DrawingTracer.cc

/*
 * DrawingTracer.cc
 *
 *  Created on: 2014-6-15
 *      Author: duanyao
 */

#include "GfxFont.h"

#include "util/math.h"
#include "DrawingTracer.h"

#if !ENABLE_SVG
#warning "Cairo is disabled because ENABLE_SVG is off, --correct-text-visibility has limited functionality."
#endif

static constexpr bool DT_DEBUG = false;

namespace pdf2htmlEX
{

DrawingTracer::DrawingTracer(const Param & param): param(param)
#if ENABLE_SVG
, cairo(nullptr)
#endif
{
}

DrawingTracer::~DrawingTracer()
{
    finish();
}

void DrawingTracer::reset(GfxState *state)
{
    if (!param.correct_text_visibility)
        return;
    finish();

#if ENABLE_SVG
    // pbox is defined in device space, which is affected by zooming;
    // We want to trace in page space which is stable, so invert pbox by ctm.
    double pbox[] { 0, 0, state->getPageWidth(), state->getPageHeight() };
    Matrix ctm, ictm;
    state->getCTM(&ctm);
    ctm.invertTo(&ictm);
    tm_transform_bbox(ictm.m, pbox);
    cairo_rectangle_t page_box { pbox[0], pbox[1], pbox[2] - pbox[0], pbox[3] - pbox[1] };
    cairo_surface_t * surface = cairo_recording_surface_create(CAIRO_CONTENT_COLOR_ALPHA, &page_box);
    cairo = cairo_create(surface);
    if (DT_DEBUG)
        printf("DrawingTracer::reset:page bbox:[%f,%f,%f,%f]\n",pbox[0], pbox[1], pbox[2], pbox[3]);
#endif
}

void DrawingTracer::finish()
{
#if ENABLE_SVG
    if (cairo)
    {
        cairo_destroy(cairo);
        cairo = nullptr;
    }
#endif
}

// Poppler won't inform us its initial CTM, and the initial CTM is affected by zoom level.
// OutputDev::clip() may be called before OutputDev::updateCTM(), so we can't rely on GfxState::getCTM(),
// and should trace ctm changes ourself (via cairo).
void DrawingTracer::update_ctm(GfxState *state, double m11, double m12, double m21, double m22, double m31, double m32)
{
    if (!param.correct_text_visibility)
        return;

#if ENABLE_SVG
    cairo_matrix_t matrix;
    matrix.xx = m11;
    matrix.yx = m12;
    matrix.xy = m21;
    matrix.yy = m22;
    matrix.x0 = m31;
    matrix.y0 = m32;
    cairo_transform(cairo, &matrix);

    if (DT_DEBUG)
    {
        cairo_matrix_t mat;
        cairo_get_matrix(cairo, &mat);
        printf("DrawingTracer::update_ctm:ctm:[%f,%f,%f,%f,%f,%f]\n", mat.xx, mat.yx, mat.xy, mat.yy, mat.x0, mat.y0);
    }
#endif
}

void DrawingTracer::clip(GfxState * state, bool even_odd)
{
    if (!param.correct_text_visibility)
        return;
#if ENABLE_SVG
    do_path(state, state->getPath());
    cairo_set_fill_rule(cairo, even_odd? CAIRO_FILL_RULE_EVEN_ODD : CAIRO_FILL_RULE_WINDING);
    cairo_clip (cairo);

    if (DT_DEBUG)
    {
        double cbox[4];
        cairo_clip_extents(cairo, cbox, cbox + 1, cbox + 2, cbox + 3);
        printf("DrawingTracer::clip:extents:[%f,%f,%f,%f]\n", cbox[0],cbox[1],cbox[2],cbox[3]);
    }
#endif
}

void DrawingTracer::clip_to_stroke_path(GfxState * state)
{
    if (!param.correct_text_visibility)
        return;
    // TODO cairo_stroke_to_path() ?
}

void DrawingTracer::save()
{
    if (!param.correct_text_visibility)
        return;
#if ENABLE_SVG
    cairo_save(cairo);
    if (DT_DEBUG)
        printf("DrawingTracer::save\n");
#endif
}
void DrawingTracer::restore()
{
    if (!param.correct_text_visibility)
        return;
#if ENABLE_SVG
    cairo_restore(cairo);
    if (DT_DEBUG)
        printf("DrawingTracer::restore\n");
#endif
}

