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<title>Graphics/Gloss/Internals/Interface/Animate/Timing.hs</title>
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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE RankNTypes #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-# OPTIONS_HADDOCK hide #-}</span>
<a name="line-3"></a>
<a name="line-4"></a><span class='hs-comment'>-- | Handles timing of animation.</span>
<a name="line-5"></a><span class='hs-comment'>-- The main point is that we want to restrict the framerate to something</span>
<a name="line-6"></a><span class='hs-comment'>-- sensible, instead of just displaying at the machines maximum possible</span>
<a name="line-7"></a><span class='hs-comment'>-- rate and soaking up 100% cpu. </span>
<a name="line-8"></a><span class='hs-comment'>--</span>
<a name="line-9"></a><span class='hs-comment'>-- We also keep track of the elapsed time since the start of the program,</span>
<a name="line-10"></a><span class='hs-comment'>-- so we can pass this to the user's animation function.</span>
<a name="line-11"></a><span class='hs-comment'>-- </span>
<a name="line-12"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Graphics</span><span class='hs-varop'>.</span><span class='hs-conid'>Gloss</span><span class='hs-varop'>.</span><span class='hs-conid'>Internals</span><span class='hs-varop'>.</span><span class='hs-conid'>Interface</span><span class='hs-varop'>.</span><span class='hs-conid'>Animate</span><span class='hs-varop'>.</span><span class='hs-conid'>Timing</span>
<a name="line-13"></a> <span class='hs-layout'>(</span> <span class='hs-varid'>animateBegin</span>
<a name="line-14"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>animateEnd</span> <span class='hs-layout'>)</span>
<a name="line-15"></a><span class='hs-keyword'>where</span>
<a name="line-16"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Graphics</span><span class='hs-varop'>.</span><span class='hs-conid'>Gloss</span><span class='hs-varop'>.</span><span class='hs-conid'>Internals</span><span class='hs-varop'>.</span><span class='hs-conid'>Interface</span><span class='hs-varop'>.</span><span class='hs-conid'>Backend</span>
<a name="line-17"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Graphics</span><span class='hs-varop'>.</span><span class='hs-conid'>Gloss</span><span class='hs-varop'>.</span><span class='hs-conid'>Internals</span><span class='hs-varop'>.</span><span class='hs-conid'>Interface</span><span class='hs-varop'>.</span><span class='hs-conid'>Animate</span><span class='hs-varop'>.</span><span class='hs-conid'>State</span>
<a name="line-18"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Control</span><span class='hs-varop'>.</span><span class='hs-conid'>Monad</span>
<a name="line-19"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>IORef</span>
<a name="line-20"></a>
<a name="line-21"></a>
<a name="line-22"></a><a name="animateBegin"></a><span class='hs-comment'>-- | Handles animation timing details.</span>
<a name="line-23"></a><span class='hs-comment'>-- Call this function at the start of each frame.</span>
<a name="line-24"></a><span class='hs-definition'>animateBegin</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IORef</span> <span class='hs-conid'>State</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>DisplayCallback</span>
<a name="line-25"></a><span class='hs-definition'>animateBegin</span> <span class='hs-varid'>stateRef</span> <span class='hs-varid'>backendRef</span>
<a name="line-26"></a> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-27"></a> <span class='hs-comment'>-- write the current time into the display state</span>
<a name="line-28"></a> <span class='hs-varid'>displayTime</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>elapsedTime</span> <span class='hs-varid'>backendRef</span>
<a name="line-29"></a> <span class='hs-varid'>displayTimeLast</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`getsIORef`</span> <span class='hs-varid'>stateDisplayTime</span>
<a name="line-30"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>displayTimeElapsed</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>displayTime</span> <span class='hs-comment'>-</span> <span class='hs-varid'>displayTimeLast</span>
<a name="line-31"></a>
<a name="line-32"></a> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`modifyIORef`</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>s</span>
<a name="line-33"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>stateDisplayTime</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>displayTime</span>
<a name="line-34"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>stateDisplayTimeLast</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>displayTimeLast</span> <span class='hs-layout'>}</span>
<a name="line-35"></a>
<a name="line-36"></a> <span class='hs-comment'>-- increment the animation time</span>
<a name="line-37"></a> <span class='hs-varid'>animate</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`getsIORef`</span> <span class='hs-varid'>stateAnimate</span>
<a name="line-38"></a> <span class='hs-varid'>animateCount</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`getsIORef`</span> <span class='hs-varid'>stateAnimateCount</span>
<a name="line-39"></a> <span class='hs-varid'>animateTime</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`getsIORef`</span> <span class='hs-varid'>stateAnimateTime</span>
<a name="line-40"></a> <span class='hs-varid'>animateStart</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`getsIORef`</span> <span class='hs-varid'>stateAnimateStart</span>
<a name="line-41"></a>
<a name="line-42"></a><span class='hs-comment'>{- when (animateCount `mod` 5 == 0)
<a name="line-43"></a> $ putStr $ " displayTime = " ++ show displayTime ++ "\n"
