orbithub/third_party/FreeRDP/libfreerdp/codec/region.c

/**
 * FreeRDP: A Remote Desktop Protocol Implementation
 *
 * Copyright 2014 Thincast Technologies GmbH
 * Copyright 2014 Hardening <contact@hardening-consulting.com>
 * Copyright 2017 Armin Novak <armin.novak@thincast.com>
 * Copyright 2017 Thincast Technologies GmbH
 *
 * Licensed 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.
 */

#include <winpr/assert.h>
#include <winpr/memory.h>
#include <freerdp/log.h>
#include <freerdp/codec/region.h>

#define TAG FREERDP_TAG("codec")

/*
 * The functions in this file implement the Region abstraction largely inspired from
 * pixman library. The following comment is taken from the pixman code.
 *
 * A Region is simply a set of disjoint(non-overlapping) rectangles, plus an
 * "extent" rectangle which is the smallest single rectangle that contains all
 * the non-overlapping rectangles.
 *
 * A Region is implemented as a "y-x-banded" array of rectangles.  This array
 * imposes two degrees of order.  First, all rectangles are sorted by top side
 * y coordinate first (y1), and then by left side x coordinate (x1).
 *
 * Furthermore, the rectangles are grouped into "bands".  Each rectangle in a
 * band has the same top y coordinate (y1), and each has the same bottom y
 * coordinate (y2).  Thus all rectangles in a band differ only in their left
 * and right side (x1 and x2).  Bands are implicit in the array of rectangles:
 * there is no separate list of band start pointers.
 *
 * The y-x band representation does not minimize rectangles.  In particular,
 * if a rectangle vertically crosses a band (the rectangle has scanlines in
 * the y1 to y2 area spanned by the band), then the rectangle may be broken
 * down into two or more smaller rectangles stacked one atop the other.
 *
 *  -----------                             -----------
 *  |         |                             |         |             band 0
 *  |         |  --------                   -----------  --------
 *  |         |  |      |  in y-x banded    |         |  |      |   band 1
 *  |         |  |      |  form is          |         |  |      |
 *  -----------  |      |                   -----------  --------
 *               |      |                                |      |   band 2
 *               --------                                --------
 *
 * An added constraint on the rectangles is that they must cover as much
 * horizontal area as possible: no two rectangles within a band are allowed
 * to touch.
 *
 * Whenever possible, bands will be merged together to cover a greater vertical
 * distance (and thus reduce the number of rectangles). Two bands can be merged
 * only if the bottom of one touches the top of the other and they have
 * rectangles in the same places (of the same width, of course).
 */

struct S_REGION16_DATA
{
	size_t nbRects;
	RECTANGLE_16* rects;
};

void region16_init(REGION16* region)
{
	WINPR_ASSERT(region);

	const REGION16 empty = WINPR_C_ARRAY_INIT;
	*region = empty;
}

int region16_n_rects(const REGION16* region)
{
	WINPR_ASSERT(region);
	if (!region->data)
		return 0;

	return WINPR_ASSERTING_INT_CAST(int, region->data->nbRects);
}

const RECTANGLE_16* region16_rects(const REGION16* region, UINT32* nbRects)
{
	if (nbRects)
		*nbRects = 0;

	if (!region)
		return nullptr;

	REGION16_DATA* data = region->data;
	if (!data)
		return nullptr;

	if (nbRects)
		*nbRects = WINPR_ASSERTING_INT_CAST(UINT32, data->nbRects);

	return data->rects;
}

static inline RECTANGLE_16* region16_rects_noconst(REGION16* region)
{
	WINPR_ASSERT(region);

	REGION16_DATA* data = region->data;

	if (!data)
		return nullptr;

	return data->rects;
}

const RECTANGLE_16* region16_extents(const REGION16* region)
{
	if (!region)
		return nullptr;

	return &region->extents;
}

static RECTANGLE_16* region16_extents_noconst(REGION16* region)
{
	if (!region)
		return nullptr;

	return &region->extents;
}

BOOL rectangle_is_empty(const RECTANGLE_16* rect)
{
	WINPR_ASSERT(rect);

	/* A rectangle with width <= 0 or height <= 0 should be regarded
	 * as empty.
	 */
	return ((rect->left >= rect->right) || (rect->top >= rect->bottom));
}

BOOL region16_is_empty(const REGION16* region)
{
	WINPR_ASSERT(region);
	if (!region->data)
		return TRUE;
	return (region->data->nbRects == 0);
}

