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.

src/citra_qt/bootmanager.cpp

@@ -216,9 +216,8 @@ void GRenderWindow::mousePressEvent(QMouseEvent* event) {
 
     auto pos = event->pos();
     if (event->button() == Qt::LeftButton) {
-        qreal pixelRatio = windowPixelRatio();
+        auto [x, y] = ScaleTouch(QPointF(pos));
-        this->TouchPressed(static_cast<unsigned>(pos.x() * pixelRatio),
+        this->TouchPressed(x, y);
-                           static_cast<unsigned>(pos.y() * pixelRatio));
     } else if (event->button() == Qt::RightButton) {
         InputCommon::GetMotionEmu()->BeginTilt(pos.x(), pos.y());
     }
@@ -229,9 +228,8 @@ void GRenderWindow::mouseMoveEvent(QMouseEvent* event) {
         return; // touch input is handled in TouchUpdateEvent
 
     auto pos = event->pos();
-    qreal pixelRatio = windowPixelRatio();
+    auto [x, y] = ScaleTouch(QPointF(pos));
-    this->TouchMoved(std::max(static_cast<unsigned>(pos.x() * pixelRatio), 0u),
+    this->TouchMoved(x, y);
-                     std::max(static_cast<unsigned>(pos.y() * pixelRatio), 0u));
     InputCommon::GetMotionEmu()->Tilt(pos.x(), pos.y());
 }
 
@@ -245,39 +243,37 @@ void GRenderWindow::mouseReleaseEvent(QMouseEvent* event) {
         InputCommon::GetMotionEmu()->EndTilt();
 }
 
-void GRenderWindow::TouchBeginEvent(const QTouchEvent* event) {
+std::pair<unsigned, unsigned> GRenderWindow::ScaleTouch(QPointF pos) {
-    auto points = event->touchPoints();
+    qreal pixel_ratio = windowPixelRatio();
-    auto tp = points.first(); // there should only be 1 point in TouchBegin
+    return {static_cast<unsigned>(std::max(std::round(pos.x() * pixel_ratio), qreal{0.0})),
-    auto pos = tp.pos();
+            static_cast<unsigned>(std::max(std::round(pos.y() * pixel_ratio), qreal{0.0}))};
+}
 
-    // Copied from mousePressEvent:
+void GRenderWindow::TouchBeginEvent(const QTouchEvent* event) {
-    qreal pixelRatio = windowPixelRatio();
+    auto pos = event->touchPoints().first().pos(); // there should only be 1 point in TouchBegin
-    this->TouchPressed(static_cast<unsigned>(pos.x() * pixelRatio),
+
-                       static_cast<unsigned>(pos.y() * pixelRatio));
+    auto [x, y] = ScaleTouch(pos);
+
+    this->TouchPressed(x, y);
 }
 
 void GRenderWindow::TouchUpdateEvent(const QTouchEvent* event) {
-    qreal x = 0.0;
+    QPointF pos;
-    qreal y = 0.0;
     int active_points = 0;
     const auto points = event->touchPoints();
 
+    // 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();
-            x += tp.pos().x();
-            y += tp.pos().y();
         }
     }
 
-    x /= active_points;
+    pos /= active_points;
-    y /= active_points;
 
-    // Copied from mouseMoveEvent:
+    auto [x, y] = ScaleTouch(pos);
-    qreal pixelRatio = windowPixelRatio();
+    this->TouchMoved(x, y);
-    this->TouchMoved(std::max(static_cast<unsigned>(x * pixelRatio), 0u),
-                     std::max(static_cast<unsigned>(y * pixelRatio), 0u));
 }
 
 void GRenderWindow::TouchEndEvent() {

src/citra_qt/bootmanager.h

@@ -151,6 +151,7 @@ signals:
     void Closed();
 
 private:
+    std::pair<unsigned, unsigned> ScaleTouch(QPointF pos);
     void TouchBeginEvent(const QTouchEvent* event);
     void TouchUpdateEvent(const QTouchEvent* event);
     void TouchEndEvent();