src/utils/SkDeferredCanvas.cpp

/*
 * Copyright 2011 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "SkDeferredCanvas.h"

#include "SkPaint.h"
#include "SkShader.h"
#include "SkColorFilter.h"
#include "SkDrawFilter.h"

namespace {

bool isPaintOpaque(const SkPaint* paint, const SkBitmap* bmpReplacesShader = NULL) {
    // TODO: SkXfermode should have a virtual isOpaque method, which would
    // make it possible to test modes that do not have a Coeff representation.

    if (!paint) {
        return bmpReplacesShader ? bmpReplacesShader->isOpaque() : true;
    }

    SkXfermode::Coeff srcCoeff, dstCoeff;
    if (SkXfermode::AsCoeff(paint->getXfermode(), &srcCoeff, &dstCoeff)){
        switch (dstCoeff) {
        case SkXfermode::kZero_Coeff:
            return true;
        case SkXfermode::kISA_Coeff:
            if (paint->getAlpha() != 255) {
                break;
            }
            if (bmpReplacesShader) {
                if (!bmpReplacesShader->isOpaque()) {
                    break;
                }
            } else if (paint->getShader() && !paint->getShader()->isOpaque()) {
                break;
            }
            if (paint->getColorFilter() && ((paint->getColorFilter()->getFlags() &
                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
                break;
            }
            return true;
        case SkXfermode::kSA_Coeff:
            if (paint->getAlpha() != 0) {
                break;
            }
            if (paint->getColorFilter() && ((paint->getColorFilter()->getFlags() &
                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
                break;
            }
            return true;
        case SkXfermode::kSC_Coeff:
            if (paint->getColor() != 0) { // all components must be 0
                break;
            }
            if (bmpReplacesShader || paint->getShader()) {
                break;
            }
            if (paint->getColorFilter() && ((paint->getColorFilter()->getFlags() &
                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
                break;
            }
            return true;
        default:
            break;
        }
    }
    return false;
}

} // unnamed namespace

SkDeferredCanvas::SkDeferredCanvas()
{
    init();
}

SkDeferredCanvas::SkDeferredCanvas(SkDevice* device)
{
    init();
    setDevice(device);
}

SkDeferredCanvas::SkDeferredCanvas(SkDevice* device, 
                                   DeviceContext* deviceContext)
{
    init();
    setDevice(device);
    setDeviceContext(deviceContext);
}

void SkDeferredCanvas::init()
{
    fDeferredDrawing = true; // On by default
}

void SkDeferredCanvas::validate() const
{
    SkASSERT(getDevice());
}

SkCanvas* SkDeferredCanvas::drawingCanvas() const
{
    validate();
    return fDeferredDrawing ? getDeferredDevice()->recordingCanvas() :
        getDeferredDevice()->immediateCanvas();
}

void SkDeferredCanvas::flushIfNeeded(const SkBitmap& bitmap)
{
    validate();
    if (fDeferredDrawing) {
        getDeferredDevice()->flushIfNeeded(bitmap);
    }
}

SkDeferredCanvas::DeferredDevice* SkDeferredCanvas::getDeferredDevice() const
{
    return static_cast<SkDeferredCanvas::DeferredDevice*>(getDevice());
}

void SkDeferredCanvas::setDeferredDrawing(bool val)
{
    validate(); // Must set device before calling this method
    SkASSERT(drawingCanvas()->getSaveCount() == 1);
    if (val != fDeferredDrawing) {
        if (fDeferredDrawing) {
            // Going live.
            getDeferredDevice()->flushPending();
        }
        fDeferredDrawing = val;
    }
}

SkDeferredCanvas::~SkDeferredCanvas()
{
}

SkDevice* SkDeferredCanvas::setDevice(SkDevice* device)
{
    INHERITED::setDevice(SkNEW_ARGS(DeferredDevice, (device)))->unref();
    return device;
}

SkDeferredCanvas::DeviceContext* SkDeferredCanvas::setDeviceContext(
    DeviceContext* deviceContext) 
{
    DeferredDevice* deferredDevice = getDeferredDevice();
    SkASSERT(deferredDevice);
    if (deferredDevice) {
        deferredDevice->setDeviceContext(deviceContext);
    }
    return deviceContext;
}

bool SkDeferredCanvas::isFullFrame(const SkRect* rect,
                                   const SkPaint* paint) const
{
    SkCanvas* canvas = drawingCanvas();
    SkISize canvasSize = getDeviceSize();
    if (rect) {
        if (!canvas->getTotalMatrix().rectStaysRect()) {
            return false; // conservative
        }

