canvas

draw a line

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draw a rect or a angle

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draw a rect simply

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something is wrong?!

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why is black?
change it to red!

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ok ,got it !

draw a green rect

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draw a xx rect

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draw a circle

and we got nothing! we need fill() method. why ? no reason. maybe because there isn't a fillarc() method!

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darw a semi cycle

just set the start angle and the end angle

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