2 files changed, 50 insertions, 1 deletions

diff --git a/src/video_core/renderer_opengl/renderer_opengl.cpp b/src/video_core/renderer_opengl/renderer_opengl.cpp
index 8483f79be..3757482db 100644
--- a/src/video_core/renderer_opengl/renderer_opengl.cpp
+++ b/src/video_core/renderer_opengl/renderer_opengl.cpp
@@ -191,7 +191,8 @@ void RendererOpenGL::DrawSingleScreenRotated(const TextureInfo& texture, float x
  * Draws the emulated screens to the emulator window.
  */
 void RendererOpenGL::DrawScreens() {
-    glViewport(0, 0, resolution_width, resolution_height);
+    UpdateViewportExtent();
+    glViewport(viewport_extent.x, viewport_extent.y, viewport_extent.width, viewport_extent.height);
     glClear(GL_COLOR_BUFFER_BIT);
 
     glUseProgram(program_id);
@@ -228,6 +229,39 @@ void RendererOpenGL::SetWindow(EmuWindow* window) {
     render_window = window;
 }
 
+void RendererOpenGL::UpdateViewportExtent() {
+    int width_in_pixels;
+    int height_in_pixels;
+
+    render_window->GetFramebufferSize(&width_in_pixels, &height_in_pixels);
+
+    // No update needed if framebuffer size hasn't changed
+    if (width_in_pixels == framebuffer_size.width && height_in_pixels == framebuffer_size.height) {
+        return;
+    }
+
+    framebuffer_size.width = width_in_pixels;
+    framebuffer_size.height = height_in_pixels;
+
+    float window_aspect_ratio = static_cast<float>(height_in_pixels) / width_in_pixels;
+    float emulation_aspect_ratio = static_cast<float>(resolution_height) / resolution_width;
+
+    if (window_aspect_ratio > emulation_aspect_ratio) {
+        // If the window is more narrow than the emulation content, borders are applied on the
+        // top and bottom of the window.
+        viewport_extent.width = width_in_pixels;
+        viewport_extent.height = emulation_aspect_ratio * viewport_extent.width;
+        viewport_extent.x = 0;
+        viewport_extent.y = (height_in_pixels - viewport_extent.height) / 2;
+    } else {
+        // Otherwise, borders are applied on the left and right sides of the window.
+        viewport_extent.height = height_in_pixels;
+        viewport_extent.width = (1 / emulation_aspect_ratio) * viewport_extent.height;
+        viewport_extent.x = (width_in_pixels - viewport_extent.width) / 2;
+        viewport_extent.y = 0;
+    }
+}
+
 /// Initialize the renderer
 void RendererOpenGL::Init() {
     render_window->MakeCurrent();
diff --git a/src/video_core/renderer_opengl/renderer_opengl.h b/src/video_core/renderer_opengl/renderer_opengl.h
index eed201a95..d440e2bc7 100644
--- a/src/video_core/renderer_opengl/renderer_opengl.h
+++ b/src/video_core/renderer_opengl/renderer_opengl.h
@@ -52,12 +52,27 @@ private:
     static void LoadFBToActiveGLTexture(const GPU::Regs::FramebufferConfig& framebuffer,
                                         const TextureInfo& texture);
 
+    /// Updates the viewport rectangle
+    void UpdateViewportExtent();
+
     EmuWindow*  render_window;                    ///< Handle to render window
     u32         last_mode;                        ///< Last render mode
 
     int resolution_width;                         ///< Current resolution width
     int resolution_height;                        ///< Current resolution height
 
+    struct {
+        int width;
+        int height;
+    } framebuffer_size;                           ///< Current framebuffer size
+
+    struct {
+        int x;
+        int y;
+        int width;
+        int height;
+    } viewport_extent;                            ///< Current viewport rectangle
+
     // OpenGL object IDs
     GLuint vertex_array_handle;
     GLuint vertex_buffer_handle;