Separate legend font from plot font for more control. Unset parameters default to plot parameters.

Author: J. Ian Johnson

plot-doc/plot/scribblings/params.scrbl

@@ -95,6 +95,12 @@ The opacity of the background and foreground colors.
 The font size (in drawing units), face, and family of the title, axis labels, tick labels, and other labels.
 }
 
+@deftogether[((defparam plot-legend-font-size size (or/c (>=/c 0) #f) #:value #f)
+              (defparam plot-legend-font-face face (or/c string? #f) #:value #f)
+              (defparam plot-legend-font-family family (or/c font-family/c #f) #:value #f))]{
+The font size (in drawing units), face, and family to prefer for the legend text. If set to @racket[#f], then the corresponding @racket[plot-font-X] parameter is used.
+}
+
 @deftogether[((defparam plot-legend-anchor anchor anchor/c #:value 'top-left)
               (defparam plot-legend-box-alpha alpha (real-in 0 1) #:value 2/3))]{
 The placement of the legend and the opacity of its background.

plot-lib/plot/private/common/parameter-groups.rkt

@@ -28,6 +28,7 @@
      plot-background plot-background-alpha
      plot-line-width plot-tick-size
      plot-font-size plot-font-face plot-font-family
+     plot-legend-font-size plot-legend-font-face plot-legend-font-family
      plot-legend-anchor plot-legend-box-alpha
      plot-axes? plot-tick-labels
      plot-decorations?
@@ -86,6 +87,9 @@
       Nonnegative-Real
       (U False String)
       Font-Family
+      (U False Nonnegative-Real)
+      (U False String)
+      (U False Font-Family)
       Anchor
       Nonnegative-Real
       (List Boolean Boolean Boolean Boolean Boolean Boolean)

plot-lib/plot/private/common/parameters.rkt

@@ -71,6 +71,9 @@
 (defparam2 plot-font-size size Real Nonnegative-Real 11 (nonnegative-rational 'plot-font-size))
 (defparam plot-font-face face (U String #f) #f)
 (defparam plot-font-family family Font-Family 'roman)
+(defparam plot-legend-font-size size (U Nonnegative-Real #f) #f)
+(defparam plot-legend-font-face face (U String #f) #f)
+(defparam plot-legend-font-family family (U Font-Family #f) #f)
 (defparam plot-legend-anchor anchor Anchor 'top-left)
 (defparam2 plot-legend-box-alpha alpha Real Nonnegative-Real 2/3 (unit-ivl 'plot-legend-box-alpha))
 (defparam plot-animating? Boolean #f)

plot-lib/plot/private/common/plot-device.rkt

@@ -587,6 +587,14 @@
 
       (match-define (vector (ivl x-min x-max) (ivl y-min y-max)) rect)
 
+      (define old-size (send (send dc get-font) get-point-size))
+      (define old-face (send (send dc get-font) get-face))
+      (define old-family (send (send dc get-font) get-family))
+      (set-font-attribs
+       (or (plot-legend-font-size) old-size)
+       (or (plot-legend-font-face) old-face)
+       (or (plot-legend-font-family) old-family))
+
       (define-values (_1 label-y-size baseline _2) (get-text-extent (first labels)))
       (define horiz-gap (get-text-width " "))
       (define top-gap baseline)
@@ -656,6 +664,9 @@
         (send entry-pd reset-drawing-params #f)
         (draw-proc this draw-x-size draw-y-size)
         (send entry-pd restore-drawing-params))
+
+      ;; reset plot font attributes
+      (set-font-attribs old-size old-face old-family)
 
       (clear-clipping-rect))
     ))  ; end class

plot-lib/plot/private/utils-and-no-gui.rkt

@@ -76,6 +76,9 @@
  plot-font-size
  plot-font-face
  plot-font-family
+ plot-legend-font-size
+ plot-legend-font-face
+ plot-legend-font-family
  plot-legend-anchor
  plot-legend-box-alpha
  plot-decorations?