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// Copyright (c) 2011 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.
#ifndef PPAPI_CPP_GRAPHICS_2D_H_
#define PPAPI_CPP_GRAPHICS_2D_H_
#include "ppapi/c/pp_stdint.h"
#include "ppapi/cpp/resource.h"
#include "ppapi/cpp/size.h"
/// @file
/// This file defines the API to create a 2D graphics context in the browser.
namespace pp {
class CompletionCallback;
class ImageData;
class Instance;
class Point;
class Rect;
class Graphics2D : public Resource {
public:
/// Default constructor for creating an is_null() <code>Graphics2D</code>
/// object.
Graphics2D();
/// The copy constructor for Graphics2D. The underlying 2D context is not
/// copied; this constructor creates another reference to the original 2D
/// context.
///
/// @param[in] other A pointer to a <code>Graphics2D</code> context.
Graphics2D(const Graphics2D& other);
/// A constructor allocating a new 2D graphics context with the given size
/// in the browser, resulting object will be is_null() if the allocation
/// failed.
///
/// @param[in] instance The module instance.
/// @param[in] size The size of the 2D graphics context in the browser,
/// measured in device pixels.
/// @param[in] is_always_opaque Set the <code>is_always_opaque</code> flag
/// to true if you know that you will be painting only opaque data to this
/// context. This option will disable blending when compositing the module
/// with the web page, which might give higher performance on some computers.
///
/// If you set <code>is_always_opaque</code>, your alpha channel should
/// always be set to 0xFF or there may be painting artifacts. The alpha values
/// overwrite the destination alpha values without blending when
/// <code>is_always_opaque</code> is true.
Graphics2D(Instance* instance, const Size& size, bool is_always_opaque);
/// A destructor that decrements the reference count of a
/// <code>Graphics2D</code> object made using the previous copy constructor.
/// It is possible that the destructor does not toally destroy the underlying
/// 2D context if there are outstanding references to it.
virtual ~Graphics2D();
/// This function assigns one 2D graphics context to this 2D graphics
/// context. This function increases the reference count of the 2D resource
/// of the other 2D graphics context while decrementing the reference counter
/// of this 2D graphics context.
///
/// @param[in] other An other 2D graphics context.
///
/// @return A new Graphics2D context.
Graphics2D& operator=(const Graphics2D& other);
/// Getter function for returning size of the 2D graphics context.
///
/// @return The size of the 2D graphics context measured in device pixels.
const Size& size() const { return size_; }
/// PaintImageData() enqueues a paint command of the given image into
/// the context. This command has no effect until you call Flush(). As a
/// result, what counts is the contents of the bitmap when you call Flush,
/// not when you call this function.
///
/// The provided image will be placed at <code>top_left</code> from the top
/// left of the context's internal backing store. This version of
/// PaintImageData paints the entire image. Refer to the other version of
/// this function to paint only part of the area.
///
/// The painted area of the source bitmap must fall entirely within the
/// context. Attempting to paint outside of the context will result in an
/// error.
///
/// There are two methods most modules will use for painting. The first
/// method is to generate a new <code>ImageData</code> and then paint it.
/// In this case, you'll set the location of your painting to
/// <code>top_left</code> and set <code>src_rect</code> to <code>NULL</code>.
/// The second is that you're generating small invalid regions out of a larger
/// bitmap representing your entire module's image.
///
/// @param[in] image The <code>ImageData</code> to be painted.
/// @param[in] top_left A <code>Point</code> representing the
/// <code>top_left</code> location where the <code>ImageData</code> will be
/// painted.
void PaintImageData(const ImageData& image,
const Point& top_left);
/// PaintImageData() enqueues a paint command of the given image into
/// the context. This command has no effect until you call Flush(). As a
/// result, what counts is the contents of the bitmap when you call Flush(),
/// not when you call this function.
///
/// The provided image will be placed at <code>top_left</code> from the top
/// left of the context's internal backing store. Then the pixels contained
/// in <code>src_rect</code> will be copied into the backing store. This
/// means that the rectangle being painted will be at <code>src_rect</code>
/// offset by <code>top_left</code>.
///
/// The <code>src_rect</code> is specified in the coordinate system of the
/// image being painted, not the context. For the common case of copying the
/// entire image, you may specify an empty <code>src_rect</code>.
///
/// The painted area of the source bitmap must fall entirely within the
/// context. Attempting to paint outside of the context will result in an
/// error. However, the source bitmap may fall outside the context, as long
/// as the <code>src_rect</code> subset of it falls entirely within the
/// context.
///
/// There are two methods most modules will use for painting. The first
/// method is to generate a new <code>ImageData</code> and then paint it. In
/// this case, you'll set the location of your painting to
/// <code>top_left</code> and set <code>src_rect</code> to <code>NULL</code>.
/// The second is that you're generating small invalid regions out of a larger
/// bitmap representing your entire module. In this case, you would set the
/// location of your image to (0,0) and then set <code>src_rect</code> to the
/// pixels you changed.
///
/// @param[in] image The <code>ImageData</code> to be painted.
/// @param[in] top_left A <code>Point</code> representing the
/// <code>top_left</code> location where the <code>ImageData</code> will be
/// painted.
