WebGL 2: add read/write framebuffer binding points to related APIs

Source/core/html/canvas/WebGLFramebuffer.h

Index: Source/core/html/canvas/WebGLFramebuffer.h
diff --git a/Source/core/html/canvas/WebGLFramebuffer.h b/Source/core/html/canvas/WebGLFramebuffer.h
index f15ae11db68379276210d8d5091a95b5b065b57c..c37b0d79f493ee690d88fe7bbf43a7677cc1bafd 100644
--- a/Source/core/html/canvas/WebGLFramebuffer.h
+++ b/Source/core/html/canvas/WebGLFramebuffer.h
@@ -55,8 +55,8 @@ public:
         virtual bool isSharedObject(WebGLSharedObject*) const = 0;
         virtual bool valid() const = 0;
         virtual void onDetached(WebGraphicsContext3D*) = 0;
-        virtual void attach(WebGraphicsContext3D*, GLenum attachment) = 0;
-        virtual void unattach(WebGraphicsContext3D*, GLenum attachment) = 0;
+        virtual void attach(WebGraphicsContext3D*, GLenum target, GLenum attachment) = 0;
+        virtual void unattach(WebGraphicsContext3D*, GLenum target, GLenum attachment) = 0;
 
         DEFINE_INLINE_VIRTUAL_TRACE() { }
 
@@ -70,12 +70,12 @@ public:
 
     Platform3DObject object() const { return m_object; }
 
-    void setAttachmentForBoundFramebuffer(GLenum attachment, GLenum texTarget, WebGLTexture*, GLint level);
-    void setAttachmentForBoundFramebuffer(GLenum attachment, WebGLRenderbuffer*);
+    void setAttachmentForBoundFramebuffer(GLenum target, GLenum attachment, GLenum texTarget, WebGLTexture*, GLint level);
+    void setAttachmentForBoundFramebuffer(GLenum target, GLenum attachment, WebGLRenderbuffer*);
     // If an object is attached to the currently bound framebuffer, remove it.
-    void removeAttachmentFromBoundFramebuffer(WebGLSharedObject*);
+    void removeAttachmentFromBoundFramebuffer(WebGLSharedObject*, GLenum target);
     // If a given attachment point for the currently bound framebuffer is not null, remove the attached object.
-    void removeAttachmentFromBoundFramebuffer(GLenum);
+    void removeAttachmentFromBoundFramebuffer(GLenum, GLenum);
     WebGLSharedObject* getAttachmentObject(GLenum) const;
 
     GLenum colorBufferFormat() const;
@@ -84,13 +84,13 @@ public:
     // readPixels, copyTexImage2D, copyTexSubImage2D if this framebuffer is
     // currently bound.
     // Return false if the framebuffer is incomplete.
-    bool onAccess(WebGraphicsContext3D*, const char** reason);
+    bool onAccess(WebGraphicsContext3D*, GLenum target, const char** reason);
 
     // Software version of glCheckFramebufferStatus(), except that when
     // FRAMEBUFFER_COMPLETE is returned, it is still possible for
     // glCheckFramebufferStatus() to return FRAMEBUFFER_UNSUPPORTED,
     // depending on hardware implementation.
-    GLenum checkStatus(const char** reason) const;
+    GLenum checkStatus(const char** reason, GLenum target) const;
 
     bool hasEverBeenBound() const { return object() && m_hasEverBeenBound; }
 
@@ -112,14 +112,14 @@ protected:
     void deleteObjectImpl(WebGraphicsContext3D*) override;
 
 private:
-    WebGLAttachment* getAttachment(GLenum) const;
+    WebGLAttachment* getAttachment(GLenum target, GLenum attachment) const;
     bool isAttachmentComplete(WebGLAttachment* attachedObject, GLenum attachment, const char** reason) const;
 
     // Check if the framebuffer is currently bound.
     bool isBound() const;
 
     // attach 'attachment' at 'attachmentPoint'.
-    void attach(GLenum attachment, GLenum attachmentPoint);
+    void attach(GLenum target, GLenum attachment, GLenum attachmentPoint);
 
     // Check if a new drawBuffers call should be issued. This is called when we add or remove an attachment.
     void drawBuffersIfNecessary(bool force);
@@ -129,6 +129,7 @@ private:
     typedef WillBeHeapHashMap<GLenum, RefPtrWillBeMember<WebGLAttachment>> AttachmentMap;
 
     AttachmentMap m_attachments;
+    AttachmentMap m_attachmentsForReadFramebuffer;

[Ken Russell (switch to Gerrit), 2015/05/22 21:45:46]

This still doesn't model the OpenGL state correctly. Framebuffers don't have
attachments specifically for the "read" framebuffer binindg point.

The way to make this patch more correct is to split m_framebufferBinding in
WebGLRenderingContextBase into m_drawFramebufferBinding and
m_readFramebufferBinding. I don't see any way around the need to teach the WebGL
1.0 context's code about these two binding points. WebGL 1.0 apps can only set
both at the same time, but WebGL 2.0 apps can set each individually. The
WebGLFramebuffer class should only have one set of attachments. It can
potentially call back into the WebGLRenderingContextBase if needed in order to
do work with the context's currently bound draw and read framebuffers.

If I'm not explaining this clearly, or if you'd like me to take over this patch,
please let me know.

[yunchao, 2015/05/25 08:01:19]

I got it. WebGLFramebuffer don't have attachments specific for read/draw
framebuffer binding points. They just have attachments, don't need to know its
binding points. It is its user's duty to keep the info of binding points on top
of WebGLFramebuffer. I mean the infomation of draw or read binding point should
be kept in WebGLRenderingContext: WebGLRenderingContext should have two
WebGLFramebuffer for draw and read binding points separately in WebGL 2
rendering context.

And this has already been done. We have m_framebufferBinding for WebGL 1.0
rendering context. m_readFramebufferBinding is added for WebGL 2.0
(m_framebufferBinding is degenerated to draw binding points only in this
situation, just like GL_FRAMEBUFFER is equivalent to GL_DRAW_FRAMEBUFFER for
most of WebGL2 APIs except bindFramebuffer).

I just removed the m_attachmentsForReadFramebuffer. I think it is OK now.

 
     bool m_hasEverBeenBound;