SHM extension");
+	}
 
 	// Present extension
 
@@ -560,6 +597,13 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	xcb_create_colormap(x11->xcb, XCB_COLORMAP_ALLOC_NONE, x11->colormap,
 		x11->screen->root, x11->visualid);
 
+	if (!query_formats(x11)) {
+		wlr_log(WLR_ERROR, "Failed to query supported DRM formats");
+		return false;
+	}
+
+	const struct wlr_drm_format_set *pixmap_formats;
+	if (x11->have_dri3) {
 		// DRI3 may return a render node (Xwayland) or an authenticated primary
 		// node (plain Glamor).
 		x11->drm_fd = query_dri3_drm_fd(x11);
@@ -585,6 +629,21 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 			goto error_event;
 		}
 		x11->allocator = &gbm_alloc->base;
+		pixmap_formats = &x11->dri3_formats;
+	} else if (x11->have_shm) {
+		x11->drm_fd = -1;
+		struct wlr_shm_allocator *shm_alloc = wlr_shm_allocator_create();
+		if (shm_alloc == NULL) {
+			wlr_log(WLR_ERROR, "Failed to create shared memory allocator");
+			goto error_event;
+		}
+		x11->allocator = &shm_alloc->base;
+		pixmap_formats = &x11->shm_formats;
+	} else {
+		wlr_log(WLR_ERROR,
+			"Failed to create allocator (DRI3 and SHM unavailable)");
+		goto error_event;
+	}
 
 	x11->renderer = wlr_renderer_autocreate(&x11->backend);
 	if (x11->renderer == NULL) {
@@ -595,7 +654,7 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 	const struct wlr_drm_format_set *render_formats =
 		wlr_renderer_get_render_formats(x11->renderer);
 	if (render_formats == NULL) {
-		wlr_log(WLR_ERROR, "Failed to get available DMA-BUF formats from renderer");
+		wlr_log(WLR_ERROR, "Failed to get available DRM formats from renderer");
 		return false;
 	}
 	const struct wlr_drm_format *render_format =
@@ -606,22 +665,17 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 		return false;
 	}
 
-	if (!query_dri3_formats(x11)) {
-		wlr_log(WLR_ERROR, "Failed to query supported DRI3 formats");
-		return false;
-	}
-
-	const struct wlr_drm_format *dri3_format =
-		wlr_drm_format_set_get(&x11->dri3_formats, x11->x11_format->drm);
-	if (dri3_format == NULL) {
+	const struct wlr_drm_format *pixmap_format = wlr_drm_format_set_get(
+		pixmap_formats, x11->x11_format->drm);
+	if (pixmap_format == NULL) {
 		wlr_log(WLR_ERROR, "X11 server doesn't support DRM format 0x%"PRIX32,
 			x11->x11_format->drm);
 		return false;
 	}
 
-	x11->drm_format = wlr_drm_format_intersect(dri3_format, render_format);
+	x11->drm_format = wlr_drm_format_intersect(pixmap_format, render_format);
 	if (x11->drm_format == NULL) {
-		wlr_log(WLR_ERROR, "Failed to intersect DRI3 and render modifiers for "
+		wlr_log(WLR_ERROR, "Failed to intersect X11 and render modifiers for "
 			"format 0x%"PRIX32, x11->x11_format->drm);
 		return false;
 	}

backend/x11/meson.build

@@ -5,6 +5,7 @@ x11_required = [
 	'xcb-present',
 	'xcb-render',
 	'xcb-renderutil',
+	'xcb-shm',
 	'xcb-xfixes',
 	'xcb-xinput',
 ]

backend/x11/output.c

@@ -3,11 +3,13 @@
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
+#include <fcntl.h>
 
 #include <drm_fourcc.h>
 #include <xcb/dri3.h>
 #include <xcb/present.h>
 #include <xcb/render.h>
+#include <xcb/shm.h>
 #include <xcb/xcb.h>
 #include <xcb/xinput.h>
 
@@ -143,53 +145,99 @@ static void buffer_handle_buffer_destroy(struct wl_listener *listener,
 	destroy_x11_buffer(buffer);
 }
 
-static struct wlr_x11_buffer *create_x11_buffer(struct wlr_x11_output *output,
-		struct wlr_buffer *wlr_buffer) {
+static xcb_pixmap_t import_dmabuf(struct wlr_x11_output *output,
+		struct wlr_dmabuf_attributes *dmabuf) {
 	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) {
+	if (dmabuf->format != x11->x11_format->drm) {
 		// The pixmap's depth must match the window's depth, otherwise Present
 		// will throw a Match error
-		return NULL;
+		return XCB_PIXMAP_NONE;
 	}
 
-	if (attrs.flags != 0) {
-		return NULL;
+	if (dmabuf->flags != 0) {
+		return XCB_PIXMAP_NONE;
 	}
 
