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devguide-3.html
General Remarks
devguide.html
Developer's Guide
devguide-8.html
Curve Objects
Coordinate Systems
All coordinates used by the document and graphics objects are given in
the
document coordinate system
. This coordinate system has its
origin in the lower left corner of the page; x increases to the right, y
increases to the top. The unit for these coordinates is the DTP-point
(or PostScript-point), that is, 1/72 inch. Thus Skencil's document
coordinate system is the same as the default coordinate system of a
PostScript interpreter. Coordinates are stored as floats.
The page size is a user settable document property, usually `A4',
`letter' or something similar. Skencil can display the outline of the
page if desired to allow the user to position the drawing on the page.
When displaying the document in a window, the canvas widget (to be more
precise, the graphics device object the canvas uses) converts document
coordinates to
window coordinates
. These are the standard X-Window
coordinates with the origin in the top left corner of the window and x
increasing to the right and y increasing downwards. The unit is 1 pixel.
Skencil defines a few builtin objects to represent and manipulate
coordinates: Points, Rects and Transformations. All of the related
functions, objects and constants are exported by the
Sketch
package.
devguide-5.html
Point Objects
devguide-6.html
Rect Objects
devguide-7.html
Transformation Objects
devguide-3.html
General Remarks
devguide.html
Developer's Guide
devguide-8.html
Curve Objects
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