Wait for EWMH WM to add _NET_SUPPORTING_WM_CHECK property, addresses #54

render.c

@@ -681,6 +681,8 @@ static struct gl_bind_src* lookup_bind_src(const char* str) {
 
 struct renderer* rd_new(const char** paths, const char* entry,
                         const char* force_mod, const char* force_backend) {
+
+    xwin_wait_for_wm();
     
     renderer* r = malloc(sizeof(struct renderer));
     *r = (struct renderer) {

xwin.c

@@ -8,6 +8,8 @@
 #include <limits.h>
 #include <errno.h>
 
+#include <time.h>
+
 #include <sys/ipc.h>
 #include <sys/shm.h>
 
@@ -53,6 +55,33 @@ static Window find_desktop(struct renderer* r) {
     return desktop;
 }
 
+void xwin_wait_for_wm(void) {
+    Display* d = XOpenDisplay(0);
+
+    Atom check = None;
+    bool exists = false;
+    struct timespec tv = { .tv_sec = 0, .tv_nsec = 50 * 1000000 };
+    
+     do {
+        if (check == None) {
+            check = XInternAtom(d, "_NET_SUPPORTING_WM_CHECK", true);
+        }
+        if (check) {
+            int num_prop, idx;
+            Atom* props = XListProperties(d, DefaultRootWindow(d), &num_prop);
+            for (idx = 0; idx < num_prop; ++idx) {
+                if (props[idx] == check) {
+                    exists = true;
+                    break;
+                }
+            } 
+        }
+        if (!exists) nanosleep(&tv, NULL);
+    } while (!exists);
+
+    XCloseDisplay(d);
+}
+
 bool xwin_should_render(struct renderer* rd) {
     bool ret = true, should_close = false;
     Display* d = rd_get_wcb(rd)->get_x11_display();

xwin.h

@@ -2,6 +2,7 @@
 #define XWIN_ALL_DESKTOPS 0xFFFFFFFF
 
 bool xwin_should_render(struct renderer* rd);
+void xwin_wait_for_wm(void);
 bool xwin_settype(struct gl_wcb* wcb, void* impl, const char* type);
 void xwin_setdesktop(struct gl_wcb* wcb, void* impl, unsigned long desktop);
 void xwin_addstate(struct gl_wcb* wcb, void* impl, const char* state);