Platform: ability to negotiate context in {Glut,NaCl,Sdl2}Application.

doc/platform.dox

@@ -169,5 +169,29 @@ MyApplication::MyApplication(int& argc, char** argv): Platform::GlutApplication(
 }
 @endcode
 
+The configuration passed to constructor and @ref GlutApplication::createContext() "createContext()"
+is automaticall deleted afterwards and if the context creation fails, the
+application exits. However, it is also possible to negotiate the context using
+@ref GlutApplication::tryCreateContext() "tryCreateContext()". The major
+difference is that this function returns `false` instead of exiting and it
+doesn't delete the configuration afterwards so you can reuse it. You can for
+example try enabling MSAA and if the context creation fails, fall back to
+no-AA rendering:
+@code
+MyApplication::MyApplication(int& argc, char** argv): Platform::GlutApplication(argc, argv, nullptr) {
+    // ...
+
+    auto conf = new Configuration;
+    conf->setTitle("My Application")
+        ->setSampleCount(16);
+
+    if(!tryCreateContext(conf))
+        createContext(conf->setSampleCount(0));
+    else delete conf;
+
+    // ...
+}
+@endcode
+
 */
 }}

src/Platform/GlutApplication.cpp

@@ -47,12 +47,20 @@ void GlutApplication::initialize(int& argc, char** argv) {
 
     /* Init GLUT */
     glutInit(&argc, argv);
+    glutSetOption(GLUT_ACTION_ON_WINDOW_CLOSE, GLUT_ACTION_CONTINUE_EXECUTION);
 }
 
 void GlutApplication::createContext(Configuration* configuration) {
-    CORRADE_ASSERT(!c, "GlutApplication::createContext(): context already created", );
+    if(!tryCreateContext(configuration)) {
+        Error() << "Platform::GlutApplication::createContext(): cannot create context";
+        delete configuration;
+        std::exit(1);
 
-    glutSetOption(GLUT_ACTION_ON_WINDOW_CLOSE, GLUT_ACTION_CONTINUE_EXECUTION);
+    } else delete configuration;
+}
+
+bool GlutApplication::tryCreateContext(Configuration* configuration) {
+    CORRADE_ASSERT(!c, "Platform::GlutApplication::tryCreateContext(): context already created", false);
 
     unsigned int flags = GLUT_DOUBLE|GLUT_RGBA|GLUT_DEPTH|GLUT_STENCIL;
 
@@ -61,7 +69,8 @@ void GlutApplication::createContext(Configuration* configuration) {
 
     glutInitDisplayMode(flags);
     glutInitWindowSize(configuration->size().x(), configuration->size().y());
-    glutCreateWindow(configuration->title().c_str());
+    if(!glutCreateWindow(configuration->title().c_str()))
+        return false;
     glutReshapeFunc(staticViewportEvent);
     glutSpecialFunc(staticKeyEvent);
     glutMouseFunc(staticMouseEvent);
@@ -71,7 +80,7 @@ void GlutApplication::createContext(Configuration* configuration) {
     ExtensionWrangler::initialize();
 
     c = new Context;
-    delete configuration;
+    return true;
 }
 
 GlutApplication::~GlutApplication() {

src/Platform/GlutApplication.h

@@ -81,7 +81,8 @@ class GlutApplication {
          * @param arguments     Application arguments
          *
          * Creates application with default configuration. See Configuration
-         * for more information.
+         * for more information. The program exits if the context cannot be
+         * created, see tryCreateContext() for an alternative.
          */
         explicit GlutApplication(const Arguments& arguments);
 
@@ -92,7 +93,8 @@ class GlutApplication {
          *
          * The @p configuration is deleted afterwards. If `nullptr` is passed
          * as @p configuration, the context is not created and must be created
-         * with createContext().
+         * with createContext(). The program exits if the context cannot be
+         * created, see tryCreateContext() for an alternative.
          */
         explicit GlutApplication(const Arguments& arguments, Configuration* configuration);
 
@@ -112,10 +114,21 @@ class GlutApplication {
          * @brief Create context with given configuration
          *
          * The @p configuration is deleted afterwards. Must be called if and
-         * only if the context wasn't created by the constructor itself.
+         * only if the context wasn't created by the constructor itself. The
+         * program exits if the context cannot be created, see tryCreateContext()
+         * for an alternative.
          */
         void createContext(Configuration* configuration);
 
+        /**
+         * @brief Try to create context with given configuration
+         *
+         * Unlike createContext() the @p configuration is *not* deleted
+         * afterwards. Returns `false` if the context cannot be created, `true`
+         * otherwise.
+         */
+        bool tryCreateContext(Configuration* configuration);
+
         /** @{ @name Drawing functions */
 
         /**

src/Platform/NaClApplication.cpp

@@ -36,12 +36,21 @@ NaClApplication::NaClApplication(const Arguments& arguments): Instance(arguments
     createContext(new Configuration);
 }
 
