On Mon, Sep 22, 2014 at 12:27 PM, Jason Ekstrand <ja...@jlekstrand.net>
wrote:
>
>
> On Mon, Sep 22, 2014 at 9:30 AM, Nils Chr. Brause <nilschrbra...@gmail.com
> > wrote:
>
>> On Mon, Sep 22, 2014 at 11:21 AM, Pekka Paalanen <ppaala...@gmail.com>
>> wrote:
>> >
>> > On Wed, 3 Sep 2014 19:44:04 +0200
>> > "Nils Chr. Brause" <nilschrbra...@gmail.com> wrote:
>> >
>> > > This replaces "[PATCH wayland] Add "enum" attribute to "arg"
>> elements".
>> > > Previous concers have be incorporated and it is meant for 1.7.
>> > >
>> > > From 733fb18b163de93276f092a4be100c7e0c0c723f Mon Sep 17 00:00:00 2001
>> > > From: "Nils Chr. Brause" <nilschrbra...@googlemail.com>
>> > > Date: Wed, 3 Sep 2014 19:18:28 +0200
>> > > Subject: [PATCH] wayland.xml: add "enum", "bitfield" and "is_bitfield"
>> > > attributes
>> > >
>> > > There are programming languages, that are more strongly typed than
>> > > C. People creating Wayland bindings for these languages will want to
>> > > make use of this strong type system by declaring each enumeration a
>> > > distinct type and differentiating between enumerations and bit fields.
>> > >
>> > > For code generation to work with these languages, there needs to be
>> > > information about which enumerations are actually bit fields and which
>> > > enumerations or bit fields may be passed/received in which
>> > > request/event arguments.
>> > >
>> > > This is accomplished by adding an "is_bitfield" attribute to "enum"
>> > > elements, which are actually bitfields and by adding "enum" or
>> > > "bitfield" attributes to the "arg" elements of requests and
>> > > events. The values of the "enum" and "bitfield" attributes have the
>> > > format "$interface.$name", where "$interface" is the name of the
>> > > interface, where the enumeration or bit field is declared and "$name"
>> > > is the name of the enumeration or bit field, which is used in this
>> > > argument.
>> > >
>> > > The scanner has been modified to enforce those rules.
>> > > ---
>> > > protocol/wayland.dtd | 3 ++
>> > > protocol/wayland.xml | 42 ++++++++++-----------
>> > > src/scanner.c | 101
>> ++++++++++++++++++++++++++++++++++++++++++++++++++-
>> > > 3 files changed, 124 insertions(+), 22 deletions(-)
>> > >
>> > > diff --git a/protocol/wayland.dtd b/protocol/wayland.dtd
>> > > index b8b1573..4506201 100644
>> > > --- a/protocol/wayland.dtd
>> > > +++ b/protocol/wayland.dtd
>> > > @@ -14,6 +14,7 @@
>> > > <!ELEMENT enum (description?,entry*)>
>> > > <!ATTLIST enum name CDATA #REQUIRED>
>> > > <!ATTLIST enum since CDATA #IMPLIED>
>> > > + <!ATTLIST enum is_bitfield CDATA #IMPLIED>
>> > > <!ELEMENT entry (description?)>
>> > > <!ATTLIST entry name CDATA #REQUIRED>
>> > > <!ATTLIST entry value CDATA #REQUIRED>
>> > > @@ -25,5 +26,7 @@
>> > > <!ATTLIST arg summary CDATA #IMPLIED>
>> > > <!ATTLIST arg interface CDATA #IMPLIED>
>> > > <!ATTLIST arg allow-null CDATA #IMPLIED>
>> > > + <!ATTLIST arg enum CDATA #IMPLIED>
>> > > + <!ATTLIST arg bitfield CDATA #IMPLIED>
>> > > <!ELEMENT description (#PCDATA)>
>> > > <!ATTLIST description summary CDATA #REQUIRED>
>> > > diff --git a/protocol/wayland.xml b/protocol/wayland.xml
>> > > index bb457bc..878c347 100644
>> > > --- a/protocol/wayland.xml
>> > > +++ b/protocol/wayland.xml
>> > > @@ -229,7 +229,7 @@
>> > > <arg name="width" type="int"/>
>> > > <arg name="height" type="int"/>
>> > > <arg name="stride" type="int"/>
>> > > - <arg name="format" type="uint"/>
>> > > + <arg name="format" type="uint" enum="wl_shm.format"/>
>> > > </request>
>> > >
>> > > <request name="destroy" type="destructor">
>> > > @@ -367,7 +367,7 @@
>> > > can be used for buffers. Known formats include
>> > > argb8888 and xrgb8888.
