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notes and docs

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original commit: 2631853a283e73193ee137bfab0d655190b22638
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Matthew Flatt 2010-08-02 07:17:08 -06:00
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doc/release-notes/racket/Draw_and_GUI_5_5.txt Normal file
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Changes to the drawing toolbox:
* The drawing portion of the old GUI toolbox is now available as a
separate layer: `racket/draw'. This layer can be used from plain
Racket independent of the `racket/gui' library, although
`racket/gui' re-exports `racket/draw'.
The `racket/draw' library is built on top of the widely used Cairo
drawing library and Pango text-rendering library.
* A color bitmap can have an alpha channel, instead of just a mask
bitmap. When drawing a bitmap, alpha channels are used more
consistently and automatically than mask bitmaps. More
significantly, drawing into a bitmap with an alpha channel
preserves the drawn alphas; for example, drawing a line in the
middle of an empty bitmap produces an image with non-zero alpha
only at the drawn line.
Create a bitmap with an alpha channel by supplying #t as the new
`alpha?' argument to the `bitmap%' constructor, or by loading an
image with a type like 'unknown/alpha insteda of 'unknown or
'unknown/mask.
A newly created `bitmap%' has an empty content (i.e., white with
zero alpha), insteda of unspecified content.
Images can be read into a `bitmap%' from from input ports, instead
of requiring a file path.
* A `dc<%>' supports additional drawing transformations: a rotation
(via `set-rotation') and a general transformation matrix (via
`set-initial-matrix').
A transformation matrix has the form `(vector xx xy yx yy x0 y0)',
where a point (x1, y1) is transformed to a point (x2, y2) with
x2 = xx*x1 + yx*y1 + x0 and y2 = xy*x1 + yy*y1 + y0.
The old translation and scaling transformations apply after the
initial matrix. The new rotation transformation applies after the
other transformations. This layering is a little redundant, since
all transformations could be expressed in a single matrix, but it
is backward compatibile.
* A `region%' can be created as independent of any `dc<%>', in which
cases it uses the drawing context's current transformation at the
time that it is installed as a clipping region.
* The old 'xor mode for pens and brushes is no longer available.
Changes to the GUI toolbox:
[Nothing to report, yet.]