BOOL rectangles_equal(const RECTANGLE_16* r1, const RECTANGLE_16* r2)
{
	WINPR_ASSERT(r1);
	WINPR_ASSERT(r2);

	return ((r1->left == r2->left) && (r1->top == r2->top) && (r1->right == r2->right) &&
	        (r1->bottom == r2->bottom));
}

BOOL rectangles_intersects(const RECTANGLE_16* r1, const RECTANGLE_16* r2)
{
	RECTANGLE_16 tmp = WINPR_C_ARRAY_INIT;
	return rectangles_intersection(r1, r2, &tmp);
}

BOOL rectangles_intersection(const RECTANGLE_16* r1, const RECTANGLE_16* r2, RECTANGLE_16* dst)
{
	WINPR_ASSERT(r1);
	WINPR_ASSERT(r2);
	WINPR_ASSERT(dst);

	dst->left = MAX(r1->left, r2->left);
	dst->right = MIN(r1->right, r2->right);
	dst->top = MAX(r1->top, r2->top);
	dst->bottom = MIN(r1->bottom, r2->bottom);
	return (dst->left < dst->right) && (dst->top < dst->bottom);
}

static void freeRegion(REGION16_DATA* data)
{
	if (data)
		free(data->rects);
	free(data);
}

void region16_clear(REGION16* region)
{
	WINPR_ASSERT(region);

	freeRegion(region->data);
	region->data = nullptr;

	const RECTANGLE_16 empty = WINPR_C_ARRAY_INIT;
	region->extents = empty;
}

WINPR_ATTR_MALLOC(freeRegion, 1)
WINPR_ATTR_NODISCARD
static REGION16_DATA* allocateRegion(size_t nbItems)
{
	REGION16_DATA* data = calloc(1, sizeof(REGION16_DATA));
	if (!data)
		return nullptr;

	if (nbItems > 0)
	{
		data->rects = calloc(nbItems, sizeof(RECTANGLE_16));
		if (!data->rects)
		{
			free(data);
			return nullptr;
		}
	}

	data->nbRects = nbItems;
	return data;
}

static inline RECTANGLE_16* nextRect(REGION16_DATA* data, size_t index)
{
	WINPR_ASSERT(data);
	if (index + 1 > data->nbRects)
	{
		RECTANGLE_16* rects = realloc(data->rects, (index + 1) * sizeof(RECTANGLE_16));
		if (!rects)
		{
			freeRegion(data);
			return nullptr;
		}

		const RECTANGLE_16 empty = WINPR_C_ARRAY_INIT;
		rects[index] = empty;
		data->nbRects = index + 1;
		data->rects = rects;
	}
	return &data->rects[index];
}

static BOOL resizeRegion(REGION16* region, size_t nbItems)
{
	WINPR_ASSERT(region);
	if (nbItems == 0)
	{
		freeRegion(region->data);
		region->data = nullptr;
		return TRUE;
	}

	if (!region->data)
	{
		region->data = allocateRegion(nbItems);
		return region->data != nullptr;
	}

	RECTANGLE_16* rects = realloc(region->data->rects, nbItems * sizeof(RECTANGLE_16));
	if (!rects)
	{
		free(region->data->rects);
		region->data->nbRects = 0;
		region->data->rects = nullptr;
		return FALSE;
	}

	for (size_t x = region->data->nbRects; x < nbItems; x++)
	{
		const RECTANGLE_16 empty = WINPR_C_ARRAY_INIT;
		rects[x] = empty;
	}
	region->data->rects = rects;
	region->data->nbRects = nbItems;
	return TRUE;
}

static inline BOOL region16_copy_data(REGION16* dst, const REGION16* src)
{
	WINPR_ASSERT(dst);
	WINPR_ASSERT(src);

	freeRegion(dst->data);
	dst->data = nullptr;

	if (src->data && (src->data->nbRects > 0))
	{
		dst->data = allocateRegion(src->data->nbRects);
		if (!dst->data || !dst->data->rects)
			return FALSE;
		memcpy(dst->data->rects, src->data->rects, dst->data->nbRects * sizeof(RECTANGLE_16));
	}
	return TRUE;
}

BOOL region16_copy(REGION16* dst, const REGION16* src)
{
	if (dst == src)
		return TRUE;