>> > > </description>
>> > > - <arg name="format" type="uint"/>
>> > > + <arg name="format" type="uint" enum="wl_shm.format"/>
>> > > </event>
>> > > </interface>
>> > >
>> > > @@ -723,7 +723,7 @@
>> > > <arg name="serial" type="uint" summary="serial of the implicit
>> grab on the pointer"/>
>> > > </request>
>> > >
>> > > - <enum name="resize">
>> > > + <enum name="resize" is_bitfield="true">
>> > > <description summary="edge values for resizing">
>> > > These values are used to indicate which edge of a surface
>> > > is being dragged in a resize operation. The server may
>> > > @@ -751,7 +751,7 @@
>> > > </description>
>> > > <arg name="seat" type="object" interface="wl_seat"
>> summary="the wl_seat whose pointer is used"/>
>> > > <arg name="serial" type="uint" summary="serial of the implicit
>> grab on the pointer"/>
>> > > - <arg name="edges" type="uint" summary="which edge or corner is
>> being dragged"/>
>> > > + <arg name="edges" type="uint" summary="which edge or corner is
>> being dragged" bitfield="wl_shell_surface.resize"/>
>> > > </request>
>> > >
>> > > <request name="set_toplevel">
>> > > @@ -762,7 +762,7 @@
>> > > </description>
>> > > </request>
>> > >
>> > > - <enum name="transient">
>> > > + <enum name="transient" is_bitfield="true">
>> > > <description summary="details of transient behaviour">
>> > > These flags specify details of the expected behaviour
>> > > of transient surfaces. Used in the set_transient request.
>> > > @@ -784,7 +784,7 @@
>> > > <arg name="parent" type="object" interface="wl_surface"/>
>> > > <arg name="x" type="int"/>
>> > > <arg name="y" type="int"/>
>> > > - <arg name="flags" type="uint"/>
>> > > + <arg name="flags" type="uint"
>> bitfield="wl_shell_surface.transient"/>
>> > > </request>
>> > >
>> > > <enum name="fullscreen_method">
>> > > @@ -835,7 +835,7 @@
>> > > with the dimensions for the output on which the surface will
>> > > be made fullscreen.
>> > > </description>
>> > > - <arg name="method" type="uint"/>
>> > > + <arg name="method" type="uint"
>> enum="wl_shell_surface.fullscreen_method"/>
>> > > <arg name="framerate" type="uint"/>
>> > > <arg name="output" type="object" interface="wl_output"
>> allow-null="true"/>
>> > > </request>
>> > > @@ -868,7 +868,7 @@
>> > > <arg name="parent" type="object" interface="wl_surface"/>
>> > > <arg name="x" type="int"/>
>> > > <arg name="y" type="int"/>
>> > > - <arg name="flags" type="uint"/>
>> > > + <arg name="flags" type="uint"
>> bitfield="wl_shell_surface.transient"/>
>> > > </request>
>> > >
>> > > <request name="set_maximized">
>> > > @@ -949,7 +949,7 @@
>> > > in surface local coordinates.
>> > > </description>
>> > >
>> > > - <arg name="edges" type="uint"/>
>> > > + <arg name="edges" type="uint"
>> bitfield="wl_shell_surface.resize"/>
>> > > <arg name="width" type="int"/>
>> > > <arg name="height" type="int"/>
>> > > </event>
>> > > @@ -1242,7 +1242,7 @@
>> > > wl_output.transform enum the invalid_transform protocol error
>> > > is raised.
