x11: Deal with window borders better.

- Cache the _NET_FRAME_EXTENTS data locally, so we don't have to query
the X server for them (instead, we update our cached data when PropertyNotify
events alert us to a change).

- Use our cached extents for X11_GetWindowBordersSize(), so it's a fast call.

- Window position was meant to refer to the client area, not the window
decorations, so adjust appropriately when getting/setting the position.

src/video/x11/SDL_x11events.c

@@ -835,37 +835,15 @@ X11_DispatchEvent(_THIS)
 
         /* Have we been resized or moved? */
     case ConfigureNotify:{
-            long border_left = 0;
-            long border_top = 0;
 #ifdef DEBUG_XEVENTS
             printf("window %p: ConfigureNotify! (position: %d,%d, size: %dx%d)\n", data,
                    xevent.xconfigure.x, xevent.xconfigure.y,
                    xevent.xconfigure.width, xevent.xconfigure.height);
 #endif
-            if (data->xwindow) {
-                Atom _net_frame_extents = X11_XInternAtom(display, "_NET_FRAME_EXTENTS", 0);
-                Atom type;
-                int format;
-                unsigned long nitems, bytes_after;
-                unsigned char *property;
-                if (X11_XGetWindowProperty(display, data->xwindow,
-                        _net_frame_extents, 0, 16, 0,
-                        XA_CARDINAL, &type, &format,
-                        &nitems, &bytes_after, &property) == Success) {
-                    if (type != None && nitems == 4)
-                    {
-                        border_left = ((long*)property)[0];
-                        border_top = ((long*)property)[2];
-                    }
-                    X11_XFree(property);
-                }
-            }
-
             if (xevent.xconfigure.x != data->last_xconfigure.x ||
                 xevent.xconfigure.y != data->last_xconfigure.y) {
                 SDL_SendWindowEvent(data->window, SDL_WINDOWEVENT_MOVED,
-                                    xevent.xconfigure.x - border_left,
-                                    xevent.xconfigure.y - border_top);
+                                    xevent.xconfigure.x, xevent.xconfigure.y);
 #ifdef SDL_USE_IBUS
                 if(SDL_GetEventState(SDL_TEXTINPUT) == SDL_ENABLE){
                     /* Update IBus candidate list position */
@@ -1175,6 +1153,24 @@ X11_DispatchEvent(_THIS)
                    right approach, but it seems to work. */
                 X11_UpdateKeymap(_this);
                 SDL_SendKeymapChangedEvent();
+            } else if (xevent.xproperty.atom == videodata->_NET_FRAME_EXTENTS) {
+                Atom type;
+                int format;
+                unsigned long nitems, bytes_after;
+                unsigned char *property;
+                if (X11_XGetWindowProperty(display, data->xwindow, videodata->_NET_FRAME_EXTENTS, 0, 16, 0, XA_CARDINAL, &type, &format, &nitems, &bytes_after, &property) == Success) {
+                    if (type != None && nitems == 4) {
+                        data->border_left = (int) ((long*)property)[0];
+                        data->border_right = (int) ((long*)property)[1];
+                        data->border_top = (int) ((long*)property)[2];
+                        data->border_bottom = (int) ((long*)property)[3];
+                    }
+                    X11_XFree(property);
+
+                    #ifdef DEBUG_XEVENTS
+                    printf("New _NET_FRAME_EXTENTS: left=%d right=%d, top=%d, bottom=%d\n", data->border_left, data->border_right, data->border_top, data->border_bottom);
+                    #endif
+                }
             }
         }
         break;

src/video/x11/SDL_x11video.c

@@ -414,6 +414,7 @@ X11_VideoInit(_THIS)
     GET_ATOM(_NET_WM_WINDOW_OPACITY);
     GET_ATOM(_NET_WM_USER_TIME);
     GET_ATOM(_NET_ACTIVE_WINDOW);
+    GET_ATOM(_NET_FRAME_EXTENTS);
     GET_ATOM(UTF8_STRING);
     GET_ATOM(PRIMARY);
     GET_ATOM(XdndEnter);

src/video/x11/SDL_x11video.h

@@ -108,6 +108,7 @@ typedef struct SDL_VideoData
     Atom _NET_WM_WINDOW_OPACITY;
     Atom _NET_WM_USER_TIME;
     Atom _NET_ACTIVE_WINDOW;
+    Atom _NET_FRAME_EXTENTS;
     Atom UTF8_STRING;
     Atom PRIMARY;
     Atom XdndEnter;

src/video/x11/SDL_x11window.c

@@ -781,7 +781,7 @@ X11_SetWindowPosition(_THIS, SDL_Window * window)
     SDL_WindowData *data = (SDL_WindowData *) window->driverdata;
     Display *display = data->videodata->display;
 
-    X11_XMoveWindow(display, data->xwindow, window->x, window->y);
+    X11_XMoveWindow(display, data->xwindow, window->x + data->border_left, window->y + data->border_top);
     X11_XFlush(display);
 }
 
@@ -898,28 +898,13 @@ int
 X11_GetWindowBordersSize(_THIS, SDL_Window * window, int *top, int *left, int *bottom, int *right)
 {
     SDL_WindowData *data = (SDL_WindowData *)window->driverdata;
-    Display *display = data->videodata->display;
-    Atom _NET_FRAME_EXTENTS = X11_XInternAtom(display, "_NET_FRAME_EXTENTS", 0);
-    Atom type;
-    int format;
-    unsigned long nitems, bytes_after;
-    unsigned char *property;
-    int result = -1;
-
-    if (X11_XGetWindowProperty(display, data->xwindow, _NET_FRAME_EXTENTS,
-                               0, 16, 0, XA_CARDINAL, &type, &format,
-                               &nitems, &bytes_after, &property) == Success) {
-        if (type != None && nitems == 4) {
-            *left = (int) (((long*)property)[0]);
-            *right = (int) (((long*)property)[1]);
-            *top = (int) (((long*)property)[2]);
-            *bottom = (int) (((long*)property)[3]);
-            result = 0;
-        }
-        X11_XFree(property);
-    }
 
-    return result;
+    *left = data->border_left;
+    *right = data->border_right;
+    *top = data->border_top;
+    *bottom = data->border_bottom;
+
+    return 0;
 }
 
 int

src/video/x11/SDL_x11window.h

@@ -56,6 +56,10 @@ typedef struct
     GC gc;
     XIC ic;
     SDL_bool created;
+    int border_left;
+    int border_right;
+    int border_top;
+    int border_bottom;
     PendingFocusEnum pending_focus;
     Uint32 pending_focus_time;
     XConfigureEvent last_xconfigure;