	WINPR_ASSERT(dst);
	WINPR_ASSERT(src);

	dst->extents = src->extents;

	return region16_copy_data(dst, src);
}

void region16_print(const REGION16* region)
{
	UINT32 nbRects = 0;
	int currentBandY = -1;
	const RECTANGLE_16* rects = region16_rects(region, &nbRects);

	WLog_DBG(TAG, "nrects=%" PRIu32 "", nbRects);

	for (UINT32 i = 0; i < nbRects; i++)
	{
		const RECTANGLE_16* rect = &rects[i];

		if (rect->top != currentBandY)
		{
			currentBandY = rect->top;
			WLog_DBG(TAG, "band %d: ", currentBandY);
		}

		WLog_DBG(TAG, "(%" PRIu16 ",%" PRIu16 "-%" PRIu16 ",%" PRIu16 ")", rect->left, rect->top,
		         rect->right, rect->bottom);
	}
}

static BOOL region16_copy_band_with_union(REGION16_DATA* region, const RECTANGLE_16* src,
                                          const RECTANGLE_16* end, UINT16 newTop, UINT16 newBottom,
                                          const RECTANGLE_16* unionRect, UINT32* dstCounter,
                                          const RECTANGLE_16** srcPtr)
{
	WINPR_ASSERT(region);
	WINPR_ASSERT(src);
	WINPR_ASSERT(end);
	WINPR_ASSERT(dstCounter);

	UINT16 refY = src->top;

	/* merges a band with the given rect
	 * Input:
	 *                   unionRect
	 *               |               |
	 *               |               |
	 * ==============+===============+================================
	 *   |Item1|  |Item2| |Item3|  |Item4|    |Item5|            Band
	 * ==============+===============+================================
	 *    before     |    overlap    |          after
	 *
	 * Resulting band:
	 *   +-----+  +----------------------+    +-----+
	 *   |Item1|  |      Item2           |    |Item3|
	 *   +-----+  +----------------------+    +-----+
	 *
	 *  We first copy as-is items that are before Item2, the first overlapping
	 *  item.
	 *  Then we find the last one that overlap unionRect to aggregate Item2, Item3
	 *  and Item4 to create Item2.
	 *  Finally Item5 is copied as Item3.
	 *
	 *  When no unionRect is provided, we skip the two first steps to just copy items
	 */

	if (unionRect)
	{
		/* items before unionRect */
		while ((src < end) && (src->top == refY) && (src->right < unionRect->left))
		{
			RECTANGLE_16* dst = nextRect(region, (*dstCounter)++);
			if (!dst)
				return FALSE;
			dst->top = newTop;
			dst->bottom = newBottom;
			dst->right = src->right;
			dst->left = src->left;
			src++;
		}

		/* treat items overlapping with unionRect */
		const RECTANGLE_16* startOverlap = unionRect;
		const RECTANGLE_16* endOverlap = unionRect;

		if ((src < end) && (src->top == refY) && (src->left < unionRect->left))
			startOverlap = src;

		while ((src < end) && (src->top == refY) && (src->right < unionRect->right))
		{
			src++;
		}

		if ((src < end) && (src->top == refY) && (src->left < unionRect->right))
		{
			endOverlap = src;
			src++;
		}

		{
			RECTANGLE_16* dst = nextRect(region, (*dstCounter)++);
			if (!dst)
				return FALSE;
			dst->bottom = newBottom;
			dst->top = newTop;
			dst->left = startOverlap->left;
			dst->right = endOverlap->right;
		}
	}

	/* treat remaining items on the same band */
	while ((src < end) && (src->top == refY))
	{
		RECTANGLE_16* dst = nextRect(region, (*dstCounter)++);
		if (!dst)
			return FALSE;

		dst->top = newTop;
		dst->bottom = newBottom;
		dst->right = src->right;
		dst->left = src->left;
		src++;
	}

	if (srcPtr)
		*srcPtr = src;

	return TRUE;
}

static RECTANGLE_16* next_band(RECTANGLE_16* band1, RECTANGLE_16* endPtr, int* nbItems)
{
	WINPR_ASSERT(band1);
	WINPR_ASSERT(endPtr);
	WINPR_ASSERT(nbItems);