>> > > </description>
>> > > - <arg name="transform" type="int"/>
>> > > + <arg name="transform" type="int"
>> bitfield="wl_output.transform"/>
>> > > </request>
>> > >
>> > > <!-- Version 3 additions -->
>> > > @@ -1285,7 +1285,7 @@
>> > > maintains a keyboard focus and a pointer focus.
>> > > </description>
>> > >
>> > > - <enum name="capability">
>> > > + <enum name="capability" is_bitfield="true">
>> > > <description summary="seat capability bitmask">
>> > > This is a bitmask of capabilities this seat has; if a member
>> is
>> > > set, then it is present on the seat.
>> > > @@ -1301,7 +1301,7 @@
>> > > keyboard or touch capabilities. The argument is a capability
>> > > enum containing the complete set of capabilities this seat has.
>> > > </description>
>> > > - <arg name="capabilities" type="uint"/>
>> > > + <arg name="capabilities" type="uint"
>> bitfield="wl_seat.capability"/>
>> > > </event>
>> > >
>> > > <request name="get_pointer">
>> > > @@ -1461,7 +1461,7 @@
>> > > <arg name="serial" type="uint"/>
>> > > <arg name="time" type="uint" summary="timestamp with
>> millisecond granularity"/>
>> > > <arg name="button" type="uint"/>
>> > > - <arg name="state" type="uint"/>
>> > > + <arg name="state" type="uint" enum="wl_pointer.button_state"/>
>> > > </event>
>> > >
>> > > <enum name="axis">
>> > > @@ -1493,7 +1493,7 @@
>> > > </description>
>> > >
>> > > <arg name="time" type="uint" summary="timestamp with
>> millisecond granularity"/>
>> > > - <arg name="axis" type="uint"/>
>> > > + <arg name="axis" type="uint" enum="wl_pointer.axis"/>
>> > > <arg name="value" type="fixed"/>
>> > > </event>
>> > >
>> > > @@ -1527,7 +1527,7 @@
>> > > This event provides a file descriptor to the client which can be
>> > > memory-mapped to provide a keyboard mapping description.
>> > > </description>
>> > > - <arg name="format" type="uint"/>
>> > > + <arg name="format" type="uint"
>> enum="wl_keyboard.keymap_format"/>
>> > > <arg name="fd" type="fd"/>
>> > > <arg name="size" type="uint"/>
>> > > </event>
>> > > @@ -1572,7 +1572,7 @@
>> > > <arg name="serial" type="uint"/>
>> > > <arg name="time" type="uint" summary="timestamp with
>> millisecond granularity"/>
>> > > <arg name="key" type="uint"/>
>> > > - <arg name="state" type="uint"/>
>> > > + <arg name="state" type="uint" enum="wl_keyboard.key_state"/>
>> > > </event>
>> > >
>> > > <event name="modifiers">
>> > > @@ -1714,7 +1714,7 @@
>> > > <entry name="vertical_bgr" value="5"/>
>> > > </enum>
>> > >
>> > > - <enum name="transform">
>> > > + <enum name="transform" is_bitfield="true">
>> > > <description summary="transform from framebuffer to output">
>> > > This describes the transform that a compositor will apply to a
>> > > surface to compensate for the rotation or mirroring of an
>> > > @@ -1753,17 +1753,17 @@
>> > > summary="width in millimeters of the output"/>
>> > > <arg name="physical_height" type="int"
>> > > summary="height in millimeters of the output"/>
>> > > - <arg name="subpixel" type="int"
>> > > + <arg name="subpixel" type="int" enum="wl_output.subpixel"
>> > > summary="subpixel orientation of the output"/>
>> > > <arg name="make" type="string"
>> > > summary="textual description of the manufacturer"/>
>> > > <arg name="model" type="string"
>> > > summary="textual description of the model"/>
>> > > - <arg name="transform" type="int"
>> > > + <arg name="transform" type="int" bitfield="wl_output.transform"
>> > > summary="transform that maps framebuffer to output"/>
>> > > </event>
>> > >
>> > > - <enum name="mode">
>> > > + <enum name="mode" is_bitfield="true">
>> > > <description summary="mode information">
>> > > These flags describe properties of an output mode.