        SkRect transformedRect;
        canvas->getTotalMatrix().mapRect(&transformedRect, *rect);

        if (paint) {
            SkPaint::Style paintStyle = paint->getStyle();
            if (!(paintStyle == SkPaint::kFill_Style || 
                paintStyle == SkPaint::kStrokeAndFill_Style)) {
                return false;
            }
            if (paint->getMaskFilter() || paint->getLooper()
                || paint->getPathEffect() || paint->getImageFilter()) {
                return false; // conservative
            }
        }

        // The following test holds with AA enabled, and is conservative
        // by a 0.5 pixel margin with AA disabled
        if (transformedRect.fLeft > SkIntToScalar(0) || 
            transformedRect.fTop > SkIntToScalar(0) || 
            transformedRect.fRight < SkIntToScalar(canvasSize.fWidth) ||
            transformedRect.fBottom < SkIntToScalar(canvasSize.fHeight)) {
            return false;
        }
    }

    switch (canvas->getClipType()) {
        case SkCanvas::kRect_ClipType :
            {
                SkIRect bounds;
                canvas->getClipDeviceBounds(&bounds);
                if (bounds.fLeft > 0 || bounds.fTop > 0 || 
                    bounds.fRight < canvasSize.fWidth || 
                    bounds.fBottom < canvasSize.fHeight)
                    return false;
            }
            break;
        case SkCanvas::kComplex_ClipType :
            return false; // conservative
        case SkCanvas::kEmpty_ClipType:
        default:
            break;
    };

    return true;
}

int SkDeferredCanvas::save(SaveFlags flags)
{
    drawingCanvas()->save(flags);
    return this->INHERITED::save(flags);
}

int SkDeferredCanvas::saveLayer(const SkRect* bounds, const SkPaint* paint,
                          SaveFlags flags)
{
    drawingCanvas()->saveLayer(bounds, paint, flags);
    int count = this->INHERITED::save(flags);
    this->clipRectBounds(bounds, flags, NULL);
    return count;
}

void SkDeferredCanvas::restore()
{
    drawingCanvas()->restore();
    this->INHERITED::restore();
}

bool SkDeferredCanvas::isDrawingToLayer() const
{
    return drawingCanvas()->isDrawingToLayer();
}

bool SkDeferredCanvas::translate(SkScalar dx, SkScalar dy)
{
    drawingCanvas()->translate(dx, dy);
    return this->INHERITED::translate(dx, dy);
}

bool SkDeferredCanvas::scale(SkScalar sx, SkScalar sy)
{
    drawingCanvas()->scale(sx, sy);
    return this->INHERITED::scale(sx, sy);
}

bool SkDeferredCanvas::rotate(SkScalar degrees)
{
    drawingCanvas()->rotate(degrees);
    return this->INHERITED::rotate(degrees);
}

bool SkDeferredCanvas::skew(SkScalar sx, SkScalar sy)
{
    drawingCanvas()->skew(sx, sy);
    return this->INHERITED::skew(sx, sy);
}

bool SkDeferredCanvas::concat(const SkMatrix& matrix)
{
    drawingCanvas()->concat(matrix);
    return this->INHERITED::concat(matrix);
}

void SkDeferredCanvas::setMatrix(const SkMatrix& matrix)
{
    drawingCanvas()->setMatrix(matrix);
    this->INHERITED::setMatrix(matrix);
}

bool SkDeferredCanvas::clipRect(const SkRect& rect,
                                SkRegion::Op op,
                                bool doAntiAlias)
{
    drawingCanvas()->clipRect(rect, op, doAntiAlias);
    return this->INHERITED::clipRect(rect, op, doAntiAlias);
}

bool SkDeferredCanvas::clipPath(const SkPath& path,
                                SkRegion::Op op,
                                bool doAntiAlias)
{
    drawingCanvas()->clipPath(path, op, doAntiAlias);
    return this->INHERITED::clipPath(path, op, doAntiAlias);
}

