src/gpu/GrSoftwarePathRenderer.cpp

/*
 * Copyright 2012 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "GrSoftwarePathRenderer.h"
#include "GrContext.h"
#include "GrSWMaskHelper.h"

////////////////////////////////////////////////////////////////////////////////
bool GrSoftwarePathRenderer::canDrawPath(const SkPath& path,
                                         GrPathFill fill,
                                         const GrDrawTarget* target,
                                         bool antiAlias) const {
    if (!antiAlias || NULL == fContext) {
        // TODO: We could allow the SW path to also handle non-AA paths but
        // this would mean that GrDefaultPathRenderer would never be called
        // (since it appears after the SW renderer in the path renderer
        // chain). Some testing would need to be done r.e. performance 
        // and consistency of the resulting images before removing
        // the "!antiAlias" clause from the above test
        return false;
    }

    return true;
}

namespace {

////////////////////////////////////////////////////////////////////////////////
// gets device coord bounds of path (not considering the fill) and clip. The
// path bounds will be a subset of the clip bounds. returns false if 
// path bounds would be empty.
bool get_path_and_clip_bounds(const GrDrawTarget* target,
                              const SkPath& path,
                              const GrMatrix& matrix,
                              GrIRect* pathBounds,
                              GrIRect* clipBounds) {
    // compute bounds as intersection of rt size, clip, and path
    const GrRenderTarget* rt = target->getDrawState().getRenderTarget();
    if (NULL == rt) {
        return false;
    }
    *pathBounds = GrIRect::MakeWH(rt->width(), rt->height());
    const GrClip& clip = target->getClip();
    if (clip.hasConservativeBounds()) {
        clip.getConservativeBounds().roundOut(clipBounds);
        if (!pathBounds->intersect(*clipBounds)) {
            return false;
        }
    } else {
        // pathBounds is currently the rt extent, set clip bounds to that rect.
        *clipBounds = *pathBounds;
    }
    if (!path.getBounds().isEmpty()) {
        GrRect pathSBounds;
        matrix.mapRect(&pathSBounds, path.getBounds());
        GrIRect pathIBounds;
        pathSBounds.roundOut(&pathIBounds);
        if (!pathBounds->intersect(pathIBounds)) {
            // set the correct path bounds, as this would be used later.
            *pathBounds = pathIBounds;
            return false;
        }
    } else {
        *pathBounds = GrIRect::EmptyIRect();
        return false;
    }
    return true;
}

////////////////////////////////////////////////////////////////////////////////
void draw_around_inv_path(GrDrawTarget* target,
                          GrDrawState::StageMask stageMask,
                          const GrIRect& clipBounds,
                          const GrIRect& pathBounds) {
    GrDrawTarget::AutoDeviceCoordDraw adcd(target, stageMask);
    GrRect rect;
    if (clipBounds.fTop < pathBounds.fTop) {
        rect.iset(clipBounds.fLeft, clipBounds.fTop, 
                    clipBounds.fRight, pathBounds.fTop);
        target->drawSimpleRect(rect, NULL, stageMask);
    }
    if (clipBounds.fLeft < pathBounds.fLeft) {
        rect.iset(clipBounds.fLeft, pathBounds.fTop, 
                    pathBounds.fLeft, pathBounds.fBottom);
        target->drawSimpleRect(rect, NULL, stageMask);
    }
    if (clipBounds.fRight > pathBounds.fRight) {
        rect.iset(pathBounds.fRight, pathBounds.fTop, 
                    clipBounds.fRight, pathBounds.fBottom);
        target->drawSimpleRect(rect, NULL, stageMask);
    }
    if (clipBounds.fBottom > pathBounds.fBottom) {
        rect.iset(clipBounds.fLeft, pathBounds.fBottom, 
                    clipBounds.fRight, clipBounds.fBottom);
        target->drawSimpleRect(rect, NULL, stageMask);
    }
}

}

////////////////////////////////////////////////////////////////////////////////
// return true on success; false on failure
bool GrSoftwarePathRenderer::onDrawPath(const SkPath& path,
                                        GrPathFill fill,
                                        const GrVec* translate,
                                        GrDrawTarget* target,
                                        GrDrawState::StageMask stageMask,
                                        bool antiAlias) {

    if (NULL == fContext) {
        return false;
    }

    GrDrawState* drawState = target->drawState();

    GrMatrix vm = drawState->getViewMatrix();
    if (NULL != translate) {
        vm.postTranslate(translate->fX, translate->fY);
    }

    GrIRect pathBounds, clipBounds;
    if (!get_path_and_clip_bounds(target, path, vm,
                                  &pathBounds, &clipBounds)) {
        if (GrIsFillInverted(fill)) {
            draw_around_inv_path(target, stageMask,
                                 clipBounds, pathBounds);
        }
        return true;
    }

    SkAutoTUnref<GrTexture> texture(
            GrSWMaskHelper::DrawPathMaskToTexture(fContext, path, 
                                                  pathBounds, fill, 
                                                  antiAlias, &vm));
    if (NULL == texture) {
        return false;
    }

    GrSWMaskHelper::DrawToTargetWithPathMask(texture, target, 
                                             stageMask, pathBounds);

    if (GrIsFillInverted(fill)) {
        draw_around_inv_path(target, stageMask,
                                clipBounds, pathBounds);
    }

    return true;
}