void DrawingTracer::do_path(GfxState * state, GfxPath * path)
{
#if ENABLE_SVG
    //copy from CairoOutputDev::doPath
    GfxSubpath *subpath;
    int i, j;
    double x, y;
    cairo_new_path(cairo);
    if (DT_DEBUG)
        printf("DrawingTracer::do_path:new_path\n");
    for (i = 0; i < path->getNumSubpaths(); ++i) {
        subpath = path->getSubpath(i);
        if (subpath->getNumPoints() > 0) {
            x = subpath->getX(0);
            y = subpath->getY(0);
            cairo_move_to(cairo, x, y);
            if (DT_DEBUG)
                printf("DrawingTracer::do_path:move_to[%f,%f]\n",x,y);
            j = 1;
            while (j < subpath->getNumPoints()) {
                if (subpath->getCurve(j)) {
                    x = subpath->getX(j+2);
                    y = subpath->getY(j+2);
                    cairo_curve_to(cairo,
                        subpath->getX(j), subpath->getY(j),
                        subpath->getX(j+1), subpath->getY(j+1),
                        x, y);
                    if (DT_DEBUG)
                        printf("DrawingTracer::do_path:curve_to[%f,%f]\n",x,y);
                    j += 3;
                } else {
                    x = subpath->getX(j);
                    y = subpath->getY(j);
                    cairo_line_to(cairo, x, y);
                    if (DT_DEBUG)
                        printf("DrawingTracer::do_path:line_to[%f,%f]\n",x,y);
                    ++j;
                }
            }
            if (subpath->isClosed()) {
                cairo_close_path (cairo);
                if (DT_DEBUG)
                    printf("DrawingTracer::do_path:close\n");
            }
        }
    }
#endif
}

void DrawingTracer::stroke(GfxState * state)
{
#if ENABLE_SVG
    if (!param.correct_text_visibility)
        return;

    if (DT_DEBUG)
        printf("DrawingTracer::stroke\n");

    cairo_set_line_width(cairo, state->getLineWidth());

    // GfxPath is broken into steps, each step makes up a cairo path and its bbox is used for covering test.
    // TODO
    // 1. path steps that are not vertical or horizontal lines may still falsely "cover" many chars,
    // can we slice those steps further?
    // 2. if the line width is small, can we just ignore the path?
    // 3. line join feature can't be retained. We use line-cap-square to minimize the problem that
    //   some chars actually covered by a line join are missed. However chars covered by a acute angle
    //   with line-join-miter may be still recognized as not covered.
    cairo_set_line_cap(cairo, CAIRO_LINE_CAP_SQUARE);
    GfxPath * path = state->getPath();
    for (int i = 0; i < path->getNumSubpaths(); ++i) {
        GfxSubpath * subpath = path->getSubpath(i);
        if (subpath->getNumPoints() <= 0)
            continue;
        double x = subpath->getX(0);
        double y = subpath->getY(0);
        //p: loop cursor; j: next point index
        int p =1, j = 1;
        int n = subpath->getNumPoints();
        while (p <= n) {
            cairo_new_path(cairo);
            cairo_move_to(cairo, x, y);
            if (subpath->getCurve(j)) {
                x = subpath->getX(j+2);
                y = subpath->getY(j+2);
                cairo_curve_to(cairo,
                    subpath->getX(j), subpath->getY(j),
                    subpath->getX(j+1), subpath->getY(j+1),
                    x, y);
                p += 3;
            } else {
                x = subpath->getX(j);
                y = subpath->getY(j);
                cairo_line_to(cairo, x, y);
                ++p;
            }

            if (DT_DEBUG)
                printf("DrawingTracer::stroke:new box:\n");
            double sbox[4];
            cairo_stroke_extents(cairo, sbox, sbox + 1, sbox + 2, sbox + 3);
            if (sbox[0] != sbox[2] && sbox[1] != sbox[3])
                draw_non_char_bbox(state, sbox);
            else if (DT_DEBUG)
                printf("DrawingTracer::stroke:zero box!\n");

            if (p == n)
            {
                if (subpath->isClosed())
                    j = 0; // if sub path is closed, go back to starting point
                else
                    break;
            }
            else
                j = p;
        }
    }
#endif
}

void DrawingTracer::fill(GfxState * state, bool even_odd)
{
    if (!param.correct_text_visibility)
        return;