bool SkDeferredCanvas::clipRegion(const SkRegion& deviceRgn,
                                  SkRegion::Op op)
{
    drawingCanvas()->clipRegion(deviceRgn, op);
    return this->INHERITED::clipRegion(deviceRgn, op);
}

void SkDeferredCanvas::clear(SkColor color)
{
    // purge pending commands
    if (fDeferredDrawing) {
        getDeferredDevice()->contentsCleared();
    }

    drawingCanvas()->clear(color);
}

void SkDeferredCanvas::drawPaint(const SkPaint& paint)
{
    if (fDeferredDrawing && isFullFrame(NULL, &paint) && isPaintOpaque(&paint)) {
        getDeferredDevice()->contentsCleared();
    }

    drawingCanvas()->drawPaint(paint);
}

void SkDeferredCanvas::drawPoints(PointMode mode, size_t count,
                                  const SkPoint pts[], const SkPaint& paint)
{
    drawingCanvas()->drawPoints(mode, count, pts, paint);
}

void SkDeferredCanvas::drawRect(const SkRect& rect, const SkPaint& paint)
{
    if (fDeferredDrawing && isFullFrame(&rect, &paint) && isPaintOpaque(&paint)) {
        getDeferredDevice()->contentsCleared();
    }

    drawingCanvas()->drawRect(rect, paint);
}

void SkDeferredCanvas::drawPath(const SkPath& path, const SkPaint& paint)
{
    drawingCanvas()->drawPath(path, paint);
}

void SkDeferredCanvas::drawBitmap(const SkBitmap& bitmap, SkScalar left,
                                  SkScalar top, const SkPaint* paint)
{
    SkRect bitmapRect = SkRect::MakeXYWH(left, top,
        SkIntToScalar(bitmap.width()), SkIntToScalar(bitmap.height()));
    if (fDeferredDrawing && 
        isFullFrame(&bitmapRect, paint) &&
        isPaintOpaque(paint, &bitmap)) {
        getDeferredDevice()->contentsCleared();
    }

    drawingCanvas()->drawBitmap(bitmap, left, top, paint);
    flushIfNeeded(bitmap);
}

void SkDeferredCanvas::drawBitmapRect(const SkBitmap& bitmap, 
                                      const SkIRect* src,
                                      const SkRect& dst, const SkPaint* paint)
{
    if (fDeferredDrawing && 
        isFullFrame(&dst, paint) &&
        isPaintOpaque(paint, &bitmap)) {
        getDeferredDevice()->contentsCleared();
    }

    drawingCanvas()->drawBitmapRect(bitmap, src,
                                    dst, paint);
    flushIfNeeded(bitmap);
}


void SkDeferredCanvas::drawBitmapMatrix(const SkBitmap& bitmap,
                                        const SkMatrix& m,
                                        const SkPaint* paint)
{
    // TODO: reset recording canvas if paint+bitmap is opaque and clip rect
    // covers canvas entirely and transformed bitmap covers canvas entirely
    drawingCanvas()->drawBitmapMatrix(bitmap, m, paint);
    flushIfNeeded(bitmap);
}

void SkDeferredCanvas::drawBitmapNine(const SkBitmap& bitmap,
                                      const SkIRect& center, const SkRect& dst,
                                      const SkPaint* paint)
{
    // TODO: reset recording canvas if paint+bitmap is opaque and clip rect
    // covers canvas entirely and dst covers canvas entirely
    drawingCanvas()->drawBitmapNine(bitmap, center,
                                    dst, paint);
    flushIfNeeded(bitmap);
}

void SkDeferredCanvas::drawSprite(const SkBitmap& bitmap, int left, int top,
                                  const SkPaint* paint)
{
    SkRect bitmapRect = SkRect::MakeXYWH(
        SkIntToScalar(left),
        SkIntToScalar(top), 
        SkIntToScalar(bitmap.width()),
        SkIntToScalar(bitmap.height()));
    if (fDeferredDrawing && 
        isFullFrame(&bitmapRect, paint) &&
        isPaintOpaque(paint, &bitmap)) {
        getDeferredDevice()->contentsCleared();
    }

    drawingCanvas()->drawSprite(bitmap, left, top,
                                paint);
    flushIfNeeded(bitmap);
}

