Added non-vertical axonometric grids · 7923d920

Commits:

Preliminary non-vertical axis implementation

Add option to set vertical angle for axonometric grids

Fixed the math for calculating the y axis angle in the axonometric grid

Initial grid snapping with !angle_y_vertical implemented

Update comments to clarify axis behavior in axonometric grids

Change angle_y_vertical to use RegisteredCheckButton and update preferences initialization

Add button to swap axonometric grid axes in document properties dialog

Documented & moved derived_angle_y to mathfns.h and added update_derived_angle_y method for shared behavior

Renamed gridangleyvertical to angleyvertical

Comment: "[the prefix 'grid'] should never have been used for any of the attributes, but we should start by not adding new ones" - @doctormo

I forgot the pi/2 - angle when porting to derived_angle_y rad

Fix divide-by-zero crash when using calligraphy tool · d34276f8

When getting the average color of a cairo surface, if the alpha is
zero, we were getting a divide-by-zero error, because we were
dividing r, g, and b by the cumulutive alpha of the surface.

Instead, we should return black in that case.

Fixes #6098

Remember maximized/fullscreened states · 562456be

When those states change, actually notice and save the preference
for them. This way the "remember last window state" preference will
work as expected for maximized/fullscreened windows.

Update Color API preparing for new Rendering Engine · 8fe2638e

Added isDirect to Colors::Space::* which tells us if a color space is
backed by a single icc profile, and no other processing steps with some
public method cleanups.

Removed Lab toXYZ and fromXYZ which were orphaned by previous commit.

Reformatted CairoTransform into generic SurfaceTransform so it can work
with any memory surface of pixels and in a greater number of data formats.

Split out CMS transform class from SurfaceTransforms and use a base class
Allowing for different assumptions with formatting and alpha premultiplication.

Add a forward.h header to make including color namespaces easier and cleaner.

Clean up generic testing utils for VectorIs Add colors and some better flexibility
for arrays and vectors in testing.

Add Alpha color space · c53f375f

This color space allows surfaces to be converted to luminosity masks
and varius other useful alpha related filtering for the new rendering
engine.

We use lcms2 to hold the gray scale profile for quicker conversions.

The transform-cms is modified so it can cope with outputs which do
not have an allpha channel of their own. Tests for this are added.

Allow color conversions using static arrays instead of just vectors · 363d6459

Most color conversion will be done with std::vectors of doubles
but to speed up and provide compile time checks for color converting
on Surfaces we want the ability to take an array directly at some
but not all of the various levels.

Formalise the interface for ProfileSpace and the Convertable type
using a self-referential templating pattern.

Move most conversion code to static functions and make as agnostic
to the array type as possible, allowing for convertors to use them
directly without expensive vector types.

Fix crash when selecting non-visible objects · ee480ecd

The selection describer code was assuming that a selection can only
hold visible items (SPItems) but it actually holds SPObjects, which
can include non-visible items.

This code changes the selection describer to more consistently work
with SPItems only, and to ignore SPObjects.

Fixes #6125