28 lines
1 KiB
Text
28 lines
1 KiB
Text
# transition.ludic - `transition: opacity 0.2s`: when an element's opacity changes from one frame to
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# the next it eases to the new value over that time instead of jumping (opacity is the property a
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# game fades most; the others arrive as they are)
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function tr_apply(ui_st: mut UiState, n: UiNode) -> void {
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if n.tr_dur <= 0.0 { return }
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let now = an_now(ui_st)
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let want = n.alpha
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for i in 0 .. len(ui_st.tr_keys) {
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if ui_st.tr_keys[i] == n.key {
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if ui_st.tr_to[i] != want {
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ui_st.tr_from[i] = tr_value(ui_st, i, now, n.tr_dur)
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ui_st.tr_to[i] = want
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ui_st.tr_at[i] = now
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}
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n.alpha = tr_value(ui_st, i, now, n.tr_dur)
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return
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}
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}
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ui_kept(ui_st.tr_keys, n.key)
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ui_kept(ui_st.tr_from, want)
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ui_kept(ui_st.tr_to, want)
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ui_kept(ui_st.tr_at, now)
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}
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function tr_value(ui_st: UiState, i: int, now: float, dur: float) -> float {
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let t = Math.clamp((now - ui_st.tr_at[i]) / dur, 0.0, 1.0)
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if t >= 1.0 { return ui_st.tr_to[i] }
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return ui_st.tr_from[i] + (ui_st.tr_to[i] - ui_st.tr_from[i]) * t
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}
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