void SkDeferredCanvas::drawText(const void* text, size_t byteLength,
                                SkScalar x, SkScalar y, const SkPaint& paint)
{
    drawingCanvas()->drawText(text, byteLength, x,
                              y, paint);
}

void SkDeferredCanvas::drawPosText(const void* text, size_t byteLength,
                                   const SkPoint pos[], const SkPaint& paint)
{
    drawingCanvas()->drawPosText(text, byteLength,
                                 pos, paint);
}

void SkDeferredCanvas::drawPosTextH(const void* text, size_t byteLength,
                                    const SkScalar xpos[], SkScalar constY,
                                    const SkPaint& paint)
{
    drawingCanvas()->drawPosTextH(text, byteLength,
                                  xpos, constY,
                                  paint);
}

void SkDeferredCanvas::drawTextOnPath(const void* text, size_t byteLength,
                                      const SkPath& path,
                                      const SkMatrix* matrix,
                                      const SkPaint& paint)
{
    drawingCanvas()->drawTextOnPath(text, byteLength,
                                    path, matrix,
                                    paint);
}

void SkDeferredCanvas::drawPicture(SkPicture& picture)
{
    drawingCanvas()->drawPicture(picture);
}

void SkDeferredCanvas::drawVertices(VertexMode vmode, int vertexCount,
                                    const SkPoint vertices[],
                                    const SkPoint texs[],
                                    const SkColor colors[], SkXfermode* xmode,
                                    const uint16_t indices[], int indexCount,
                                    const SkPaint& paint)
{
    drawingCanvas()->drawVertices(vmode, vertexCount,
                                  vertices, texs,
                                  colors, xmode,
                                  indices, indexCount,
                                  paint);
}

SkBounder* SkDeferredCanvas::setBounder(SkBounder* bounder)
{
    drawingCanvas()->setBounder(bounder);
    return INHERITED::setBounder(bounder);
}

SkDrawFilter* SkDeferredCanvas::setDrawFilter(SkDrawFilter* filter)
{
    drawingCanvas()->setDrawFilter(filter); 
    return INHERITED::setDrawFilter(filter); // So non-virtual getDrawFilter works
}

SkCanvas* SkDeferredCanvas::canvasForDrawIter() {
    return drawingCanvas();
}

// SkDeferredCanvas::DeferredDevice
//------------------------------------

SkDeferredCanvas::DeferredDevice::DeferredDevice(
    SkDevice* immediateDevice, DeviceContext* deviceContext) :
    SkDevice(SkBitmap::kNo_Config, immediateDevice->width(),
             immediateDevice->height(), immediateDevice->isOpaque())
    , fFreshFrame(true)
{
    fDeviceContext = deviceContext;
    SkSafeRef(fDeviceContext);
    fImmediateDevice = immediateDevice; // ref counted via fImmediateCanvas
    fImmediateCanvas = SkNEW_ARGS(SkCanvas, (fImmediateDevice));
    fRecordingCanvas = fPicture.beginRecording(fImmediateDevice->width(),
        fImmediateDevice->height(), 0);
}

SkDeferredCanvas::DeferredDevice::~DeferredDevice()
{
    SkSafeUnref(fImmediateCanvas);
    SkSafeUnref(fDeviceContext);
}
    
void SkDeferredCanvas::DeferredDevice::setDeviceContext(
    DeviceContext* deviceContext)
{
    SkRefCnt_SafeAssign(fDeviceContext, deviceContext);
}

void SkDeferredCanvas::DeferredDevice::contentsCleared()
{
    if (!fRecordingCanvas->isDrawingToLayer()) {
        fFreshFrame = true;

        // TODO: find a way to transfer the state stack and layers
        // to the new recording canvas.  For now, purging only works
        // with an empty stack.
        if (fRecordingCanvas->getSaveCount() == 0) {

            // Save state that is trashed by the purge
            SkDrawFilter* drawFilter = fRecordingCanvas->getDrawFilter();
            SkSafeRef(drawFilter); // So that it survives the purge
            SkMatrix matrix = fRecordingCanvas->getTotalMatrix();
            SkRegion clipRegion = fRecordingCanvas->getTotalClip();

