tdkpin/original/reconstructed/tdkpin_object_windows.c

/*
 * Borland ObjectWindows callback bootstrap reconstructed from TDKPIN.EXE.
 *
 * Target: a9022f1894e3e6e21fc42e8f6c932f7c549ca77f63aaa0c488bb9d55d9d0174c
 * Functions: 1018:0045 and 1018:018b (NE export ordinals 208 and 211)
 */

#include "tdkpin_object_windows.h"
#include "tdkpin_borland_runtime.h"

enum {
    OBJECT_WINDOW_VMT_OFFSET = 0,
    OBJECT_WINDOW_HANDLE_OFFSET = 4,
    OBJECT_WINDOW_BOUND_PROC_OFFSET = 0x12,
    WIN16_GWL_WNDPROC = -4,
    DGROUP_OBJECT_SELECTOR_PROPERTY = 0x067a, /* "OW1" */
    DGROUP_OBJECT_OFFSET_PROPERTY = 0x067e,   /* "OW2" */
};

enum {
    VMT_MESSAGE_TABLE_OFFSET = 4,
    VMT_DEFAULT_MESSAGE_SLOT = 0x0c,
    MESSAGE_TABLE_PARENT_OFFSET = 0,
    MESSAGE_TABLE_CACHE_ID_OFFSET = 2,
    MESSAGE_TABLE_CACHE_SLOT_OFFSET = 4,
    MESSAGE_TABLE_COUNT_OFFSET = 6,
    MESSAGE_TABLE_IDS_OFFSET = 8,
};

/* DGROUP 1028:0676/0678; valid only while CreateWindow16 is in progress. */
extern Win16FarPtr g_object_windows_creating_object;

LRESULT16 SetWindowLong16(HWND16 window, INT16 index, int32_t value);
BOOL16 SetProp16(HWND16 window, Win16FarPtr name, Win16Handle value);
Win16Handle RemoveProp16(HWND16 window, Win16FarPtr name);
Win16Handle GetProp16(HWND16 window, Win16FarPtr name);
BOOL16 IsWindow16(HWND16 window);
int32_t GetWindowLong16(HWND16 window, INT16 index);

/*
 * 1018:0045 — associate a far ObjectWindows object with one HWND.
 *
 * Win16 SetProp stores only a 16-bit HANDLE, so ObjectWindows deliberately
 * splits the far pointer into two properties. OW1 holds the selector and OW2
 * holds the offset; the inverse lookup routine recombines them.
 */
void object_windows_bind_window(HWND16 window, Win16FarPtr object)
{
    (void)SetProp16(
        window,
        win16_dgroup_pointer(DGROUP_OBJECT_SELECTOR_PROPERTY),
        win16_far_selector(object));
    (void)SetProp16(
        window,
        win16_dgroup_pointer(DGROUP_OBJECT_OFFSET_PROPERTY),
        win16_far_offset(object));
}

/* 1018:0071 — remove both halves of the HWND/object association. */
void object_windows_unbind_window(HWND16 window)
{
    (void)RemoveProp16(
        window, win16_dgroup_pointer(DGROUP_OBJECT_SELECTOR_PROPERTY));
    (void)RemoveProp16(
        window, win16_dgroup_pointer(DGROUP_OBJECT_OFFSET_PROPERTY));
}

/*
 * 1018:0097 — recover the bound ObjectWindows object for one HWND.
 * Generated thunks carry the object at +3/+5; subclassed/native procedures use
 * the OW1 selector and OW2 offset properties installed by 1018:0045.
 */
Win16FarPtr object_windows_object_from_window(HWND16 window)
{
    if (!IsWindow16(window)) {
        return 0;
    }