	UINT16 refY = band1->top;
	*nbItems = 0;

	while ((band1 < endPtr) && (band1->top == refY))
	{
		band1++;
		*nbItems += 1;
	}

	return band1;
}

static BOOL band_match(const RECTANGLE_16* band1, const RECTANGLE_16* band2,
                       const RECTANGLE_16* endPtr)
{
	int refBand2 = band2->top;
	const RECTANGLE_16* band2Start = band2;

	while ((band1 < band2Start) && (band2 < endPtr) && (band2->top == refBand2))
	{
		if ((band1->left != band2->left) || (band1->right != band2->right))
			return FALSE;

		band1++;
		band2++;
	}

	if (band1 != band2Start)
		return FALSE;

	return (band2 == endPtr) || (band2->top != refBand2);
}

/** compute if the rectangle is fully included in the band
 * @param band a pointer on the beginning of the band
 * @param endPtr end of the region
 * @param rect the rectangle to test
 * @return if rect is fully included in an item of the band
 */
static BOOL rectangle_contained_in_band(const RECTANGLE_16* band, const RECTANGLE_16* endPtr,
                                        const RECTANGLE_16* rect)
{
	WINPR_ASSERT(band);
	WINPR_ASSERT(endPtr);
	WINPR_ASSERT(rect);

	UINT16 refY = band->top;

	if ((band->top > rect->top) || (rect->bottom > band->bottom))
		return FALSE;

	/* note: as the band is sorted from left to right, once we've seen an item
	 * 		that is after rect->left we're sure that the result is False.
	 */
	while ((band < endPtr) && (band->top == refY) && (band->left <= rect->left))
	{
		if (rect->right <= band->right)
			return TRUE;

		band++;
	}

	return FALSE;
}

static BOOL region16_simplify_bands(REGION16* region)
{
	/** Simplify consecutive bands that touch and have the same items
	 *
	 *  ====================          ====================
	 *     | 1 |  | 2   |               |   |  |     |
	 *  ====================            |   |  |     |
	 *     | 1 |  | 2   |	   ====>    | 1 |  |  2  |
	 *  ====================            |   |  |     |
	 *     | 1 |  | 2   |               |   |  |     |
	 *  ====================          ====================
	 *
	 */

	const int nbRects = region16_n_rects(region);
	int finalNbRects = nbRects;

	if (nbRects < 2)
		return TRUE;

	RECTANGLE_16* band1 = region16_rects_noconst(region);
	RECTANGLE_16* endPtr = band1 + nbRects;

	do
	{
		int bandItems = 0;
		RECTANGLE_16* band2 = next_band(band1, endPtr, &bandItems);

		if (band2 == endPtr)
			break;

		if ((band1->bottom == band2->top) && band_match(band1, band2, endPtr))
		{
			/* adjust the bottom of band1 items */
			RECTANGLE_16* tmp = band1;

			while (tmp < band2)
			{
				tmp->bottom = band2->bottom;
				tmp++;
			}

			/* override band2, we don't move band1 pointer as the band after band2
			 * may be merged too */
			const RECTANGLE_16* endBand = band2 + bandItems;
			const size_t toMove =
			    WINPR_ASSERTING_INT_CAST(size_t, (endPtr - endBand)) * sizeof(RECTANGLE_16);

			if (toMove)
				MoveMemory(band2, endBand, toMove);

			finalNbRects -= bandItems;
			endPtr -= bandItems;
		}
		else
		{
			band1 = band2;
		}
	} while (TRUE);

	if (finalNbRects != nbRects)
	{
		if (!resizeRegion(region, WINPR_ASSERTING_INT_CAST(size_t, finalNbRects)))
			return FALSE;
	}

	return TRUE;
}

BOOL region16_union_rect(REGION16* dst, const REGION16* src, const RECTANGLE_16* rect)
{
	const RECTANGLE_16* nextBand = nullptr;
	UINT32 srcNbRects = 0;
	UINT16 topInterBand = 0;
	WINPR_ASSERT(src);
	WINPR_ASSERT(dst);

	const RECTANGLE_16* srcExtents = region16_extents(src);
	RECTANGLE_16* dstExtents = region16_extents_noconst(dst);

	const int nrSrcRects = region16_n_rects(src);
	if (nrSrcRects == 0)
	{
		/* source is empty, so the union is rect */
		dst->extents = *rect;

		if (!resizeRegion(dst, 1))
			return FALSE;

		RECTANGLE_16* dstRect = region16_rects_noconst(dst);
		WINPR_ASSERT(dstRect);

		dstRect->top = rect->top;
		dstRect->left = rect->left;
		dstRect->right = rect->right;
		dstRect->bottom = rect->bottom;
		dst->data->nbRects = 1;
		return TRUE;
	}

