render: Refactor sprite rendering.

* chickadee/render/texture.scm (<texture-region>): Delete type.
(<texture>)[width, height, gl-size]: Delete fields.
[parent, rect, gl-rect]: Add fields.
(texture-region?): Rewrite.
(make-texture, null-texture): Use new texture constructor.
(make-texture-region): Rewrite in terms of <texture> type.
(list->texture-atlas, split-texture): Use new texture region
constructor.
* chickadee/render/sprite.scm (draw-sprite*): New procedure.
(draw-sprite): Rewrite in terms of draw-sprite*.
(draw-nine-patch*): New procedure.
(draw-nine-patch): Rewrite in terms of draw-nine-patch*.
* chickadee/render/font.scm (draw-text*): New procedure.
(draw-text): Rewrite in terms of draw-text*.
* doc/api.texi: Update draw-sprite, draw-nine-patch, and draw-text
docs.

1 files changed, 23 insertions, 9 deletions

diff --git a/doc/api.texi b/doc/api.texi
index cb3c885..e2864a5 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -681,10 +681,26 @@ players, NPCs, items, particles, text, etc.  In Chickadee, bitmaps are
 stored in textures (@pxref{Textures}) and can be used to draw sprites
 via the @code{draw-sprite} procedure.
 
-@deffn {Procedure} draw-sprite @var{texture} @var{region} @
-       [#:scale] [#:rotation] [#:blend-mode alpha] [#:texcoords] @
-       [#:shader]
+@deffn {Procedure} draw-sprite @var{texture} @var{position} @
+       [#:origin] [#:scale] [#:rotation] [#:blend-mode alpha] @
+       [#:rect] [#:shader]
+
+Draw @var{texture} at @var{position}.
+
+Optionally, other transformations may be applied to the sprite.
+@var{rotation} specifies the angle to rotate the sprite, in radians.
+@var{scale} specifies the scaling factor as a 2D vector.  All
+transformations are applied relative to @var{origin}, a 2D vector,
+which defaults to the lower-left corner.
+
+Alpha blending is used by default but the blending method can be
+changed by specifying @var{blend-mode}.
+
+The area drawn to is as big as the texture, by default.  To draw to an
+arbitrary section of the screen, specify @var{rect}.
 
+Finally, advanced users may specify @var{shader} to change the way the
+sprite is rendered entirely.
 @end deffn
 
 It's not uncommon to need to draw hundreds or thousands of sprites
@@ -740,10 +756,10 @@ interface widgets like buttons and dialog boxes.  By using a nine
 patch, they can be rendered at any size without unappealing scaling
 artifacts.
 
-@deffn {Procedure} draw-nine-patch @var{texture} @var{region} @
+@deffn {Procedure} draw-nine-patch @var{texture} @var{rect} @
        [#:margin 0] [#:top-margin margin] [#:bottom-margin margin] @
        [#:left-margin margin] [#:right-margin margin] @
-       [#:texture-region] [#:scale] [#:rotation] [#:blend-mode alpha] @
+       [#:origin] [#:scale] [#:rotation] [#:blend-mode alpha] @
        [#:shader]
 
 Draw a nine patch sprite.  A nine patch sprite renders @var{texture}
@@ -809,9 +825,7 @@ rendering technique comes in.  Introduced by
 @url{http://www.valvesoftware.com/.../2007/SIGGRAPH2007_AlphaTestedMagnification.pdf,
 Valve} in 2007, signed distance field fonts can be efficiently stored
 in a bitmap and be rendered at arbitrary scale factors with good
-results.  Chickadee can render both traditional bitmap fonts and
-signed distance field fonts.  @emph{Signed distance field font
-rendering is not yet available, so be patient.}
+results.
 
 While Chickadee does not yet offer a tool for converting TTF fonts
 into FNT fonts, tools such as
@@ -851,7 +865,7 @@ Return @code{#t} if @var{font} is an italicized font.
 @end deffn
 
 @deffn {Procedure} draw-text @var{font} @var{text} @var{position}
-       [#:scale] [#:rotation] [#:blend-mode]
+       [#:origin] [#:scale] [#:rotation] [#:blend-mode]
 
 Draw the string @var{text} with the first character starting at
 @var{position} using @var{font}.