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// Copyright (c) 2010 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_C_PPB_GRAPHICS_2D_H_
#define PPAPI_C_PPB_GRAPHICS_2D_H_
#include "ppapi/c/pp_module.h"
#include "ppapi/c/pp_resource.h"
#include "ppapi/c/pp_stdint.h"
struct PP_CompletionCallback;
struct PP_Point;
struct PP_Rect;
struct PP_Size;
#define PPB_GRAPHICS_2D_INTERFACE "PPB_Graphics2D;0.1"
/**
* @file
* Defines the PPB_Graphics2D struct.
*
* @addtogroup PPB
* @{
*/
/** {PENDING: describe PPB_Graphics2D. */
struct PPB_Graphics2D {
/**
* The returned graphics context will not be bound to any plugin instance on
* creation (call BindGraphics on the plugin instance to do that. The
* graphics context has a lifetime that can exceed that of the given plugin
* instance.
*
* Set the is_always_opaque flag if you know that you will be painting only
* opaque data to this context. This will disable blending when compositing
* the plugin with the web page, which will give slightly higher performance.
*
* If you set is_always_opaque, your alpha channel should always be set to
* 0xFF or there may be painting artifacts. Being opaque will allow the
* browser to do a memcpy rather than a blend to paint the plugin, and this
* means your alpha values will get set on the page backing store. If these
* values are incorrect, it could mess up future blending.
*
* If you aren't sure, it is always correct to specify that it it not opaque.
*/
PP_Resource (*Create)(PP_Module module,
const struct PP_Size* size,
bool is_always_opaque);
/**
* Returns true if the given resource is a valid Graphics2D, false if it
* is an invalid resource or is a resource of another type.
*/
bool (*IsGraphics2D)(PP_Resource resource);
/**
* Retrieves the configuration for the given graphics context, filling the
* given values (which must not be NULL). On success, returns true. If the
* resource is invalid, the output parameters will be set to 0 and it will
* return false.
*/
bool (*Describe)(PP_Resource graphics_2d,
struct PP_Size* size,
bool* is_always_opqaue);
/**
* Enqueues a paint of the given image into the context. THIS 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 given image will be placed at |top_left| from the top left of the
* context's internal backing store. Then the src_rect will be copied into the
* backing store. This parameter may not be NULL.
*
* The src_rect 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 a NULL |src_rect| pointer. If you are frequently updating
* the entire image, consider using SwapImageData which will give slightly
* higher performance.
*
* 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 src_rect subset of it falls entirely within the context.
*/
void (*PaintImageData)(PP_Resource graphics_2d,
PP_Resource image_data,
const struct PP_Point* top_left,
const struct PP_Rect* src_rect);
/**
* Enqueues a scroll of the context's backing store. THIS HAS NO EFFECT UNTIL
* YOU CALL Flush(). The data within the given clip rect (you may specify
* NULL to scroll the entire region) will be shifted by (dx, dy) pixels.
*
* This will result in some exposed region which will have undefined
* contents. The plugin should call PaintImageData on these exposed regions
* to give the correct contents.
*
* The scroll can be larger than the area of the clip rect, which means the
* current image will be scrolled out of the rect. This is not an error but
* will be a no-op.
*/
void (*Scroll)(PP_Resource graphics_2d,
const struct PP_Rect* clip_rect,
const struct PP_Point* amount);
/**
* This function provides a slightly more efficient way to paint the entire
* plugin'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 PPB_ImageData.GetNativeImageDataFormat to retrieve this), then
* a conversion will be done inside the browser which may slow the performance
* a little bit.
*
* 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 a Swap, 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
* plugin is painting into) are just being swapped back and forth.
*/
void (*ReplaceContents)(PP_Resource graphics_2d, PP_Resource image_data);
/**
* Flushes any enqueued paint, scroll, and swap commands for the backing
* store. This actually executes the updates, and causes a repaint of the
* webpage, assuming this graphics context is bound to a plugin instance. This
* can run in two modes:
*
* - In synchronous mode, you specify NULL for the callback and the callback
* data. This function will block the calling thread until the image has
* been painted to the screen. It is not legal to block the main thread of
* the plugin, you can use synchronous mode only from background threads.
*
* - In asynchronous mode, you 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 Flush callback, additional calls to Flush will
* fail.
*
* Because the callback is executed (or thread unblocked) only when the
* plugin's current state 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 generating
* updates faster than the screen can be updated.
*
* <dl>
* <dt>Unbound contexts</dt>
* <dd>
* If the context is not bound to a plugin instance, you will
* still get a callback. It will execute after the Flush function returns
* to avoid reentrancy. Of course, it 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.
* </dd>
*
* <dt>Off-screen instances</dt>
* <dd>
* 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.
* </dd>
*
* <dt>Detaching a context</dt>
* <dd>
* If you detach a context from a plugin instance, any
* pending flush callbacks will be converted into the "unbound context"
* case.
* </dd>
*
* <dt>Released contexts</dt>
* <dd>
* 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.
* </dd>
*
* <dt>Shutdown</dt>
* <dd>
* If a plugin instance is removed when a Flush is pending, the
* callback will not be executed.
* </dd>
* </dl>
*
* Returns PP_OK on success, PP_Error_BadResource if the graphics context is
* invalid, PP_Error_BadArgument if the callback is null and Flush is being
* called from the main thread of the plugin, or PP_Error_InProgress 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.
int32_t (*Flush)(PP_Resource graphics_2d,
struct PP_CompletionCallback callback);
};
/**
* @}
* End addtogroup PPB
*/
#endif // PPAPI_C_PPB_GRAPHICS_2D_H_
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