add linear gradient

desktop/sources/scripts/library.js

@@ -215,6 +215,12 @@ function Library (ronin) {
     return getComputedStyle(el).getPropertyValue(`--${variable}`)
   }
 
+  // Gradients
+
+  this.gradient = ([x1,y1,x2,y2], colors=['white','black']) => {
+    return ronin.surface.linearGradient(x1, y1, x2, y2, colors)
+  }
+
   // Pixels
 
   this.pixels = (rect, fn, q) => {

desktop/sources/scripts/surface.js

@@ -61,6 +61,15 @@ function Surface (ronin) {
     context.closePath()
   }
 
+  this.linearGradient = function(x1, y1, x2, y2, colors, context = this.context) {
+    const gradient = context.createLinearGradient(x1, y1, x2, y2)
+    const step = 1/(colors.length - 1)
+    colors.forEach((color,i) => {
+      gradient.addColorStop(i*step, color)
+    })
+    return gradient
+  }
+
   // Tracers
 
   this.trace = function (shape, context) {