Currently, WindowsEMF::InitForDrawing can be used once. With the change in this
patch, we can call WindowsEMF::InitForDrawing and Playback/SaveToFile in pair
as many times as we want.
MozReview-Commit-ID: 4fbY4Q6i9v5
--HG--
extra : rebase_source : 4df3fc7d8663d7f552c96204a16d73261bfc9dd7
WindowsEMF could be initialized with the path of a file where the EMF data
should be stored. If pass null point to the constructor that means the EMF data
are store in memory. Consumers can call GetDC() to get a HDC. It can be drawn to
generate the EMF output. After finishing with the HDC, call FinishDocument() to
finish writing the EMF output. Then consumers can call Playback() to play the
EMF's drawing commands onto the given DC. Once consumers don't use WindowsEMF
anymore, call ReleaseEMFHandle() to release object's handle. If the EMF output
is in memory, it is deleted. If it is on disk, it is not.
Consumers also can initialize WindowsEMF with an existing EMF file. They can
only use Playback().
MozReview-Commit-ID: 8hUsx8b2CXz
--HG--
extra : rebase_source : 99e38e61a00bfae45ec9102b3b23a095a7f3af1e
cku
Farmer Tseng