/// @param[in] src_rect The rectangular area where the <code>ImageData</code>
/// will be painted.
void PaintImageData(const ImageData& image,
const Point& top_left,
const Rect& src_rect);
/// Scroll() enqueues a scroll of the context's backing store. This
/// function has no effect until you call Flush(). The data within the
/// provided clipping rectangle will be shifted by (dx, dy) pixels.
///
/// This function will result in some exposed region which will have
/// undefined contents. The module should call PaintImageData() on
/// these exposed regions to give the correct contents.
///
/// The scroll can be larger than the area of the clipping rectangle, which
/// means the current image will be scrolled out of the rectangle. This
/// scenario is not an error but will result in a no-op.
///
/// @param[in] clip The clipping rectangle.
/// @param[in] amount The amount the area in the clipping rectangle will
/// shifted.
void Scroll(const Rect& clip, const Point& amount);
/// ReplaceContents() provides a slightly more efficient way to paint the
/// entire module's image. Normally, calling PaintImageData() requires that
/// the browser copy the pixels out of the image and into the graphics
/// context's backing store. This function replaces the graphics context's
/// backing store with the given image, avoiding the copy.
///
/// The new image must be the exact same size as this graphics context. If
/// the new image uses a different image format than the browser's native
/// bitmap format (use ImageData::GetNativeImageDataFormat() to retrieve the
/// format), then a conversion will be done inside the browser which may slow
/// the performance a little bit.
///
/// <strong>Note:</strong> The new image will not be painted until you call
/// Flush().
///
/// After this call, you should take care to release your references to the
/// image. If you paint to the image after ReplaceContents(), there is the
/// possibility of significant painting artifacts because the page might use
/// partially-rendered data when copying out of the backing store.
///
/// In the case of an animation, you will want to allocate a new image for
/// the next frame. It is best if you wait until the flush callback has
/// executed before allocating this bitmap. This gives the browser the option
/// of caching the previous backing store and handing it back to you
/// (assuming the sizes match). In the optimal case, this means no bitmaps are
/// allocated during the animation, and the backing store and "front buffer"
/// (which the module is painting into) are just being swapped back and forth.
///
/// @param[in] image The <code>ImageData</code> to be painted.
void ReplaceContents(ImageData* image);
/// Flush() flushes any enqueued paint, scroll, and replace commands
/// to the backing store. This actually executes the updates, and causes a
/// repaint of the webpage, assuming this graphics context is bound to a
/// module instance.
///
/// Flush() runs in asynchronous mode. Specify a callback function and
/// the argument for that callback function. The callback function will be
/// executed on the calling thread when the image has been painted to the
/// screen. While you are waiting for a <code>Flush</code> callback,
/// additional calls to Flush() will fail.
///
/// Because the callback is executed (or thread unblocked) only when the
/// module's image is actually on the screen, this function provides
/// a way to rate limit animations. By waiting until the image is on the
/// screen before painting the next frame, you can ensure you're not
/// flushing 2D graphics faster than the screen can be updated.
///
/// <strong>Unbound contexts</strong>
/// If the context is not bound to a module instance, you will
/// still get a callback. The callback will execute after Flush() returns
/// to avoid reentrancy. The callback will not wait until anything is
/// painted to the screen because there will be nothing on the screen. The
/// timing of this callback is not guaranteed and may be deprioritized by
/// the browser because it is not affecting the user experience.
///
/// <strong>Off-screen instances</strong>
/// If the context is bound to an instance that is
/// currently not visible (for example, scrolled out of view) it will
/// behave like the "unbound context" case.
///
/// <strong>Detaching a context</strong>
/// If you detach a context from a module instance, any
/// pending flush callbacks will be converted into the "unbound context"
/// case.
///
/// <strong>Released contexts</strong>
/// A callback may or may not still get called even if you have released all
/// of your references to the context. This can occur if there are internal
/// references to the context that means it has not been internally
/// destroyed (for example, if it is still bound to an instance) or due to
/// other implementation details. As a result, you should be careful to
/// check that flush callbacks are for the context you expect and that
/// you're capable of handling callbacks for context that you may have
/// released your reference to.
///
/// <strong>Shutdown</strong>
/// If a module instance is removed when a Flush is pending, the
/// callback will not be executed.
///
/// @param[in] cc A <code>CompletionCallback</code> to be called when the
/// image has been painted on the screen.
///
/// @return Returns <code>PP_OK</code> on success or
/// <code>PP_Error_BadResource</code> if the graphics context is invalid,
/// <code>PP_Error_BadArgument</code> if the callback is null and
/// flush is being called from the main thread of the module, or
/// <code>PP_Error_InProgress</code> if a flush is already pending that has
/// not issued its callback yet. In the failure case, nothing will be
/// updated and no callback will be scheduled.
// TODO(darin): We should ensure that the completion callback always runs, so
// that it is easier for consumers to manage memory referenced by a callback.
// TODO(): Add back in the synchronous mode description once we have support
// for it.
int32_t Flush(const CompletionCallback& cc);
private:
Size size_;
};
} // namespace pp
#endif // PPAPI_CPP_GRAPHICS_2D_H_