To avoid pixel jitter, the top and bottom of each line in the waveview must be computed together in a single computation,
rather than independently.
Also, remove various height corrections and cairo translations that are not necessary or relevant anymore. A subsequent
commit for the GUI will pick up on this work to get the appearance completely correct
Rebasing the feature branch against master was too messy, and only these two files were
changed. The development history of this branch could easily have been --squash'ed anyway,
so not much of a loss
Technically it doesn't make much difference but from what I can tell, the only files which #include 'gtk2_ardour/gui_thread.h' are the source files from gtk2_ardour itself. The support libraries always #include 'gtkmm2ext/gui_thread.h' directly (which seems sensible). So for consistency's sake, let's keep it the same for libcanvas.
Invalidate all source entries from the image cache when we get our
region's DropReferences signal, while ignoring any subsequent regions with
no source.
In summary:
* no antialiasing of waveviews
* no diagonal lines
* simplify clip detection
* don't use LINE_CAP_ROUND for outline
* use the wave colour when drawing outline only
* proper y-pixel alignment (+.5px offset)
* outline: draw dots (not 1px lines)
* shape: round towards peak (use signal, not top/bot)
* honor 2px red selection border
* work-around canvas rect +1 issue
* always draw clipping line towards center
* draw at most one clip-line at either side of 0.
* exact 1px wide zero line
* fix spread calculation for rectified view
There are 3 possible components to draw at each x-axis position: the waveform "line", the zero line and an outline/clip indicator.
We have to decide which of the 3 to draw at each position, pixel by pixel. This makes the rendering less efficient but it is
the only way I can see to do this correctly.
Items no longer need a parent group (they require a Canvas pointer instead), so all constructors have been rationalized
and have two variants, one with a parent and one with a canvas.
All Items now inherit from Fill and Outline, to banish diagonal inheritance and virtual base classes and all that.
There were zero changes to the Ardour GUI arising from these changes.