>> > > They are used in the flags bitfield of the mode event.
>> > > @@ -1790,7 +1790,7 @@
>> > > the output may be scaled, as described in wl_output.scale,
>> > > or transformed , as described in wl_output.transform.
>> > > </description>
>> > > - <arg name="flags" type="uint" summary="bitfield of mode
>> flags"/>
>> > > + <arg name="flags" type="uint" summary="bitfield of mode flags"
>> bitfield="wl_output.mode"/>
>> > > <arg name="width" type="int" summary="width of the mode in
>> hardware units"/>
>> > > <arg name="height" type="int" summary="height of the mode in
>> hardware units"/>
>> > > <arg name="refresh" type="int" summary="vertical refresh rate
>> in mHz"/>
>> > > diff --git a/src/scanner.c b/src/scanner.c
>> > > index 72fd3e8..b240790 100644
>> > > --- a/src/scanner.c
>> > > +++ b/src/scanner.c
>> > > @@ -112,6 +112,8 @@ struct arg {
>> > > enum arg_type type;
>> > > int nullable;
>> > > char *interface_name;
>> > > + char *enum_name;
>> > > + char *bitfield_name;
>> > > struct wl_list link;
>> > > char *summary;
>> > > };
>> > > @@ -119,6 +121,7 @@ struct arg {
>> > > struct enumeration {
>> > > char *name;
>> > > char *uppercase_name;
>> > > + int is_bitfield;
>> > > struct wl_list entry_list;
>> > > struct wl_list link;
>> > > struct description *description;
>> > > @@ -314,7 +317,7 @@ start_element(void *data, const char
>> *element_name, const char **atts)
>> > > struct entry *entry;
>> > > struct description *description;
>> > > const char *name, *type, *interface_name, *value, *summary,
>> *since;
>> > > - const char *allow_null;
>> > > + const char *allow_null, *enum_name, *bitfield_name,
>> *is_bitfield;
>> > > char *end;
>> > > int i, version;
>> > >
>> > > @@ -323,11 +326,14 @@ start_element(void *data, const char
>> *element_name, const char **atts)
>> > > type = NULL;
>> > > version = 0;
>> > > interface_name = NULL;
>> > > + enum_name = NULL;
>> > > + bitfield_name = NULL;
>> > > value = NULL;
>> > > summary = NULL;
>> > > description = NULL;
>> > > since = NULL;
>> > > allow_null = NULL;
>> > > + is_bitfield = NULL;
>> > > for (i = 0; atts[i]; i += 2) {
>> > > if (strcmp(atts[i], "name") == 0)
>> > > name = atts[i + 1];
>> > > @@ -339,12 +345,18 @@ start_element(void *data, const char
>> *element_name, const char **atts)
>> > > value = atts[i + 1];
>> > > if (strcmp(atts[i], "interface") == 0)
>> > > interface_name = atts[i + 1];
>> > > + if (strcmp(atts[i], "enum") == 0)
>> > > + enum_name = atts[i + 1];
>> > > + if (strcmp(atts[i], "bitfield") == 0)
>> > > + bitfield_name = atts[i + 1];
>> > > if (strcmp(atts[i], "summary") == 0)
>> > > summary = atts[i + 1];
>> > > if (strcmp(atts[i], "since") == 0)
>> > > since = atts[i + 1];
>> > > if (strcmp(atts[i], "allow-null") == 0)
>> > > allow_null = atts[i + 1];
>> > > + if (strcmp(atts[i], "is_bitfield") == 0)
>> > > + is_bitfield = atts[i + 1];
>> > > }
>> > >
>> > > ctx->character_data_length = 0;
>> > > @@ -461,9 +473,31 @@ start_element(void *data, const char
>> *element_name, const char **atts)
>> > > else
>> > > arg->interface_name = NULL;
>> > > break;
>> > > + case UNSIGNED:
>> > > + case INT:
>> > > + if (enum_name) {
>> > > + arg->enum_name = xstrdup(enum_name);
>> > > + arg->bitfield_name = NULL;
>> > > + }
>> > > + else if (bitfield_name) {
>> > > + arg->bitfield_name =
>> xstrdup(bitfield_name);
>> > > + arg->enum_name = NULL;
>> > > + }
>> > > + else {
>> > > + arg->bitfield_name = NULL;
>> > > + arg->enum_name = NULL;
>> > > + }
>> > > +
>> > > + if (enum_name && bitfield_name)
>> > > + fail(&ctx->loc, "bitfield and enum
>> attribute cannot both be set");
>> > > + break;
>> > > default:
>> > > if (interface_name != NULL)
>> > > fail(&ctx->loc, "interface attribute
>> not allowed for type %s", type);
>> > > + if (enum_name != NULL)
>> > > + fail(&ctx->loc, "enum attribute not
>> allowed for type %s", type);
>> > > + if (bitfield_name != NULL)
>> > > + fail(&ctx->loc, "bitfield attribute not
>> allowed for type %s", type);
>> >
>> > This looks broken.
