Plugins:CoreAnimationDrawingModelR2: Difference between revisions

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Plugins:CoreAnimationDrawingModelR2 (view source)

Revision as of 16:06, 9 March 2010

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== Background ==  
== Background ==  


Currently, the only way for a plug-in on Mac to use OpenGL is to attach an AGL surface manually. This has a number of drawbacks:
This defines an extension to the Core Animation drawing model which adds support for event-driven drawing. We propose adding the following "Redrawing" section. This should be backwards compatible with the existing spec.
 
* The plug-in has to move the surface in response to page scrolling, window resizing, etc
* The plug-in needs access to the browser window's WindowRef
* AGL is a Carbon based API and does not work in 64-bit
 
The Core Animation drawing model aims to solve these problems (and more) by letting the plug-in hand off a Core Animation layer to the browser. It is then up to the browser to position and size the layer.  


== Current Proposal ==
== Current Proposal ==


Last modified: March 9, 2010
Last modified: March 9, 2010
Authors: Anders Carlsson (Apple Inc), Kevin Decker (Apple Inc)
Authors: Josh Aas (Mozilla Corporation), Benoit Girard (Mozilla Corporation)
Contributors: Josh Aas (Mozilla Corporation), Benoit Girard (Mozilla Corporation)
Contributors: Stuart Morgan (Google)
 
== Querying for availability ==
 
A plug-in may, in its NPP_New callback negotiate a drawing model. It can call NPN_GetValue with the
 
NPNVsupportsCoreAnimationBool = 2003
 
NPNVariable to query the browser for whether the Core Animation drawing model is supported. The argument is an NPBool.
 
The plug-in can then call NPN_SetValue to tell the browser to use the Core Animation drawing model, using the
 
NPNVpluginDrawingModel = 1000
 
NPNVariable and the
 
NPDrawingModelCoreAnimation = 3
 
drawing model enumeration, cast to a void pointer.
 
The Core Animation drawing model only works together with the [https://wiki.mozilla.org/Mac:NPAPI_Event_Models#The_Cocoa_event_model Cocoa Event Model]. If the plug-in tries to use the Carbon Event model with the Core Animation drawing model, the browser will destroy the plug-in after it has been instantiated.
 
== Vending a layer ==
 
When the plug-in has selected the drawing model, the browser will call NPP_GetValue with the
 
NPPVpluginCoreAnimationLayer = 1003
 
NPPVariable. The value should be treated as a CALayer * pointer, which the plug-in should fill in with a ''retain''ed layer. For example:
 
NPError NPP_GetValue(NPP instance, NPPVariable variable, void *value)
{
    PluginObject *obj = instance->pdata;
    switch (variable) {
        case NPPVpluginCoreAnimationLayer:
            if (!obj->layer) {
                obj->layer = makeLayer();
            }
           
            // Make sure to return a retained layer
            *((CALayer **)value) = [obj->layer retain];
           
            return NPERR_NO_ERROR;
           
        default:
            return NPERR_GENERIC_ERROR;
    }
}
 
== CALayer lifecycle ==
 
The browser is not responsible for releasing retained CALayer objects it receives via the "NPPVpluginCoreAnimationLayer" variable. The browser may additionally retain layers (perhaps by attaching them to views). A plugin may release the layer for an instance during or after the instance's NPP_Destroy call.


== Redrawing ==
== Redrawing ==
Josh
Confirmed users, Bureaucrats and Sysops emeriti
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