all: Replace tagged unions with a more traditional object model

This rewrites the bulk of Waffle's code.

When I first began writing Waffle, I wanted to experiment with
a non-traditional object model that used tagged unions. Very soon I began
to abhor the "innovative" decision. This patch replaces the tagged-union
model with a more traditional object model (as found in the Linux kernel
[1], Google's NaCl, libdrm, and many other places) that uses vtables and
embedded structures.

[1] Neil Brown. LWN, 2011 June 1. Object-oriented design patterns in the kernel.
    (Part 1: http://lwn.net/Articles/444910/).
    (Part 2: http://lwn.net/Articles/446317/).

As an example of the new object model, below is an outline of how
waffle_window_swap_buffers() is now implemeneted.

// file: waffle_window.c

bool
waffle_window_swap_buffers(struct waffle_window *self)
{
    struct wcore_window *wc_self = wcore_window(self); // safe cast
    // Check preconditions ...
    return wc_self->vtbl->swap_buffers(wc_self);
}

// file: wcore_window.h

struct wcore_window_vtbl {
    bool
    (*swap_buffers)(struct wcore_window *self);
    // More member functions ...
};

struct wcore_window {
    const struct wcore_window_vtbl *vtbl;
    struct waffle_window {} wfl;
    // More members ...
};

// file: glx_window.h

struct glx_window {
    struct wcore_window wcore;
    // More members ...
};

// file: glx_window.c

static bool
glx_window_swap_buffers(struct wcore_window *wc_self)
{
    struct glx_window *self = glx_window(wc_self); // safe cast
    // Call glXSwapBuffers ...
    return true;
}

static const struct wcore_window_vtbl glx_window_wcore_vtbl = {
    .swap_buffers = glx_window_swap_buffers,
    // More members ...
};

Signed-off-by: Chad Versace <chad.versace@linux.intel.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/src/waffle/core/wcore_window.h b/src/waffle/core/wcore_window.h
new file mode 100644
index 0000000..c642e80
--- /dev/null
+++ b/src/waffle/core/wcore_window.h
@@ -0,0 +1,80 @@
+// Copyright 2012 Intel Corporation
+//
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are met:
+//
+// - Redistributions of source code must retain the above copyright notice, this
+//   list of conditions and the following disclaimer.
+//
+// - Redistributions in binary form must reproduce the above copyright notice,
+//   this list of conditions and the following disclaimer in the documentation
+//   and/or other materials provided with the distribution.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdlib.h>
+
+#include "wcore_config.h"
+#include "wcore_util.h"
+
+struct wcore_window;
+
+struct wcore_window_vtbl {
+    bool
+    (*destroy)(struct wcore_window *self);
+
+    bool
+    (*show)(struct wcore_window *self);
+
+    bool
+    (*swap_buffers)(struct wcore_window *self);
+};
+
+struct wcore_window {
+    const struct wcore_window_vtbl *vtbl;
+
+    struct waffle_window {} wfl;
+    struct api_object api;
+
+    struct wcore_display *display;
+};
+
+DEFINE_CONTAINER_CAST_FUNC(wcore_window,
+                           struct wcore_window,
+                           struct waffle_window,
+                           wfl)
+
+
+static inline bool
+wcore_window_init(struct wcore_window *self,
+                  struct wcore_config *config)
+{
+    assert(self);
+    assert(config);
+
+    self->api.display_id = config->display->api.display_id;
+    self->display = config->display;
+
+    return true;
+}
+
+static inline bool
+wcore_window_teardown(struct wcore_window *self)
+{
+    assert(self);
+    return true;
+}