I like this idea. I cannot find any harm if we have this functionality. When a pixel test is more succinct, we can make a pixel test. When a 'getPixel on Javascript' test is more succinct, we can make a 'getPixel' test. As http://trac.webkit.org/wiki/Writing%20Layout%20Tests%20for%20DumpRenderTree said 'Pixel tests are a burden on every ports as any small change in the engine could lead to your test needing a new pixel result.', new test functionality that can be an alternative of pixel test is good! philip canvas tests (LayoutTests/canvas/philip) has no pixel test because of the power of getImageData API in canvas spec.
I can put two examples for the power of functionality that Noam suggested, Case 1: CSS Filters & Shaders I wanted this test functionality when I commented http://webkit.org/b/97859#c19 If I want to make gaussian blur test, I prefer using 'getPixel' test as follows, ASSERT(getPixel(10, 10) = rgba(255, 0, 0, 255)); ASSERT(getPixel(10, 15) > rgba(255, 0, 0, 98) && getPixel(10, 15) < rgba(255, 0, 0, 102)); If we don't have 'getPixel', we need to capture all port's image results because all port's painting engine would make a bit different result. As you know, it is painful. Case 2: Fixed Position Element I guess it is one of reasons why Noam suggested. Currently, Qt and EFL AC (a.k.a Coordinated Graphics) has a problem related to fixed position element. During panning animation, Fixed position element is slightly flickering. If we have 'getPixel', we can make a succinct test case. PRECONDITION : a green fixed position div is on the white body. The rect of the div is rect(10, 10, 30, 30). function repeatedlyCalledDuringScrolling() { ASSERT(getPixel(15, 9) == white); ASSERT(getPixel(15, 10) == green); ASSERT(getPixel(9, 15) == white); ASSERT(getPixel(10, 15) == green); .... } WDYT? Best regards, Dongsung Huang
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