Re: [PATCH v2 2/2] Added parameter to take screenshot with screendump as

[Kshitij Suri]

On 16/03/22 6:55 pm, Markus Armbruster wrote:
> Kshitij Suri <kshitij.suri@nutanix.com> writes:
>
> > From: "kshitij.suri" <kshitij.suri@nutanix.com>
> >
> > Currently screendump only supports PPM format, which is un-compressed and not
> > standard. Added a "format" parameter to qemu monitor screendump capabilites
> > to support PNG image capture using libpng. The param was added in QAPI schema
> > of screendump present in ui.json along with png_save() function which converts
> > pixman_image to PNG. HMP command equivalent was also modified to support the
> > feature.
> >
> > Example usage:
> > { "execute": "screendump", "arguments": { "filename": "/tmp/image",
> > "format":"png" } }
> >
> > Resolves: 
> > https://urldefense.proofpoint.com/v2/url?u=https-3A__gitlab.com_qemu-2Dproject_qemu_-2D_issues_718&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=utjv19Ej9Fb0TB7_DX0o3faQ-OAm2ypPniPyqVSoj_w&m=UZZDywEeidD1LndEhKddMf_0v-jePIgMYErGImjYyvjYRJFdnv6LAHgRmZ0IpvIL&s=jc09kdvD1ULKCC9RgwWcsK6eweue3ZkyD8F9kCx5yUs&e=
> >
> > Signed-off-by: Kshitij Suri <kshitij.suri@nutanix.com>
> > ---
> > diff to v1:
> >    - Removed repeated alpha conversion operation.
> >    - Modified logic to mirror png conversion in vnc-enc-tight.c file.
> >    - Added a new CONFIG_PNG parameter for libpng support.
> >    - Changed input format to enum instead of string.
> >    - Improved error handling.
> >   hmp-commands.hx    |  11 ++---
> >   monitor/hmp-cmds.c |  19 ++++++++-
> >   qapi/ui.json       |  24 +++++++++--
> >   ui/console.c       | 102 +++++++++++++++++++++++++++++++++++++++++++--
> >   4 files changed, 144 insertions(+), 12 deletions(-)
> >
> > diff --git a/hmp-commands.hx b/hmp-commands.hx
> > index 70a9136ac2..5eda4eeb24 100644
> > --- a/hmp-commands.hx
> > +++ b/hmp-commands.hx
> > @@ -244,17 +244,18 @@ ERST
> >   
> >       {
> >           .name       = "screendump",
> > -        .args_type  = "filename:F,device:s?,head:i?",
> > -        .params     = "filename [device [head]]",
> > -        .help       = "save screen from head 'head' of display device 'device' 
> > "
> > -                      "into PPM image 'filename'",
> > +        .args_type  = "filename:F,device:s?,head:i?,format:f?",
> > +        .params     = "filename [device [head]] [format]",
> > +        .help       = "save screen from head 'head' of display device 'device'"
> > +                      "in specified format 'format' as image 'filename'."
> > +                      "Currently only 'png' and 'ppm' formats are supported.",
> >           .cmd        = hmp_screendump,
> >           .coroutine  = true,
> >       },
> >   
> >   SRST
> >   ``screendump`` *filename*
> > -  Save screen into PPM image *filename*.
> > +  Save screen as an image *filename*, with default format of PPM.
> >   ERST
> >   
> >       {
> > diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c
> > index 8c384dc1b2..9a640146eb 100644
> > --- a/monitor/hmp-cmds.c
> > +++ b/monitor/hmp-cmds.c
> > @@ -1677,9 +1677,26 @@ hmp_screendump(Monitor *mon, const QDict *qdict)
> >       const char *filename = qdict_get_str(qdict, "filename");
> >       const char *id = qdict_get_try_str(qdict, "device");
> >       int64_t head = qdict_get_try_int(qdict, "head", 0);
> > +    const char *input_format  = qdict_get_str(qdict, "format");
> >       Error *err = NULL;
> > +    ImageFormat format;
> >   
> > -    qmp_screendump(filename, id != NULL, id, id != NULL, head, &err);
> The second id != NULL looks wrong.  Shouldn't it be head != NULL?
> Not your patch's fault, of course.

As per hmp-commands.hx input is of format [device [head]] so maybe

works as a pair. Is it alright if I investigate and send in another patch

after this?