>> >
>> > What if
>> > - int or unsigned has "interface" attribute? It should be an error.
>> > - new_id or object has "enum" or "bitfield" attribute? Should be an
>> > error.
>> >
>> > You probably want your own switch-clause.
>>
>> Wouldn't a separate switch-clause require a new type? I thought,
>> this is not what we want, since this would break other parsers.
>>
>> I would probably just check for additional unwanted combinations.
>>
>> >
>> > > break;
>> > > }
>> > >
>> > > @@ -497,6 +531,13 @@ start_element(void *data, const char
>> *element_name, const char **atts)
>> > > &enumeration->link);
>> > >
>> > > ctx->enumeration = enumeration;
>> > > +
>> > > + if (is_bitfield == NULL || strcmp(is_bitfield, "false")
>> == 0)
>> > > + enumeration->is_bitfield = 0;
>> > > + else if (strcmp(is_bitfield, "true") == 0)
>> > > + enumeration->is_bitfield = 1;
>> > > + else
>> > > + fail(&ctx->loc, "invalid value for is_bitfield
>> attribute (%s)", is_bitfield);
>> > > } else if (strcmp(element_name, "entry") == 0) {
>> > > if (name == NULL)
>> > > fail(&ctx->loc, "no entry name given");
>> > > @@ -1246,6 +1287,60 @@ emit_code(struct protocol *protocol)
>> > > }
>> > > }
>> > >
>> > > +static int
>> > > +enum_exists(struct protocol *protocol, const char *enum_name, int
>> is_bitfield)
>> > > +{
>> > > + struct interface *i;
>> > > + struct enumeration *e;
>> > > + char full_name[64];
>> > > +
>> > > + wl_list_for_each(i, &protocol->interface_list, link) {
>> > > + wl_list_for_each(e, &i->enumeration_list, link) {
>> > > + sprintf(full_name, "%s.%s", i->name, e->name);
>> >
>> > Use snprintf to avoid buffer overflows.
>> > Or split enum_name, and match both halves separately.
>>
>> I will split enum_name then.
