From acdde129bb47690b2948e200ba32d23aa494d406 Mon Sep 17 00:00:00 2001
From: Alex Maese <memaese@hotmail.com>
Date: Sat, 8 Jul 2023 12:52:41 -0500
Subject: [PATCH] X11: Use XFixes to detect clipboard updates

Currently, SDL_CLIPBOARDUPDATE events are only sent when an SDL window
has its selection cleared.  This change sends the event anytime the
XFixesSelectionNotify event is raised, and when the selection is either
the clipboard or the primary selection.
---
 src/video/x11/SDL_x11events.c | 21 +++++++++++++++++++++
 src/video/x11/SDL_x11sym.h    |  1 +
 src/video/x11/SDL_x11xfixes.c | 15 +++++++++++++++
 src/video/x11/SDL_x11xfixes.h |  2 +-
 4 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/src/video/x11/SDL_x11events.c b/src/video/x11/SDL_x11events.c
index a28ccce3dd..55d151e63c 100644
--- a/src/video/x11/SDL_x11events.c
+++ b/src/video/x11/SDL_x11events.c
@@ -869,6 +869,27 @@ static void X11_DispatchEvent(_THIS, XEvent *xevent)
            xevent->type, xevent->xany.display, xevent->xany.window);
 #endif
 
+#ifdef SDL_VIDEO_DRIVER_X11_XFIXES
+    if (SDL_X11_HAVE_XFIXES &&
+            xevent->type == X11_GetXFixesSelectionNotifyEvent()) {
+        XFixesSelectionNotifyEvent *ev = (XFixesSelectionNotifyEvent *) xevent;
+
+        /* !!! FIXME: cache atoms */
+        Atom XA_CLIPBOARD = X11_XInternAtom(display, "CLIPBOARD", 0);
+
+#ifdef DEBUG_XEVENTS
+        printf("window CLIPBOARD: XFixesSelectionNotify (selection = %s)\n",
+                X11_XGetAtomName(display, ev->selection));
+#endif
+
+        if (ev->selection == XA_PRIMARY ||
+                (XA_CLIPBOARD != None && ev->selection == XA_CLIPBOARD)) {
+            SDL_SendClipboardUpdate();
+            return;
+        }
+    }
+#endif /* SDL_VIDEO_DRIVER_X11_XFIXES */
+
     if ((videodata->clipboard_window != None) &&
         (videodata->clipboard_window == xevent->xany.window)) {
         X11_HandleClipboardEvent(_this, xevent);
diff --git a/src/video/x11/SDL_x11sym.h b/src/video/x11/SDL_x11sym.h
index beb0d38115..2d9cbfdf2e 100644
--- a/src/video/x11/SDL_x11sym.h
+++ b/src/video/x11/SDL_x11sym.h
@@ -162,6 +162,7 @@ SDL_X11_SYM(PointerBarrier, XFixesCreatePointerBarrier, (Display* a, Window b, i
 SDL_X11_SYM(void, XFixesDestroyPointerBarrier, (Display* a, PointerBarrier b), (a,b),)
 SDL_X11_SYM(int, XIBarrierReleasePointer,(Display* a,  int b, PointerBarrier c, BarrierEventID d), (a,b,c,d), return) /* this is actually Xinput2 */
 SDL_X11_SYM(Status, XFixesQueryVersion,(Display* a, int* b, int* c), (a,b,c), return)
+SDL_X11_SYM(Status, XFixesSelectSelectionInput, (Display* a, Window b, Atom c, unsigned long d), (a,b,c,d), return)
 #endif
 
 #if SDL_VIDEO_DRIVER_X11_SUPPORTS_GENERIC_EVENTS
diff --git a/src/video/x11/SDL_x11xfixes.c b/src/video/x11/SDL_x11xfixes.c
index 662759f67d..2189f231d5 100644
--- a/src/video/x11/SDL_x11xfixes.c
+++ b/src/video/x11/SDL_x11xfixes.c
@@ -29,6 +29,7 @@
 #include "../../events/SDL_touch_c.h"
 
 static int xfixes_initialized = 0;
+static int xfixes_selection_notify_event = 0;
 
 static int query_xfixes_version(Display *display, int major, int minor)
 {
@@ -50,11 +51,20 @@ void X11_InitXfixes(_THIS)
     int event, error;
     int fixes_opcode;
 
+    Atom XA_CLIPBOARD = X11_XInternAtom(data->display, "CLIPBOARD", 0);
+
     if (!SDL_X11_HAVE_XFIXES ||
         !X11_XQueryExtension(data->display, "XFIXES", &fixes_opcode, &event, &error)) {
         return;
     }
 
+    /* Selection tracking is available in all versions of XFixes */
+    xfixes_selection_notify_event = event + XFixesSelectionNotify;
+    X11_XFixesSelectSelectionInput(data->display, DefaultRootWindow(data->display),
+            XA_CLIPBOARD, XFixesSetSelectionOwnerNotifyMask);
+    X11_XFixesSelectSelectionInput(data->display, DefaultRootWindow(data->display),
+            XA_PRIMARY, XFixesSetSelectionOwnerNotifyMask);
+
     /* We need at least 5.0 for barriers. */
     version = query_xfixes_version(data->display, 5, 0);
     if (!xfixes_version_atleast(version, 5, 0)) {
@@ -69,6 +79,11 @@ int X11_XfixesIsInitialized()
     return xfixes_initialized;
 }
 
+int X11_GetXFixesSelectionNotifyEvent()
+{
+    return xfixes_selection_notify_event;
+}
+
 void X11_SetWindowMouseRect(_THIS, SDL_Window *window)
 {
     if (SDL_RectEmpty(&window->mouse_rect)) {
diff --git a/src/video/x11/SDL_x11xfixes.h b/src/video/x11/SDL_x11xfixes.h
index 92c659406e..bba4095156 100644
--- a/src/video/x11/SDL_x11xfixes.h
+++ b/src/video/x11/SDL_x11xfixes.h
@@ -33,7 +33,7 @@ extern int X11_XfixesIsInitialized(void);
 extern void X11_SetWindowMouseRect(_THIS, SDL_Window *window);
 extern int X11_ConfineCursorWithFlags(_THIS, SDL_Window *window, const SDL_Rect *rect, int flags);
 extern void X11_DestroyPointerBarrier(_THIS, SDL_Window *window);
-
+extern int X11_GetXFixesSelectionNotifyEvent(void);
 #endif /* SDL_VIDEO_DRIVER_X11_XFIXES */
 
 #endif /* SDL_x11xfixes_h_ */