 	// 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;
+	if (!wlr_dmabuf_attributes_copy(&dup_attrs, dmabuf)) {
+		return XCB_PIXMAP_NONE;
 	}
 
 	const struct wlr_x11_format *x11_fmt = x11->x11_format;
 	xcb_pixmap_t pixmap = xcb_generate_id(x11->xcb);
 
 	if (x11->dri3_major_version > 1 || x11->dri3_minor_version >= 2) {
-		if (attrs.n_planes > 4) {
+		if (dmabuf->n_planes > 4) {
 			wlr_dmabuf_attributes_finish(&dup_attrs);
-			return NULL;
+			return XCB_PIXMAP_NONE;
 		}
 		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);
+			dmabuf->n_planes, dmabuf->width, dmabuf->height, dmabuf->stride[0],
+			dmabuf->offset[0], dmabuf->stride[1], dmabuf->offset[1],
+			dmabuf->stride[2], dmabuf->offset[2], dmabuf->stride[3],
+			dmabuf->offset[3], x11_fmt->depth, x11_fmt->bpp, dmabuf->modifier,
+			dup_attrs.fd);
 	} else {
 		// PixmapFromBuffers requires DRI3 1.2
-		if (attrs.n_planes != 1 || attrs.modifier != DRM_FORMAT_MOD_INVALID) {
+		if (dmabuf->n_planes != 1
+				|| dmabuf->modifier != DRM_FORMAT_MOD_INVALID) {
 			wlr_dmabuf_attributes_finish(&dup_attrs);
-			return NULL;
+			return XCB_PIXMAP_NONE;
 		}
 		xcb_dri3_pixmap_from_buffer(x11->xcb, pixmap, output->win,
-			attrs.height * attrs.stride[0], attrs.width, attrs.height,
-			attrs.stride[0], x11_fmt->depth, x11_fmt->bpp, dup_attrs.fd[0]);
+			dmabuf->height * dmabuf->stride[0], dmabuf->width, dmabuf->height,
+			dmabuf->stride[0], x11_fmt->depth, x11_fmt->bpp, dup_attrs.fd[0]);
+	}
+
+	return pixmap;
+}
+
+static xcb_pixmap_t import_shm(struct wlr_x11_output *output,
+		struct wlr_shm_attributes *shm) {
+	struct wlr_x11_backend *x11 = output->x11;
+
+	if (shm->format != x11->x11_format->drm) {
+		// The pixmap's depth must match the window's depth, otherwise Present
+		// will throw a Match error
+		return XCB_PIXMAP_NONE;
+	}
+
+	// xcb closes the FD after sending it
+	int fd = fcntl(shm->fd, F_DUPFD_CLOEXEC, 0);
+	if (fd < 0) {
+		wlr_log_errno(WLR_ERROR, "fcntl(F_DUPFD_CLOEXEC) failed");
+		return XCB_PIXMAP_NONE;
+	}
+
+	xcb_shm_seg_t seg = xcb_generate_id(x11->xcb);
+	xcb_shm_attach_fd(x11->xcb, seg, fd, false);
+
+	xcb_pixmap_t pixmap = xcb_generate_id(x11->xcb);
+	xcb_shm_create_pixmap(x11->xcb, pixmap, output->win, shm->width,
+		shm->height, x11->x11_format->depth, seg, shm->offset);
+
+	xcb_shm_detach(x11->xcb, seg);
+
+	return pixmap;
+}
+
+static struct wlr_x11_buffer *create_x11_buffer(struct wlr_x11_output *output,
+		struct wlr_buffer *wlr_buffer) {
+	struct wlr_x11_backend *x11 = output->x11;
+	xcb_pixmap_t pixmap = XCB_PIXMAP_NONE;
+
+	struct wlr_dmabuf_attributes dmabuf_attrs;
+	struct wlr_shm_attributes shm_attrs;
+	if (wlr_buffer_get_dmabuf(wlr_buffer, &dmabuf_attrs)) {
+		pixmap = import_dmabuf(output, &dmabuf_attrs);
+	} else if (wlr_buffer_get_shm(wlr_buffer, &shm_attrs)) {
+		pixmap = import_shm(output, &shm_attrs);
+	}
+
+	if (pixmap == XCB_PIXMAP_NONE) {
+		return NULL;
 	}
 
 	struct wlr_x11_buffer *buffer = calloc(1, sizeof(struct wlr_x11_buffer));

include/backend/x11.h

@@ -75,6 +75,9 @@ struct wlr_x11_backend {
 	xcb_colormap_t colormap;
 	xcb_cursor_t transparent_cursor;
 	xcb_render_pictformat_t argb32;
+
+	bool have_shm;
+	bool have_dri3;
 	uint32_t dri3_major_version, dri3_minor_version;
 
 	size_t requested_outputs;
@@ -87,6 +90,7 @@ struct wlr_x11_backend {
 	int drm_fd;
 	struct wlr_renderer *renderer;
 	struct wlr_drm_format_set dri3_formats;
+	struct wlr_drm_format_set shm_formats;
 	const struct wlr_x11_format *x11_format;
 	struct wlr_drm_format *drm_format;
 	struct wlr_allocator *allocator;