![]() Bill figured out the animation was accomplished by a mask layer moving beneath the surface of the sign that varied which portion of the image was visible. The beer sign featured an impressive animated waterfall, with the water seeming to flow down the waterfall into the lake. He ordered a beer, looked around the bar, and noticed a Hamm's beer sign. He was thinking about the selection problem one evening when he went to dinner at an old beer and hamburger joint in Los Gatos, the kind of place where decades worth of initials are carved into the wooden tables. Bill knew he had to find a better way to do it. The selection rectangle was depicted by inverting the pixels beneath it, which worked well enough over solid areas, but was confusing and hard to see when the underlying image was complex, like a digitized picture. He added a rectangular selection tool, to allow the user to perform operations on a subset of the document. It also enabled fast drawing, because it was very easy to access the original state of the document in the second buffer as an object was being modified.Īfter getting basic updating working well, Bill began to add more tools to the palette. This made it very easy to implement undo, by just copying the old buffer to the new. In fact, despite the Macintosh's limited memory, he used two offscreen buffers, each the size of the document window, with one containing the current pixels of the document, and the other containing the pixels of its previous state, before the most recent operation. Bill completely eliminated flicker by composing everything in an offscreen memory buffer, which was transferred to the screen in one fell swoop, so the interim states were never visible. As you dragged a shape or image across the screen, it had to be erased from its old position before being drawn in the new one, which caused a distracting flicker as the video sometimes displayed interim, partially rendered states. ![]() The first big advance that Bill worked on was eliminating flicker. More tools would be added over time, but the basic structure of MacPaint was there from its earliest stages. SketchPad used menus to select patterns and styles to draw with, but Bill replaced them with permanent palettes at the bottom of the screen and added another large, prominent palette on the left, containing a variety of drawing tools. ![]() He began by dusting off his old SketchPad code, and getting it running on the Mac as MacSketch. Steve Jobs thought that he should work on a structured drawing program, something like Mark Cutter's LisaDraw, but Bill thought that structured drawing was too complex, and wanted to create something that was simple, elegant and fun to use. In early 1983, soon after the Lisa was announced at the 1983 annual shareholders meeting, Bill switched from working on Lisa system software to writing a killer graphics application for the Macintosh. SketchPad enabled mouse-based drawing with a selection of paintbrushes and patterns, and gave Bill a quick way to test out and show off new features or improvements as they were added to LisaGraf. ![]() While Bill Atkinson was developing LisaGraf, the crucial, lightning fast graphics package that was the foundation of both the Lisa and Macintosh user interface (it was renamed QuickDraw for the Mac), he also worked sporadically on a simple bitmap-based drawing program for the Lisa called SketchPad.
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