# Cheat Sheet For Converting to 2geom

If you are just starting I suggest you pick a header file and convert just one function at a time. That will give you a feel for the process as you get more comfortable do more at one time.

In Inkscape and in 2geom there are two types of emptiness for rectangles.

Rectangles with no coordinates. Rectangles with zero area.

What is the difference?

A Rect that has the coordinates 0f (1,2 - 2,6) has both points and area. A Rect that has the coordinates 0f (0,0 - 0,0) has points but no area. A boost::optional::<Geom::Rect> that has no coordinates has neither points or area.

Geom::Rect can not have no coordinates please use boost::optional::<Geom::Rect> .

rect.isEmpty() checks if a rectangles has coordinates NOT for Area of the rect.

## Items That you Can Switch NR:: for Geom::

• `NR::Matrix`
• `NR::Rect`
• `NR::Dim2`
• `NR::L2`
• `NR::Y`
• `NR::X`
• `NR::identify`
• `NR::Coord`

## Things that need small adjustments or complete replacement

 Error looks like NR Function or Code 2geom Replacement `NR::scale` `Geom::Scale` (note the capital letter S) `NR::translate` `Geom::Translate` (capital) `nrrect.extent(NR::X)` `geomrect.dimensions()[Geom::X]` OR `geomRect[X].extent()` `height = r->extent(NR::Y);` `height = r->dimensions()[Geom::Y];` `NR::expansion(nrmatrix)` `geommatrix.descrim()` desktop.cpp:754: error: 'expand' is not a member of 'Geom' `NR::Rect const viewbox = NR::expand(canvas->getViewbox(), border);` `Geom::Rect viewbox = canvas->getViewbox();` `viewbox.expandBy(border);` desktop.cpp:162: error: 'class Geom::Matrix' has no member named 'set_identity' `Mymatrix = set_identity (Nrmatrix)` `identity(Nrmatrix)` OR `matrix.setIdentity()` desktop.cpp: In member function 'bool SPDesktop::isWithinViewport(SPItem*) const': desktop.cpp:532: error: conversion from 'boost::optional' to non-scalar type 'boost::optional >' requested `boost::optional` `boost::optional` desktop.cpp:1004: error: no matching function for call to 'Geom::D2::isEmpty(double)' ./2geom/rect.h:105: note: candidates are: bool Geom::D2::isEmpty() const ```if ( !d || d->isEmpty(0.1) ) { return; } ``` ``` if ( !d || d->width() < 0.1 || d->height() < 0.1) { return; }``` display/nr-arena-item.cpp:734: error: ‘const class Geom::Matrix’ has no member named ‘test_identity’ `NR::matrix.test_identity()` `local.isIdentity()` selection-chemistry.cpp:1424: error: no match for ‘operator[]’ in ‘center[X]’ center is a boost::optional you're missing the * `Geom::Rotate` doesn't seem have a operator/ what is the trick for turning division in to multiplication, again `r1/r2` `r1 * r2.inverse()` `NR::Rect`'s can be changed to `Geom::Rect` But it is better not to do this. `geomrect = to_2geom(nrrect)` `NR::union_bounds()` `Geom::unify()` sp-item.cpp:814: error: ‘expansionX’ is not a member of ‘Geom’ `dy0 *= NR::expansionY(i2d);` `dx0 *= NR::expansionX(i2d);` `dy0 *= i2d.expansionY();` `dx0 *= i2d.expansionX();` sp-item.cpp:1447: error: ‘const class Geom::Matrix’ has no member named ‘is_translation’ `!(!transform.is_translation() && SP_OBJECT_STYLE(item) && SP_OBJECT_STYLE(item)->getFilter())` `!(!transform.isTranslation() && SP_OBJECT_STYLE(item) && SP_OBJECT_STYLE(item)->getFilter())` text-context.cpp:1610: error: no matching function for call to ‘to_2geom(boost::optional >)’ `boost::optional frame_bbox = to_2geom(sp_item_bbox_desktop(frame));` `boost::optional frame_bbox = sp_item_bbox_desktop(frame);`