gfx/blit.cc

// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "gfx/blit.h"

#include "base/logging.h"
#include "build/build_config.h"
#include "gfx/point.h"
#include "gfx/rect.h"
#include "skia/ext/platform_canvas.h"
#include "skia/ext/platform_device.h"

#if defined(OS_POSIX) && !defined(OS_MACOSX)
#include <cairo/cairo.h>
#endif

#if defined(OS_MACOSX)
#include "base/mac_util.h"
#include "base/scoped_cftyperef.h"
#endif

namespace gfx {

namespace {

// Returns true if the given canvas has any part of itself clipped out or
// any non-identity tranform.
bool HasClipOrTransform(const skia::PlatformCanvas& canvas) {
  if (!canvas.getTotalMatrix().isIdentity())
    return true;

  const SkRegion& clip_region = canvas.getTotalClip();
  if (clip_region.isEmpty() || clip_region.isComplex())
    return true;

  // Now we know the clip is a regular rectangle, make sure it covers the
  // entire canvas.
  const SkBitmap& bitmap = canvas.getTopPlatformDevice().accessBitmap(false);
  const SkIRect& clip_bounds = clip_region.getBounds();
  if (clip_bounds.fLeft != 0 || clip_bounds.fTop != 0 ||
      clip_bounds.fRight != bitmap.width() ||
      clip_bounds.fBottom != bitmap.height())
    return true;

  return false;
}

}  // namespace

void BlitContextToContext(NativeDrawingContext dst_context,
                          const Rect& dst_rect,
                          NativeDrawingContext src_context,
                          const Point& src_origin) {
#if defined(OS_WIN)
  BitBlt(dst_context, dst_rect.x(), dst_rect.y(),
         dst_rect.width(), dst_rect.height(),
         src_context, src_origin.x(), src_origin.y(), SRCCOPY);
#elif defined(OS_MACOSX)
  // Only translations and/or vertical flips in the source context are
  // supported; more complex source context transforms will be ignored.

  // If there is a translation on the source context, we need to account for
  // it ourselves since CGBitmapContextCreateImage will bypass it.
  Rect src_rect(src_origin, dst_rect.size());
  CGAffineTransform transform = CGContextGetCTM(src_context);
  bool flipped = fabs(transform.d + 1) < 0.0001;
  CGFloat delta_y = flipped ? CGBitmapContextGetHeight(src_context) -
                              transform.ty
                            : transform.ty;
  src_rect.Offset(transform.tx, delta_y);

  scoped_cftyperef<CGImageRef>
      src_image(CGBitmapContextCreateImage(src_context));
  scoped_cftyperef<CGImageRef> src_sub_image(
      CGImageCreateWithImageInRect(src_image, src_rect.ToCGRect()));
  CGContextDrawImage(dst_context, dst_rect.ToCGRect(), src_sub_image);
#else  // Linux, BSD, others
  // Only translations in the source context are supported; more complex
  // source context transforms will be ignored.
  cairo_save(dst_context);
  double surface_x = src_origin.x();
  double surface_y = src_origin.y();
  cairo_user_to_device(src_context, &surface_x, &surface_y);
  cairo_set_source_surface(dst_context, cairo_get_target(src_context),
                           dst_rect.x()-surface_x, dst_rect.y()-surface_y);
  cairo_rectangle(dst_context, dst_rect.x(), dst_rect.y(),
                  dst_rect.width(), dst_rect.height());
  cairo_clip(dst_context);
  cairo_paint(dst_context);
  cairo_restore(dst_context);
#endif
}

static NativeDrawingContext GetContextFromCanvas(
    skia::PlatformCanvas *canvas) {
  skia::PlatformDevice& device = canvas->getTopPlatformDevice();
#if defined(OS_WIN)
  return device.getBitmapDC();
#elif defined(OS_MACOSX)
  return device.GetBitmapContext();
#else  // Linux, BSD, others
  return device.beginPlatformPaint();
#endif
}

