citra_qt: improve touchscreen mapping UI

src/citra_qt/configuration/configure_touch_widget.h

@@ -0,0 +1,61 @@
+// Copyright 2020 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <optional>
+#include <utility>
+#include <vector>
+#include <QFrame>
+#include <QPointer>
+
+class QLabel;
+
+// Widget for representing touchscreen coordinates
+class TouchScreenPreview : public QFrame {
+    Q_OBJECT
+    Q_PROPERTY(QColor dotHighlightColor MEMBER dot_highlight_color)
+
+public:
+    TouchScreenPreview(QWidget* parent);
+    ~TouchScreenPreview() override;
+
+    void SetCoordLabel(QLabel* const);
+    int AddDot(const int device_x, const int device_y);
+    void RemoveDot(const int id);
+    void HighlightDot(const int id, const bool active = true) const;
+    void MoveDot(const int id, const int device_x, const int device_y) const;
+
+signals:
+    void DotAdded(const QPoint& pos);
+    void DotSelected(const int dot_id);
+    void DotMoved(const int dot_id, const QPoint& pos);
+
+protected:
+    virtual void resizeEvent(QResizeEvent*) override;
+    virtual void mouseMoveEvent(QMouseEvent*) override;
+    virtual void leaveEvent(QEvent*) override;
+    virtual void mousePressEvent(QMouseEvent*) override;
+    virtual bool eventFilter(QObject*, QEvent*) override;
+
+private:
+    std::optional<QPoint> MapToDeviceCoords(const int screen_x, const int screen_y) const;
+    void PositionDot(QLabel* const dot, const int device_x = -1, const int device_y = -1) const;
+
+    bool ignore_resize = false;
+    QPointer<QLabel> coord_label;
+
+    std::vector<std::pair<int, QLabel*>> dots;
+    int max_dot_id = 0;
+    QColor dot_highlight_color;
+    static constexpr char prop_id[] = "dot_id";
+    static constexpr char prop_x[] = "device_x";
+    static constexpr char prop_y[] = "device_y";
+
+    struct {
+        bool active = false;
+        QPointer<QLabel> dot;
+        QPoint start_pos;
+    } drag_state;
+};