linux: dynamically load libX11 (#20)

Removing linking of libX11 and replacing it with dlopen to call the
functions dynamically.
For the future wayland support, the library will not require the libX11
library to be installed on the running system.
For compiling it we need it, because of the huge and complicated type
definitions, but the compiled binary will run also on a system without
libX11.

References: #6
Signed-off-by: Vladimír Magyar <[email protected]>

Author: microo8

clipboard_linux.c

@@ -11,36 +11,86 @@
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
+#include <dlfcn.h>
 #include <X11/Xlib.h>
 #include <X11/Xatom.h>
 
 // syncStatus is a function from the Go side.
 extern void syncStatus(uintptr_t handle, int status);
 
+void *libX11;
+
+Display* (*P_XOpenDisplay)(int);
+void (*P_XCloseDisplay)(Display*);
+Window (*P_XDefaultRootWindow)(Display*);
+Window (*P_XCreateSimpleWindow)(Display*, Window, int, int, int, int, int, int, int);
+Atom (*P_XInternAtom)(Display*, char*, int);
+void (*P_XSetSelectionOwner)(Display*, Atom, Window, unsigned long);
+Window (*P_XGetSelectionOwner)(Display*, Atom);
+void (*P_XNextEvent)(Display*, XEvent*);
+int (*P_XChangeProperty)(Display*, Window, Atom, Atom, int, int, unsigned char*, int);
+void (*P_XSendEvent)(Display*, Window, int, long , XEvent*);
+int (*P_XGetWindowProperty) (Display*, Window, Atom, long, long, Bool, Atom, Atom*, int*, unsigned long *, unsigned long *, unsigned char **);
+void (*P_XFree) (void*);
+void (*P_XDeleteProperty) (Display*, Window, Atom);
+void (*P_XConvertSelection)(Display*, Atom, Atom, Atom, Window, Time);
+
+int initX11() {
+	if (libX11) {
+		return 1;
+	}
+	libX11 = dlopen("libX11.so", RTLD_LAZY);
+	if (!libX11) {
+		return -1;
+	}
+	P_XOpenDisplay = (Display* (*)(int)) dlsym(libX11, "XOpenDisplay");
+	P_XCloseDisplay = (void (*)(Display*)) dlsym(libX11, "XCloseDisplay");
+	P_XDefaultRootWindow = (Window (*)(Display*)) dlsym(libX11, "XDefaultRootWindow");
+	P_XCreateSimpleWindow = (Window (*)(Display*, Window, int, int, int, int, int, int, int)) dlsym(libX11, "XCreateSimpleWindow");
+	P_XInternAtom = (Atom (*)(Display*, char*, int)) dlsym(libX11, "XInternAtom");
+	P_XSetSelectionOwner = (void (*)(Display*, Atom, Window, unsigned long)) dlsym(libX11, "XSetSelectionOwner");
+	P_XGetSelectionOwner = (Window (*)(Display*, Atom)) dlsym(libX11, "XGetSelectionOwner");
+	P_XNextEvent = (void (*)(Display*, XEvent*)) dlsym(libX11, "XNextEvent");
+	P_XChangeProperty = (int (*)(Display*, Window, Atom, Atom, int, int, unsigned char*, int)) dlsym(libX11, "XChangeProperty");
+	P_XSendEvent = (void (*)(Display*, Window, int, long , XEvent*)) dlsym(libX11, "XSendEvent");
+	P_XGetWindowProperty = (int (*)(Display*, Window, Atom, long, long, Bool, Atom, Atom*, int*, unsigned long *, unsigned long *, unsigned char **)) dlsym(libX11, "XGetWindowProperty");
+	P_XFree = (void (*)(void*)) dlsym(libX11, "XFree");
+	P_XDeleteProperty = (void (*)(Display*, Window, Atom)) dlsym(libX11, "XDeleteProperty");
+	P_XConvertSelection = (void (*)(Display*, Atom, Atom, Atom, Window, Time)) dlsym(libX11, "XConvertSelection");
+	return 1;
+}
+
 int clipboard_test() {
+	if (!initX11()) {
+		return -1;
+	}
+
     Display* d = NULL;
     for (int i = 0; i < 42; i++) {
-        d = XOpenDisplay(0);
+        d = (*P_XOpenDisplay)(0);
         if (d == NULL) {
             continue;
         }
         break;
     }
-
     if (d == NULL) {
         return -1;
     }
-    XCloseDisplay(d);
+    (*P_XCloseDisplay)(d);
     return 0;
 }
 
