object.rb

# This module provides an interface to the top level bits of libvips
# via ruby-ffi.
#
# Author::    John Cupitt  (mailto:jcupitt@gmail.com)
# License::   MIT

require "ffi"

module Vips
  private

  # debugging support
  attach_function :vips_object_print_all, [], :void

  # we must init these by hand, since they are usually made on first image
  # create
  attach_function :vips_band_format_get_type, [], :GType
  attach_function :vips_interpretation_get_type, [], :GType
  attach_function :vips_coding_get_type, [], :GType

  public

  # some handy gtypes
  IMAGE_TYPE = GObject.g_type_from_name "VipsImage"
  ARRAY_INT_TYPE = GObject.g_type_from_name "VipsArrayInt"
  ARRAY_DOUBLE_TYPE = GObject.g_type_from_name "VipsArrayDouble"
  ARRAY_IMAGE_TYPE = GObject.g_type_from_name "VipsArrayImage"
  REFSTR_TYPE = GObject.g_type_from_name "VipsRefString"
  BLOB_TYPE = GObject.g_type_from_name "VipsBlob"

  BAND_FORMAT_TYPE = Vips.vips_band_format_get_type
  INTERPRETATION_TYPE = Vips.vips_interpretation_get_type
  CODING_TYPE = Vips.vips_coding_get_type

  if Vips.at_least_libvips?(8, 6)
    attach_function :vips_blend_mode_get_type, [], :GType
    BLEND_MODE_TYPE = Vips.vips_blend_mode_get_type
  else
    BLEND_MODE_TYPE = nil
  end

  private

  class Progress < FFI::Struct
    layout :im, :pointer,
      :run, :int,
      :eta, :int,
      :tpels, :int64_t,
      :npels, :int64_t,
      :percent, :int,
      :start, :pointer
  end

  # Our signal marshalers.
  #
  # These are functions which take the handler as a param and return a
  # closure with the right FFI signature for g_signal_connect for this
  # specific signal.
  #
  # ruby-ffi makes it hard to use the g_signal_connect user data param
  # to pass the function pointer through, unfortunately.
  #
  # We can't throw exceptions across C, so we must catch everything.

  MARSHAL_PROGRESS = proc do |handler|
    FFI::Function.new(:void, [:pointer, :pointer, :pointer]) do |vi, prog, cb|
      # this can't throw an exception, so no catch is necessary
      handler.call(Progress.new(prog))
    end
  end

  MARSHAL_READ = proc do |handler|
    FFI::Function.new(:int64_t, [:pointer, :pointer, :int64_t]) do |i, p, len|
      begin
        result = handler.call(p, len)
      rescue Exception => e
        puts "read: #{e}"
        result = 0
      end

      result
    end
  end

  MARSHAL_SEEK = proc do |handler|
    FFI::Function.new(:int64_t, [:pointer, :int64_t, :int]) do |i, off, whence|
      begin
        result = handler.call(off, whence)
      rescue Exception => e
        puts "seek: #{e}"
        result = -1
      end

      result
    end
  end

  MARSHAL_WRITE = proc do |handler|
    FFI::Function.new(:int64_t, [:pointer, :pointer, :int64_t]) do |i, p, len|
      begin
        result = handler.call(p, len)
      rescue Exception => e
        puts "write: #{e}"
        result = 0
      end

      result
    end
  end

  MARSHAL_END = proc do |handler|
    FFI::Function.new(:int, [:pointer, :pointer]) do |i, cb|
      # this can't throw an exception, so no catch is necessary
      handler.call
    end
  end

  MARSHAL_FINISH = proc do |handler|
    FFI::Function.new(:void, [:pointer, :pointer]) do |i, cb|
      # this can't throw an exception, so no catch is necessary
      handler.call
    end
  end

  # map signal name to marshal proc
  MARSHAL_ALL = {
    preeval: MARSHAL_PROGRESS,
    eval: MARSHAL_PROGRESS,
    posteval: MARSHAL_PROGRESS,
    read: MARSHAL_READ,
    seek: MARSHAL_SEEK,
    write: MARSHAL_WRITE,
    end: MARSHAL_END,
    finish: MARSHAL_FINISH
  }

  attach_function :vips_enum_from_nick, [:string, :GType, :string], :int
  attach_function :vips_enum_nick, [:GType, :int], :string

  attach_function :vips_value_set_ref_string,
    [GObject::GValue.ptr, :string], :void
  attach_function :vips_value_set_array_double,
    [GObject::GValue.ptr, :pointer, :int], :void
  attach_function :vips_value_set_array_int,
    [GObject::GValue.ptr, :pointer, :int], :void
  attach_function :vips_value_set_array_image,
    [GObject::GValue.ptr, :int], :void
  callback :free_fn, [:pointer], :void
  attach_function :vips_value_set_blob,
    [GObject::GValue.ptr, :free_fn, :pointer, :size_t], :void

  class SizeStruct < FFI::Struct
    layout :value, :size_t
  end

  class IntStruct < FFI::Struct
    layout :value, :int
  end

  attach_function :vips_value_get_ref_string,
    [GObject::GValue.ptr, SizeStruct.ptr], :string
  attach_function :vips_value_get_array_double,
    [GObject::GValue.ptr, IntStruct.ptr], :pointer
  attach_function :vips_value_get_array_int,
    [GObject::GValue.ptr, IntStruct.ptr], :pointer
  attach_function :vips_value_get_array_image,
    [GObject::GValue.ptr, IntStruct.ptr], :pointer
  attach_function :vips_value_get_blob,
    [GObject::GValue.ptr, SizeStruct.ptr], :pointer

  attach_function :type_find, :vips_type_find, [:string, :string], :GType

  class Object < GObject::GObject
    # print all active VipsObjects, with their reference counts. Handy for
    # debugging ruby-vips.
    def self.print_all
      GC.start
      Vips.vips_object_print_all
    end

