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Re: [PATCH v2 8/9] vnc: add support for extended desktop resize
From: |
Daniel P . Berrangé |
Subject: |
Re: [PATCH v2 8/9] vnc: add support for extended desktop resize |
Date: |
Tue, 8 Dec 2020 18:13:28 +0000 |
User-agent: |
Mutt/1.14.6 (2020-07-11) |
On Tue, Dec 08, 2020 at 12:57:36PM +0100, Gerd Hoffmann wrote:
> The extended desktop resize encoding adds support for (a) clients
> sending resize requests to the server, and (b) multihead support.
>
> This patch implements (a). All resize requests are rejected by qemu.
> Qemu can't resize the framebuffer on its own, this is in the hands of
> the guest, so all qemu can do is forward the request to the guest.
> Should the guest actually resize the framebuffer we can notify the vnc
> client later with a separate message.
>
> This requires support in the display device. Works with virtio-gpu.
>
> https://github.com/rfbproto/rfbproto/blob/master/rfbproto.rst#extendeddesktopsize-pseudo-encoding
The spec says
"The server must send an ExtendedDesktopSize rectangle in response
to a FramebufferUpdateRequest with incremental set to zero, assuming
the client has requested the ExtendedDesktopSize pseudo-encoding
using the SetEncodings message. This requirement is needed so that
the client has a reliable way of fetching the initial screen
configuration, and to determine if the server supports the
SetDesktopSize message.
A consequence of this is that a client must not respond to an
ExtendedDesktopSize rectangle by sending a FramebufferUpdateRequest
with incremental set to zero. Doing so would make the system go into
an infinite loop."
Historically gtk-vnc always sets incremental=0 after a resize message,
so it should trigger an infinite loop. This doesn't happen with QEMU's
impl, so I think QEMU isn't correctly following the sec here. IIUC,
tt needs to force send an ExtendedDesktopSize message every time
incremental=0, not merely when a resize happens.
Having said that, I find this part of the spec rather crazy. I dont
see why clients need more than the first ExtendedDesktopSize message
in order to detect the feature, rather than after every single
incremental=0 update request.
None the less the spec says we should get an infinite loop and with
my intentional attempt to cause this, QEMU doesn't play ball.
>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
> ui/vnc.h | 2 ++
> ui/vnc.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 65 insertions(+), 1 deletion(-)
>
> diff --git a/ui/vnc.h b/ui/vnc.h
> index c8d3ad9ec496..77a310947bd6 100644
> --- a/ui/vnc.h
> +++ b/ui/vnc.h
> @@ -442,6 +442,7 @@ enum {
>
> enum VncFeatures {
> VNC_FEATURE_RESIZE,
> + VNC_FEATURE_RESIZE_EXT,
> VNC_FEATURE_HEXTILE,
> VNC_FEATURE_POINTER_TYPE_CHANGE,
> VNC_FEATURE_WMVI,
> @@ -456,6 +457,7 @@ enum VncFeatures {
> };
>
> #define VNC_FEATURE_RESIZE_MASK (1 << VNC_FEATURE_RESIZE)
> +#define VNC_FEATURE_RESIZE_EXT_MASK (1 << VNC_FEATURE_RESIZE_EXT)
> #define VNC_FEATURE_HEXTILE_MASK (1 << VNC_FEATURE_HEXTILE)
> #define VNC_FEATURE_POINTER_TYPE_CHANGE_MASK (1 <<
> VNC_FEATURE_POINTER_TYPE_CHANGE)
> #define VNC_FEATURE_WMVI_MASK (1 << VNC_FEATURE_WMVI)
> diff --git a/ui/vnc.c b/ui/vnc.c
> index bdaf384f71a4..094ba6cd14cb 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -663,10 +663,35 @@ void vnc_framebuffer_update(VncState *vs, int x, int y,
> int w, int h,
> vnc_write_s32(vs, encoding);
> }
>
> +static void vnc_desktop_resize_ext(VncState *vs, int reject_reason)
> +{
> + vnc_lock_output(vs);
> + vnc_write_u8(vs, VNC_MSG_SERVER_FRAMEBUFFER_UPDATE);
> + vnc_write_u8(vs, 0);
> + vnc_write_u16(vs, 1); /* number of rects */
