plasma-bitcoin-price/contents/ui/DisplayFlip.qml

/*
 * Split-flap display mode — airport departure board style.
 * Only digits are shown as flaps; the euro sign is rendered as plain
 * text (default font, white) next to the board, and the trend shows
 * on a small LED. Changed characters flip with a cascading animation
 * spread over the configured number of seconds.
 * Pure QtQuick so it can be tested outside the plasmoid shell.
 */

import QtQuick 2.15

Row {
    id: root

    // wired by the parent loader
    property string display: "--"
    property color trendColor: "#9e9e9e"
    // seconds over which the cascade to a new price is spread
    property int flapSeconds: 3

    spacing: height * 0.06

    function digitsOf(s) {
        var out = "";
        for (var i = 0; i < s.length; i++) {
            var ch = s.charAt(i);
            if ((ch >= "0" && ch <= "9") || ch === "-") {
                out += ch;
            }
        }
        return out;
    }

    // UI-only derived values (euro visibility); logic must not rely on these —
    // QML gives no ordering guarantee between a change handler and the
    // re-evaluation of dependent bindings.
    readonly property string digitsOnly: digitsOf(display)
    readonly property string boardText: digitsOnly.length > 0 ? digitsOnly : "--"

    property var chars: []
    property bool ready: false
    readonly property real cellFont: height * 0.72
    readonly property real cellWidth: cellFont * 0.80
    // one flap open+close takes 260 ms; keep delays above that
    readonly property int flapDuration: 260

    Component.onCompleted: {
        chars = boardText.split("");
        ready = true;
    }

    onDisplayChanged: {
        if (!ready) {
            return;
        }
        // compute from display directly: derived bindings may still be
        // stale at this point (QML makes no ordering guarantee)
        var digits = digitsOf(display);
        var nc = (digits.length > 0 ? digits : "--").split("");
        var n = Math.max(chars.length, nc.length);
        // spread the changed cells evenly across flapSeconds
        var changed = [];
        for (var i = 0; i < n; i++) {
            var from = i < chars.length ? chars[i] : "";
            var to = i < nc.length ? nc[i] : "";
            if (from !== to) {
                changed.push([i, to]);
            }
        }
        var span = Math.max(1, flapSeconds) * 1000 - flapDuration;
        var step = changed.length > 1 ? Math.max(0, Math.floor(span / (changed.length - 1))) : 0;
        for (var j = 0; j < changed.length; j++) {
            var cell = rep.itemAt(changed[j][0]);
            if (cell) {
                cell.flipTo(changed[j][1], j * step);
            }
        }
        chars = nc;
    }

    Repeater {
        id: rep
        model: root.chars.length

        delegate: Rectangle {
            id: cell

            width: root.cellWidth
            height: root.height
            radius: 2
            color: "#0b0b0d"
            border.color: "#26262b"
            border.width: 1

            // plain property (not a binding) so the flip animation
            // controls when the character actually changes
            property string ch: ""
            property string pendingCh: ""

            Component.onCompleted: {
                ch = root.chars[index] !== undefined ? root.chars[index] : "";
            }

            function flipTo(newCh, delay) {
                if (newCh === ch) {
                    return;
                }
                pendingCh = newCh;
                delayTimer.interval = Math.max(0, delay);
                delayTimer.restart();
            }

            Timer {
                id: delayTimer
                interval: 0
                onTriggered: flipAnim.start()
            }

            transform: Scale {
                id: scaleTransform
                origin.y: cell.height / 2
                yScale: 1
            }

            SequentialAnimation {
                id: flipAnim
                NumberAnimation {
                    target: scaleTransform
                    property: "yScale"
                    to: 0.06
                    duration: 130
                    easing.type: Easing.InQuad
                }
                ScriptAction {
                    script: cell.ch = cell.pendingCh
                }
                NumberAnimation {
                    target: scaleTransform
                    property: "yScale"
                    to: 1
                    duration: 130
                    easing.type: Easing.OutQuad
                }
            }

            Text {
                anchors.centerIn: parent
                text: cell.ch
                color: "#f2f2f2"
                font.family: "DejaVu Sans Mono"
                font.pixelSize: root.cellFont
            }

            // the flap split line across the middle
            Rectangle {
                anchors.horizontalCenter: parent.horizontalCenter
                y: parent.height / 2 - 1
                width: parent.width
                height: 2
                color: "#000000"
                opacity: 0.55
            }
        }
    }

    // euro sign in the plain-text font, white
    Text {
        anchors.verticalCenter: parent.verticalCenter
        text: "\u20AC"
        visible: root.digitsOnly.length > 0
        color: "#ffffff"
        font.family: Qt.application.font.family
        font.pixelSize: root.height * 0.66
    }

    // trend LED (green/red/grey)
    Rectangle {
        width: root.height * 0.14
        height: width
        radius: width / 2
        anchors.verticalCenter: parent.verticalCenter
        color: root.trendColor
        border.color: "#26262b"
        border.width: 1
    }
}