Don't cull error bars based on plot area (#108)

... this allows the plot to show partial error bars if the plot area is not
set up to show them entirely.

The previous code would remove error bars whose center was not inside the plot
area, we could have fixed the algorithm to consider a full line-rectangle
intersection, however that code would probably would have run slower than just
letting racket/draw do the clipping.

A test was added to ensure the expected behavior is not reverted by accident
in the future.

Author: alex-hhh

.github/workflows/ci.yml

@@ -9,11 +9,11 @@ jobs:
       # the failure is specific to a Racket version.
       fail-fast: false
       matrix:
-        racket-version: ["current"]
+        racket-version: ["8.4", "current"]
         racket-variant: ["BC", "CS"]
     steps:
       - uses: actions/checkout@v2
-      - uses: Bogdanp/setup-racket@v1.6
+      - uses: Bogdanp/setup-racket@v1.7
         with:
           architecture: x64
           distribution: minimal

plot-lib/plot/private/plot2d/point.rkt

@@ -190,7 +190,6 @@
                              Nonnegative-Real Nonnegative-Real Boolean
                              2D-Render-Proc))
 (define ((error-bars-render-fun xs ys hs color line-width line-style width alpha invert?) area)
-  (define clip-rect (send area get-clip-rect))
   (define radius (* 1/2 width))
   (define angle (if invert? (/ pi 2) 0))
 
@@ -200,12 +199,11 @@
   (send area put-alpha alpha)
   (send area put-pen color line-width line-style)
   (for ([x  (in-list xs)] [y  (in-list ys)] [h  (in-list hs)])
-    (when (rect-contains? clip-rect (maybe-invert x y))
-      (define v1 (maybe-invert x (- y h)))
-      (define v2 (maybe-invert x (+ y h)))
-      (send area put-line v1 v2)
-      (send area put-tick v1 radius angle)
-      (send area put-tick v2 radius angle))))
+    (define v1 (maybe-invert x (- y h)))
+    (define v2 (maybe-invert x (+ y h)))
+    (send area put-line v1 v2)
+    (send area put-tick v1 radius angle)
+    (send area put-tick v2 radius angle)))
 
 (:: error-bars
     (->* [(Sequenceof (Sequenceof Real))]

plot-test/plot/tests/PRs/108.rkt

@@ -0,0 +1,33 @@
+#lang racket
+
+(require rackunit
+         plot racket/runtime-path
+         "../helpers.rkt")
+
+;; Tests for https://github.com/racket/plot/issues/108, error bars are not
+;; culled out based on their center location, and partial error bars should be
+;; visible when the plot area does not include the entire error bar
+
+(define-runtime-path pr108-data "./test-data/pr108.dat")
+
+;; This plot  is set up  to have the  area such that  the center and  edges of
+;; error  bars are  not in  the plot,  it should  still draw  a line  from the
+;; partial error bar at 4.
+(define (do-plot-pr108 output-fn)
+  (output-fn
+   (list (function sqr 1 7)
+         (error-bars (list (vector 2 4 12)
+                           (vector 4 16 20)
+                           (vector 6 36 10))))
+   #:x-min 3.5 #:x-max 4.5
+   #:y-min 20 #:y-max 30))
+
+(define pr108-test-suite
+  (test-suite
+   "PR#108: Zoom in for error-bars (plot package) not working properly."
+   (test-case "pr108"
+     (check-draw-steps do-plot-pr108 pr108-data))))
+
+(module+ test
+  (require rackunit/text-ui)
+  (run-tests pr108-test-suite))