    Win16FarPtr procedure =
        (Win16FarPtr)GetWindowLong16(window, WIN16_GWL_WNDPROC);
    uint16_t procedure_offset = win16_far_offset(procedure);
    bool generated_thunk =
        win16_read_u8(procedure) == 0xe8 &&
        win16_read_u16(win16_far_add_offset(procedure, 1)) ==
            (uint16_t)(0xffff - procedure_offset) &&
        win16_read_u16(win16_make_far_pointer(
            win16_far_selector(procedure), 2)) == 0x2e5b;
    if (generated_thunk) {
        return win16_read_far_pointer(procedure, 3);
    }

    uint16_t selector = GetProp16(
        window, win16_dgroup_pointer(DGROUP_OBJECT_SELECTOR_PROPERTY));
    uint16_t offset = GetProp16(
        window, win16_dgroup_pointer(DGROUP_OBJECT_OFFSET_PROPERTY));
    return win16_make_far_pointer(selector, offset);
}

/*
 * 1018:018b — class bootstrap WNDPROC16.
 *
 * The initial class procedure is used for the first message only. It replaces
 * itself with the object's generated 7-byte bound thunk, publishes the HWND to
 * object association, then tail-dispatches the unchanged 10-byte WNDPROC frame.
 * AX:DX from that direct far call is returned unchanged.
 */
LRESULT16 object_window_bootstrap_proc(
    HWND16 window, UINT16 message, WPARAM16 wparam, LPARAM16 lparam)
{
    Win16FarPtr object = g_object_windows_creating_object;
    Win16FarPtr bound_proc =
        win16_read_far_pointer(object, OBJECT_WINDOW_BOUND_PROC_OFFSET);

    (void)SetWindowLong16(window, WIN16_GWL_WNDPROC, (int32_t)bound_proc);
    object_windows_bind_window(window, object);
    return win16_call_window_proc(bound_proc, window, message, wparam, lparam);
}

/*
 * 1018:0002 — resolve a nonnegative ObjectWindows message id.
 *
 * The most-derived VMT points at a linked dynamic-message table. Every node
 * contains a parent pointer, ids, and far handler slots in the same compact
 * layout as Borland dynamic methods. Unlike 1020:16e6, a miss selects a caller-
 * supplied VMT fallback slot, and a parent hit is cached in the most-derived
 * table rather than in the node where it was found.
 */
Win16FarPtr object_windows_resolve_message_handler(
    uint16_t vmt, uint16_t message, uint16_t fallback_slot)
{
    uint16_t root_table = win16_read_u16(win16_dgroup_pointer(
        (uint16_t)(vmt + VMT_MESSAGE_TABLE_OFFSET)));
    if (root_table == 0) {
        return win16_dgroup_pointer((uint16_t)(vmt + fallback_slot));
    }

    Win16FarPtr root = win16_dgroup_pointer(root_table);
    if (message == win16_read_u16(win16_far_add_offset(
                       root, MESSAGE_TABLE_CACHE_ID_OFFSET))) {
        uint16_t cached_slot = win16_read_u16(win16_far_add_offset(
            root, MESSAGE_TABLE_CACHE_SLOT_OFFSET));
        return win16_dgroup_pointer(cached_slot);
    }

    uint16_t table = root_table;
    while (table != 0) {
        Win16FarPtr node = win16_dgroup_pointer(table);
        uint16_t count = win16_read_u16(win16_far_add_offset(
            node, MESSAGE_TABLE_COUNT_OFFSET));
        for (uint16_t index = 0; index < count; index++) {
            uint16_t id = win16_read_u16(win16_far_add_offset(
                node,
                (uint16_t)(MESSAGE_TABLE_IDS_OFFSET + index * 2u)));
            if (id != message) {
                continue;
            }

            uint16_t slot = (uint16_t)(
                table + MESSAGE_TABLE_IDS_OFFSET + count * 2u +
                index * 4u);
            win16_write_u16(
                root, MESSAGE_TABLE_CACHE_ID_OFFSET, message);
            win16_write_u16(
                root, MESSAGE_TABLE_CACHE_SLOT_OFFSET, slot);
            return win16_dgroup_pointer(slot);
        }
        table = win16_read_u16(win16_far_add_offset(
            node, MESSAGE_TABLE_PARENT_OFFSET));
    }
    return win16_dgroup_pointer((uint16_t)(vmt + fallback_slot));
}

