first step at optional single buffered OpenGL rendering

Change-Id: I064de6ca7d40b8e6e378a01dd39a6cd09f040b68
prevent crash with empty chart scene

Change-Id: I9eb8adf887532c62af6efeac5b0eeec1419b7252
add possibility to check if system can run OpenGL VCL backend

Change-Id: If3475c6b2c76e4634f16053928b43a94c83be6ee
make that file platform independent

Change-Id: I65c056faaa95af3493b73a7403f199c8c826d724
fix windows compile error

Change-Id: I9154cd0c0352b8807b5a5eae2444629c9cfe3d48
start to bring some sanity to windows backend

Just moving some of our variables from public to private to understand which ones are actively set from outside objects.

Change-Id: I33998bb95c93195c6c39778e37ac1071b917c8fa
remove unused code and const-ify some methods

Change-Id: I4c8da0cdf39f31ec757e87687dcec79a4ac83681
a little bit more sanity

Change-Id: I080984c5faaa8cf349ba37ffdb116b6d8d016552
use false instead of 0

Change-Id: I7210493b98e8ed778eeba6518dc131e63863ff67
at least some sanity for WinSalGraphics

we no longer invite everyone to change our member variables.

This was obviously written by a C programmer and needs further refactoring.

Change-Id: I896576a5abc24e8d03787d30e6ba6c11b0bf84c6
improve OpenGL rendering engine selection for Windows backend

Change-Id: Ibcf520aac1441e5ce86b83372061550f8957ab17
don't try to use OpenGL for printing

Change-Id: I88403bcb5b1974deba237c497885d3793a29315c
init the OpenGL context in the windows backend

Change-Id: Ic4fb491c95170639015a4452f355354ad01612bc
forgot to remove the env variable based OpenGL setting

Change-Id: Ib4d0c4730eceac483bb179ce4e75fe555bba91fa
support rendering to memory device contexts on Windows

Change-Id: I91fdd429663fae76bfe17d37de86d118621cf160
use the new virtual device support in OpenGL for win backend

Change-Id: Icd67dd7bad1399c861db41c418095c2b6b1d6d78
vcl: Implement basic SalGraphics methods for OpenGL backend

Change-Id: Iade3960c38f0de5594bc98e535450abcf88e9a6d
extract shaders from source code

Conflicts:
	vcl/opengl/gdiimpl.cxx

Change-Id: Ifbb55e58e0854cc491703b8ca8d8e582741a9bd9
vcl: Some fixes to the OpenGL impl

Change-Id: I58466142e0a47beb892e10113c1bc34d5ac3abcd
vcl: Add methods to get size of OpenGLSalGraphicsImpl

Change-Id: I7eecbc236db12fb9453384985245eb5ca781e0f5