EmuWindow: Clip mouse input coordinates to emulated screen dimensions.

If the mouse position for a mouse move/drag would take it outside the emulated screen dimensions, clip the coordinates to
the emulated screen dimensions.
Qt and GLFW will report negative coordinates for mouse positions to the left, or above citra window. Added restriction
to mouse coordinates passed to touchmoved by Qt/GLFW to be greater or equal to zero.

src/citra/emu_window/emu_window_glfw.cpp

@@ -31,7 +31,7 @@ void EmuWindow_GLFW::OnMouseButtonEvent(GLFWwindow* win, int button, int action,
 }
 
 void EmuWindow_GLFW::OnCursorPosEvent(GLFWwindow* win, double x, double y) {
-    GetEmuWindow(win)->TouchMoved(static_cast<unsigned>(x), static_cast<unsigned>(y));
+    GetEmuWindow(win)->TouchMoved(static_cast<unsigned>(std::max(x, 0.0)), static_cast<unsigned>(std::max(y, 0.0)));
 }
 
 /// Called by GLFW when a key event occurs

src/citra_qt/bootmanager.cpp

@@ -288,7 +288,7 @@ void GRenderWindow::mousePressEvent(QMouseEvent *event)
 void GRenderWindow::mouseMoveEvent(QMouseEvent *event)
 {
     auto pos = event->pos();
-    this->TouchMoved(static_cast<unsigned>(pos.x()), static_cast<unsigned>(pos.y()));
+    this->TouchMoved(static_cast<unsigned>(std::max(pos.x(), 0)), static_cast<unsigned>(std::max(pos.y(), 0)));
 }
 
 void GRenderWindow::mouseReleaseEvent(QMouseEvent *event)

src/common/emu_window.cpp

@@ -28,6 +28,17 @@ static bool IsWithinTouchscreen(const EmuWindow::FramebufferLayout& layout, unsi
             framebuffer_x <  layout.bottom_screen.right);
 }
 
+std::tuple<unsigned,unsigned> EmuWindow::ClipToTouchScreen(unsigned new_x, unsigned new_y) {
+
+    new_x = std::max(new_x, framebuffer_layout.bottom_screen.left);
+    new_x = std::min(new_x, framebuffer_layout.bottom_screen.right-1);
+    
+    new_y = std::max(new_y, framebuffer_layout.bottom_screen.top);
+    new_y = std::min(new_y, framebuffer_layout.bottom_screen.bottom-1);
+
+    return std::make_tuple(new_x, new_y);
+}
+
 void EmuWindow::TouchPressed(unsigned framebuffer_x, unsigned framebuffer_y) {
     if (!IsWithinTouchscreen(framebuffer_layout, framebuffer_x, framebuffer_y))
         return;
@@ -52,14 +63,13 @@ void EmuWindow::TouchMoved(unsigned framebuffer_x, unsigned framebuffer_y) {
     if (!touch_pressed)
         return;
 
-    if (IsWithinTouchscreen(framebuffer_layout, framebuffer_x, framebuffer_y))
-        TouchPressed(framebuffer_x, framebuffer_y);
-    else
-        TouchReleased();
+    if (!IsWithinTouchscreen(framebuffer_layout, framebuffer_x, framebuffer_y))
+        std::tie(framebuffer_x, framebuffer_y) = ClipToTouchScreen(framebuffer_x, framebuffer_y);
+
+    TouchPressed(framebuffer_x, framebuffer_y);
 }
 
-EmuWindow::FramebufferLayout EmuWindow::FramebufferLayout::DefaultScreenLayout(unsigned width,
-    unsigned height) {
+EmuWindow::FramebufferLayout EmuWindow::FramebufferLayout::DefaultScreenLayout(unsigned width, unsigned height) {
 
     ASSERT(width > 0);
     ASSERT(height > 0);

src/common/emu_window.h

@@ -206,5 +206,10 @@ private:
     u16 touch_x;    ///< Touchpad X-position in native 3DS pixel coordinates (0-320)
     u16 touch_y;    ///< Touchpad Y-position in native 3DS pixel coordinates (0-240)
 
+   /**
+    * Clip the provided coordinates to be inside the touchscreen area.
+    */
+    std::tuple<unsigned,unsigned> ClipToTouchScreen(unsigned new_x, unsigned new_y);
+
     Service::HID::PadState pad_state;
 };