/* 1018:0103 — invoke the optional process-wide message instrumentation hook. */
void object_windows_call_message_hook(
    Win16FarPtr object,
    Win16FarPtr handler,
    const ObjectWindowsMessage *message)
{
    win16_call_object_message_hook(
        g_object_windows_message_hook,
        object,
        handler,
        message->window,
        message->message,
        message->wparam,
        message->lparam);
}

/*
 * 1018:0133 — shared WNDPROC16/DLGPROC16 reached by every generated thunk.
 * The thunk supplies ES:BX = object. The Pascal Win16 argument order places
 * HWND at BP+0e and LPARAM at BP+06/+08; the explicit C signature restores the
 * logical API order while preserving all original field widths.
 */
LRESULT16 object_dispatch_window_or_dialog_proc(
    Win16FarPtr object,
    HWND16 window,
    UINT16 message,
    WPARAM16 wparam,
    LPARAM16 lparam)
{
    win16_write_u16(object, OBJECT_WINDOW_HANDLE_OFFSET, window);
    ObjectWindowsMessage record = {
        .window = window,
        .message = message,
        .wparam = wparam,
        .lparam = lparam,
        .result = 1,
    };

    uint16_t vmt = win16_read_u16(win16_far_add_offset(
        object, OBJECT_WINDOW_VMT_OFFSET));
    Win16FarPtr handler_slot;
    if ((int16_t)message < 0) {
        handler_slot = win16_dgroup_pointer(
            (uint16_t)(vmt + VMT_DEFAULT_MESSAGE_SLOT));
    } else {
        handler_slot = object_windows_resolve_message_handler(
            vmt, message, VMT_DEFAULT_MESSAGE_SLOT);
    }
    Win16FarPtr handler = win16_read_far_pointer(handler_slot, 0);

    if (win16_far_selector(g_object_windows_message_hook) != 0) {
        object_windows_call_message_hook(object, handler, &record);
    }
    win16_call_object_message_handler(handler, object, &record);
    return record.result;
}

/*
 * 1018:08c3 — generic ObjectWindows event dispatch used by command/focus/menu
 * paths. DX supplies the fallback VMT slot and AX the dynamic method id. The
 * existing far event record is passed unchanged to the selected handler.
 */
void object_windows_dispatch_event(
    uint16_t fallback_slot,
    uint16_t method_id,
    Win16FarPtr event,
    Win16FarPtr object)
{
    uint16_t vmt = win16_read_u16(object);
    Win16FarPtr handler_slot = object_windows_resolve_message_handler(
        vmt, method_id, fallback_slot);
    Win16FarPtr handler = win16_read_far_pointer(handler_slot, 0);

    if (win16_far_selector(g_object_windows_message_hook) != 0) {
        ObjectWindowsMessage hook_record = {
            .window = win16_read_u16(event),
            .message = win16_read_u16(win16_far_add_offset(event, 2)),
            .wparam = win16_read_u16(win16_far_add_offset(event, 4)),
            .lparam = (LPARAM16)(uint32_t)(
                win16_read_u16(win16_far_add_offset(event, 6)) |
                ((uint32_t)win16_read_u16(
                     win16_far_add_offset(event, 8))
                 << 16)),
            .result = 0,
        };
        object_windows_call_message_hook(object, handler, &hook_record);
    }
    win16_call_object_event_handler(handler, object, event);
}

enum {
    BOUND_THUNK_POOL_BYTES = 0x0100,
    BOUND_THUNK_SHARED_CODE_OFFSET = 2,
    BOUND_THUNK_SHARED_CODE_BYTES = 5,
    BOUND_THUNK_DISPATCH_PROC_OFFSET = 7,
    BOUND_THUNK_FIRST_OFFSET = 0x000b,
    BOUND_THUNK_BYTES = 7,
    BOUND_THUNK_OBJECT_OFFSET = 3,
    DGROUP_BOUND_THUNK_TEMPLATE = 0x0686,
};

static void write_far_pointer(
    Win16FarPtr destination, uint16_t byte_offset, Win16FarPtr value)
{
    win16_write_u16(destination, byte_offset, win16_far_offset(value));
    win16_write_u16(
        destination,
        (uint16_t)(byte_offset + 2),
        win16_far_selector(value));
}

