Project tabs drag to reorder; tabs that don't fit gather in a menu (13.14)

src/UI/ProjectTabs.h

@@ -1,14 +1,18 @@
 #pragma once
 #include "Document/ProjectWorkspace.h"
-#include <QScrollArea>
+#include "UI/ProjectTabLayout.h"
 #include <QToolButton>
 #include <QWidget>
 
+// Swift's TabDragPhase: a reorder drag goes on, or ends.
+enum class TabDragPhase { changed, ended };
+
 // One tab: its title, the unsaved dot, its close button.
 class ProjectTabButton : public QWidget {
     Q_OBJECT
 public:
-    ProjectTabButton(ProjectWorkspace &workspace, std::shared_ptr<ProjectTab> tab, QWidget *parent = nullptr);
+    ProjectTabButton(ProjectWorkspace &workspace, std::shared_ptr<ProjectTab> tab, std::function<void(TabDragPhase, double)> onReorder,
+                     QWidget *parent = nullptr);
 
     const std::shared_ptr<ProjectTab> tab;
     // What the session and the workspace hold, shown.
@@ -16,6 +20,7 @@ public:
     bool isActive() const;
 
 protected:
+    bool eventFilter(QObject *watched, QEvent *event) override;
     void paintEvent(QPaintEvent *event) override;
     void dragEnterEvent(QDragEnterEvent *event) override;
     void dragMoveEvent(QDragMoveEvent *event) override;
@@ -27,9 +32,13 @@ private:
     void setTargeted(bool targeted);
 
     ProjectWorkspace &m_workspace;
+    const std::function<void(TabDragPhase, double)> m_onReorder;
     QToolButton *const m_select;
     QToolButton *const m_close;
     bool m_targeted = false;
+    // Swift's DragGesture: the press, in the window's space.
+    std::optional<QPointF> m_press;
+    bool m_dragging = false;
 };
 
 // Swift's NewProjectDropTarget: the New canvas button takes drops.
@@ -53,23 +62,67 @@ private:
     bool m_targeted = false;
 };
 
-// The row of tabs, one a project, scrolling when long.
-class ProjectTabStrip : public QScrollArea {
+// Swift's OverflowTabsPill: the tabs that do not fit, a menu.
+class OverflowTabsPill : public QToolButton {
+    Q_OBJECT
+public:
+    explicit OverflowTabsPill(ProjectWorkspace &workspace, QWidget *parent = nullptr);
+
+    // Swift's projectTabOverflowPillWidth.
+    static double pillWidth(int hiddenCount);
+    void setHiddenIDs(std::vector<QUuid> hiddenIDs);
+
+protected:
+    void paintEvent(QPaintEvent *event) override;
+
+private:
+    void showMenu();
+
+    ProjectWorkspace &m_workspace;
+    std::vector<QUuid> m_hiddenIDs;
+};
+
+// The row of tabs; the rest gather in a menu.
+class ProjectTabStrip : public QWidget {
     Q_OBJECT
 public:
     explicit ProjectTabStrip(ProjectWorkspace &workspace, QWidget *parent = nullptr);
 
     QList<ProjectTabButton *> buttons() const;
+    OverflowTabsPill *pill() const { return m_pill; }
+
+    QSize sizeHint() const override;
+    QSize minimumSizeHint() const override;
 
 protected:
-    bool eventFilter(QObject *watched, QEvent *event) override;
+    void resizeEvent(QResizeEvent *event) override;
 
 private:
+    // Swift's TabReorderState, taken once as the drag starts.
+    struct Reorder {
+        QUuid id;
+        std::vector<QUuid> others;
+        std::map<QUuid, double> widths;
+        std::map<QUuid, double> compactedX;
+        double startX;
+        double originX;
+        double translation = 0;
+        int targetIndex = 0;
+        int nearestSlot() const;
+    };
+
     void synchronize();
-    void showFront();
+    std::map<QUuid, double> widths() const;
+    ProjectTabOverflow overflow() const;
+    // Places the pill and the tabs; others slide when `animated`.
+    void layOut(bool animated = false);
+    double renderX(const ProjectTabSlot &slot, double contentWidth) const;
+    void handleReorder(QUuid id, TabDragPhase phase, double translation);
+    Reorder makeReorder(QUuid id) const;
+    void commitReorder(const Reorder &state);
 
     ProjectWorkspace &m_workspace;
-    QWidget *const m_row;
-    // Swift's lastSelectedID: only a new front tab scrolls.
-    std::optional<QUuid> m_shownFront;
+    OverflowTabsPill *const m_pill;
+    std::vector<ProjectTabButton *> m_buttons;
+    std::optional<Reorder> m_reorder;
 };