 // clipboard_write writes the given buf of size n as type typ.
 // if start is provided, the value of start will be changed to 1 to indicate
 // if the write is availiable for reading.
 int clipboard_write(char *typ, unsigned char *buf, size_t n, uintptr_t handle) {
+	if (!initX11()) {
+		return -1;
+	}
+
     Display* d = NULL;
     for (int i = 0; i < 42; i++) {
-        d = XOpenDisplay(0);
+        d = (*P_XOpenDisplay)(0);
         if (d == NULL) {
             continue;
         }
@@ -50,26 +100,25 @@ int clipboard_write(char *typ, unsigned char *buf, size_t n, uintptr_t handle) {
         syncStatus(handle, -1);
         return -1;
     }
-
-    Window w = XCreateSimpleWindow(d, DefaultRootWindow(d), 0, 0, 1, 1, 0, 0, 0);
+    Window w = (*P_XCreateSimpleWindow)(d, (*P_XDefaultRootWindow)(d), 0, 0, 1, 1, 0, 0, 0);
 
     // Use False because these may not available for the first time.
-    Atom sel         = XInternAtom(d, "CLIPBOARD", False);
-    Atom atomString  = XInternAtom(d, "UTF8_STRING", False);
-    Atom atomImage   = XInternAtom(d, "image/png", False);
-    Atom targetsAtom = XInternAtom(d, "TARGETS", False);
+    Atom sel         = (*P_XInternAtom)(d, "CLIPBOARD", 0);
+    Atom atomString  = (*P_XInternAtom)(d, "UTF8_STRING", 0);
+    Atom atomImage   = (*P_XInternAtom)(d, "image/png", 0);
+    Atom targetsAtom = (*P_XInternAtom)(d, "TARGETS", 0);
 
     // Use True to makesure the requested type is a valid type.
-    Atom target = XInternAtom(d, typ, True);
+    Atom target = (*P_XInternAtom)(d, typ, 1);
     if (target == None) {
-        XCloseDisplay(d);
+        (*P_XCloseDisplay)(d);
         syncStatus(handle, -2);
         return -2;
     }
 
-    XSetSelectionOwner(d, sel, w, CurrentTime);
-    if (XGetSelectionOwner(d, sel) != w) {
-        XCloseDisplay(d);
+    (*P_XSetSelectionOwner)(d, sel, w, CurrentTime);
+    if ((*P_XGetSelectionOwner)(d, sel) != w) {
+        (*P_XCloseDisplay)(d);
         syncStatus(handle, -3);
         return -3;
     }
@@ -83,13 +132,13 @@ int clipboard_write(char *typ, unsigned char *buf, size_t n, uintptr_t handle) {
             notified = 1;
         }
 
-        XNextEvent(d, &event);
+        (*P_XNextEvent)(d, &event);
         switch (event.type) {
         case SelectionClear:
             // For debugging:
             // printf("x11write: lost ownership of clipboard selection.\n");
             // fflush(stdout);
-            XCloseDisplay(d);
+            (*P_XCloseDisplay)(d);
             return 0;
         case SelectionNotify:
             // For debugging:
@@ -114,24 +163,24 @@ int clipboard_write(char *typ, unsigned char *buf, size_t n, uintptr_t handle) {
             ev.property  = xsr->property;
 
             if (ev.target == atomString && ev.target == target) {
-                R = XChangeProperty(ev.display, ev.requestor, ev.property,
+                R = (*P_XChangeProperty)(ev.display, ev.requestor, ev.property,
                     atomString, 8, PropModeReplace, buf, n);
             } else if (ev.target == atomImage && ev.target == target) {
-                R = XChangeProperty(ev.display, ev.requestor, ev.property,
+                R = (*P_XChangeProperty)(ev.display, ev.requestor, ev.property,
                     atomImage, 8, PropModeReplace, buf, n);
             } else if (ev.target == targetsAtom) {
                 // Reply atoms for supported targets, other clients should
                 // request the clipboard again and obtain the data if their
                 // implementation is correct.
                 Atom targets[] = { atomString, atomImage };
-                R = XChangeProperty(ev.display, ev.requestor, ev.property,
+                R = (*P_XChangeProperty)(ev.display, ev.requestor, ev.property,
                     XA_ATOM, 32, PropModeReplace,
                     (unsigned char *)&targets, sizeof(targets)/sizeof(Atom));
             } else {
                 ev.property = None;
             }
 
