92 lines
2.5 KiB
Text
92 lines
2.5 KiB
Text
Ease :: enum {
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linear;
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quad;
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cubic;
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quart;
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quint;
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expo;
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sine;
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circ;
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back;
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elastic;
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}
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Transition :: enum {
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in;
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out;
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in_out;
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}
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/*
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Calculate a tween value for the given process, easing function, and transition.
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The value returned can be used like so:
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progress := 1.0 / time_in_seconds;
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current = original + ease(progress, .cubic, .in_out);
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@Note: Progress must be between 0.0 and 1.0
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*/
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ease :: (progress: $T, $$ease: Ease = .linear, $$transition: Transition = .in) -> T
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#modify { return meta.type_is_float(T); }
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{
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p := progress;
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#insert -> string {
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expressions :: string.[
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"p", // linear
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"p * p", // quad
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"p * p * p", // cubic
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"p * p * p * p", // quart
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"p * p * p * p * p", // quint
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"math.pow(2, (10 * (p - 1)))", // expo
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"-math.cos(p * (math.PI * 0.5)) + 1", // sine
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"-(math.sqrt(1 - (p * p)) - 1)", // circ
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"p * p * (2.7 * p - 1.7)", // back
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"-math.pow(2, 10 * (p - 1)) * math.sin((p - 1.075) * (math.PI * 2) / 0.3)" // elastic
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];
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b: basic.String_Builder;
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if is_constant(ease) basic.append(*b, "#");
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basic.append(*b, "if ease == {\n");
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info := type_info(Ease);
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for info.names {
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basic.print_to_builder(*b, #string END
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case .%1; %2if transition == {
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case .in;
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return %3;
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case .out;
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p = 1 - p;
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return p - (%3);
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case .in_out;
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p *= 2;
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if p < 1 {
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return 0.5 * (%3);
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}
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p = 2 - p;
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return 0.5 * (1 - (%3)) + 0.5;
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}
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END, it, ifx is_constant(transition) "#" else "", expressions[it_index]);
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}
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basic.append(*b, "}\n");
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return basic.builder_to_string(*b);
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}
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return p;
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}
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#scope_file;
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meta :: #import "jc/meta";
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math :: #import "Math"; // @future
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basic :: #import "Basic"; // @future
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