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, 0 insertions, 7 deletions

diff --git a/include/waffle/waffle_init.h b/include/waffle/waffle_init.h
index 086de27..c52c90d 100644
--- a/include/waffle/waffle_init.h
+++ b/include/waffle/waffle_init.h
@@ -90,13 +90,6 @@ extern "C" {
 WAFFLE_API bool
 waffle_init(const int32_t *attrib_list);
 
-/// @brief Get the platform given to waffle_init().
-///
-/// This may be called before waffle_init(), in which `WAFFLE_NONE`
-/// is returned. Otherwise, one of `WAFFLE_PLATFORM_*` is returned.
-WAFFLE_API int32_t
-waffle_get_platform(void);
-
 #ifdef __cplusplus
 } // end extern "C"
 #endif