| // 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. |
| |
| #ifndef PPAPI_CPP_VIEW_H_ |
| #define PPAPI_CPP_VIEW_H_ |
| |
| #include "ppapi/cpp/resource.h" |
| #include "ppapi/cpp/rect.h" |
| #include "ppapi/cpp/size.h" |
| |
| /// @file |
| /// This file defines the API for getting the state of a the view for an |
| /// instance. |
| |
| namespace pp { |
| |
| /// This class represents the state of the view for an instance and contains |
| /// functions for retrieving the current state of that view. |
| class View : public Resource { |
| public: |
| /// Default constructor for creating an is_null() <code>View</code> object. |
| View(); |
| |
| /// Creates a View resource, taking and holding an additional reference to |
| /// the given resource handle. |
| explicit View(PP_Resource view_resource); |
| |
| /// GetRect() retrieves the rectangle of the module instance associated |
| /// with a view changed notification relative to the upper-left of the browser |
| /// viewport. This position changes when the page is scrolled. |
| /// |
| /// The returned rectangle may not be inside the visible portion of the |
| /// viewport if the module instance is scrolled off the page. Therefore, the |
| /// position may be negative or larger than the size of the page. The size |
| /// will always reflect the size of the module were it to be scrolled |
| /// entirely into view. |
| /// |
| /// In general, most modules will not need to worry about the position of the |
| ///module instance in the viewport, and only need to use the size. |
| /// |
| /// @return The rectangle of the instance. The default return value for |
| /// an invalid View is the empty rectangle. |
| Rect GetRect() const; |
| |
| /// IsFullscreen() returns whether the instance is currently |
| /// displaying in fullscreen mode. |
| /// |
| /// @return <code>true</code> if the instance is in full screen mode, |
| /// or <code>false</code> if it's not or the resource is invalid. |
| bool IsFullscreen() const; |
| |
| /// IsVisible() determines whether the module instance might be visible to |
| /// the user. For example, the Chrome window could be minimized or another |
| /// window could be over it. In both of these cases, the module instance |
| /// would not be visible to the user, but IsVisible() will return true. |
| /// |
| /// Use the result to speed up or stop updates for invisible module |
| /// instances. |
| /// |
| /// This function performs the duties of GetRect() (determining whether the |
| /// module instance is scrolled into view and the clip rectangle is nonempty) |
| /// and IsPageVisible() (whether the page is visible to the user). |
| /// |
| /// @return <code>true</code> if the instance might be visible to the |
| /// user, <code>false</code> if it is definitely not visible. |
| bool IsVisible() const; |
| |
| /// IsPageVisible() determines if the page that contains the module instance |
| /// is visible. The most common cause of invisible pages is that |
| /// the page is in a background tab in the browser. |
| /// |
| /// Most applications should use IsVisible() instead of this function since |
| /// the module instance could be scrolled off of a visible page, and this |
| /// function will still return true. However, depending on how your module |
| /// interacts with the page, there may be certain updates that you may want |
| /// to perform when the page is visible even if your specific module instance |
| /// is not visible. |
| /// |
| /// @return <code>true</code> if the instance might be visible to the |
| /// user, <code>false</code> if it is definitely not visible. |
| bool IsPageVisible() const; |
| |
| /// GetClipRect() returns the clip rectangle relative to the upper-left corner |
| /// of the module instance. This rectangle indicates the portions of the |
| /// module instance that are scrolled into view. |
| /// |
| /// If the module instance is scrolled off the view, the return value will be |
| /// (0, 0, 0, 0). This clip rectangle does <i>not</i> take into account page |
| /// visibility. Therefore, if the module instance is scrolled into view, but |
| /// the page itself is on a tab that is not visible, the return rectangle will |
| /// contain the visible rectangle as though the page were visible. Refer to |
| /// IsPageVisible() and IsVisible() if you want to account for page |
| /// visibility. |
| /// |
| /// Most applications will not need to worry about the clip rectangle. The |
| /// recommended behavior is to do full updates if the module instance is |
| /// visible, as determined by IsVisible(), and do no updates if it is not |
| /// visible. |
| /// |
| /// However, if the cost for computing pixels is very high for your |
| /// application, or the pages you're targeting frequently have very large |
| /// module instances with small visible portions, you may wish to optimize |
| /// further. In this case, the clip rectangle will tell you which parts of |
| /// the module to update. |
| /// |
| /// Note that painting of the page and sending of view changed updates |
| /// happens asynchronously. This means when the user scrolls, for example, |
| /// it is likely that the previous backing store of the module instance will |
| /// be used for the first paint, and will be updated later when your |
| /// application generates new content with the new clip. This may cause |
| /// flickering at the boundaries when scrolling. If you do choose to do |
| /// partial updates, you may want to think about what color the invisible |
| /// portions of your backing store contain (be it transparent or some |
| /// background color) or to paint a certain region outside the clip to reduce |
| /// the visual distraction when this happens. |
| /// |
| /// @return The rectangle representing the visible part of the module |
| /// instance. If the resource is invalid, the empty rectangle is returned. |
| Rect GetClipRect() const; |
| |
| /// GetDeviceScale returns the scale factor between device pixels and DIPs |
| /// (also known as logical pixels or UI pixels on some platforms). This allows |
| /// the developer to render their contents at device resolution, even as |
| /// coordinates / sizes are given in DIPs through the API. |
| /// |
| /// Note that the coordinate system for Pepper APIs is DIPs. Also note that |
| /// one DIP might not equal one CSS pixel - when page scale/zoom is in effect. |
| /// |
| /// @return A <code>float</code> value representing the number of device |
| /// pixels per DIP. |
| float GetDeviceScale() const; |
| |
| /// GetCSSScale returns the scale factor between DIPs and CSS pixels. This |
| /// allows proper scaling between DIPs - as sent via the Pepper API - and CSS |
| /// pixel coordinates used for Web content. |
| /// |
| /// @return A <code>float</code> value representing the number of DIPs per CSS |
| /// pixel. |
| float GetCSSScale() const; |
| |
| /// GetScrollOffset returns the scroll offset of the window containing the |
| /// plugin. |
| /// |
| /// @return A <code>Point</code> which is set to the value of the scroll |
| /// offset in CSS pixels. |
| Point GetScrollOffset() const; |
| }; |
| |
| } // namespace pp |
| |
| #endif // PPAPI_CPP_VIEW_H_ |