delegatesizehelper updates

Make `DelegateSizeHelper` take a `QQuickItem` rather than a width value and move `TimelineDelegate` to use it rather than duplicting the code.

This requires the creation of `LibNeoChat` so that both the main and timeline modules can get access to the class.

Note: ideally more stuff will go into `LibNeoChat` but it turns out our dependencies are kinda spaghetti like and so will take some untangling.

src/libneochat/delegatesizehelper.h

@@ -0,0 +1,152 @@
+// SPDX-FileCopyrightText: 2023 James Graham <james.h.graham@protonmail.com>
+// SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+
+#pragma once
+
+#include <QObject>
+#include <QQmlEngine>
+#include <QQuickItem>
+
+/**
+ * @class DelegateSizeHelper
+ *
+ * A class to help calculate the current width of a chat delegate/bar.
+ *
+ * The aim is to support a dynamic sizing based upon the width of the page. There is
+ * a built in curve that allows the width to transition between two percentages based
+ * upon a start and finish break point. This is to provide better convergence where
+ * generally the delegate will need to fill all or most the screen when thin but
+ * should max out in size and only fill a lower percentage of the screen when wide.
+ *
+ * @note While the main intended usage is to start with a high percentage when the parentWidth
+ *       is small and transition to a lower one when large, the math is setup for the
+ *       general case so any combination of parameters works.
+ */
+class DelegateSizeHelper : public QObject
+{
+    Q_OBJECT
+    QML_ELEMENT
+
+    /**
+     * @brief The parent item that defines the available content area.
+     */
+    Q_PROPERTY(QQuickItem *parentItem READ parentItem WRITE setParentItem NOTIFY parentItemChanged)
+
+    /**
+     * @brief The amount of padding to be removed from the left of the available content area.
+     *
+     * The padding is removed before calculating the available width, i.e. max available width
+     * at 100% is equal to parent width minus padding.
+     */
+    Q_PROPERTY(qreal leftPadding READ leftPadding WRITE setLeftPadding NOTIFY leftPaddingChanged)
+
+    /**
+     * @brief The amount of padding to be removed from the right of the available content area.
+     *
+     * The padding is removed before calculating the available width, i.e. max available width
+     * at 100% is equal to parent width minus padding.
+     */
+    Q_PROPERTY(qreal rightPadding READ rightPadding WRITE setRightPadding NOTIFY rightPaddingChanged)
+
+    /**
+     * @brief The width (in px) when the width percentage should start to transition.
+     */
+    Q_PROPERTY(qreal startBreakpoint READ startBreakpoint WRITE setStartBreakpoint NOTIFY startBreakpointChanged)
+
+    /**
+     * @brief The width (in px) when the width percentage should finish transitioning.
+     */
+    Q_PROPERTY(qreal endBreakpoint READ endBreakpoint WRITE setEndBreakpoint NOTIFY endBreakpointChanged)
+
+    /**
+     * @brief The width (in %) of the component at or before the startBreakpoint.
+     *
+     * @sa startBreakpoint
+     */
+    Q_PROPERTY(int startPercentWidth READ startPercentWidth WRITE setStartPercentWidth NOTIFY startPercentWidthChanged)
+
+    /**
+     * @brief The width (in %) of the component at or after the endBreakpoint.
+     *
+     * @sa endBreakpoint
+     */
+    Q_PROPERTY(int endPercentWidth READ endPercentWidth WRITE setEndPercentWidth NOTIFY endPercentWidthChanged)
+
+    /**
+     * @brief The absolute maximum width (in px) the component can be.
+     */
+    Q_PROPERTY(qreal maxWidth READ maxWidth WRITE setMaxWidth NOTIFY maxWidthChanged)
+
+    /**
+     * @brief The width (in %) of the component at the current parentWidth.
+     *
+     * Will return -1 if no parentWidth is set or startBreakpoint == endBreakpoint.
+     *
+     * @sa parentWidth, startBreakpoint, endBreakpoint
+     */
+    Q_PROPERTY(int availablePercentageWidth READ availablePercentageWidth NOTIFY availablePercentageWidthChanged)
+
+    /**
+     * @brief The width (in px) of the component at the current parentWidth.
+     *
+     * Will return 0.0 if no parentWidth is set.
+     *
+     * @sa parentWidth
+     */
+    Q_PROPERTY(qreal availableWidth READ availableWidth NOTIFY availableWidthChanged)
+
+public:
+    explicit DelegateSizeHelper(QObject *parent = nullptr);
+
+    QQuickItem *parentItem() const;
+    void setParentItem(QQuickItem *parentItem);
+
+    qreal leftPadding() const;
+    void setLeftPadding(qreal leftPadding);
+    qreal rightPadding() const;
+    void setRightPadding(qreal rightPadding);
+
+    qreal startBreakpoint() const;
+    void setStartBreakpoint(qreal startBreakpoint);
+    qreal endBreakpoint() const;
+    void setEndBreakpoint(qreal endBreakpoint);
+
+    int startPercentWidth() const;
+    void setStartPercentWidth(int startPercentWidth);
+    int endPercentWidth() const;
+    void setEndPercentWidth(int endPercentWidth);
+
+    qreal maxWidth() const;
+    void setMaxWidth(qreal maxWidth);
+
+    qreal maxAvailableWidth() const;
+
+    int availablePercentageWidth() const;
+    qreal availableWidth() const;
+
+Q_SIGNALS:
+    void parentItemChanged();
+    void leftPaddingChanged();
+    void rightPaddingChanged();
+    void startBreakpointChanged();
+    void endBreakpointChanged();
+    void startPercentWidthChanged();
+    void endPercentWidthChanged();
+    void maxWidthChanged();
+    void availablePercentageWidthChanged();
+    void availableWidthChanged();
+
+private:
+    QPointer<QQuickItem> m_parentItem;
+
+    qreal m_leftPadding = 0.0;
+    qreal m_rightPadding = 0.0;
+
+    qreal m_startBreakpoint = 0.0;
+    qreal m_endBreakpoint = 0.0;
+    int m_startPercentWidth = 100;
+    int m_endPercentWidth = 85;
+    std::optional<qreal> m_maxWidth = std::nullopt;
+
+    int calculateAvailablePercentageWidth() const;
+};