master 4ce2322894: Improve compatibility when receiving drops from early XDND programs

[Po Lu]

branch: master
commit 4ce2322894a21a1bd3045a6c0dcb2069b31a9c05
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Improve compatibility when receiving drops from early XDND programs
    
    * lisp/x-dnd.el (x-dnd-handle-xdnd): Save version in state.
    If version is less than 5, don't put action and success in
    XdndFinished events.  If less than 2, always use `copy' as
    the selected action.
---
 lisp/x-dnd.el | 57 ++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 36 insertions(+), 21 deletions(-)

diff --git a/lisp/x-dnd.el b/lisp/x-dnd.el
index 81aa565818..d4aa68a10d 100644
--- a/lisp/x-dnd.el
+++ b/lisp/x-dnd.el
@@ -572,19 +572,23 @@ FORMAT is 32 (not used).  MESSAGE is the data part of an 
XClientMessageEvent."
                (version (x-dnd-version-from-flags flags))
                (more-than-3 (x-dnd-more-than-3-from-flags flags))
                (dnd-source (aref data 0)))
-          (if version  ;; If flags is bad, version will be nil.
-              (x-dnd-save-state
-               window nil nil
-               (if (> more-than-3 0)
-                   (x-window-property "XdndTypeList"
-                                      frame "AnyPropertyType"
-                                      dnd-source nil t)
-                 (vector (x-get-atom-name (aref data 2))
-                         (x-get-atom-name (aref data 3))
-                         (x-get-atom-name (aref data 4))))))))
+          (when version  ;; If flags is bad, version will be nil.
+            (x-dnd-save-state
+             window nil nil
+             (if (> more-than-3 0)
+                 (x-window-property "XdndTypeList"
+                                    frame "AnyPropertyType"
+                                    dnd-source nil t)
+               (vector (x-get-atom-name (aref data 2))
+                       (x-get-atom-name (aref data 3))
+                       (x-get-atom-name (aref data 4))))
+              version))))
 
        ((equal "XdndPosition" message)
-        (let* ((action (x-get-atom-name (aref data 4)))
+        (let* ((state (x-dnd-get-state-for-frame window))
+                (version (aref state 6))
+                (action (if (< version 2) 'copy ; `copy' is the default action.
+                          (x-get-atom-name (aref data 4))))
                (dnd-source (aref data 0))
                (action-type (x-dnd-maybe-call-test-function
                              window
@@ -604,7 +608,14 @@ FORMAT is 32 (not used).  MESSAGE is the data part of an 
XClientMessageEvent."
                       (x-dnd-get-drop-x-y frame window)
                       (x-dnd-get-drop-width-height
                        frame window (eq accept 1))
-                      (or reply-action 0))))
+                       ;; The no-toolkit Emacs build can actually
+                       ;; receive drops from programs that speak
+                       ;; versions of XDND earlier than 3 (such as
+                       ;; GNUstep), since the toplevel window is the
+                       ;; innermost window.
+                      (if (>= version 2)
+                           (or reply-action 0)
+                         0))))
           (x-send-client-message
            frame dnd-source frame "XdndStatus" 32 list-to-send)
            (dnd-handle-movement (event-start event))))
@@ -614,7 +625,9 @@ FORMAT is 32 (not used).  MESSAGE is the data part of an 
XClientMessageEvent."
 
        ((equal "XdndDrop" message)
         (if (windowp window) (select-window window))
-        (let* ((dnd-source (aref data 0))
+        (let* ((state (x-dnd-get-state-for-frame frame))
+                (version (aref state 6))
+                (dnd-source (aref data 0))
                (timestamp (aref data 2))
                (value (and (x-dnd-current-type window)
                            (x-get-selection-internal
@@ -630,15 +643,17 @@ FORMAT is 32 (not used).  MESSAGE is the data part of an 
XClientMessageEvent."
                              (error
                               (message "Error: %s" info)
                               nil))))
-
           (setq success (if action 1 0))
-
-          (x-send-client-message
-           frame dnd-source frame "XdndFinished" 32
-           (list (string-to-number (frame-parameter frame 'outer-window-id))
-                 success       ;; 1 = Success, 0 = Error
-                 (if success "XdndActionPrivate" 0)
-                 ))
+           (when (>= version 2)
+            (x-send-client-message
+             frame dnd-source frame "XdndFinished" 32
+             (list (string-to-number
+                     (frame-parameter frame 'outer-window-id))
+                   (if (>= version 5) success 0) ;; 1 = Success, 0 = Error
+                    (when (>= version 5)
+                     (if (not success) 0
+                        (car (rassoc action
+                                     x-dnd-xdnd-to-action)))))))
           (x-dnd-forget-drop window)))
 
        (t (error "Unknown XDND message %s %s" message data))))