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, 19 insertions, 19 deletions

diff --git a/src/waffle/x11_egl/xegl_display.h b/src/waffle/x11_egl/xegl_display.h
index 68595d8..062f088 100644
--- a/src/waffle/x11_egl/xegl_display.h
+++ b/src/waffle/x11_egl/xegl_display.h
@@ -23,31 +23,31 @@
 // 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.
 
-/// @defgroup xegl_display xegl_display
-/// @ingroup xegl
-/// @{
-
-/// @file
-
 #pragma once
 
 #include <stdbool.h>
 #include <stdint.h>
 
-union native_display;
-union native_platform;
+#include <EGL/egl.h>
+#include <X11/Xlib-xcb.h>
+
+#include <waffle/core/wcore_display.h>
+#include <waffle/core/wcore_util.h>
+#include <waffle/x11/x11_display.h>
 
-union native_display*
-xegl_display_connect(
-        union native_platform *platform,
-        const char *name);
+struct wcore_platform;
 
-bool
-xegl_display_disconnect(union native_display *self);
+struct xegl_display {
+    struct wcore_display wcore;
+    struct x11_display x11;
+    EGLDisplay egl;
+};
 
-bool
-xegl_display_supports_context_api(
-        union native_display *self,
-        int32_t context_api);
+DEFINE_CONTAINER_CAST_FUNC(xegl_display,
+                           struct xegl_display,
+                           struct wcore_display,
+                           wcore)
 
-/// @}
+struct wcore_display*
+xegl_display_connect(struct wcore_platform *wc_plat,
+                     const char *name);