Add Xlib support to viewer

tools/viewer/sk_app/unix/main_unix.cpp

+/*
+* Copyright 2016 Google Inc.
+*
+* Use of this source code is governed by a BSD-style license that can be
+* found in the LICENSE file.
+*/
+
+#include "SkTypes.h"
+#include "Timer.h"
+#include "Window_unix.h"
+#include "../Application.h"
+
+using sk_app::Application;
+
+static double now_ms() { return SkTime::GetNSecs() * 1e-6; }
+
+int main(int argc, char**argv) {
+
+    Display* display = XOpenDisplay(nullptr);
+
+    Application* app = Application::Create(argc, argv, (void*)display);
+
+    double currentTime = 0.0;
+    double previousTime = 0.0;
+
+    // Get the file descriptor for the X display
+    int x11_fd = ConnectionNumber(display);
+    fd_set in_fds;
+
+    bool done = false;
+    while (!done) {
+        // Create a file description set containing x11_fd
+        FD_ZERO(&in_fds);
+        FD_SET(x11_fd, &in_fds);
+
+        // Set a sleep timer
+        struct timeval tv;
+        tv.tv_usec = 100;
+        tv.tv_sec = 0;
+
+        // Wait for an event on the file descriptor or for timer expiration
+        (void) select(1, &in_fds, NULL, NULL, &tv);
+
+        // Handle XEvents (if any) and flush the input 
+        XEvent event;
+        while (XPending(display)) {
+            XNextEvent(display, &event);
+
+            sk_app::Window_unix* win = sk_app::Window_unix::gWindowMap.find(event.xany.window);
+            if (win->handleEvent(event)) {
+                done = true;
+                break;
+            }
+        }
+
+        previousTime = currentTime;
+        currentTime = now_ms();
+        app->onIdle(currentTime - previousTime);        
+    }
+
+    delete app;
+
+    XCloseDisplay(display);
+
+    return 0;
+}