disable (minimize?) smoothing for `draw-bitmap' in 'unsmoothed mode

collects/racket/draw/private/bitmap-dc.rkt

@@ -100,6 +100,8 @@
              get-size
              get-transformation
              set-transformation
+             get-smoothing
+             set-smoothing
              scale
              get-font)
     
@@ -163,10 +165,13 @@
                                             [(make-or-false bitmap%) [mask #f]])
       (let ([sx (if (zero? src-w) 1.0 (/ dest-w src-w))]
             [sy (if (zero? src-h) 1.0 (/ dest-h src-h))])
-        (let ([t (get-transformation)])
+        (let ([t (get-transformation)]
+              [s (get-smoothing)])
           (scale sx sy)
+          (when (eq? s 'unsmoothed) (set-smoothing 'aligned))
           (begin0
            (draw-bitmap-section src (/ dest-x sx) (/ dest-y sy) src-x src-y src-w src-h style color mask)
+           (when (eq? s 'unsmoothed) (set-smoothing 'unsmoothed))
            (set-transformation t)))))
 
     (def/override (get-char-width)

collects/racket/draw/private/dc.rkt

@@ -1634,12 +1634,17 @@
               [a-src-y (floor src-y)]
               [a-msrc-x (floor msrc-x)]
               [a-msrc-y (floor msrc-y)]
+              [adjust-pattern-filter
+               (lambda (p)
+                 (when (eq? smoothing 'unsmoothed)
+                   (cairo_pattern_set_filter p CAIRO_FILTER_NEAREST)))]
               [stamp-pattern
                (lambda (src a-src-x a-src-y)
                  (let ([p (cairo_pattern_create_for_surface (send src get-cairo-alpha-surface))]
                        [m (make-cairo_matrix_t 0.0 0.0 0.0 0.0 0.0 0.0)])
                    (cairo_matrix_init_translate m (- a-src-x a-dest-x) (- a-src-y a-dest-y))
                    (cairo_pattern_set_matrix p m)
+                   (adjust-pattern-filter (cairo_get_source cr))
                    ;; clip to the section that we're supposed to draw:
                    (cairo_save cr)
                    (when op (cairo_set_operator cr op))
@@ -1663,6 +1668,7 @@
                                        (send src get-cairo-surface)
                                        (- a-dest-x a-src-x)
                                        (- a-dest-y a-src-y))
+             (adjust-pattern-filter (cairo_get_source cr))
              (if mask
                  (stamp-pattern mask a-msrc-x a-msrc-y)
                  (begin

collects/racket/draw/unsafe/cairo.rkt

@@ -410,4 +410,13 @@
   CAIRO_PATTERN_TYPE_LINEAR
   CAIRO_PATTERN_TYPE_RADIAL)
 
+(define-enum
+  0
+  CAIRO_FILTER_FAST
+  CAIRO_FILTER_GOOD
+  CAIRO_FILTER_BEST
+  CAIRO_FILTER_NEAREST
+  CAIRO_FILTER_BILINEAR
+  CAIRO_FILTER_GAUSSIAN)
+
 (define/provide CAIRO_CONTENT_COLOR_ALPHA #x3000)

collects/scribblings/draw/bitmap-dc-class.scrbl

@@ -41,13 +41,10 @@ Creates a new memory DC. If @racket[bitmap] is not @racket[#f], it is
 
 The same as @method[dc<%> draw-bitmap-section], except that
  @racket[dest-width] and @racket[dest-height] cause the DC's
- transformation to be adjusted while drawing the bitmap so 
+ transformation to be adjusted while drawing the bitmap so that the
- that the bitmap is scaled.
+ bitmap is scaled; and, if the DC's smoothing mode is
-
+ @racket['unsmoothed], it is changed to @racket['aligned] while
-In older versions, this method smoothed drawing more than
+ drawing.}
- @method[dc<%> draw-bitmap-section], but smoothing is now provided by
- @method[dc<%> draw-bitmap-section].
-}
 
 @defmethod[(get-argb-pixels [x real?]
                             [y real?]