Merge pull request #1422 from yinguangyao/master

feature: add native context types

Author: lavrton

src/Context.ts

@@ -86,7 +86,7 @@ var CONTEXT_PROPERTIES = [
   'globalAlpha',
   'globalCompositeOperation',
   'imageSmoothingEnabled',
-];
+] as const;
 
 const traceArrMax = 100;
 /**
@@ -701,6 +701,11 @@ export class Context {
   }
 }
 
+// supported context properties
+type CanvasContextProps = Pick<CanvasRenderingContext2D, typeof CONTEXT_PROPERTIES[number]>;
+
+export interface Context extends CanvasContextProps {};
+
 CONTEXT_PROPERTIES.forEach(function (prop) {
   Object.defineProperty(Context.prototype, prop, {
     get() {

test/unit/Context-test.ts

@@ -57,7 +57,7 @@ describe('Context', function () {
     'textBaseline',
     'globalAlpha',
     'globalCompositeOperation',
-  ];
+  ] as const;
 
   it('context wrapper should work like native context', function () {
     var stage = addStage();
@@ -108,10 +108,10 @@ describe('Context', function () {
 
     // test get
     nativeContext.fillStyle = '#ff0000';
-    assert.equal(context['fillStyle'], '#ff0000');
+    assert.equal(context.fillStyle, '#ff0000');
 
     // test set
-    context['globalAlpha'] = 0.5;
-    assert.equal(context['globalAlpha'], 0.5);
+    context.globalAlpha = 0.5;
+    assert.equal(context.globalAlpha, 0.5);
   });
 });