ScrollableListDemo

ScrollableListDemo.lua

ScrollableListItemMixin = {};

function ScrollableListItemMixin:Init(elementData)
    self.Background:SetColorTexture(elementData.color:GetRGBA());
    self.Text:SetText(elementData.text);
end

ScrollableListMixin = {};

function ScrollableListMixin:OnLoad()
    -- The data provider acts as the backing model for a scrollview; each
    -- element ("elementData") in the data provider corresponds to one row
    -- in the displayed list. The actual values can be anything. The default
    -- below creates an empty data provider, but you can pass a table in as
    -- the first argument to pre-populate it with values.

    self.DataProvider = CreateDataProvider();

    -- The scroll view is responsible for managing the acquisition of pooled
    -- frames and laying them out for display. This needs to be supplied with
    -- a data provider, an element extent (size), and an element factory or
    -- initializer at minimum.
    --
    -- The extent must be the actual height of each row. It can be dynamically
    -- calculated with a function, but a fixed extent is much more performant.

    local elementExtent = 21;

    self.ScrollView = CreateScrollBoxListLinearView();
    self.ScrollView:SetDataProvider(self.DataProvider);
    self.ScrollView:SetElementExtent(elementExtent);
    self.ScrollView:SetElementInitializer("Frame", "ScrollableListItemTemplate", function(frame, elementData)
        -- This is called each time the scrollview acquires a frame; this
        -- should generally call a method on the acquired frame and update
        -- its visual state accordingly.

        frame:Init(elementData);
    end);

    -- Padding and spacing are optional; these are just demo values. The
    -- defaults if no padding is configured will all be zero.

    local paddingT = 10;
    local paddingB = 10;
    local paddingL = 10;
    local paddingR = 10;
    local spacing = 5;

    self.ScrollView:SetPadding(paddingT, paddingB, paddingL, paddingR, spacing);

    -- The below call is required to hook everything up automatically.

    ScrollUtil.InitScrollBoxListWithScrollBar(self.ScrollBox, self.ScrollBar, self.ScrollView);

    -- If you want the scrollbar to show or hide automatically based on
    -- whether or not the region can be scrolled, you'll need two anchor
    -- tables to configure the managed scroll visibility behavior.

    local anchorsWithBar = {
        CreateAnchor("TOPLEFT", self, "TOPLEFT", 4, -4),
        CreateAnchor("BOTTOMRIGHT", self.ScrollBar, "BOTTOMLEFT", 0, 4),
    };

    local anchorsWithoutBar = {
        CreateAnchor("TOPLEFT", self, "TOPLEFT", 4, -4),
        CreateAnchor("BOTTOMRIGHT", self, "BOTTOMRIGHT", -4, 4),
    };

    ScrollUtil.AddManagedScrollBarVisibilityBehavior(self.ScrollBox, self.ScrollBar, anchorsWithBar, anchorsWithoutBar);
end

function ScrollableListMixin:AppendListItem()
    local color = CreateColor(fastrandom(), fastrandom(), fastrandom());
    local text = string.format("Time: %.5f", GetTime());

    local elementData =
    {
        color = color,
        text = text,
    };

    self.DataProvider:Insert(elementData);
    self.ScrollBox:ScrollToEnd(ScrollBoxConstants.NoScrollInterpolation);
end

function ScrollableListMixin:RemoveListItem()
    local lastIndex = self.DataProvider:GetSize();
    self.DataProvider:RemoveIndex(lastIndex);
end

ScrollableListDemoMixin = {};

function ScrollableListDemoMixin:OnLoad()
    ButtonFrameTemplate_HideAttic(self);
    ButtonFrameTemplate_HidePortrait(self);

    self.TitleText:SetText("Scrollable List Demo");

    self.AddButton:RegisterCallback("OnClick", self.ListFrame.AppendListItem, self.ListFrame);
    self.RemoveButton:RegisterCallback("OnClick", self.ListFrame.RemoveListItem, self.ListFrame);

    for _ = 1, 10 do
        self.ListFrame:AppendListItem();
    end
end

ScrollableListDemo.xml

<Ui>
    <Include file="ScrollableListDemo.lua"/>

    <Frame name="ScrollableListItemTemplate" mixin="ScrollableListItemMixin" virtual="true">
        <Size y="21"/>
        <Layers>
            <Layer level="BACKGROUND">
                <Texture parentKey="Background" setAllPoints="true"/>
            </Layer>
            <Layer level="OVERLAY">
                <FontString parentKey="Text" inherits="GameFontHighlight" setAllPoints="true"/>
            </Layer>
        </Layers>
    </Frame>

    <Frame name="ScrollableListTemplate" mixin="ScrollableListMixin" virtual="true">
        <Frames>
            <Frame parentKey="ScrollBox" inherits="WowScrollBoxList"/>
            <EventFrame parentKey="ScrollBar" inherits="WowTrimScrollBar">
                <Anchors>
                    <Anchor point="TOPRIGHT"/>
                    <Anchor point="BOTTOMRIGHT"/>
                </Anchors>
            </EventFrame>
        </Frames>
        <Scripts>
            <OnLoad method="OnLoad"/>
        </Scripts>
    </Frame>

    <Frame name="ScrollableListDemo" mixin="ScrollableListDemoMixin" inherits="ButtonFrameTemplate" toplevel="true">
        <Size x="640" y="480"/>
        <Anchors>
            <Anchor point="CENTER"/>
        </Anchors>
        <Frames>
            <Frame parentKey="ListFrame" inherits="ScrollableListTemplate">
                <Anchors>
                    <Anchor point="TOPLEFT" relativeKey="$parent.Inset"/>
                    <Anchor point="BOTTOMRIGHT" relativeKey="$parent.Inset"/>
                </Anchors>
            </Frame>
            <EventButton parentKey="AddButton" inherits="MagicButtonTemplate" text="Add Item">
                <Size x="125" y="22"/>
                <Anchors>
                    <Anchor point="BOTTOMRIGHT"/>
                </Anchors>
            </EventButton>
            <EventButton parentKey="RemoveButton" inherits="MagicButtonTemplate" text="Remove Item">
                <Size x="125" y="22"/>
                <Anchors>
                    <Anchor point="TOPRIGHT" relativeKey="$parent.AddButton" relativePoint="TOPLEFT"/>
                </Anchors>
            </EventButton>
        </Frames>
        <Scripts>
            <OnLoad method="OnLoad"/>
        </Scripts>
    </Frame>
</Ui>

For this to work on DF, on line 35 you need to remove the 1st argument.

self.ScrollView:SetElementInitializer("Frame", "ScrollableListItemTemplate", function(frame, elementData)
becomes
self.ScrollView:SetElementInitializer("ScrollableListItemTemplate", function(frame, elementData)