Add non-raising clipboard getter

src/espresso/window.cr

@@ -1065,6 +1065,17 @@ module Espresso
       String.new(chars)
     end
 
+    # Retrieves the contents of the system clipboard,
+    # if it contains or is convertible to a UTF-8 encoded string.
+    # If the clipboard is empty or if its contents cannot be converted,
+    # nil is returned..
+    #
+    # Possible errors that could be raised are: `NotInitializedError` and `PlatformError`.
+    def clipboard?
+      chars = LibGLFW.get_clipboard_string(@pointer)
+      chars ? String.new(chars) : nil
+    end
+
     # Sets the contents of the system clipboard,
     # to the specified UTF-8 encoded *string*.
     #
@@ -1092,6 +1103,17 @@ module Espresso
       ErrorHandling.static_checked { LibGLFW.set_clipboard_string(nil, string) }
     end
 
+    # Retrieves the contents of the system clipboard,
+    # if it contains or is convertible to a UTF-8 encoded string.
+    # If the clipboard is empty or if its contents cannot be converted,
+    # nil is returned..
+    #
+    # Possible errors that could be raised are: `NotInitializedError` and `PlatformError`.
+    def self.clipboard?
+      chars = LibGLFW.get_clipboard_string(nil)
+      chars ? String.new(chars) : nil
+    end
+
     # Attempts to retrieve the monitor the full screen window is using.
     # If the window isn't full screen, then nil is returned.
     #

tests/clipboard.cr

@@ -22,17 +22,16 @@ Espresso.run do
         event.window.closing = true
       when Espresso::Key::V
         if event.mods == MODIFIER
-          begin
-            string = event.window.clipboard
+          if (string = Espresso::Window.clipboard?)
             puts "Clipboard contains \"#{string}\""
-          rescue Espresso::FormatUnavailableError
+          else
             puts "Clipboard does not contain a string"
           end
         end
       when Espresso::Key::C
         if event.mods == MODIFIER
           string = "Hello GLFW World!"
-          event.window.clipboard = string
+          Espresso::Window.clipboard = string
           puts "Setting clipboard to \"#{string}\""
         end
       end