Don't capture the cursor by default in windowed mode

Closes #1872

app/streaming/session.cpp

@@ -1888,6 +1888,11 @@ void Session::exec()
     bool needsFirstEnterCapture = false;
     bool needsPostDecoderCreationCapture = false;
 
+    // Avoid capturing the mouse initially for windowed relative mode.
+    // We still capture in windowed absolute mode because it doesn't
+    // constrain the motion of the cursor. This allows the user to
+    // easily reposition or resize the window.
+    if (m_IsFullScreen || m_Preferences->absoluteMouseMode) {
         // HACK: For Wayland, we wait until we get the first SDL_WINDOWEVENT_ENTER
         // event where it seems to work consistently on GNOME. For other platforms,
         // especially where SDL may call SDL_RecreateWindow(), we must only capture
@@ -1900,6 +1905,7 @@ void Session::exec()
             // X11/XWayland: Capture after decoder creation
             needsPostDecoderCreationCapture = true;
         }
+    }
 
     // Stop text input. SDL enables it by default
     // when we initialize the video subsystem, but this