lib/shoes/swt/gradient.rb in shoes-swt-4.0.0.pre12 vs lib/shoes/swt/gradient.rb in shoes-swt-4.0.0.rc1

@@ -1,14 +1,28 @@
 # frozen_string_literal: true
+
+# Gradients are a little confusing, but don't let all the math below scare you.
+# Here's the (relatively) simple explanation of what's going on.
+#
+# ::SWT::Pattern, the underlying class we use, defines a gradient by a starting
+# and ending point. We account the angle into it by changing these points.
+#
+# To look right, the start/end points must be outside our shape! If not, then
+# we get a hard line where the color resets without fading, which looks bad.
+# Given that, we must keep those points outside our bounds of the element,
+# which are reported via the redraw_left, redraw_top, etc. methods.
+
 class Shoes
   module Swt
     class Gradient
       include Common::Remove
 
       def initialize(dsl)
         @dsl = dsl
         @patterns = []
+        @color1 = nil
+        @color2 = nil
       end
 
       def dispose
         @color1&.dispose
         @color2&.dispose
@@ -40,15 +54,19 @@
         gc.set_foreground_pattern pattern
       end
 
       private
 
-      def create_pattern(dsl)
-        width  = dsl.element_width * 0.5
-        height = dsl.element_height * 0.5
-        angle  = normalize_angle(-dsl.angle)
-        left, top, width, height = determine_args_based_on_angle(angle, dsl.element_left,
-                                                                 dsl.element_top, width, height)
+      def create_pattern(gui)
+        dsl    = gui.dsl
+        width  = dsl.redraw_width * 0.5
+        height = dsl.redraw_height * 0.5
+        angle  = normalize_angle(-(dsl.angle || 0))
+        left, top, width, height = determine_args_based_on_angle(angle,
+                                                                 dsl.redraw_left,
+                                                                 dsl.redraw_top,
+                                                                 width,
+                                                                 height)
 
         pattern = ::Swt::Pattern.new Shoes.display, left, top, width, height,
                                      color1.real, color2.real
         @patterns << pattern
         pattern