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#!/usr/bin/env ruby
###################################################
## Display screen dimensions in macOS using ruby ##
##################################################
# found https://developer.apple.com/reference/coregraphics/1456395-cgdisplaybounds?language=objc
# --> use CoreGraphics framework
# --> CGRect CGDisplayBounds(CGDirectDisplayID display);
#############################################
## How to bind (objective)C code in ruby ? ##
#############################################
# found https://github.com/ffi/ffi/wiki
# --> gem install ffi
require 'ffi'
module Display
extend FFI::Library
######################################
## How to find CoreGraphics dynlib? ##
######################################
# --> it's in "/System/Library/Frameworks" ;-)
ffi_lib '/System/Library/Frameworks/CoreGraphics.framework/CoreGraphics'
###########################################################
## How to find and bind (objective)C functions in ruby ? ##
###########################################################
# 1. $ nm
# --> nm -gU '/System/Library/Frameworks/CoreGraphics.framework/CoreGraphics'
# --> not really helpful :-(
# 2. xml
# --> "/System/Library/Frameworks/CoreGraphics.framework/Versions/A/Resources/BridgeSupport/CoreGraphics.bridgesupport"
# <function name='CGMainDisplayID'>
# <retval type='I'/>
# </function>
# What is 'I' ?
# 1. https://github.com/ffi/ffi/wiki/Types / xml / dtd ...
# --> not really helpful :-(
# 2. https://github.com/patrickhno/cocoa/blob/master/lib/cocoa/objc/method_def.rb#L5
# It's :uint
###################################
## Use cocoa in the first place? ##
###################################
# --> tried, turns out there's a bug when using CGDirectDisplayID :-(
# require 'cocoa'
# Cocoa.CGMainDisplayID
# --> ArgumentError: wrong number of arguments (given 1, expected 2)
# Cocoa.CGMainDisplayID(0)
# --> ArgumentError: wrong number of arguments (given 1, expected 0)
# However, when falling back to default CGDirectDisplayID, Cocoa.CGDisplayBounds(0)
# Cocoa.CGDisplayBounds(0)
# --> <Cocoa::CGRect:0x007fa118b39078>
# I don'd want to use unmaintained gems anyway (https://github.com/patrickhno/cocoa/commits/master)
# What was 'I' again...?
# CGRect CGDisplayBounds(CGDirectDisplayID display);
# Define a new type from :uint called :CGDirectDisplayID
typedef :uint, :CGDirectDisplayID
###################################################
## How to bind (objective)C functions using ffi? ##
###################################################
# attach_function
# --> http://www.rubydoc.info/github/ffi/ffi/FFI/Library:attach_function
# --> https://github.com/ffi/ffi/blob/master/lib/ffi/library.rb#L204
# <function name='CGMainDisplayID'>
# <retval type='I'/>
# </function>
attach_function :CGMainDisplayID, [], :CGDirectDisplayID
# Display.CGMainDisplayID
# --> 69732928
# weird number, but it seems to work
# CGRect CGDisplayBounds(CGDirectDisplayID display);
###########################
## How to define CGRect? ##
###########################
# --> <struct name="CGRect"
# type="{CGRect="origin"{CGPoint="x"f"y"f}"size"{CGSize="width"f"height"f}}"
# type64="{CGRect="origin"{CGPoint="x"d"y"d}"size"{CGSize="width"d"height"d}}"/>
######################
## What's all this? ##
######################
# --> "name" is prefixed in quotes
# --> {} defined a struct(ure)
# --> f is :float
# --> d is :double
# CGPoint and CGSize need to be defined first
##################################
## How to define those structs? ##
##################################
# --> use FFI::Struct
# https://github.com/ffi/ffi/wiki/Basic-Usage#passing-structs-as-value-parameters-to-functions
# http://www.rubydoc.info/github/ffi/ffi/FFI/Struct
# <struct name="CGPoint" type="{CGPoint="x"f"y"f}" type64="{CGPoint="x"d"y"d}"/>
class CGPoint < FFI::Struct
layout :x, :double, :y, :double
end
# <struct name="CGSize" type="{CGSize="width"f"height"f}" type64="{CGSize="width"d"height"d}"/>
class CGSize < FFI::Struct
layout :width, :double, :height, :double
end
# <struct name="CGRect" type="{CGRect="origin"{CGPoint="x"f"y"f}"size"{CGSize="width"f"height"f}}" type64="{CGRect="origin"{CGPoint="x"d"y"d}"size"{CGSize="width"d"height"d}}"/>
class CGRect < FFI::Struct
layout :origin, CGPoint, :size, CGSize
end
# finally bind CGDisplayBounds
# <function name='CGDisplayBounds'>
# <arg type='I'/>
# <retval type='{CGRect={CGPoint=ff}{CGSize=ff}}' type64='{CGRect={CGPoint=dd}{CGSize=dd}}'/>
# </function>
attach_function :CGDisplayBounds, [:CGDirectDisplayID], CGRect.by_value
# Done!
end
displayID = Display.CGMainDisplayID
bounds = Display.CGDisplayBounds(displayID)
puts "width: #{'%d' % bounds[:size][:width]}, height: #{'%d' % bounds[:size][:height]}"
# There are helper methods like CGRectGetHeight, so you could spare the definition of CGSize.
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