inkscape-manual

The Canvas is the main workspace, and is the most central and important part of the interface, since it is here
that the drawing is created and viewed. It is located in the middle of the window and is represented as a blank
"page" with open space around it. By default, there is a Ruler above and a Ruler to the left of the Canvas
which is set to measure in pixels (the standard SVG unit), but these defaults (ruler visibility and unit) can be
adjusted in Document Properties.
While the "page" defines the boundaries of a document intended for certain media (print, export, etc.), an
SVG is not limited to the page boundaries. In fact, the page border and shadow can be made invisible in the
Document Properties. Some artists will prefer to use a particular page boundary and use the white space as
"scratch paper"; others will prefer not to be limited by page boundaries.
Rulers
The Rulers are graduated lines placed on top and left of the canvas. The first is called "horizontal" and the
second "vertical". Graduations represent distances and are expressed in units that can be set in the Units
option of the Page tab of the File > Document Preferences.
When the mouse is over the canvas, two triangles appear in the rulers to show its X and Y coordinates,
relative to the page's bottom left corner. Those coordinates are also displayed in the Status Bar (at the bottom
of the document window) on the left, near the Zoom Control.
Note : In SVG, coordinates begin at the bottom left of the document like in Cartesian geometry.
Ctrl + R is a quick way to hide or display the Rulers. One can also do that with the View>Show/Hide>Rulers
The Canvas 5