Editing html5 double layer canvas vs on layer canvas

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Test case details

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Preparation code

Preparation code HTML (this will be inserted in the <body> of a valid HTML5 document in standards mode) (useful when testing DOM operations or including libraries)

Include JavaScript libraries as follows: <script src="//cdn.ext/library.js"></script>

Define setup for all tests (variables, functions, arrays or other objects that will be used in the tests) (runs before each clocked test loop, outside of the timed code region) (e.g. define local test variables, reset global variables, clear canvas, etc.) (see FAQ)

Define teardown for all tests (runs after each clocked test loop, outside of the timed code region) (see FAQ)

Code snippets to compare

Test 1

Title

Async (check if this is an asynchronous test)

Code

fgCtx.clearRect(0,0,400,400);
fgCtx.drawImage(imgBg,0,0);
fgCtx.drawImage(imgFg,200,200);

Test 2

Title

Async (check if this is an asynchronous test)

Code

fgCtx.clearRect(0,0,400,400);
bgCtx.clearRect(0,0,400,400);
bgCtx.drawImage(imgBg,0,0);
fgCtx.drawImage(imgFg,200,200);