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// Copyright (c) 2012 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 "ui/gfx/blit.h"
#include <stddef.h>
#include "base/check.h"
#include "build/build_config.h"
#include "skia/ext/platform_canvas.h"
#include "third_party/skia/include/core/SkPixmap.h"
#include "ui/gfx/geometry/point.h"
#include "ui/gfx/geometry/rect.h"
#include "ui/gfx/geometry/vector2d.h"
namespace gfx {
namespace {
// Returns true if the given canvas has any part of itself clipped out or
// any non-identity tranform.
bool HasClipOrTransform(SkCanvas& canvas) {
if (!canvas.getTotalMatrix().isIdentity())
return true;
if (!canvas.isClipRect())
return true;
// Now we know the clip is a regular rectangle, make sure it covers the
// entire canvas.
SkIRect clip_bounds = canvas.getDeviceClipBounds();
SkImageInfo info;
size_t row_bytes;
void* pixels = canvas.accessTopLayerPixels(&info, &row_bytes);
DCHECK(pixels);
if (!pixels)
return true;
if (clip_bounds.fLeft != 0 || clip_bounds.fTop != 0 ||
clip_bounds.fRight != info.width() ||
clip_bounds.fBottom != info.height())
return true;
return false;
}
} // namespace
void ScrollCanvas(SkCanvas* canvas,
const gfx::Rect& in_clip,
const gfx::Vector2d& offset) {
DCHECK(!HasClipOrTransform(*canvas)); // Don't support special stuff.
SkPixmap pixmap;
bool success = skia::GetWritablePixels(canvas, &pixmap);
DCHECK(success);
// We expect all coords to be inside the canvas, so clip here.
gfx::Rect clip = gfx::IntersectRects(
in_clip, gfx::Rect(0, 0, pixmap.width(), pixmap.height()));
// Compute the set of pixels we'll actually end up painting.
gfx::Rect dest_rect = gfx::IntersectRects(clip + offset, clip);
if (dest_rect.size().IsEmpty())
return; // Nothing to do.
// Compute the source pixels that will map to the dest_rect
gfx::Rect src_rect = dest_rect - offset;
size_t row_bytes = dest_rect.width() * 4;
if (offset.y() > 0) {
// Data is moving down, copy from the bottom up.
for (int y = dest_rect.height() - 1; y >= 0; y--) {
memcpy(pixmap.writable_addr32(dest_rect.x(), dest_rect.y() + y),
pixmap.addr32(src_rect.x(), src_rect.y() + y),
row_bytes);
}
} else if (offset.y() < 0) {
// Data is moving up, copy from the top down.
for (int y = 0; y < dest_rect.height(); y++) {
memcpy(pixmap.writable_addr32(dest_rect.x(), dest_rect.y() + y),
pixmap.addr32(src_rect.x(), src_rect.y() + y),
row_bytes);
}
} else if (offset.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(pixmap.writable_addr32(dest_rect.x(), dest_rect.y() + y),
pixmap.addr32(src_rect.x(), src_rect.y() + y),
row_bytes);
}
}
}
} // namespace gfx
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