nuttx/graphics/nxbe/nxbe_clipper.c

/****************************************************************************
 * graphics/nxbe/nxbe_clipper.c
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <debug.h>

#include <nuttx/kmalloc.h>
#include <nuttx/nx/nxglib.h>

#include "nxbe.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

#define NX_INITIAL_STACKSIZE (32)

/****************************************************************************
 * Private Types
 ****************************************************************************/

/* This structure is a container that retains an associated between a
 * window instance and a rectangle.
 */

struct nxbe_cliprect_s
{
  FAR struct nxbe_window_s *wnd;
  struct nxgl_rect_s        rect;
};

/* This is the stack of pending clip operations */

struct nxbe_clipstack_s
{
  uint16_t                npushed; /* Number of deferred rectangles in stack */
  uint16_t                mxrects; /* The capacity of the stack */
  struct nxbe_cliprect_s   *stack; /* The stack of deferred rectangles */
};

/****************************************************************************
 * Private Data
 ****************************************************************************/

static const uint8_t g_nxcliporder[4][4] =
{
  { NX_TOP_NDX,    NX_LEFT_NDX,  NX_RIGHT_NDX, NX_BOTTOM_NDX }, /* index = NX_CLIPORDER_TLRB */
  { NX_TOP_NDX,    NX_RIGHT_NDX, NX_LEFT_NDX,  NX_BOTTOM_NDX }, /*         NX_CLIPORDER_TRLB */
  { NX_BOTTOM_NDX, NX_LEFT_NDX,  NX_RIGHT_NDX, NX_TOP_NDX    }, /*         NX_CLIPORDER_BLRT */
  { NX_BOTTOM_NDX, NX_RIGHT_NDX, NX_LEFT_NDX,  NX_TOP_NDX    }, /*         NX_CLIPORDER_BRLT */
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: nxbe_pushrectangle
 ****************************************************************************/

static inline void nxbe_pushrectangle(FAR struct nxbe_clipstack_s *stack,
                                      FAR struct nxbe_window_s *wnd,
                                      FAR const struct nxgl_rect_s *rect)
{
  /* Check if there is room on the stack to hold another rectangle */

  if ((stack->npushed + 1) > stack->mxrects)
    {
      /* No then we will need to reallocate the stack to hold more */

      int mxrects = stack->mxrects ? 2 *
                    stack->mxrects : NX_INITIAL_STACKSIZE;
      struct nxbe_cliprect_s *newstack;

      newstack = kmm_realloc(stack->stack,
                             sizeof(struct nxbe_cliprect_s) * mxrects);
      if (!newstack)
        {
          gerr("ERROR: Failed to reallocate stack\n");
          return;
        }

      stack->stack   = newstack;
      stack->mxrects = mxrects;
    }

  /* Then push the new rectangle onto the stack */

  stack->stack[stack->npushed].wnd  = wnd;
  nxgl_rectcopy(&stack->stack[stack->npushed].rect, rect);
  stack->npushed++;
}

/****************************************************************************
 * Name: nxbe_poprectangle
 ****************************************************************************/

static inline bool nxbe_poprectangle(struct nxbe_clipstack_s *stack,
                                     FAR struct nxbe_window_s **wnd,
                                     struct nxgl_rect_s *rect)
{
  if (stack->npushed > 0)
    {
      stack->npushed--;
      *wnd = stack->stack[stack->npushed].wnd;
      nxgl_rectcopy(rect, &stack->stack[stack->npushed].rect);
      return true;
    }

  return false;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: nxbe_clipper
 *
 * Description:
 *   Perform flexible clipping operations.  Callbacks are executed for
 *   each oscured and visible portions of the window.
 *
 * Input Parameters:
 *   wnd    - The window to be clipped.
 *   rect   - The region of concern within the window
 *   order  - Specifies the order to process the parts of the
 *            non-intersecting sub-rectangles.
 *   cops   - The callbacks to handle obscured and visible parts of the
 *            sub-rectangles.
 *   plane  - The raster operations to be used by the callback functions.
 *            These may vary with different color formats.
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

void nxbe_clipper(FAR struct nxbe_window_s *wnd,
                  FAR const struct nxgl_rect_s *dest, uint8_t order,
                  FAR struct nxbe_clipops_s *cops,
                  FAR struct nxbe_plane_s *plane)
{
  struct nxbe_clipstack_s   stack;
  FAR struct nxbe_window_s *currw;
  struct nxgl_rect_s        rect;
  struct nxgl_rect_s        obscuredrect;
  struct nxgl_rect_s        currbounds;
  struct nxgl_rect_s        nonoverlapped[4];
  int                       i;

  /* Initialize the stack where we will keep deferred rectangle operations */

  stack.npushed = 0;
  stack.mxrects = 0;
  stack.stack   = NULL;

  /* Loop until there are no further pending operations */

  nxgl_rectcopy(&rect, dest); /* Start with the whole dest rectangle */
  do
    {
      /* Loop for every window from the current window and above.
       * Only windows above the current window can obscure the current window
       */

      for (currw = wnd; currw; currw = currw->above)
        {
          /* Does the current window overlap the dest rectangle? */

          currbounds = currw->bounds;
          if (nxgl_rectoverlap(&rect, &currbounds))
            {
              /* Yes.. then it obscures all or part of the dest rectangle.
               * Divide the potentially visible, non-overlapping regions into
               * 4 smaller rectangles and push them onto the stack for
               * processing on the next time through the outer loop.
               */

              nxgl_nonintersecting(nonoverlapped, &rect, &currbounds);
              for (i = 3; i >= 0; i--)
                {
                  /* Push the rectangles in the order specific by the input
                   * argument of that name.
                   */

                  struct nxgl_rect_s *candidate =
                                     &nonoverlapped[g_nxcliporder[order][i]];
                  if (!nxgl_nullrect(candidate))
                    {
                      nxbe_pushrectangle(&stack, currw->above, candidate);
                    }
                }

              /* Now performed any required processing on the obscurred,
               * overlapped region.
               */

              nxgl_rectintersect(&obscuredrect, &rect, &currbounds);
              cops->obscured(cops, plane, &obscuredrect);

              /* Break out of the loop to process the pushed rectangles */

              break;
            }
        }

      /* If there are no other windows overlapping this rectangle, then this
       * rectangular region must be visible.
       */

      if (!currw && !nxgl_nullrect(&rect))
        {
          cops->visible(cops, plane, &rect);
        }
    }
  while (nxbe_poprectangle(&stack, &wnd, &rect));

  /* Done! If any stack was allocated, then free it before exit-ting */

  if (stack.stack)
    {
      kmm_free(stack.stack);
    }
}

/****************************************************************************
 * Name: nxbe_clipnull
 *
 * Description:
 *   The do-nothing clipping callback function
 *
 ****************************************************************************/

void nxbe_clipnull(FAR struct nxbe_clipops_s *cops,
                   FAR struct nxbe_plane_s *plane,
                   FAR const struct nxgl_rect_s *rect)
{
}