Make examples folder somewhat more focused

examples/gui.c

@@ -7,9 +7,73 @@
 │   • http://creativecommons.org/publicdomain/zero/1.0/            │
 ╚─────────────────────────────────────────────────────────────────*/
 #endif
+#include "libc/dce.h"
+#include "libc/nexgen32e/nt2sysv.h"
+#include "libc/nt/dll.h"
+#include "libc/nt/enum/cw.h"
 #include "libc/nt/enum/mb.h"
+#include "libc/nt/enum/sw.h"
+#include "libc/nt/enum/wm.h"
+#include "libc/nt/enum/ws.h"
+#include "libc/nt/events.h"
 #include "libc/nt/messagebox.h"
+#include "libc/nt/struct/msg.h"
+#include "libc/nt/struct/wndclass.h"
+#include "libc/nt/windows.h"
+#include "libc/stdio/stdio.h"
+#include "libc/str/str.h"
+
+/**
+ * @fileoverview GUI Example
+ *
+ * Cosmopolitan has had a razor sharp focus on making sockets and stdio
+ * work well across platforms. When you call a function like read(), it
+ * will just work on platforms like Windows too. In order to do that we
+ * need to support the WIN32 API, which you can use, but please note it
+ * isn't polyfilled on other platforms in the same way as POSIX APIs.
+ */
+
+static const char16_t kClassName[] = u"cosmopolitan";
+
+static int64_t WindowProc(int64_t hwnd, uint32_t uMsg, uint64_t wParam,
+                          int64_t lParam) {
+  switch (uMsg) {
+    case kNtWmDestroy:
+      PostQuitMessage(0);
+      return 0;
+    default:
+      return DefWindowProc(hwnd, uMsg, wParam, lParam);
+  }
+}
+
+static void Gui(void) {
+  int64_t h;
+  struct NtMsg msg;
+  struct NtWndClass wc;
+  memset(&wc, 0, sizeof(wc));
+  wc.lpfnWndProc = NT2SYSV(WindowProc);
+  wc.hInstance = GetModuleHandle(NULL);
+  wc.lpszClassName = kClassName;
+  RegisterClass(&wc);
+  h = CreateWindowEx(0, kClassName, u"Hello Cosmopolitan",
+                     kNtWsOverlappedwindow, kNtCwUsedefault, kNtCwUsedefault,
+                     kNtCwUsedefault, kNtCwUsedefault, 0, 0, wc.hInstance, 0);
+  ShowWindow(h, kNtSwNormal);
+  /*
+   * NOTE: Cosmopolitan linker script is hard-coded to change the
+   *       subsystem from CUI to GUI when GetMessage() is linked.
+   */
+  while (GetMessage(&msg, 0, 0, 0)) {
+    TranslateMessage(&msg);
+    DispatchMessage(&msg);
+  }
+}
 
 int main(int argc, char *argv[]) {
-  return MessageBox(0, u"hello world", u"cosmopolitan", kNtMbOk) ? 0 : 1;
+  if (!IsWindows()) {
+    fputs("Sorry! This GUI demo only runs on Windows\n", stderr);
+    fputs("https://github.com/jart/cosmopolitan/issues/57\n", stderr);
+    return 1;
+  }
+  Gui();
 }