42 lines
2.0 KiB
Plaintext
42 lines
2.0 KiB
Plaintext
There are two separate wrappers for V8 here. One is called FXJS, and
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it is used by the non-XFA code. The other is called FXJSE, and it is
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used only by the XFA code. Additionally FXJSE may request services
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from FXJS to bridge the two.
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Both the FXJS and FXJSE binding code needs to be replaced by something
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saner, perhaps Gin or perhaps some IDL. See
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https://bugs.chromium.org/p/pdfium/issues/detail?id=716
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for progress on the issue.
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FXJS binds objects by sticking a pointer to a CFXJS_PerObjectData in
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the V8 object's internal slot. FXJSE binds objects by sticking a
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pointer to either an actual v8 function object or a CFXJSE_HostObject
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in the V8 object's internal slot, depending upon whether the object
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represents (in some notion) a "class" or an "instance". Also, V8 objects
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bound in one library may unexpectedly arrive at the other given a script
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that's trying to mess with us.
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To distinguish these cases, we use two internal slots for all bound
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objects, regardless of the FXJS/FXJSE distinction. Slot 0 is the
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tag and contains either:
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kPerObjectDataTag for FXJS objects, or
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g_FXJSEHostObjectTag for FXJSE Host objects, or
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g_FXJSEProxyObjectTag for a global proxy object under FXJSE, or
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One of 4 specific FXJSE_CLASS_DESCRIPTOR globals for FXJSE classes:
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GlobalClassDescriptor
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NormalClassDescriptor
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VariablesClassDescriptor
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formcalc_fm2js_descriptor
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Slot 1's contents are determined by these tags:
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kPerObjectDataTag means an aligned pointer to CFXJS_PerObjectData.
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g_FXJSEHostObjectTag means an aligned pointer to CFXJSE_HostObject.
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g_FXJSEProxyObjectTag means nullptr, and to check the prototype instead.
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A FXJSE_CLASS_DESCRIPTOR pointer means to expect an actual v8 function
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object (or a string naming that function), and not an aligned pointer.
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Because PDFium uses V8 for various unrelated purposes, there may be up to
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four v8::Contexts (JS Global Objects) associated with each document. One is
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used by FXJS and holds objects as described by the js_api_reference.pdf
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specification. The others are used by FXJSE.
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