main: Fix borderless fullscreen for high dpi scaled displays

On Windows, a borderless window will be treated the same as exclusive fullscreen
when the window geometry matches the physical dimensions of the screen.
However, with High DPI scaling, when the devicePixelRatioF() is > 1, the borderless
window apparently is not treated as exclusive fullscreen and functions correctly.
One can verify and replicate this behavior by using a high resolution (4K) display,
and switching between 100% and 200% scaling in Windows' display settings.
At 100%, without the addition of 1, it is treated as exclusive fullscreen.
At 200%, with or without the addition of 1, it is treated as borderless windowed.
Therefore, we can use (read: abuse) this difference in behavior to fix this issue for
those with higher resolution displays when the Qt scaling ratio is > 1.
Should this behavior be changed in the future, please revisit this workaround.

1 files changed, 13 insertions, 1 deletions

diff --git a/src/yuzu/main.cpp b/src/yuzu/main.cpp
index c278d8dab..62dfc526a 100644
--- a/src/yuzu/main.cpp
+++ b/src/yuzu/main.cpp
@@ -3167,8 +3167,20 @@ void GMainWindow::ShowFullscreen() {
         window->hide();
         window->setWindowFlags(window->windowFlags() | Qt::FramelessWindowHint);
         const auto screen_geometry = GuessCurrentScreen(window)->geometry();
+        // NB: On Windows, a borderless window will be treated the same as exclusive fullscreen
+        //     when the window geometry matches the physical dimensions of the screen.
+        //     However, with High DPI scaling, when the devicePixelRatioF() is > 1, the borderless
+        //     window apparently is not treated as exclusive fullscreen and functions correctly.
+        //     One can verify and replicate this behavior by using a high resolution (4K) display,
+        //     and switching between 100% and 200% scaling in Windows' display settings.
+        //     At 100%, without the addition of 1, it is treated as exclusive fullscreen.
+        //     At 200%, with or without the addition of 1, it is treated as borderless windowed.
+        //     Therefore, we can use (read: abuse) this difference in behavior to fix this issue for
+        //     those with higher resolution displays when the Qt scaling ratio is > 1.
+        //     Should this behavior be changed in the future, please revisit this workaround.
+        const bool must_add_one = devicePixelRatioF() == 1.0f;
         window->setGeometry(screen_geometry.x(), screen_geometry.y(), screen_geometry.width(),
-                            screen_geometry.height() + 1);
+                            screen_geometry.height() + (must_add_one ? 1 : 0));
         window->raise();
         window->showNormal();
     };