Add a small utility for dumping the system clipboard's contents on GTK.

tools/gtk_clipboard_dump/gtk_clipboard_dump.cc

Index: tools/gtk_clipboard_dump/gtk_clipboard_dump.cc
===================================================================
--- tools/gtk_clipboard_dump/gtk_clipboard_dump.cc	(revision 0)
+++ tools/gtk_clipboard_dump/gtk_clipboard_dump.cc	(revision 0)
@@ -0,0 +1,41 @@
+// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <gtk/gtk.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Small program to dump the contents of GTK's clipboard to the terminal.
+ * Feel free to add to it or improve formatting or whatnot.
+ */
+int main(int argc, char* argv[]) {
+  gtk_init(&argc, &argv);
+  GdkAtom* targets;
+  int num_targets = 0;
+  // For now only look at GDK_SELECTION_CLIPBOARD. This could be extended
+  // to look at GDK_SELECTION_PRIMARY (the X clipboard).
+  GtkClipboard* clip = gtk_clipboard_get(GDK_SELECTION_CLIPBOARD);
+
+  gtk_clipboard_wait_for_targets(clip, &targets, &num_targets);
+
+  printf("Available targets:\n---------------\n");
+
+  for (int i = 0; i < num_targets; i++) {
+    printf("  [format: %s", gdk_atom_name(targets[i]));
+    GtkSelectionData* data = gtk_clipboard_wait_for_contents(clip, targets[i]);
+    if (!data) {
+      printf("]: NULL\n\n");
+      continue;
+    }
+
+    printf(" / length: %d / bits %d]: ", data->length, data->format);
+    for (int j = 0; j < data->length; j++) {
+      // Output data one byte at a time. Currently wide strings look
+      // pretty weird.
+      printf("%c", (data->data[j] == 0 ? '_' : data->data[j]));
+    }
+    printf("\n\n");
+  }
+}
+