Process SelectionRequestor::PerformBlockingConvertSelection() requests one at a time

ui/base/x/selection_requestor.h

 // Copyright (c) 2013 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.
 
 #ifndef UI_BASE_X_SELECTION_REQUESTOR_H_
 #define UI_BASE_X_SELECTION_REQUESTOR_H_
 
 #include <X11/Xlib.h>
 
-// Get rid of a macro from Xlib.h that conflicts with Aura's RootWindow class.
-#undef RootWindow
-
 #include <list>
-#include <vector>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/ref_counted_memory.h"
 #include "ui/base/ui_base_export.h"
 #include "ui/gfx/x/x11_atom_cache.h"
 
 namespace ui {
 class PlatformEventDispatcher;
 class SelectionData;
 
 // Requests and later receives data from the X11 server through the selection
 // system.
 //
 // X11 uses a system called "selections" to implement clipboards and drag and
 // drop. This class interprets messages from the statefull selection request
 // API. SelectionRequestor should only deal with the X11 details; it does not
 // implement per-component fast-paths.
 class UI_BASE_EXPORT SelectionRequestor {
  public:
   SelectionRequestor(Display* xdisplay,
                      ::Window xwindow,
-                     ::Atom selection_name,
                      PlatformEventDispatcher* dispatcher);
   ~SelectionRequestor();
 
-  // Does the work of requesting |target| from the selection we handle,
-  // spinning up the nested message loop, and reading the resulting data
-  // back. The result is stored in |out_data|.
+  // Does the work of requesting |target| from |selection|, spinning up the
+  // nested message loop, and reading the resulting data back. The result is
+  // stored in |out_data|.
   // |out_data_items| is the length of |out_data| in |out_type| items.
   bool PerformBlockingConvertSelection(
+      ::Atom selection,
       ::Atom target,
       scoped_refptr<base::RefCountedMemory>* out_data,
       size_t* out_data_items,
       ::Atom* out_type);
 
-  // Requests |target| from the selection that we handle, passing |parameter|
-  // as a parameter to XConvertSelection().
+  // Requests |target| from |selection|, passing |parameter| as a parameter to
+  // XConvertSelection().
   void PerformBlockingConvertSelectionWithParameter(
+      ::Atom selection,
       ::Atom target,
       const std::vector< ::Atom>& parameter);
 
-  // Returns the first of |types| offered by the current selection holder, or
-  // returns NULL if none of those types are available.
-  SelectionData RequestAndWaitForTypes(const std::vector< ::Atom>& types);
+  // Returns the first of |types| offered by the current owner of |selection|,
+  // or returns NULL if none of those types are available.
+  SelectionData RequestAndWaitForTypes(::Atom selection,
+                                       const std::vector< ::Atom>& types);
 
   // It is our owner's responsibility to plumb X11 SelectionNotify events on
   // |xwindow_| to us.
   void OnSelectionNotify(const XSelectionEvent& event);
 
  private:
   // A request that has been issued and we are waiting for a response to.
   struct PendingRequest {
-    explicit PendingRequest(Atom target);
+    PendingRequest(::Atom requested_selection, ::Atom requested_target);
     ~PendingRequest();
 
-    // Data to the current XConvertSelection request. Used for error detection;
-    // we verify it on the return message.
+    // The target and selection requested in the XConvertSelection() request.
+    // Used for error detection.
+    ::Atom selection;
     ::Atom target;
 
     // Called to terminate the nested message loop.
     base::Closure quit_closure;
 
     // The property in the returning SelectNotify message is used to signal
     // success. If None, our request failed somehow. If equal to the property
     // atom that we sent in the XConvertSelection call, we can read that
     // property on |x_window_| for the requested data.
     ::Atom returned_property;
 
     // Set to true when return_property is populated.
     bool returned;
   };
 
+  // Helper method for PerformBlockingConvertSelection() and
+  // PerformBlockingConvertSelectionWithParameter().
+  bool PerformBlockingConvertSelectionImpl(
+      ::Atom selection,
+      ::Atom target,
+      const char* property_name,
+      scoped_refptr<base::RefCountedMemory>* out_data,
+      size_t* out_data_items,
+      ::Atom* out_type);
+
   // Blocks till SelectionNotify is received for the target specified in
   // |request|.
   void BlockTillSelectionNotifyForRequest(PendingRequest* request);
 
   // Our X11 state.
   Display* x_display_;
   ::Window x_window_;
 
-  // The X11 selection that this instance communicates on.
-  ::Atom selection_name_;
-
   // Dispatcher which handles SelectionNotify and SelectionRequest for
   // |selection_name_|. PerformBlockingConvertSelection() calls the
   // dispatcher directly if PerformBlockingConvertSelection() is called after
   // the PlatformEventSource is destroyed.
   // Not owned.
   PlatformEventDispatcher* dispatcher_;
 
+  // A pool of properties which can be used in XConvertSelection() requests.
+  std::list<const char*> property_pool_;
+
   // A list of requests for which we are waiting for responses.
   std::list<PendingRequest*> pending_requests_;
 
   X11AtomCache atom_cache_;
 
   DISALLOW_COPY_AND_ASSIGN(SelectionRequestor);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_X_SELECTION_REQUESTOR_H_