implemented touch in Qt and SDL

change TouchToPixelPos to return std::pair<int, int>

static_cast (SDL)

various minor style and code improvements

style - PascalCase for function names

made touch events private

const pointer arg in touch events

make TouchToPixelPos a const member function

did I do this right?

braces on barely-multiline if

remove question comment (confirmed in Discord)

fixed consts

remove unused parameter from TouchEndEvent

DRY - High-DPI scaled touch put in separate function

also fixes a bug where if you start touching (with either mouse or touchscreen) and drag the mouse to the LEFT of the emulator window, the touch point jumps to the RIGHT side of the touchscreen; draggin to above the window would make it jump to the bottom.

implicit conversion from QPoint to QPointF, apparently

I have no idea what const even means but I'll put it here anyway

remove unused or used-once variables

make touch scaling functions const, and put their implementations together

removed unused FingerID parameters

QTouchEvent forward declaration; add comment to TouchBegin that was lost in an edit

better DRY in SDL

To do -> TODO(NeatNit)

remove unused include

src/citra_qt/bootmanager.cpp

@@ -112,6 +112,7 @@ GRenderWindow::GRenderWindow(QWidget* parent, EmuThread* emu_thread)
     std::string window_title = fmt::format("Citra {} | {}-{}", Common::g_build_name,
                                            Common::g_scm_branch, Common::g_scm_desc);
     setWindowTitle(QString::fromStdString(window_title));
+    setAttribute(Qt::WA_AcceptTouchEvents);
 
     InputCommon::Init();
 }
@@ -191,11 +192,17 @@ QByteArray GRenderWindow::saveGeometry() {
         return geometry;
 }
 
-qreal GRenderWindow::windowPixelRatio() {
+qreal GRenderWindow::windowPixelRatio() const {
     // windowHandle() might not be accessible until the window is displayed to screen.
     return windowHandle() ? windowHandle()->screen()->devicePixelRatio() : 1.0f;
 }
 
+std::pair<unsigned, unsigned> GRenderWindow::ScaleTouch(const QPointF pos) const {
+    const qreal pixel_ratio = windowPixelRatio();
+    return {static_cast<unsigned>(std::max(std::round(pos.x() * pixel_ratio), qreal{0.0})),
+            static_cast<unsigned>(std::max(std::round(pos.y() * pixel_ratio), qreal{0.0}))};
+}
+
 void GRenderWindow::closeEvent(QCloseEvent* event) {
     emit Closed();
     QWidget::closeEvent(event);
@@ -210,31 +217,81 @@ void GRenderWindow::keyReleaseEvent(QKeyEvent* event) {
 }
 
 void GRenderWindow::mousePressEvent(QMouseEvent* event) {
+    if (event->source() == Qt::MouseEventSynthesizedBySystem)
+        return; // touch input is handled in TouchBeginEvent
+
     auto pos = event->pos();
     if (event->button() == Qt::LeftButton) {
-        qreal pixelRatio = windowPixelRatio();
-        this->TouchPressed(static_cast<unsigned>(pos.x() * pixelRatio),
-                           static_cast<unsigned>(pos.y() * pixelRatio));
+        const auto [x, y] = ScaleTouch(pos);
+        this->TouchPressed(x, y);
     } else if (event->button() == Qt::RightButton) {
         InputCommon::GetMotionEmu()->BeginTilt(pos.x(), pos.y());
     }
 }
 
 void GRenderWindow::mouseMoveEvent(QMouseEvent* event) {
+    if (event->source() == Qt::MouseEventSynthesizedBySystem)
+        return; // touch input is handled in TouchUpdateEvent
+
     auto pos = event->pos();
-    qreal pixelRatio = windowPixelRatio();
-    this->TouchMoved(std::max(static_cast<unsigned>(pos.x() * pixelRatio), 0u),
-                     std::max(static_cast<unsigned>(pos.y() * pixelRatio), 0u));
+    const auto [x, y] = ScaleTouch(pos);
+    this->TouchMoved(x, y);
     InputCommon::GetMotionEmu()->Tilt(pos.x(), pos.y());
 }
 
 void GRenderWindow::mouseReleaseEvent(QMouseEvent* event) {
+    if (event->source() == Qt::MouseEventSynthesizedBySystem)
+        return; // touch input is handled in TouchEndEvent
+
     if (event->button() == Qt::LeftButton)
         this->TouchReleased();
     else if (event->button() == Qt::RightButton)
         InputCommon::GetMotionEmu()->EndTilt();
 }
 
+void GRenderWindow::TouchBeginEvent(const QTouchEvent* event) {
+    // TouchBegin always has exactly one touch point, so take the .first()
+    const auto [x, y] = ScaleTouch(event->touchPoints().first().pos());
+    this->TouchPressed(x, y);
+}
+
+void GRenderWindow::TouchUpdateEvent(const QTouchEvent* event) {
+    QPointF pos;
+    int active_points = 0;
+
+    // average all active touch points
+    for (const auto tp : event->touchPoints()) {
+        if (tp.state() & (Qt::TouchPointPressed | Qt::TouchPointMoved | Qt::TouchPointStationary)) {
+            active_points++;
+            pos += tp.pos();
+        }
+    }
+
+    pos /= active_points;
+
+    const auto [x, y] = ScaleTouch(pos);
+    this->TouchMoved(x, y);
+}
+
+void GRenderWindow::TouchEndEvent() {
+    this->TouchReleased();
+}
+
+bool GRenderWindow::event(QEvent* event) {
+    if (event->type() == QEvent::TouchBegin) {
+        TouchBeginEvent(static_cast<QTouchEvent*>(event));
+        return true;
+    } else if (event->type() == QEvent::TouchUpdate) {
+        TouchUpdateEvent(static_cast<QTouchEvent*>(event));
+        return true;
+    } else if (event->type() == QEvent::TouchEnd || event->type() == QEvent::TouchCancel) {
+        TouchEndEvent();
+        return true;
+    }
+
+    return QWidget::event(event);
+}
+
 void GRenderWindow::focusOutEvent(QFocusEvent* event) {
     QWidget::focusOutEvent(event);
     InputCommon::GetKeyboard()->ReleaseAllKeys();