	REGION16_DATA* newItems = allocateRegion(WINPR_ASSERTING_INT_CAST(size_t, nrSrcRects + 1));

	if (!newItems)
		return FALSE;

	UINT32 usedRects = 0;

	/* adds the piece of rect that is on the top of src */
	if (rect->top < srcExtents->top)
	{
		RECTANGLE_16* dstRect = nextRect(newItems, usedRects++);
		if (!dstRect)
			return FALSE;

		dstRect->top = rect->top;
		dstRect->left = rect->left;
		dstRect->right = rect->right;
		dstRect->bottom = MIN(srcExtents->top, rect->bottom);
	}

	/* treat possibly overlapping region */
	const RECTANGLE_16* currentBand = region16_rects(src, &srcNbRects);
	const RECTANGLE_16* endSrcRect = currentBand + srcNbRects;

	while (currentBand < endSrcRect)
	{
		if ((currentBand->bottom <= rect->top) || (rect->bottom <= currentBand->top) ||
		    rectangle_contained_in_band(currentBand, endSrcRect, rect))
		{
			/* no overlap between rect and the band, rect is totally below or totally above
			 * the current band, or rect is already covered by an item of the band.
			 * let's copy all the rectangles from this band
			            +----+
			            |    |   rect (case 1)
			            +----+

			   =================
			band of srcRect
			 =================
			        +----+
			        |    |   rect (case 2)
			        +----+
			*/
			if (!region16_copy_band_with_union(newItems, currentBand, endSrcRect, currentBand->top,
			                                   currentBand->bottom, nullptr, &usedRects, &nextBand))
				return FALSE;
			topInterBand = rect->top;
		}
		else
		{
			/* rect overlaps the band:
			           |    |  |    |
			====^=================|    |==|    |=========================== band
			|   top split     |    |  |    |
			v                 | 1  |  | 2  |
			^                 |    |  |    |  +----+   +----+
			|   merge zone    |    |  |    |  |    |   | 4  |
			v                 +----+  |    |  |    |   +----+
			^                         |    |  | 3  |
			|   bottom split          |    |  |    |
			====v=========================|    |==|    |===================
			           |    |  |    |

			 possible cases:
			 1) no top split, merge zone then a bottom split. The band will be split
			  in two
			 2) not band split, only the merge zone, band merged with rect but not split
			 3) a top split, the merge zone and no bottom split. The band will be split
			 in two
			 4) a top split, the merge zone and also a bottom split. The band will be
			 split in 3, but the coalesce algorithm may merge the created bands
			 */
			UINT16 mergeTop = currentBand->top;
			UINT16 mergeBottom = currentBand->bottom;

			/* test if we need a top split, case 3 and 4 */
			if (rect->top > currentBand->top)
			{
				if (!region16_copy_band_with_union(newItems, currentBand, endSrcRect,
				                                   currentBand->top, rect->top, nullptr, &usedRects,
				                                   &nextBand))
					return FALSE;
				mergeTop = rect->top;
			}

			/* do the merge zone (all cases) */
			if (rect->bottom < currentBand->bottom)
				mergeBottom = rect->bottom;

			if (!region16_copy_band_with_union(newItems, currentBand, endSrcRect, mergeTop,
			                                   mergeBottom, rect, &usedRects, &nextBand))
				return FALSE;

			/* test if we need a bottom split, case 1 and 4 */
			if (rect->bottom < currentBand->bottom)
			{
				if (!region16_copy_band_with_union(newItems, currentBand, endSrcRect, mergeBottom,
				                                   currentBand->bottom, nullptr, &usedRects,
				                                   &nextBand))
					return FALSE;
			}

			topInterBand = currentBand->bottom;
		}

		/* test if a piece of rect should be inserted as a new band between
		 * the current band and the next one. band n and n+1 shouldn't touch.
		 *
		 * ==============================================================
		 *                                                        band n
		 *            +------+                    +------+
		 * ===========| rect |====================|      |===============
		 *            |      |    +------+        |      |
		 *            +------+    | rect |        | rect |
		 *                        +------+        |      |
		 * =======================================|      |================
		 *                                        +------+         band n+1
		 * ===============================================================
		 *
		 */
		if ((nextBand < endSrcRect) && (nextBand->top != currentBand->bottom) &&
		    (rect->bottom > currentBand->bottom) && (rect->top < nextBand->top))
		{
			RECTANGLE_16* dstRect = nextRect(newItems, usedRects++);
			if (!dstRect)
				return FALSE;