void BlitContextToCanvas(skia::PlatformCanvas *dst_canvas,
                         const Rect& dst_rect,
                         NativeDrawingContext src_context,
                         const Point& src_origin) {
  BlitContextToContext(GetContextFromCanvas(dst_canvas), dst_rect,
                       src_context, src_origin);
}

void BlitCanvasToContext(NativeDrawingContext dst_context,
                         const Rect& dst_rect,
                         skia::PlatformCanvas *src_canvas,
                         const Point& src_origin) {
  BlitContextToContext(dst_context, dst_rect,
                       GetContextFromCanvas(src_canvas), src_origin);
}

void BlitCanvasToCanvas(skia::PlatformCanvas *dst_canvas,
                        const Rect& dst_rect,
                        skia::PlatformCanvas *src_canvas,
                        const Point& src_origin) {
  BlitContextToContext(GetContextFromCanvas(dst_canvas), dst_rect,
                       GetContextFromCanvas(src_canvas), src_origin);
}

#if defined(OS_WIN)

void ScrollCanvas(skia::PlatformCanvas* canvas,
                  const gfx::Rect& clip,
                  const gfx::Point& amount) {
  DCHECK(!HasClipOrTransform(*canvas));  // Don't support special stuff.
  HDC hdc = canvas->beginPlatformPaint();

  RECT damaged_rect;
  RECT r = clip.ToRECT();
  ScrollDC(hdc, amount.x(), amount.y(), NULL, &r, NULL, &damaged_rect);

  canvas->endPlatformPaint();
}

#elif defined(OS_POSIX)
// Cairo has no nice scroll function so we do our own. On Mac it's possible to
// use platform scroll code, but it's complex so we just use the same path
// here. Either way it will be software-only, so it shouldn't matter much.

void ScrollCanvas(skia::PlatformCanvas* canvas,
                  const gfx::Rect& in_clip,
                  const gfx::Point& amount) {
  DCHECK(!HasClipOrTransform(*canvas));  // Don't support special stuff.
  SkBitmap& bitmap = const_cast<SkBitmap&>(
      canvas->getTopPlatformDevice().accessBitmap(true));
  SkAutoLockPixels lock(bitmap);

  // We expect all coords to be inside the canvas, so clip here.
  gfx::Rect clip = in_clip.Intersect(
      gfx::Rect(0, 0, bitmap.width(), bitmap.height()));

  // Compute the set of pixels we'll actually end up painting.
  gfx::Rect dest_rect = clip;
  dest_rect.Offset(amount);
  dest_rect = dest_rect.Intersect(clip);
  if (dest_rect.size() == gfx::Size())
    return;  // Nothing to do.

  // Compute the source pixels that will map to the dest_rect
  gfx::Rect src_rect = dest_rect;
  src_rect.Offset(-amount.x(), -amount.y());

  size_t row_bytes = dest_rect.width() * 4;
  if (amount.y() > 0) {
    // Data is moving down, copy from the bottom up.
    for (int y = dest_rect.height() - 1; y >= 0; y--) {
      memcpy(bitmap.getAddr32(dest_rect.x(), dest_rect.y() + y),
             bitmap.getAddr32(src_rect.x(), src_rect.y() + y),
             row_bytes);
    }
  } else if (amount.y() < 0) {
    // Data is moving up, copy from the top down.
    for (int y = 0; y < dest_rect.height(); y++) {
      memcpy(bitmap.getAddr32(dest_rect.x(), dest_rect.y() + y),
             bitmap.getAddr32(src_rect.x(), src_rect.y() + y),
             row_bytes);
    }
  } else if (amount.x() != 0) {
    // Horizontal-only scroll. We can do it in either top-to-bottom or bottom-
    // to-top, but have to be careful about the order for copying each row.
    // Fortunately, memmove already handles this for us.
    for (int y = 0; y < dest_rect.height(); y++) {
      memmove(bitmap.getAddr32(dest_rect.x(), dest_rect.y() + y),
              bitmap.getAddr32(src_rect.x(), src_rect.y() + y),
              row_bytes);
    }
  }
}

#endif

}  // namespace gfx