src/video/dos/SDL_dosmouse.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2026 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_internal.h"

#ifdef SDL_VIDEO_DRIVER_DOSVESA

// https://stanislavs.org/helppc/int_33.html

#include "SDL_dosmouse.h"
#include "SDL_dosvideo.h"

#include "../../events/SDL_mouse_c.h"
#include "../../events/default_cursor.h"
#include "../SDL_sysvideo.h"

// Create a cursor from a surface
static SDL_Cursor *DOSVESA_CreateCursor(SDL_Surface *surface, int hot_x, int hot_y)
{
    SDL_CursorData *curdata;
    SDL_Cursor *cursor;

    SDL_assert(surface->format == SDL_PIXELFORMAT_ARGB8888);
    SDL_assert(surface->pitch == surface->w * 4);

    cursor = (SDL_Cursor *)SDL_calloc(1, sizeof(*cursor));
    if (!cursor) {
        return NULL;
    }
    curdata = (SDL_CursorData *)SDL_calloc(1, sizeof(*curdata));
    if (!curdata) {
        SDL_free(cursor);
        return NULL;
    }

    curdata->surface = SDL_DuplicateSurface(surface);
    if (!curdata->surface) {
        SDL_free(curdata);
        SDL_free(cursor);
        return NULL;
    }

    SDL_SetSurfaceBlendMode(curdata->surface, SDL_BLENDMODE_BLEND);

    curdata->hot_x = hot_x;
    curdata->hot_y = hot_y;
    curdata->w = surface->w;
    curdata->h = surface->h;

    cursor->internal = curdata;

    return cursor;
}

static SDL_Cursor *DOSVESA_CreateDefaultCursor(void)
{
    return SDL_CreateCursor(default_cdata, default_cmask, DEFAULT_CWIDTH, DEFAULT_CHEIGHT, DEFAULT_CHOTX, DEFAULT_CHOTY);
}

// Show the specified cursor, or hide if cursor is NULL
static bool DOSVESA_ShowCursor(SDL_Cursor *cursor)
{
    return true; // we handle this elsewhere.
}

// Free a window manager cursor
static void DOSVESA_FreeCursor(SDL_Cursor *cursor)
{
    SDL_CursorData *curdata;

    if (cursor) {
        curdata = cursor->internal;

        if (curdata) {
            SDL_DestroySurface(curdata->surface);
            SDL_DestroySurface(curdata->converted_surface);
            SDL_free(cursor->internal);
        }
        SDL_free(cursor);
    }
}

static bool DOSVESA_WarpMouseGlobal(float x, float y)
{
    SDL_Mouse *mouse = SDL_GetMouse();

    if (!mouse || !mouse->cur_cursor || !mouse->cur_cursor->internal) {
        return true;
    }

    // warp mouse in the driver, so we get correct screen coordinates from it.
    __dpmi_regs regs;
    regs.x.ax = 0x4;
    regs.x.cx = (Uint16)x;
    regs.x.dx = (Uint16)y;
    __dpmi_int(0x33, &regs);

    // Update internal mouse position.
    SDL_SendMouseMotion(0, mouse->focus, SDL_GLOBAL_MOUSE_ID, false, x, y);

    return true;
}

static bool DOSVESA_WarpMouse(SDL_Window *window, float x, float y)
{
    return DOSVESA_WarpMouseGlobal(x, y);
}

// This is called when a mouse motion event occurs
static bool DOSVESA_MoveCursor(SDL_Cursor *cursor)
{
    return true; // we handle this elsewhere.
}

void DOSVESA_InitMouse(SDL_VideoDevice *_this)
{
    SDL_Mouse *mouse = SDL_GetMouse();
    mouse->internal = NULL;

    __dpmi_regs regs;
    regs.x.ax = 0;
    __dpmi_int(0x33, &regs);
    if (regs.x.ax == 0) {
        return; // no mouse found, don't hook up cursor support, etc.
    }

    mouse->internal = SDL_calloc(1, 1); // just something non-NULL (and safely freeable) to say "there's a mouse available."

    // Query mouse sensitivity (mickeys per pixel) via INT 33h function 0x1B
    SDL_VideoData *data = _this->internal;
    regs.x.ax = 0x1B; // Get Mouse Sensitivity
    __dpmi_int(0x33, &regs);
    data->mickeys_per_hpixel = (regs.x.bx > 0) ? (float)regs.x.bx : 8.0f;
    data->mickeys_per_vpixel = (regs.x.cx > 0) ? (float)regs.x.cx : 16.0f;

    mouse->CreateCursor = DOSVESA_CreateCursor;
    mouse->ShowCursor = DOSVESA_ShowCursor;
    mouse->MoveCursor = DOSVESA_MoveCursor;
    mouse->FreeCursor = DOSVESA_FreeCursor;
    mouse->WarpMouse = DOSVESA_WarpMouse;
    mouse->WarpMouseGlobal = DOSVESA_WarpMouseGlobal;

    SDL_SetDefaultCursor(DOSVESA_CreateDefaultCursor());
}

void DOSVESA_QuitMouse(SDL_VideoDevice *_this)
{
    SDL_Mouse *mouse = SDL_GetMouse();
    SDL_free(mouse->internal);
    mouse->internal = NULL;
}

#endif // SDL_VIDEO_DRIVER_DOSVESA