> > +    int val = qapi_enum_parse(&ImageFormat_lookup, input_format, -1, &err);
> > +    if (val < 0) {
> > +        goto end;
> > +    }
> > +
> > +    switch (val) {
> > +    case IMAGE_FORMAT_PNG:
> > +        format = IMAGE_FORMAT_PNG;
> > +        break;
> > +    default:
> > +        format = IMAGE_FORMAT_PPM;
> > +    }
> > +
> > +    qmp_screendump(filename, id != NULL, id, id != NULL, head,
> > +                   input_format != NULL, format, &err);
> > +end:
> >       hmp_handle_error(mon, err);
> >   }
> This isn't quite right.
>
> qapi_enum_parse() is awkward to use.
>
> If its second argument @input_format is null, it returns its third
> argument -1.
>
> Else, it @input_format is a valid enum string, it returns the
> enumeration value, i.e. either IMAGE_FORMAT_PPM or IMAGE_FORMAT_PNG.
>
> Else, it sets an error and returns its third argument -1.
>
> If @input_format is null, I suspect your code jumps to
> hmp_handle_error() with a null @err.  Silently does nothing.
>
> It should default to IMAGE_FORMAT_PPM instead.
>
> I think you want something like this (completely untested):
>
>      val = qapi_enum_parse(&ImageFormat_lookup, input_format,
>                            IMAGE_FORMAT_PPM, &err);
>      if (err) {
>          goto end;
>      }
>
>      qmp_screendump(filename, id != NULL, id, head != NULL, head,
>                     input_format != NULL, val, &err);
Oh okay. Will add it in the updated patch.
> >   
> > diff --git a/qapi/ui.json b/qapi/ui.json
> > index 9354f4c467..a6d994ba2c 100644
> > --- a/qapi/ui.json
> > +++ b/qapi/ui.json
> > @@ -73,12 +73,27 @@
> >   ##
> >   { 'command': 'expire_password', 'data': {'protocol': 'str', 'time': 'str'} }
> >   
> > +##
> > +# @ImageFormat:
> > +#
> > +# Supported image format types.
> > +#
> > +# @png: PNG format
> > +#
> > +# @ppm: PPM format
> > +#
> > +# Since: 7.0
> > +#
> > +##
> > +{ 'enum': 'ImageFormat',
> > +  'data': ['ppm', 'png'] }
> > +
> >   ##
> >   # @screendump:
> >   #
> > -# Write a PPM of the VGA screen to a file.
> > +# Write a screenshot of the VGA screen to a file.
> Let's improve this to
>
>     # Capture the contents of a screen and write it to a file.
Yes will send it in the updated patch.
> >   #
> > -# @filename: the path of a new PPM file to store the image
> > +# @filename: the path of a new file to store the image
> >   #
> >   # @device: ID of the display device that should be dumped. If this parameter
> >   #          is missing, the primary display will be used. (Since 2.12)
> > @@ -87,6 +102,8 @@
> >   #        parameter is missing, head #0 will be used. Also note that the head
> >   #        can only be specified in conjunction with the device ID. (Since 2.12)
> >   #
> > +# @format: image format for screendump is specified. (default: ppm) (Since 7.0)
> > +#
> >   # Returns: Nothing on success
> >   #
> >   # Since: 0.14
> > @@ -99,7 +116,8 @@
> >   #
> >   ##
> >   { 'command': 'screendump',
> > -  'data': {'filename': 'str', '*device': 'str', '*head': 'int'},
> > +  'data': {'filename': 'str', '*device': 'str', '*head': 'int',
> > +           '*format': 'ImageFormat'},
> >     'coroutine': true }
> >   
> >   ##
> [...]
>
> > @@ -327,7 +413,8 @@ static void graphic_hw_update_bh(void *con)
> >   /* Safety: coroutine-only, concurrent-coroutine safe, main thread only */
> >   void coroutine_fn
> >   qmp_screendump(const char *filename, bool has_device, const char *device,
> > -               bool has_head, int64_t head, Error **errp)
> > +               bool has_head, int64_t head, bool has_format,
> > +               ImageFormat format, Error **errp)
> Please break the line like
>
>                    bool has_head, int64_t head,
>                    bool has_format, ImageFormat format, Error **errp)
This does look better. Will update it thank you!
> >   {
> >       g_autoptr(pixman_image_t) image = NULL;
> >       QemuConsole *con;
> > @@ -383,8 +470,17 @@ qmp_screendump(const char *filename, bool has_device, 
> > const char *device,
> >        * yields and releases the BQL. It could produce corrupted dump, but
> >        * it should be otherwise safe.
> >        */
> > -    if (!ppm_save(fd, image, errp)) {
> > -        qemu_unlink(filename);
> > +
> > +    if (has_format && format == IMAGE_FORMAT_PNG) {
> > +        /* PNG format specified for screendump */
> > +        if (!png_save(fd, image, errp)) {
> > +            qemu_unlink(filename);
> > +        }
> > +    } else {
> > +        /* PPM format specified/default for screendump */
> > +        if (!ppm_save(fd, image, errp)) {
> > +            qemu_unlink(filename);
> > +        }
> >       }
> >   }

Thank you for your review!

Regards,
Kshitij Suri