            // beginRecording creates a new recording canvas and discards the
            // old one, hence purging deferred draw ops.
            fRecordingCanvas = fPicture.beginRecording(
                fImmediateDevice->width(),
                fImmediateDevice->height(), 0);

            // Restore pre-purge state
            if (!clipRegion.isEmpty()) {
                fRecordingCanvas->clipRegion(clipRegion, SkRegion::kReplace_Op);
            }
            if (!matrix.isIdentity()) {
                fRecordingCanvas->setMatrix(matrix);
            }
            if (drawFilter) {
                fRecordingCanvas->setDrawFilter(drawFilter)->unref();
            }
        }
    }
}

bool SkDeferredCanvas::DeferredDevice::isFreshFrame() {
    bool ret = fFreshFrame;
    fFreshFrame = false;
    return ret;
}

void SkDeferredCanvas::DeferredDevice::flushPending()
{
    if (fDeviceContext) {
        fDeviceContext->prepareForDraw();
    }
    fPicture.draw(fImmediateCanvas);
    fRecordingCanvas = fPicture.beginRecording(fImmediateDevice->width(), 
        fImmediateDevice->height(), 0);
}

void SkDeferredCanvas::DeferredDevice::flush()
{
    flushPending();
    fImmediateCanvas->flush();
}

void SkDeferredCanvas::DeferredDevice::flushIfNeeded(const SkBitmap& bitmap)
{
    if (bitmap.isImmutable()) {
        return; // safe to deffer without registering a dependency
    }

    // For now, drawing a writable bitmap triggers a flush
    // TODO: implement read-only semantics and auto buffer duplication on write
    // in SkBitmap/SkPixelRef, which will make deferral possible in this case.
    flushPending();
}

uint32_t SkDeferredCanvas::DeferredDevice::getDeviceCapabilities() 
{ 
    return fImmediateDevice->getDeviceCapabilities();
}

int SkDeferredCanvas::DeferredDevice::width() const
{ 
    return fImmediateDevice->width();
}

int SkDeferredCanvas::DeferredDevice::height() const
{
    return fImmediateDevice->height(); 
}

SkGpuRenderTarget* SkDeferredCanvas::DeferredDevice::accessRenderTarget()
{
    flushPending();
    return fImmediateDevice->accessRenderTarget();
}

void SkDeferredCanvas::DeferredDevice::writePixels(const SkBitmap& bitmap,
    int x, int y, SkCanvas::Config8888 config8888)
{
    if (x <= 0 && y <= 0 && (x + bitmap.width()) >= width() &&
        (y + bitmap.height()) >= height()) {
        contentsCleared();
    }

    if (SkBitmap::kARGB_8888_Config == bitmap.config() &&
        SkCanvas::kNative_Premul_Config8888 != config8888 &&
        kPMColorAlias != config8888) {
        //Special case config: no deferral
        flushPending();
        fImmediateDevice->writePixels(bitmap, x, y, config8888);
    }

    SkPaint paint;
    paint.setXfermodeMode(SkXfermode::kSrc_Mode);
    fRecordingCanvas->drawSprite(bitmap, x, y, &paint);
    flushIfNeeded(bitmap);
}

const SkBitmap& SkDeferredCanvas::DeferredDevice::onAccessBitmap(SkBitmap*)
{
    flushPending();
    return fImmediateDevice->accessBitmap(false);
}

SkDevice* SkDeferredCanvas::DeferredDevice::onCreateCompatibleDevice(
    SkBitmap::Config config, int width, int height, bool isOpaque, Usage usage)
{
    // Save layer usage not supported, and not required by SkDeferredCanvas.
    SkASSERT(usage != kSaveLayer_Usage);
    // Create a compatible non-deferred device.
    SkDevice* compatibleDevice = fImmediateDevice->createCompatibleDevice(config, width,
        height, isOpaque);
    return SkNEW_ARGS(DeferredDevice, (compatibleDevice, fDeviceContext));
}

bool SkDeferredCanvas::DeferredDevice::onReadPixels(
    const SkBitmap& bitmap, int x, int y, SkCanvas::Config8888 config8888)
{
    flushPending();
    return fImmediateCanvas->readPixels(const_cast<SkBitmap*>(&bitmap),
                                                   x, y, config8888);
}