backend/x11: add support for DRI3 1.0

Add fallbacks when DRI3 1.2 isn't supported.

Closes: https://github.com/swaywm/wlroots/issues/2586

backend/x11/backend.c

@@ -297,6 +297,10 @@ static int query_dri3_drm_fd(struct wlr_x11_backend *x11) {
 
 static bool query_dri3_modifiers(struct wlr_x11_backend *x11,
 		const struct wlr_x11_format *format) {
+	if (x11->dri3_major_version == 1 && x11->dri3_minor_version < 2) {
+		return true; // GetSupportedModifiers requires DRI3 1.2
+	}
+
 	// Query the root window's supported modifiers, because we only care about
 	// screen_modifiers for now
 	xcb_dri3_get_supported_modifiers_cookie_t modifiers_cookie =
@@ -415,13 +419,14 @@ struct wlr_backend *wlr_x11_backend_create(struct wl_display *display,
 		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) {
+	if (!dri3_reply || dri3_reply->major_version < 1) {
 		wlr_log(WLR_ERROR, "X11 does not support required DRI3 version "
-			"(has %"PRIu32".%"PRIu32", want 1.2)",
+			"(has %"PRIu32".%"PRIu32", want 1.0)",
 			dri3_reply->major_version, dri3_reply->minor_version);
 		goto error_display;
 	}
+	x11->dri3_major_version = dri3_reply->major_version;
+	x11->dri3_minor_version = dri3_reply->minor_version;
 	free(dri3_reply);
 
 	// Present extension

backend/x11/output.c

@@ -164,11 +164,23 @@ static struct wlr_x11_buffer *create_x11_buffer(struct wlr_x11_output *output,
 
 	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) {
 		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);
+	} else {
+		// PixmapFromBuffers requires DRI3 1.2
+		if (attrs.n_planes != 1 || attrs.modifier != DRM_FORMAT_MOD_INVALID) {
+			wlr_dmabuf_attributes_finish(&dup_attrs);
+			return NULL;
+		}
+		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]);
+	}
 
 	struct wlr_x11_buffer *buffer = calloc(1, sizeof(struct wlr_x11_buffer));
 	if (!buffer) {

include/backend/x11.h

@@ -68,6 +68,7 @@ struct wlr_x11_backend {
 	xcb_depth_t *depth;
 	xcb_visualid_t visualid;
 	xcb_colormap_t colormap;
+	uint32_t dri3_major_version, dri3_minor_version;
 
 	size_t requested_outputs;
 	size_t last_output_num;