>>
>> >
>> > > + if (strcmp(full_name, enum_name) == 0 &&
>> > > + e->is_bitfield == is_bitfield)
>> > > + return 1;
>> > > + }
>> > > + }
>> > > + return 0;
>> > > +}
>> > > +
>> > > +static void
>> > > +check_message(struct protocol *protocol, struct message *m)
>> > > +{
>> > > + struct arg *a;
>> > > +
>> > > + wl_list_for_each(a, &m->arg_list, link)
>> > > + if ((a->type == UNSIGNED || a->type == INT)) {
>> > > + if (a->enum_name != NULL &&
>> > > + !enum_exists(protocol, a->enum_name, 0)) {
>> > > + fprintf(stderr, "enum %s does not
>> exist\n",
>> > > + a->enum_name);
>> > > + exit(EXIT_FAILURE);
>> > > + }
>> > > + else if (a->bitfield_name != NULL &&
>> > > + !enum_exists(protocol,
>> a->bitfield_name, 1)) {
>> > > + fprintf(stderr, "bitfield %s does not
>> exist\n",
>> > > + a->enum_name);
>> > > + exit(EXIT_FAILURE);
>> > > + }
>> > > + }
>> > > +}
>> > > +
>> > > +static void
>> > > +check_protocol(struct protocol *protocol)
>> > > +{
>> > > + struct interface *i;
>> > > + struct message *m;
>> > > +
>> > > + wl_list_for_each(i, &protocol->interface_list, link) {
>> > > + wl_list_for_each(m, &i->request_list, link)
>> > > + check_message(protocol, m);
>> > > + wl_list_for_each(m, &i->event_list, link)
>> > > + check_message(protocol, m);
>> > > + }
>> > > +}
>> > > +
>> > > int main(int argc, char *argv[])
>> > > {
>> > > struct parse_context ctx;
>> > > @@ -1302,6 +1397,10 @@ int main(int argc, char *argv[])
>> > >
>> > > XML_ParserFree(ctx.parser);
>> > >
>> > > + /* some checks can only be performed after *
>> > > + * the whole protocol has been read in */
>> > > + check_protocol(&protocol);
>> > > +
>> > > switch (mode) {
>> > > case CLIENT_HEADER:
>> > > emit_header(&protocol, CLIENT);
>> >
>> > Should we also enforce, that only UNSIGNED is valid for bitfields?
>>
>> I would certainly like to do this, but wl_output.transform is
>> always passed as a signed integer and I'm not sure if this is a
>> bitfield or not. I assumed it is, because you can
>> reconstruct "270", "flipped_90", "flipped_180" and "flipped_270"
>> out of "90", "180" and "flipped". Or is this just a coincidence?
>>
>
> It's both... More in a couple of lines
>
>
>> Also, is there a reason why some enumerations are passed as
>> a signed integer (wl_output.subpixel) and others aren't?
>>
>> >
>> > So, what do other people think of the idea in this patch?
>>
>
> I'm a little unsure. I think trying to completely solve this problem in a
> way that will truly make strongly typed languages happy is insanity. That
> said, I'm cautiously ok with defining bitfields and enums as long as we are
> very careful in scoping what "bitfield" and "enum" mean. A "bitfield"
> should have only power of two values and the result should always be
> interpreted as an OR of those values. An enum should have every possible
> value enumerated. If anyone has a good example of something that validly
> doesn't fit into either of these, please speak up.
>
xdg_shell.resize_edges. It is both a bitfield (top / left / right / bottom
edges are powers of two) and an enum (top right / bottom left corner
convenience values, with top / bottom being left out as it is undefined).
> The example of wl_output.transform is an enum because every possibility is
> enumerated. From C or a similar language, you can do fun stuff like "if
> (transform & WL_OUTPUT_TRANSFORM_FLIPPED)" to determine if there is a
> flip. In a strongly typed language, you can't do this and we shouldn't
> bend over backwards to make it possible. If we try and come up with some
> convoluted system that makes this possible with typed languages, we're
> going to cause far more pain than it's worth.
>
> One other thing that we need to keep in mind here is the primary target
> audience of Wayland and its libraries. That audience is compositors and
> toolkits. Most of those are written in C and C++. What we don't want to
> do is to do a bunch of things for the sake of 1% of the target audience
> that makes the rest have to bend over backwards. When I said "cautiously
> OK", I mean that I don't see that happening yet and I don't see a valid use
> for an enum that doesn't follow one of those two rules. However, if we
> have a plausible case where doing so would make everyone's lives easier,
> I'm going to not be a big fan.
>
> Please note that I'm not trying to insult Haskel or other functional or
> strongly typed languages or the people who use them. I'm simply trying to
> be pragmatic and recognize that people who want to write an app in haskel
> that manually bangs the Wayland protocol isn't the target audience.
>
> --Jason
>
> > I want to see some other Wayland developers support this, as I am not
>> > confident with my own judgement here.
>> >
>> >
>> > Thanks,
>> > pq
>>
>> Cheers,
>> Nils
>> _______________________________________________
>> wayland-devel mailing list
>> wayland-devel@lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/wayland-devel
>>
>
>
> _______________________________________________
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> wayland-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/wayland-devel
>
>
--
Jasper
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