[waffle] Approaches to JSON

[Chad Versace]

There are two sets of very different json patchsets on the list. Each
has advantages and disadvantages.

Dylan's patchset duplicates a small amount of code. And it doesn't teach
wflinfo to print any additional info, such as GLX or EGL specific info.
However, the patchset is short, sweet, has no major flaw, and is
the correct approach for what he wished to accomplish: teach wflinfo to
print its current output in a new format, json.

Having json output makes Dylan's life easier as a Piglit developer, and
the sooner he can get json the better. So I'm inclined to expedite
Dylan's patchset and merge it soon, pending fixes.

Frank's patchset adds platform-specific info the wflinfo's output, which
is a feature it really needs. And the code for the platform-specific
info rightly belongs in core waffle, which the patchset gets right.
However, the patchset is much larger, needs lots more review, and needs
to undergo some API changes.

In other words, Frank's patches will take more time to land, and Dylan's
are nearly ready to land as-is. And I don't want to artificially stall
Dylan's Piglit work.

I've decided my preferred format for wflinfo's json output. If the
format is acceptable to everyone, then I want to see Dylan fixup
patch 4/4 of his series and resubmit.

I've been taking notes on Frank's patchset, but won't have time to
provide real feedback until Tuesday (tomorrow) morning.


JSON Format
-----------
Below is the json format I prefer. Is this acceptable to everyone? Did I
underspecify the format?

The major things I considered when deciding the format are:
  1. Keep it simple.
  2. Explicit is better than implicit.
  3. Make life easy for existing wflinfo parsers
     that wish to begin consuming the json. That means existing keys and
     values should closely resemble eachother, and preferably be
     identical.

Definition:
  * All key names are lower case, for consistency.
  * Key names use ' ', not '-' nor '_', as the separator. This is
    consistent with wflinfo's current output and glxinfo's output.
  * For existing keys in wflinfo's current output, the JSON key names
    should match modulo case.
  * For existing values in wflinfo's current output, the JSON value
    should be identical.
  * The "opengl" table contains all info specific to the OpenGL context.
    That includes GLSL info, as that is a property of the OpenGL
    context.

  {
    "waffle": {
      "platform": String,
      "api": String,
    },
    "opengl": {
      "vendor string": String,
      "renderer string": String,
      "version string": String,
      "shading language version string": String,
      "extensions": [String],
    },
    <if platform uses EGL>
    "egl": {
      "vendor string": String,
      "version string": String,
      "version": [Int, Int],
      "extensions": [String],
      "client apis": [String],
    },
    <endif>
    <if platform is GLX>
    "glx": {
      "server": {
        "vendor string": String,
        "version string": String,
        "extensions string": [String],
      },
      "client": {
        "vendor string": String,
        "version string": String,
        "extensions": [String],
      }
      "common": {
        "version": [Int, Int],
        "extensions": [String],
      },
    },
    <endif>
  }

The GLX and EGL tables can be extended in the future to contain
additional information, such as visual configs.