			dstRect->right = rect->right;
			dstRect->left = rect->left;
			dstRect->top = topInterBand;
			dstRect->bottom = MIN(nextBand->top, rect->bottom);
		}

		currentBand = nextBand;
	}

	/* adds the piece of rect that is below src */
	if (srcExtents->bottom < rect->bottom)
	{
		RECTANGLE_16* dstRect = nextRect(newItems, usedRects++);
		if (!dstRect)
			return FALSE;

		dstRect->top = MAX(srcExtents->bottom, rect->top);
		dstRect->left = rect->left;
		dstRect->right = rect->right;
		dstRect->bottom = rect->bottom;
	}

	dstExtents->top = MIN(rect->top, srcExtents->top);
	dstExtents->left = MIN(rect->left, srcExtents->left);
	dstExtents->bottom = MAX(rect->bottom, srcExtents->bottom);
	dstExtents->right = MAX(rect->right, srcExtents->right);

	newItems->nbRects = usedRects;
	freeRegion(dst->data);
	dst->data = newItems;

	return region16_simplify_bands(dst);
}

BOOL region16_intersects_rect(const REGION16* src, const RECTANGLE_16* arg2)
{
	const RECTANGLE_16* endPtr = nullptr;
	UINT32 nbRects = 0;

	if (!src || !src->data || !arg2)
		return FALSE;

	const RECTANGLE_16* rect = region16_rects(src, &nbRects);

	if (!nbRects)
		return FALSE;

	const RECTANGLE_16* srcExtents = region16_extents(src);

	if (nbRects == 1)
		return rectangles_intersects(srcExtents, arg2);

	if (!rectangles_intersects(srcExtents, arg2))
		return FALSE;

	for (endPtr = rect + nbRects; (rect < endPtr) && (arg2->bottom > rect->top); rect++)
	{
		if (rectangles_intersects(rect, arg2))
			return TRUE;
	}

	return FALSE;
}

BOOL region16_intersect_rect(REGION16* dst, const REGION16* src, const RECTANGLE_16* rect)
{
	const RECTANGLE_16* endPtr = nullptr;
	UINT32 nbRects = 0;
	RECTANGLE_16 common = WINPR_C_ARRAY_INIT;

	WINPR_ASSERT(dst);
	WINPR_ASSERT(src);

	const RECTANGLE_16* srcPtr = region16_rects(src, &nbRects);

	if (!nbRects)
	{
		region16_clear(dst);
		return TRUE;
	}

	const RECTANGLE_16* srcExtents = region16_extents(src);

	if (nbRects == 1)
	{
		BOOL intersects = rectangles_intersection(srcExtents, rect, &common);
		region16_clear(dst);

		if (intersects)
			return region16_union_rect(dst, dst, &common);

		return TRUE;
	}

	REGION16_DATA* newItems = allocateRegion(nbRects);

	if (!newItems)
		return FALSE;

	RECTANGLE_16* dstPtr = newItems->rects;
	UINT32 usedRects = 0;
	RECTANGLE_16 newExtents = WINPR_C_ARRAY_INIT;

	/* accumulate intersecting rectangles, the final region16_simplify_bands() will
	 * do all the bad job to recreate correct rectangles
	 */
	for (endPtr = srcPtr + nbRects; (srcPtr < endPtr) && (rect->bottom > srcPtr->top); srcPtr++)
	{
		if (usedRects > nbRects)
		{
			freeRegion(newItems);
			return FALSE;
		}

		if (rectangles_intersection(srcPtr, rect, &common))
		{
			*dstPtr = common;
			usedRects++;
			dstPtr++;

			if (rectangle_is_empty(&newExtents))
			{
				/* Check if the existing newExtents is empty. If it is empty, use
				 * new common directly. We do not need to check common rectangle
				 * because the rectangles_intersection() ensures that it is not empty.
				 */
				newExtents = common;
			}
			else
			{
				newExtents.top = MIN(common.top, newExtents.top);
				newExtents.left = MIN(common.left, newExtents.left);
				newExtents.bottom = MAX(common.bottom, newExtents.bottom);
				newExtents.right = MAX(common.right, newExtents.right);
			}
		}
	}

	newItems->nbRects = usedRects;

	freeRegion(dst->data);
	dst->data = newItems;
	dst->extents = newExtents;
	return region16_simplify_bands(dst);
}

void region16_uninit(REGION16* region)
{
	WINPR_ASSERT(region);

	freeRegion(region->data);
	region->data = nullptr;
}