WINGs: route selection acquire/release/request through vtable

- WMDeleteSelectionHandler: X11 grab/release replaced with selection_release vtable
- WMRequestSelection: XGetSelectionOwner+XConvertSelection replaced with selection_request vtable
- x11_selection_release: now properly releases ownership (was no-op)
- x11_selection_request: new vtable impl for X11 selection conversion
- Wayland selection_request: NULL (no-op, returns False)

WINGs/WINGs/WINGsP.h.in

@@ -620,6 +620,7 @@ typedef struct W_ViewBackend {
     /* Selection ownership */
     Bool  (*selection_acquire)(void *vctx, struct W_View *view, Atom selection, Time timestamp);
     void  (*selection_release)(void *vctx, struct W_View *view, Atom selection);
+    Bool  (*selection_request)(void *vctx, struct W_View *view, Atom selection, Atom target, Time timestamp);
 
     /* Platform-specific post-init (e.g. X11 atoms, IM setup) */
     void  (*platform_init)(struct W_Screen *scr);

WINGs/selection.c

@@ -45,8 +45,6 @@ static Bool gotXError = False;
 void WMDeleteSelectionHandler(WMView * view, Atom selection, Time timestamp)
 {
 	SelectionHandler *handler;
-	Display *dpy = W_VIEW_SCREEN(view)->display;
-	Window win = W_VIEW_DRAWABLE(view);
 	WMArrayIterator iter;
 
 	if (!selHandlers)
@@ -71,11 +69,8 @@ void WMDeleteSelectionHandler(WMView * view, Atom selection, Time timestamp)
 
 	/*//printf("\n"); */
 
-	XGrabServer(dpy);
+	const W_ViewBackend *vb = view->screen->viewBackend;
-	if (XGetSelectionOwner(dpy, selection) == win) {
+	vb->selection_release(view->screen->viewBackendCtx, view, selection);
-		XSetSelectionOwner(dpy, selection, None, timestamp);
-	}
-	XUngrabServer(dpy);
 }
 
 static void WMDeleteSelectionCallback(WMView * view, Atom selection, Time timestamp)
@@ -366,14 +361,11 @@ WMRequestSelection(WMView * view, Atom selection, Atom target, Time timestamp,
 {
 	SelectionCallback *handler;
 
-	if (XGetSelectionOwner(W_VIEW_SCREEN(view)->display, selection) == None)
+	const W_ViewBackend *vb = view->screen->viewBackend;
+	if (!vb->selection_request ||
+	    !vb->selection_request(view->screen->viewBackendCtx, view, selection, target, timestamp))
 		return False;
 
-	if (!XConvertSelection(W_VIEW_SCREEN(view)->display, selection, target,
-			       W_VIEW_SCREEN(view)->clipboardAtom, W_VIEW_DRAWABLE(view), timestamp)) {
-		return False;
-	}
-
 	handler = wmalloc(sizeof(SelectionCallback));
 	handler->view = view;
 	handler->selection = selection;

WINGs/wview_wl.c

@@ -604,6 +604,7 @@ const W_ViewBackend W_ViewBackendWL = {
 	.get_screen_position  = wl_get_screen_position,
 	.selection_acquire    = wl_selection_acquire,
 	.selection_release    = wl_selection_release,
+	.selection_request    = NULL,
 	.platform_init        = NULL,
 	.flush                = wl_flush,
 	.clipboard_store      = wl_clipboard_store,

WINGs/wview_x11.c

@@ -206,7 +206,23 @@ static Bool x11_selection_acquire(void *vctx, W_View *view, Atom selection, Time
 
 static void x11_selection_release(void *vctx, W_View *view, Atom selection)
 {
-	(void)vctx; (void)view; (void)selection;
+	W_Screen *scr = (W_Screen *)vctx;
+	Display *dpy = scr->display;
+	Window win = W_VIEW_DRAWABLE(view);
+	XGrabServer(dpy);
+	if (XGetSelectionOwner(dpy, selection) == win)
+		XSetSelectionOwner(dpy, selection, None, CurrentTime);
+	XUngrabServer(dpy);
+}
+
+static Bool x11_selection_request(void *vctx, W_View *view, Atom selection, Atom target, Time timestamp)
+{
+	W_Screen *scr = (W_Screen *)vctx;
+	Display *dpy = scr->display;
+	if (XGetSelectionOwner(dpy, selection) == None)
+		return False;
+	return XConvertSelection(dpy, selection, target,
+				 scr->clipboardAtom, W_VIEW_DRAWABLE(view), timestamp) != 0;
 }
 
 static void x11_clipboard_store(void *vctx, const char *text, int len)
@@ -547,6 +563,7 @@ const W_ViewBackend W_ViewBackendX11 = {
 	.get_screen_position  = x11_get_screen_position,
 	.selection_acquire    = x11_selection_acquire,
 	.selection_release    = x11_selection_release,
+	.selection_request    = x11_selection_request,
 	.platform_init        = W_X11PlatformInit,
 	.flush                = x11_flush,
 	.clipboard_store      = x11_clipboard_store,