-            if ((R & 2) == 0) XSendEvent(d, ev.requestor, 0, 0, (XEvent *)&ev);
+            if ((R & 2) == 0) (*P_XSendEvent)(d, ev.requestor, 0, 0, (XEvent *)&ev);
             break;
         }
     }
@@ -140,6 +189,10 @@ int clipboard_write(char *typ, unsigned char *buf, size_t n, uintptr_t handle) {
 // read_data reads the property of a selection if the target atom matches
 // the actual atom.
 unsigned long read_data(XSelectionEvent *sev, Atom sel, Atom prop, Atom target, char **buf) {
+	if (!initX11()) {
+		return -1;
+	}
+
     unsigned char *data;
     Atom actual;
     int format;
@@ -149,7 +202,7 @@ unsigned long read_data(XSelectionEvent *sev, Atom sel, Atom prop, Atom target,
         return 0;
     }
 
-    int ret = XGetWindowProperty(sev->display, sev->requestor, sev->property,
+    int ret = (*P_XGetWindowProperty)(sev->display, sev->requestor, sev->property,
         0L, (~0L), 0, AnyPropertyType, &actual, &format, &size, &n, &data);
     if (ret != Success) {
         return 0;
@@ -159,8 +212,8 @@ unsigned long read_data(XSelectionEvent *sev, Atom sel, Atom prop, Atom target,
         *buf = (char *)malloc(size * sizeof(char));
         memcpy(*buf, data, size*sizeof(char));
     }
-    XFree(data);
-    XDeleteProperty(sev->display, sev->requestor, sev->property);
+    (*P_XFree)(data);
+    (*P_XDeleteProperty)(sev->display, sev->requestor, sev->property);
     return size * sizeof(char);
 }
 
@@ -169,9 +222,13 @@ unsigned long read_data(XSelectionEvent *sev, Atom sel, Atom prop, Atom target,
 //
 // The caller of this function should responsible for the free of the buf.
 unsigned long clipboard_read(char* typ, char **buf) {
+	if (!initX11()) {
+		return -1;
+	}
+
     Display* d = NULL;
     for (int i = 0; i < 42; i++) {
-        d = XOpenDisplay(0);
+        d = (*P_XOpenDisplay)(0);
         if (d == NULL) {
             continue;
         }
@@ -181,27 +238,27 @@ unsigned long clipboard_read(char* typ, char **buf) {
         return -1;
     }
 
-    Window w = XCreateSimpleWindow(d, DefaultRootWindow(d), 0, 0, 1, 1, 0, 0, 0);
+    Window w = (*P_XCreateSimpleWindow)(d, (*P_XDefaultRootWindow)(d), 0, 0, 1, 1, 0, 0, 0);
 
     // Use False because these may not available for the first time.
-    Atom sel  = XInternAtom(d, "CLIPBOARD", False);
-    Atom prop = XInternAtom(d, "GOLANG_DESIGN_DATA", False);
+    Atom sel  = (*P_XInternAtom)(d, "CLIPBOARD", False);
+    Atom prop = (*P_XInternAtom)(d, "GOLANG_DESIGN_DATA", False);
 
     // Use True to makesure the requested type is a valid type.
-    Atom target = XInternAtom(d, typ, True);
+    Atom target = (*P_XInternAtom)(d, typ, True);
     if (target == None) {
-        XCloseDisplay(d);
+        (*P_XCloseDisplay)(d);
         return -2;
     }
 
-    XConvertSelection(d, sel, target, prop, w, CurrentTime);
+    (*P_XConvertSelection)(d, sel, target, prop, w, CurrentTime);
     XEvent event;
     for (;;) {
-        XNextEvent(d, &event);
+        (*P_XNextEvent)(d, &event);
         if (event.type != SelectionNotify) continue;
         break;
     }
     unsigned long n = read_data((XSelectionEvent *)&event.xselection, sel, prop, target, buf);
-    XCloseDisplay(d);
+    (*P_XCloseDisplay)(d);
     return n;
-}
+}

clipboard_linux.go

@@ -10,14 +10,11 @@
 package clipboard
 
 /*
-#cgo LDFLAGS: -lX11
+#cgo LDFLAGS: -ldl
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdint.h>
 #include <string.h>
-#include <X11/Xlib.h>
-#include <X11/Xatom.h>
-#include <stdatomic.h>
 
 int clipboard_test();
 int clipboard_write(