> + vnc_framebuffer_update(vs,
> + reject_reason ? 1 : 0,
> + reject_reason,
> + vs->client_width, vs->client_height,
> + VNC_ENCODING_DESKTOP_RESIZE_EXT);
> + vnc_write_u8(vs, 1); /* number of screens */
> + vnc_write_u8(vs, 0); /* padding */
> + vnc_write_u8(vs, 0); /* padding */
> + vnc_write_u8(vs, 0); /* padding */
> + vnc_write_u32(vs, 0); /* screen id */
> + vnc_write_u16(vs, 0); /* screen x-pos */
> + vnc_write_u16(vs, 0); /* screen y-pos */
> + vnc_write_u16(vs, vs->client_width);
> + vnc_write_u16(vs, vs->client_height);
> + vnc_write_u32(vs, 0); /* screen flags */
> + vnc_unlock_output(vs);
> + vnc_flush(vs);
> +}
>
> static void vnc_desktop_resize(VncState *vs, bool force)
> {
> - if (vs->ioc == NULL || !vnc_has_feature(vs, VNC_FEATURE_RESIZE)) {
> + if (vs->ioc == NULL || (!vnc_has_feature(vs, VNC_FEATURE_RESIZE) &&
> + !vnc_has_feature(vs, VNC_FEATURE_RESIZE_EXT))) {
> return;
> }
> if (vs->client_width == pixman_image_get_width(vs->vd->server) &&
> @@ -681,6 +706,12 @@ static void vnc_desktop_resize(VncState *vs, bool force)
> pixman_image_get_height(vs->vd->server) >= 0);
> vs->client_width = pixman_image_get_width(vs->vd->server);
> vs->client_height = pixman_image_get_height(vs->vd->server);
> +
> + if (vnc_has_feature(vs, VNC_FEATURE_RESIZE_EXT)) {
> + vnc_desktop_resize_ext(vs, 0);
> + return;
> + }
> +
> vnc_lock_output(vs);
> vnc_write_u8(vs, VNC_MSG_SERVER_FRAMEBUFFER_UPDATE);
> vnc_write_u8(vs, 0);
> @@ -2110,6 +2141,9 @@ static void set_encodings(VncState *vs, int32_t
> *encodings, size_t n_encodings)
> case VNC_ENCODING_DESKTOPRESIZE:
> vs->features |= VNC_FEATURE_RESIZE_MASK;
> break;
> + case VNC_ENCODING_DESKTOP_RESIZE_EXT:
> + vs->features |= VNC_FEATURE_RESIZE_EXT_MASK;
> + break;
> case VNC_ENCODING_POINTER_TYPE_CHANGE:
> vs->features |= VNC_FEATURE_POINTER_TYPE_CHANGE_MASK;
> break;
> @@ -2431,6 +2465,34 @@ static int protocol_client_msg(VncState *vs, uint8_t
> *data, size_t len)
> break;
> }
> break;
> + case VNC_MSG_CLIENT_SET_DESKTOP_SIZE:
> + {
> + size_t size;
> + uint8_t screens;
> +
> + if (len < 8) {
> + return 8;
> + }
> +
> + screens = read_u8(data, 6);
> + size = 8 + screens * 16;
> + if (len < size) {
> + return size;
> + }
> +
> + if (dpy_ui_info_supported(vs->vd->dcl.con)) {
> + QemuUIInfo info;
> + memset(&info, 0, sizeof(info));
> + info.width = read_u16(data, 2);
> + info.height = read_u16(data, 4);
> + dpy_set_ui_info(vs->vd->dcl.con, &info);
> + vnc_desktop_resize_ext(vs, 4 /* Request forwarded */);
> + } else {
> + vnc_desktop_resize_ext(vs, 3 /* Invalid screen layout */);
> + }
> +
> + break;
> + }
> default:
> VNC_DEBUG("Msg: %d\n", data[0]);
> vnc_client_error(vs);
> --
> 2.27.0
>
>
Regards,
Daniel
--
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- Re: [PATCH v2 2/9] console: allow con==NULL in dpy_{get, set}_ui_info and dpy_ui_info_supported, (continued)
- [PATCH v2 1/9] console: drop qemu_console_get_ui_info, Gerd Hoffmann, 2020/12/08
- [PATCH v2 4/9] vnc: drop unused copyrect feature, Gerd Hoffmann, 2020/12/08
- [PATCH v2 9/9] vnc: move check into vnc_cursor_define, Gerd Hoffmann, 2020/12/08
- [PATCH v2 7/9] vnc: force initial resize message, Gerd Hoffmann, 2020/12/08
- [PATCH v2 8/9] vnc: add support for extended desktop resize, Gerd Hoffmann, 2020/12/08
- Re: [PATCH v2 8/9] vnc: add support for extended desktop resize,
Daniel P . Berrangé <=
[PATCH v2 3/9] vnc: use enum for features, Gerd Hoffmann, 2020/12/08
[PATCH v2 6/9] vnc: add alpha cursor support, Gerd Hoffmann, 2020/12/08
[PATCH v2 5/9] vnc: add pseudo encodings, Gerd Hoffmann, 2020/12/08
Re: [PATCH v2 0/9] vnc: support some new extensions., Daniel P . Berrangé, 2020/12/08