2 files changed, 43 insertions, 0 deletions
diff --git a/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb b/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb
new file mode 100644
index 000000000..ae4f5b8ed
--- /dev/null
+++ b/Library/Homebrew/extend/os/mac/requirements/x11_requirement.rb
@@ -0,0 +1,42 @@
+require "requirement"
+
+class XQuartzRequirement < Requirement
+  include Comparable
+
+  fatal true
+  cask "xquartz"
+  download "https://xquartz.macosforge.org"
+
+  env { ENV.x11 }
+
+  def initialize(name = "x11", tags = [])
+    @name = name
+    # no-op on version specified as a tag argument
+    tags.shift if /(\d\.)+\d/ =~ tags.first
+    super(tags)
+  end
+
+  def min_version
+    MacOS::XQuartz.minimum_version
+  end
+
+  satisfy build_env: false do
+    next false unless MacOS::XQuartz.installed?
+    min_version <= MacOS::XQuartz.version
+  end
+
+  def message
+    "XQuartz #{min_version} (or newer) is required to install this formula. #{super}"
+  end
+
+  def <=>(other)
+    return unless other.is_a? X11Requirement
+    0
+  end
+
+  def inspect
+    "#<#{self.class.name}: #{name.inspect} #{tags.inspect}>"
+  end
+end
+
+X11Requirement = XQuartzRequirement
diff --git a/Library/Homebrew/extend/os/requirements/x11_requirement.rb b/Library/Homebrew/extend/os/requirements/x11_requirement.rb
new file mode 100644
index 000000000..664b6c7c0
--- /dev/null
+++ b/Library/Homebrew/extend/os/requirements/x11_requirement.rb
@@ -0,0 +1 @@
+require "extend/os/mac/requirements/x11_requirement" if OS.mac?