<a name="line-44"></a> ++ " displayTimeLast = " ++ show displayTimeLast ++ "\n"
<a name="line-45"></a> ++ " displayTimeElapsed = " ++ show displayTimeElapsed ++ "\n"
<a name="line-46"></a> ++ " fps = " ++ show (truncate $ 1 / displayTimeElapsed) ++ "\n"
<a name="line-47"></a>-}</span>
<a name="line-48"></a> <span class='hs-varid'>when</span> <span class='hs-layout'>(</span><span class='hs-varid'>animate</span> <span class='hs-varop'>&&</span> <span class='hs-varid'>not</span> <span class='hs-varid'>animateStart</span><span class='hs-layout'>)</span>
<a name="line-49"></a> <span class='hs-varop'>$</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`modifyIORef`</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>s</span>
<a name="line-50"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>stateAnimateTime</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>animateTime</span> <span class='hs-varop'>+</span> <span class='hs-varid'>displayTimeElapsed</span> <span class='hs-layout'>}</span>
<a name="line-51"></a>
<a name="line-52"></a> <span class='hs-varid'>when</span> <span class='hs-varid'>animate</span>
<a name="line-53"></a> <span class='hs-varop'>$</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`modifyIORef`</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>s</span>
<a name="line-54"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>stateAnimateCount</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>animateCount</span> <span class='hs-varop'>+</span> <span class='hs-num'>1</span>
<a name="line-55"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>stateAnimateStart</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>False</span> <span class='hs-layout'>}</span>
<a name="line-56"></a>
<a name="line-57"></a>
<a name="line-58"></a>
<a name="line-59"></a><a name="animateEnd"></a><span class='hs-comment'>-- | Handles animation timing details.</span>
<a name="line-60"></a><span class='hs-comment'>-- Call this function at the end of each frame.</span>
<a name="line-61"></a><span class='hs-definition'>animateEnd</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IORef</span> <span class='hs-conid'>State</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>DisplayCallback</span>
<a name="line-62"></a><span class='hs-definition'>animateEnd</span> <span class='hs-varid'>stateRef</span> <span class='hs-varid'>backendRef</span>
<a name="line-63"></a> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>do</span>
<a name="line-64"></a> <span class='hs-comment'>-- timing gate, limits the maximum frame frequency (FPS)</span>
<a name="line-65"></a> <span class='hs-varid'>timeClamp</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`getsIORef`</span> <span class='hs-varid'>stateDisplayTimeClamp</span>
<a name="line-66"></a>
<a name="line-67"></a> <span class='hs-varid'>gateTimeStart</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>elapsedTime</span> <span class='hs-varid'>backendRef</span> <span class='hs-comment'>-- the start of this gate</span>
<a name="line-68"></a> <span class='hs-varid'>gateTimeEnd</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`getsIORef`</span> <span class='hs-varid'>stateGateTimeEnd</span> <span class='hs-comment'>-- end of the previous gate</span>
<a name="line-69"></a> <span class='hs-keyword'>let</span> <span class='hs-varid'>gateTimeElapsed</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>gateTimeStart</span> <span class='hs-comment'>-</span> <span class='hs-varid'>gateTimeEnd</span>
<a name="line-70"></a>
<a name="line-71"></a> <span class='hs-varid'>when</span> <span class='hs-layout'>(</span><span class='hs-varid'>gateTimeElapsed</span> <span class='hs-varop'><</span> <span class='hs-varid'>timeClamp</span><span class='hs-layout'>)</span>
<a name="line-72"></a> <span class='hs-varop'>$</span> <span class='hs-keyword'>do</span> <span class='hs-varid'>sleep</span> <span class='hs-varid'>backendRef</span> <span class='hs-layout'>(</span><span class='hs-varid'>timeClamp</span> <span class='hs-comment'>-</span> <span class='hs-varid'>gateTimeElapsed</span><span class='hs-layout'>)</span>
<a name="line-73"></a>
<a name="line-74"></a> <span class='hs-varid'>gateTimeFinal</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>elapsedTime</span> <span class='hs-varid'>backendRef</span>
<a name="line-75"></a>
<a name="line-76"></a> <span class='hs-varid'>stateRef</span> <span class='hs-varop'>`modifyIORef`</span> <span class='hs-keyglyph'>\</span><span class='hs-varid'>s</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>s</span>
<a name="line-77"></a> <span class='hs-layout'>{</span> <span class='hs-varid'>stateGateTimeEnd</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>gateTimeFinal</span>
<a name="line-78"></a> <span class='hs-layout'>,</span> <span class='hs-varid'>stateGateTimeElapsed</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>gateTimeElapsed</span> <span class='hs-layout'>}</span>
<a name="line-79"></a>
<a name="line-80"></a>
<a name="line-81"></a><a name="getsIORef"></a><span class='hs-definition'>getsIORef</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>IORef</span> <span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-layout'>(</span><span class='hs-varid'>a</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>r</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>IO</span> <span class='hs-varid'>r</span>
<a name="line-82"></a><span class='hs-definition'>getsIORef</span> <span class='hs-varid'>ref</span> <span class='hs-varid'>fun</span>
<a name="line-83"></a> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>liftM</span> <span class='hs-varid'>fun</span> <span class='hs-varop'>$</span> <span class='hs-varid'>readIORef</span> <span class='hs-varid'>ref</span>
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