/*
 * Build one 256-byte executable block. Offset 2 contains the shared sequence
 * `POP BX; CS: LES BX,[BX]; JMP FAR dispatch_proc`. Each seven-byte thunk is
 * `CALL block:0002` followed by a mutable far object/free-list pointer. The
 * near displacement -1-offset makes every CALL land at block offset 2.
 */
static void allocate_bound_thunk_pool(void)
{
    HGLOBAL16 allocation = GlobalAlloc16(0, BOUND_THUNK_POOL_BYTES);
    Win16FarPtr block = GlobalLock16(allocation);
    uint16_t selector = win16_far_selector(block);

    win16_write_u16(block, 0, g_object_windows_thunk_code_selector);
    borland_move_bytes(
        win16_far_add_offset(block, BOUND_THUNK_SHARED_CODE_OFFSET),
        win16_dgroup_pointer(DGROUP_BOUND_THUNK_TEMPLATE),
        BOUND_THUNK_SHARED_CODE_BYTES);
    write_far_pointer(
        block,
        BOUND_THUNK_DISPATCH_PROC_OFFSET,
        g_object_windows_dispatch_proc);

    uint16_t offset = BOUND_THUNK_FIRST_OFFSET;
    do {
        Win16FarPtr thunk = win16_make_far_pointer(selector, offset);
        win16_write_u8(thunk, 0xe8);
        win16_write_u16(
            thunk, 1, (uint16_t)(0xffffu - offset));
        write_far_pointer(
            thunk, BOUND_THUNK_OBJECT_OFFSET, g_object_windows_free_thunk);
        g_object_windows_free_thunk = thunk;
        offset = (uint16_t)(offset + BOUND_THUNK_BYTES);
    } while (offset != BOUND_THUNK_POOL_BYTES);

    g_object_windows_thunk_code_selector = selector;
    (void)PrestoChangoSelector16(selector, selector);
}

/*
 * 1018:01dc — pop a generated WNDPROC thunk and bind its embedded far object.
 * Executable selectors are modified only through a temporary CS-to-DS alias.
 */
Win16FarPtr object_windows_allocate_bound_thunk(Win16FarPtr object)
{
    if (g_object_windows_free_thunk == 0) {
        allocate_bound_thunk_pool();
    }

    Win16FarPtr thunk = g_object_windows_free_thunk;
    uint16_t alias =
        AllocCStoDSAlias16(win16_far_selector(thunk));
    Win16FarPtr writable = win16_make_far_pointer(
        alias, win16_far_offset(thunk));
    g_object_windows_free_thunk =
        win16_read_far_pointer(writable, BOUND_THUNK_OBJECT_OFFSET);
    write_far_pointer(writable, BOUND_THUNK_OBJECT_OFFSET, object);
    (void)FreeSelector16(alias);
    return thunk;
}

/* 1018:02fa — push one bound WNDPROC thunk back onto the global free list. */
void object_windows_release_bound_thunk(Win16FarPtr thunk)
{
    uint16_t alias =
        AllocCStoDSAlias16(win16_far_selector(thunk));
    Win16FarPtr writable = win16_make_far_pointer(
        alias, win16_far_offset(thunk));
    write_far_pointer(
        writable,
        BOUND_THUNK_OBJECT_OFFSET,
        g_object_windows_free_thunk);
    (void)FreeSelector16(alias);
    g_object_windows_free_thunk = thunk;
}