    # the layout of the VipsObject struct
    module ObjectLayout
      def self.included base
        base.class_eval do
          # don't actually need most of these
          layout :parent, GObject::GObject::Struct,
            :constructed, :int,
            :static_object, :int,
            :argument_table, :pointer,
            :nickname, :string,
            :description, :string,
            :preclose, :int,
            :close, :int,
            :postclose, :int,
            :local_memory, :size_t
        end
      end
    end

    class Struct < GObject::GObject::Struct
      include ObjectLayout
    end

    class ManagedStruct < GObject::GObject::ManagedStruct
      include ObjectLayout
    end

    # return a pspec, or nil ... nil wil leave a message in the error log
    # which you must clear
    def get_pspec name
      ppspec = GObject::GParamSpecPtr.new
      argument_class = Vips::ArgumentClassPtr.new
      argument_instance = Vips::ArgumentInstancePtr.new

      result = Vips.vips_object_get_argument self, name,
        ppspec, argument_class, argument_instance
      return nil if result != 0

      ppspec[:value]
    end

    # return a gtype, raise an error on not found
    def get_typeof_error name
      pspec = get_pspec name
      raise Vips::Error unless pspec

      pspec[:value_type]
    end

    # return a gtype, 0 on not found
    def get_typeof name
      pspec = get_pspec name
      unless pspec
        Vips.vips_error_clear
        return 0
      end

      pspec[:value_type]
    end

    def get name
      gtype = get_typeof_error name
      gvalue = GObject::GValue.alloc
      gvalue.init gtype
      GObject.g_object_get_property self, name, gvalue
      result = gvalue.get
      gvalue.unset

      GLib.logger.debug("Vips::Object.get") { "#{name} == #{result}" }

      result
    end

    def set name, value
      GLib.logger.debug("Vips::Object.set") { "#{name} = #{value}" }

      gtype = get_typeof_error name
      gvalue = GObject::GValue.alloc
      gvalue.init gtype
      gvalue.set value
      GObject.g_object_set_property self, name, gvalue
      gvalue.unset
    end

    def signal_connect name, handler = nil, &block
      marshal = MARSHAL_ALL[name.to_sym]
      raise Vips::Error, "unsupported signal #{name}" if marshal.nil?

      if block
        # our block as a Proc
        prc = block
      elsif handler
        # We assume the hander is a Proc (perhaps we should test)
        prc = handler
      else
        raise Vips::Error, "must supply either block or handler"
      end

      # The marshal function will make a closure with the right type signature
      # for the selected signal
      callback = marshal.call(prc)

      # we need to make sure this is not GCd while self is alive
      @references << callback

      GObject.g_signal_connect_data(self, name.to_s, callback, nil, nil, 0)
    end
  end

  class ObjectClass < FFI::Struct
    # opaque
  end

  class Argument < FFI::Struct
    layout :pspec, GObject::GParamSpec.ptr
  end

  class ArgumentInstance < Argument
    layout :parent, Argument
    # rest opaque
  end

  # enum VipsArgumentFlags
  ARGUMENT_REQUIRED = 1
  ARGUMENT_CONSTRUCT = 2
  ARGUMENT_SET_ONCE = 4
  ARGUMENT_SET_ALWAYS = 8
  ARGUMENT_INPUT = 16
  ARGUMENT_OUTPUT = 32
  ARGUMENT_DEPRECATED = 64
  ARGUMENT_MODIFY = 128

  ARGUMENT_FLAGS = {
    required: ARGUMENT_REQUIRED,
    construct: ARGUMENT_CONSTRUCT,
    set_once: ARGUMENT_SET_ONCE,
    set_always: ARGUMENT_SET_ALWAYS,
    input: ARGUMENT_INPUT,
    output: ARGUMENT_OUTPUT,
    deprecated: ARGUMENT_DEPRECATED,
    modify: ARGUMENT_MODIFY
  }

  class ArgumentClass < Argument
    layout :parent, Argument,
      :object_class, ObjectClass.ptr,
      :flags, :uint,
      :priority, :int,
      :offset, :ulong_long
  end

  class ArgumentClassPtr < FFI::Struct
    layout :value, ArgumentClass.ptr
  end

  class ArgumentInstancePtr < FFI::Struct
    layout :value, ArgumentInstance.ptr
  end

  # just use :pointer, not VipsObject.ptr, to avoid casting gobject
  # subclasses
  attach_function :vips_object_get_argument,
    [:pointer, :string,
      GObject::GParamSpecPtr.ptr,
      ArgumentClassPtr.ptr, ArgumentInstancePtr.ptr],
    :int

  attach_function :vips_object_print_all, [], :void

  attach_function :vips_object_set_from_string, [:pointer, :string], :int

  callback :type_map_fn, [:GType, :pointer], :pointer
  attach_function :vips_type_map, [:GType, :type_map_fn, :pointer], :pointer

  attach_function :vips_object_get_description, [:pointer], :string
end