SkLineClipper Class Reference

#include <SkLineClipper.h>

Public Types
enum	{ kMaxPoints = 4 , kMaxClippedLineSegments = kMaxPoints - 1 }

Static Public Member Functions
static int	ClipLine (const SkPoint pts[2], const SkRect &clip, SkPoint lines[kMaxPoints], bool canCullToTheRight)
static bool	IntersectLine (const SkPoint src[2], const SkRect &clip, SkPoint dst[2])

Detailed Description

Definition at line 13 of file SkLineClipper.h.

Member Enumeration Documentation

anonymous enum

anonymous enum

Enumerator
kMaxPoints
kMaxClippedLineSegments

Definition at line 15 of file SkLineClipper.h.

         {
        kMaxPoints = 4,
        kMaxClippedLineSegments = kMaxPoints - 1
    };

Member Function Documentation

ClipLine()

int SkLineClipper::ClipLine ( const SkPoint  pts[2], const SkRect &  clip, SkPoint  lines[kMaxPoints], bool  canCullToTheRight  )

static

Definition at line 181 of file SkLineClipper.cpp.

                                                    {
    int index0, index1;
 
    if (pts[0].fY < pts[1].fY) {
        index0 = 0;
        index1 = 1;
    } else {
        index0 = 1;
        index1 = 0;
    }
 
    // Check if we're completely clipped out in Y (above or below
 
    if (pts[index1].fY <= clip.fTop) {  // we're above the clip
        return 0;
    }
    if (pts[index0].fY >= clip.fBottom) {  // we're below the clip
        return 0;
    }
 
    // Chop in Y to produce a single segment, stored in tmp[0..1]
 
    SkPoint tmp[2];
    memcpy(tmp, pts, sizeof(tmp));
 
    // now compute intersections
    if (pts[index0].fY < clip.fTop) {
        tmp[index0].set(sect_with_horizontal(pts, clip.fTop), clip.fTop);
        SkASSERT(is_between_unsorted(tmp[index0].fX, pts[0].fX, pts[1].fX));
    }
    if (tmp[index1].fY > clip.fBottom) {
        tmp[index1].set(sect_with_horizontal(pts, clip.fBottom), clip.fBottom);
        SkASSERT(is_between_unsorted(tmp[index1].fX, pts[0].fX, pts[1].fX));
    }
 
    // Chop it into 1..3 segments that are wholly within the clip in X.
 
    // temp storage for up to 3 segments
    SkPoint resultStorage[kMaxPoints];
    SkPoint* result;    // points to our results, either tmp or resultStorage
    int lineCount = 1;
    bool reverse;
 
    if (pts[0].fX < pts[1].fX) {
        index0 = 0;
        index1 = 1;
        reverse = false;
    } else {
        index0 = 1;
        index1 = 0;
        reverse = true;
    }
 
    if (tmp[index1].fX <= clip.fLeft) {  // wholly to the left
        tmp[0].fX = tmp[1].fX = clip.fLeft;
        result = tmp;
        reverse = false;
    } else if (tmp[index0].fX >= clip.fRight) {    // wholly to the right
        if (canCullToTheRight) {
            return 0;
        }
        tmp[0].fX = tmp[1].fX = clip.fRight;
        result = tmp;
        reverse = false;
    } else {
        result = resultStorage;
        SkPoint* r = result;
 
        if (tmp[index0].fX < clip.fLeft) {
            r->set(clip.fLeft, tmp[index0].fY);
            r += 1;
            r->set(clip.fLeft, sect_clamp_with_vertical(tmp, clip.fLeft));
            SkASSERT(is_between_unsorted(r->fY, tmp[0].fY, tmp[1].fY));
        } else {
            *r = tmp[index0];
        }
        r += 1;
 
        if (tmp[index1].fX > clip.fRight) {
            r->set(clip.fRight, sect_clamp_with_vertical(tmp, clip.fRight));
            SkASSERT(is_between_unsorted(r->fY, tmp[0].fY, tmp[1].fY));
            r += 1;
            r->set(clip.fRight, tmp[index1].fY);
        } else {
            *r = tmp[index1];
        }
 
        lineCount = SkToInt(r - result);
    }
 
    // Now copy the results into the caller's lines[] parameter
    if (reverse) {
        // copy the pts in reverse order to maintain winding order
        for (int i = 0; i <= lineCount; i++) {
            lines[lineCount - i] = result[i];
        }
    } else {
        memcpy(lines, result, (lineCount + 1) * sizeof(SkPoint));
    }
    return lineCount;
}

IntersectLine()

bool SkLineClipper::IntersectLine ( const SkPoint  src[2], const SkRect &  clip, SkPoint  dst[2]  )

static

Definition at line 96 of file SkLineClipper.cpp.

                                                  {
    SkRect bounds;
 
    bounds.set(src[0], src[1]);
    if (containsNoEmptyCheck(clip, bounds)) {
        if (src != dst) {
            memcpy(dst, src, 2 * sizeof(SkPoint));
        }
        return true;
    }
    // check for no overlap, and only permit coincident edges if the line
    // and the edge are colinear
    if (nestedLT(bounds.fRight, clip.fLeft, bounds.width()) ||
        nestedLT(clip.fRight, bounds.fLeft, bounds.width()) ||
        nestedLT(bounds.fBottom, clip.fTop, bounds.height()) ||
        nestedLT(clip.fBottom, bounds.fTop, bounds.height())) {
        return false;
    }
 
    int index0, index1;
 
    if (src[0].fY < src[1].fY) {
        index0 = 0;
        index1 = 1;
    } else {
        index0 = 1;
        index1 = 0;
    }
 
    SkPoint tmp[2];
    memcpy(tmp, src, sizeof(tmp));
 
    // now compute Y intersections
    if (tmp[index0].fY < clip.fTop) {
        tmp[index0].set(sect_with_horizontal(src, clip.fTop), clip.fTop);
    }
    if (tmp[index1].fY > clip.fBottom) {
        tmp[index1].set(sect_with_horizontal(src, clip.fBottom), clip.fBottom);
    }
 
    if (tmp[0].fX < tmp[1].fX) {
        index0 = 0;
        index1 = 1;
    } else {
        index0 = 1;
        index1 = 0;
    }
 
    // check for quick-reject in X again, now that we may have been chopped
    if ((tmp[index1].fX <= clip.fLeft || tmp[index0].fX >= clip.fRight)) {
        // usually we will return false, but we don't if the line is vertical and coincident
        // with the clip.
        if (tmp[0].fX != tmp[1].fX || tmp[0].fX < clip.fLeft || tmp[0].fX > clip.fRight) {
            return false;
        }
    }
 
    if (tmp[index0].fX < clip.fLeft) {
        tmp[index0].set(clip.fLeft, sect_with_vertical(tmp, clip.fLeft));
    }
    if (tmp[index1].fX > clip.fRight) {
        tmp[index1].set(clip.fRight, sect_with_vertical(tmp, clip.fRight));
    }
#ifdef SK_DEBUG
    bounds.set(tmp[0], tmp[1]);
    SkASSERT(containsNoEmptyCheck(clip, bounds));
#endif
    memcpy(dst, tmp, sizeof(tmp));
    return true;
}

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The documentation for this class was generated from the following files:

• third_party/skia/src/core/SkLineClipper.h
• third_party/skia/src/core/SkLineClipper.cpp