overlay_dialog: Add an overlay text dialog that accepts controller input

An OverlayDialog is an interactive dialog that accepts controller input (while a game is running)
This dialog attempts to replicate the look and feel of the Nintendo Switch's overlay dialogs and
provide some extra features such as embedding HTML/Rich Text content in a QTextBrowser.
The OverlayDialog provides 2 modes: one to embed regular text into a QLabel and another to embed
HTML/Rich Text content into a QTextBrowser.

Co-authored-by: Its-Rei <kupfel@gmail.com>

src/yuzu/util/overlay_dialog.h

@@ -0,0 +1,107 @@
+// Copyright 2021 yuzu Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include <atomic>
+#include <memory>
+#include <thread>
+
+#include <QDialog>
+
+#include "common/common_types.h"
+
+enum class HIDButton : u8;
+
+class InputInterpreter;
+
+namespace Core {
+class System;
+}
+
+namespace Ui {
+class OverlayDialog;
+}
+
+/**
+ * An OverlayDialog is an interactive dialog that accepts controller input (while a game is running)
+ * This dialog attempts to replicate the look and feel of the Nintendo Switch's overlay dialogs and
+ * provide some extra features such as embedding HTML/Rich Text content in a QTextBrowser.
+ * The OverlayDialog provides 2 modes: one to embed regular text into a QLabel and another to embed
+ * HTML/Rich Text content into a QTextBrowser.
+ */
+class OverlayDialog final : public QDialog {
+    Q_OBJECT
+
+public:
+    explicit OverlayDialog(QWidget* parent, Core::System& system, const QString& title_text,
+                           const QString& body_text, const QString& left_button_text,
+                           const QString& right_button_text,
+                           Qt::Alignment alignment = Qt::AlignCenter, bool use_rich_text_ = false);
+    ~OverlayDialog() override;
+
+private:
+    /**
+     * Initializes a text dialog with a QLabel storing text.
+     * Only use this for short text as the dialog buttons would be squashed with longer text.
+     *
+     * @param title_text Title text to be displayed
+     * @param body_text Main text to be displayed
+     * @param left_button_text Left button text. If empty, the button is hidden and disabled
+     * @param right_button_text Right button text. If empty, the button is hidden and disabled
+     * @param alignment Main text alignment
+     */
+    void InitializeRegularTextDialog(const QString& title_text, const QString& body_text,
+                                     const QString& left_button_text,
+                                     const QString& right_button_text, Qt::Alignment alignment);
+
+    /**
+     * Initializes a text dialog with a QTextBrowser storing text.
+     * This is ideal for longer text or rich text content. A scrollbar is shown for longer text.
+     *
+     * @param title_text Title text to be displayed
+     * @param body_text Main text to be displayed
+     * @param left_button_text Left button text. If empty, the button is hidden and disabled
+     * @param right_button_text Right button text. If empty, the button is hidden and disabled
+     * @param alignment Main text alignment
+     */
+    void InitializeRichTextDialog(const QString& title_text, const QString& body_text,
+                                  const QString& left_button_text, const QString& right_button_text,
+                                  Qt::Alignment alignment);
+
+    /// Moves and resizes the dialog to be fully overlayed on top of the parent window.
+    void MoveAndResizeWindow();
+
+    /**
+     * Handles button presses and converts them into keyboard input.
+     *
+     * @tparam HIDButton The list of buttons that can be converted into keyboard input.
+     */
+    template <HIDButton... T>
+    void HandleButtonPressedOnce();
+
+    /**
+     * Translates a button press to focus or click either the left or right buttons.
+     *
+     * @param button The button press to process.
+     */
+    void TranslateButtonPress(HIDButton button);
+
+    void StartInputThread();
+    void StopInputThread();
+
+    /// The thread where input is being polled and processed.
+    void InputThread();
+
+    std::unique_ptr<Ui::OverlayDialog> ui;
+
+    bool use_rich_text;
+
+    std::unique_ptr<InputInterpreter> input_interpreter;
+
+    std::thread input_thread;
+
+    std::atomic<bool> input_thread_running{};
+};