#if ENABLE_SVG
    do_path(state, state->getPath());
    //cairo_fill_extents don't take fill rule into account.
    //cairo_set_fill_rule (cairo, even_odd? CAIRO_FILL_RULE_EVEN_ODD : CAIRO_FILL_RULE_WINDING);
    double fbox[4];
    cairo_fill_extents(cairo, fbox, fbox + 1, fbox + 2, fbox + 3);
    draw_non_char_bbox(state, fbox);
#endif
}

void DrawingTracer::draw_non_char_bbox(GfxState * state, double * bbox)
{
#if ENABLE_SVG
    double cbox[4];
    cairo_clip_extents(cairo, cbox, cbox + 1, cbox + 2, cbox + 3);
    if(bbox_intersect(cbox, bbox, bbox))
#endif
    {
        transform_bbox_by_ctm(bbox, state);
        if (DT_DEBUG)
            printf("DrawingTracer::draw_non_char_bbox:[%f,%f,%f,%f]\n", bbox[0],bbox[1],bbox[2],bbox[3]);
        if (on_non_char_drawn)
            on_non_char_drawn(bbox);
    }
}

void DrawingTracer::draw_char_bbox(GfxState * state, double * bbox)
{
#if ENABLE_SVG
    // Note: even if 4 corners of the char are all in or all out of the clip area,
    // it could still be partially clipped.
    // TODO better solution?
    int pt_in = 0;
    if (cairo_in_clip(cairo, bbox[0], bbox[1]))
        ++pt_in;
    if (cairo_in_clip(cairo, bbox[2], bbox[3]))
        ++pt_in;
    if (cairo_in_clip(cairo, bbox[2], bbox[1]))
        ++pt_in;
    if (cairo_in_clip(cairo, bbox[0], bbox[3]))
        ++pt_in;

    if (pt_in == 0)
    {
        transform_bbox_by_ctm(bbox);
        if(on_char_clipped)
            on_char_clipped(bbox, false);
    }
    else
    {
        if (pt_in < 4)
        {
            double cbox[4];
            cairo_clip_extents(cairo, cbox, cbox + 1, cbox + 2, cbox + 3);
            bbox_intersect(cbox, bbox, bbox);
        }
        transform_bbox_by_ctm(bbox);
        if (pt_in < 4)
        {
            if(on_char_clipped)
                on_char_clipped(bbox, true);
        }
        else
        {
            if (on_char_drawn)
                on_char_drawn(bbox);
        }
    }
#else
    transform_bbox_by_ctm(bbox, state);
    if (on_char_drawn)
        on_char_drawn(bbox);
#endif
    if (DT_DEBUG)
        printf("DrawingTracer::draw_char_bbox:[%f,%f,%f,%f]\n",bbox[0],bbox[1],bbox[2],bbox[3]);
}

void DrawingTracer::draw_image(GfxState *state)
{
    if (!param.correct_text_visibility)
        return;
    double bbox[4] {0, 0, 1, 1};
    draw_non_char_bbox(state, bbox);
}

void DrawingTracer::draw_char(GfxState *state, double x, double y, double ax, double ay)
{
    if (!param.correct_text_visibility)
        return;

    Matrix tm, itm;
    memcpy(tm.m, state->getTextMat(), sizeof(tm.m));

    double cx = state->getCurX(), cy = state->getCurY(), fs = state->getFontSize(),
            ry = state->getRise(), h = state->getHorizScaling();

    //cx and cy has been transformed by text matrix, we need to reverse them.
    tm.invertTo(&itm);
    double char_cx, char_cy;
    itm.transform(cx, cy, &char_cx, &char_cy);

    //TODO Vertical? Currently vertical/type3 chars are treated as non-chars.
    double char_m[6] {fs * h, 0, 0, fs, char_cx + x, char_cy + y + ry};

    double final_m[6];
    tm_multiply(final_m, tm.m, char_m);

    auto font = state->getFont();
    double bbox[4] {0, 0, ax, ay};
    double desc = font->getDescent(), asc = font->getAscent();
    if (font->getWMode() == 0)
    {
        bbox[1] += desc;
        bbox[3] += asc;
    }
    else
    {//TODO Vertical?
    }
    tm_transform_bbox(final_m, bbox);
    draw_char_bbox(state, bbox);
}


void DrawingTracer::transform_bbox_by_ctm(double * bbox, GfxState * state)
{
#if ENABLE_SVG
    cairo_matrix_t mat;
    cairo_get_matrix(cairo, &mat);
    double mat_a[6] {mat.xx, mat.yx, mat.xy, mat.yy, mat.x0, mat.y0};
    tm_transform_bbox(mat_a, bbox);
#else
    tm_transform_bbox(state->getCTM(), bbox);
#endif
}

} /* namespace pdf2htmlEX */