Viewport scaling and display density independence

The view is scaled to be as large as possible, without changing the aspect, within the bounds of the window.
On "retina" displays, or other displays where window units != pixels, the view should no longer draw incorrectly.

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 8483f79b..3757482d 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 eed201a9..d440e2bc 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;