Hackily fix platform-dependent gamma correction

apps/hellotriangle/hellotriangle.cpp

@@ -76,6 +76,8 @@ void main()
 
         void impl_on_draw() override
         {
+            App::upd().clear_screen();
+
             ui::context::on_start_new_frame();
 
             // ensure target texture matches screen dimensions
@@ -89,11 +91,13 @@ void main()
             const auto transform = identity<Transform>().with_rotation(angle_axis(Radians{seconds_since_startup}, Vec3{0.0f, 1.0f, 0.0f}));
             graphics::draw(mesh_, transform, material_, camera_);
             camera_.render_to(target_texture_);
-#ifdef EMSCRIPTEN
-            graphics::blit_to_screen(target_texture_, Rect{{}, App::get().main_window_dimensions()}, gamma_correcter_);
-#else
-            graphics::blit_to_screen(target_texture_, Rect{{}, App::get().main_window_dimensions()});
-#endif
+
+            if (App::get().is_main_window_gamma_corrected()) {
+                graphics::blit_to_screen(target_texture_, Rect{{}, App::get().main_window_dimensions()});
+            }
+            else {
+                graphics::blit_to_screen(target_texture_, Rect{{}, App::get().main_window_dimensions()}, gamma_correcter_);
+            }
 
             ui::begin_panel("window");
             ui::draw_float_slider("torus_radius", &edited_torus_parameters_.torus_radius, 0.0f, 5.0f);
@@ -137,10 +141,7 @@ int main(int, char**)
     return 0;
 #else
     osc::App app;
-    app.setup_main_loop<HelloTriangleScreen>();
-    ScopeGuard guard{[&app](){ app.teardown_main_loop(); }};
-    while (app.do_main_loop_step()) {
-    }
+    app.show<HelloTriangleScreen>();
     return 0;
 #endif
 }

src/OpenSimCreator/UI/MainUIScreen.cpp

@@ -326,7 +326,7 @@ class osc::MainUIScreen::Impl final :
 
         {
             OSC_PERF("MainUIScreen/clear_screen");
-            App::upd().clear_screen({0.0f, 0.0f, 0.0f, 0.0f});
+            App::upd().clear_screen();
         }
 
         ui::context::on_start_new_frame();

src/oscar/Graphics/Color.h

@@ -22,6 +22,11 @@ namespace osc
         using iterator = value_type*;
         using const_iterator = const value_type*;
 
+        static constexpr Color dark_grey()
+        {
+            return {0.5f, 0.5f, 0.5f};
+        }
+
         static constexpr Color half_grey()
         {
             return {0.5f, 0.5f, 0.5f};

src/oscar/Platform/App.cpp

@@ -423,6 +423,15 @@ class osc::App::Impl final {
         return graphics_context_.max_antialiasing_level();
     }
 
+    bool is_main_window_gamma_corrected() const
+    {
+#ifdef EMSCRIPTEN
+        return false;
+#else
+        return true;
+#endif
+    }
+
     bool is_in_debug_mode() const
     {
         return graphics_context_.is_in_debug_mode();
@@ -906,6 +915,11 @@ AntiAliasingLevel osc::App::max_anti_aliasing_level() const
     return impl_->max_anti_aliasing_level();
 }
 
+bool osc::App::is_main_window_gamma_corrected() const
+{
+    return impl_->is_main_window_gamma_corrected();
+}
+
 bool osc::App::is_in_debug_mode() const
 {
     return impl_->is_in_debug_mode();

src/oscar/Platform/App.h

@@ -189,6 +189,10 @@ namespace osc
         // returns the maximum number of anti-aliasing samples that the graphics backend supports
         AntiAliasingLevel max_anti_aliasing_level() const;
 
+        // returns true if the main window is backed by a framebuffer/renderbuffer that automatically
+        // converts the linear outputs (from shaders) into (e.g.) sRGB on-write
+        bool is_main_window_gamma_corrected() const;
+
         // returns true if the application is rendering in debug mode
         //
         // other parts of the application can use this to decide whether to render
@@ -248,7 +252,7 @@ namespace osc
         void request_redraw();  // threadsafe: used to make a waiting loop redraw
 
         // fill all pixels in the main window with the given color
-        void clear_screen(const Color&);
+        void clear_screen(const Color& = Color::clear());
 
         // sets the main window's subtitle (e.g. document name)
         void set_main_window_subtitle(std::string_view);

src/oscar/UI/Screens/TabTestingScreen.cpp

@@ -54,7 +54,7 @@ class osc::TabTestingScreen::Impl final :
 
     void impl_on_draw() override
     {
-        App::upd().clear_screen({0.0f, 0.0f, 0.0f, 0.0f});
+        App::upd().clear_screen();
         ui::context::on_start_new_frame();
         current_tab_->on_draw();
         ui::context::render();

src/oscar_demos/CookiecutterScreen.cpp

@@ -56,7 +56,7 @@ class osc::CookiecutterScreen::Impl final {
 
         ui::context::on_start_new_frame();  // prepare the 2D UI for drawing a new frame
 
-        App::upd().clear_screen(Color::clear());  // set app window bg color
+        App::upd().clear_screen();  // set app window bg color
 
         ui::begin_panel("cookiecutter panel");
         ui::draw_text("hello world");

src/oscar_learnopengl/AdvancedLighting/LOGLNormalMappingTab.cpp

@@ -121,7 +121,7 @@ class osc::LOGLNormalMappingTab::Impl final : public StandardTabImpl {
         camera_.on_draw();
 
         // clear screen and ensure camera has correct pixel rect
-        App::upd().clear_screen({0.1f, 0.1f, 0.1f, 1.0f});
+        App::upd().clear_screen(Color::dark_grey());
 
         // draw normal-mapped quad
         {

src/oscar_learnopengl/AdvancedLighting/LOGLParallaxMappingTab.cpp

@@ -116,7 +116,7 @@ class osc::LOGLParallaxMappingTab::Impl final : public StandardTabImpl {
         camera_.on_draw();
 
         // clear screen and ensure camera has correct pixel rect
-        App::upd().clear_screen({0.1f, 0.1f, 0.1f, 1.0f});
+        App::upd().clear_screen(Color::dark_grey());
 
         // draw normal-mapped quad
         {

src/oscar_learnopengl/Lighting/LOGLLightingMapsTab.cpp

@@ -74,7 +74,7 @@ class osc::LOGLLightingMapsTab::Impl final : public StandardTabImpl {
         camera_.on_draw();
 
         // clear screen and ensure camera has correct pixel rect
-        App::upd().clear_screen({0.1f, 0.1f, 0.1f, 1.0f});
+        App::upd().clear_screen(Color::dark_grey());
 
         // draw cube
         lighting_maps_material_.set_vec3("uViewPos", camera_.position());