make it possible to write canvas unittests

One of the problems is that canvas apparently works only with windows,
but tests obviously need an offscreen surface. This patch moves
Window::GetCanvas() to OutputDevice, and makes vclcanvas capable
of working with OutputDevice classes that are not windows. Other
canvas implementations still don't work, but presumably at least
cairocanvas could be fixed too.

This commit adds a "simple" test that just draws a line and tries
to verify it's been drawn properly. Adding another test should
be a matter of basing it on this existing one, and then copy&pasting
the complicated UNO way of drawing using canvas from somewhere,
such as canvas/workben/canvasdemo.cxx.

Change-Id: I42db12b09433763cd31c3dd497c10157424b8598
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/115117
Tested-by: Jenkins
Reviewed-by: Luboš Luňák <l.lunak@collabora.com>

0 files changed, 0 insertions, 0 deletions