-NaClApplication::NaClApplication(const Arguments& arguments, Configuration* configuration): Instance(arguments), Graphics3DClient(this), MouseLock(this), c(nullptr) {
+NaClApplication::NaClApplication(const Arguments& arguments, Configuration* configuration): Instance(arguments), Graphics3DClient(this), MouseLock(this), graphics(nullptr), fullscreen(nullptr), c(nullptr) {
     if(configuration) createContext(configuration);
 }
 
-void NaClApplication::createContext(NaClApplication::Configuration* configuration) {
+void NaClApplication::createContext(Configuration* configuration) {
-    CORRADE_ASSERT(!c, "NaClApplication::createContext(): context already created", );
+    if(!tryCreateContext(configuration)) {
+        Error() << "Platform::NaClApplication::createContext(): cannot create context";
+        delete configuration;
+        std::exit(1);
+
+    } else delete configuration;
+}
+
+bool NaClApplication::tryCreateContext(Configuration* configuration) {
+    CORRADE_ASSERT(!c, "Platform::NaClApplication::tryCreateContext(): context already created", false);
 
     viewportSize = configuration->size();
 
@@ -58,11 +67,12 @@ void NaClApplication::createContext(NaClApplication::Configuration* configuratio
 
     graphics = new pp::Graphics3D(this, attributes);
     if(graphics->is_null()) {
-        Error() << "Platform::NaClApplication::NaClApplication(): cannot create graphics";
+        delete graphics;
-        std::exit(1);
+        graphics = nullptr;
+        return false;
     }
     if(!BindGraphics(*graphics)) {
-        Error() << "Platform::NaClApplication::NaClApplication(): cannot bind graphics";
+        Error() << "Platform::NaClApplication::tryCreateContext(): cannot bind graphics";
         std::exit(1);
     }
 
@@ -70,8 +80,6 @@ void NaClApplication::createContext(NaClApplication::Configuration* configuratio
 
     glSetCurrentContextPPAPI(graphics->pp_resource());
 
-    c = new Context;
-
     /* Enable input handling for mouse and keyboard */
     RequestInputEvents(PP_INPUTEVENT_CLASS_MOUSE|PP_INPUTEVENT_CLASS_WHEEL);
     RequestFilteringInputEvents(PP_INPUTEVENT_CLASS_KEYBOARD);
@@ -79,7 +87,8 @@ void NaClApplication::createContext(NaClApplication::Configuration* configuratio
     /* Make sure viewportEvent() is called for first time */
     flags |= Flag::ViewportUpdated;
 
-    delete configuration;
+    c = new Context;
+    return true;
 }
 
 NaClApplication::~NaClApplication() {

src/Platform/NaClApplication.h

@@ -121,6 +121,9 @@ class NaClApplication: public pp::Instance, public pp::Graphics3DClient, public
         /** @copydoc GlutApplication::createContext() */
         void createContext(Configuration* configuration);
 
+        /** @copydoc GlutApplication::tryCreateContext() */
+        bool tryCreateContext(Configuration* configuration);
+
         /** @{ @name Drawing functions */
 
         /** @copydoc GlutApplication::viewportEvent() */

src/Platform/Sdl2Application.cpp

@@ -50,20 +50,33 @@ Sdl2Application::InputEvent::Modifiers fixedModifiers(Uint16 mod) {
 }
 
 Sdl2Application::Sdl2Application(const Arguments&): context(nullptr), flags(Flag::Redraw) {
+    initialize();
     createContext(new Configuration);
 }
 
 Sdl2Application::Sdl2Application(const Arguments&, Configuration* configuration): context(nullptr), flags(Flag::Redraw) {
+    initialize();
     if(configuration) createContext(configuration);
 }
 
-void Sdl2Application::createContext(Configuration* configuration) {
+void Sdl2Application::initialize() {
-    CORRADE_ASSERT(!context, "Sdl2Application::createContext(): context already created", );
-
     if(SDL_Init(SDL_INIT_VIDEO) < 0) {
         Error() << "Cannot initialize SDL.";
         std::exit(1);
     }
+}
+
+void Sdl2Application::createContext(Configuration* configuration) {
+    if(!tryCreateContext(configuration)) {
+        Error() << "Platform::Sdl2Application::createContext(): cannot create context:" << SDL_GetError();
+        delete configuration;
+        std::exit(1);
+
+    } else delete configuration;
+}
+
+bool Sdl2Application::tryCreateContext(Configuration* configuration) {
+    CORRADE_ASSERT(!context, "Platform::Sdl2Application::tryCreateContext(): context already created", false);
 
     /* Enable double buffering and 24bt depth buffer */
     SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
@@ -81,7 +94,11 @@ void Sdl2Application::createContext(Configuration* configuration) {
         std::exit(2);
     }
 
-    context = SDL_GL_CreateContext(window);
+    if(!(context = SDL_GL_CreateContext(window))) {
+        SDL_DestroyWindow(window);
+        window = nullptr;
+        return false;
+    }
 
     /* This must be enabled, otherwise (on my NVidia) it crashes when creating
        VAO. WTF. */
@@ -96,7 +113,7 @@ void Sdl2Application::createContext(Configuration* configuration) {
     SDL_PushEvent(sizeEvent);
 
     c = new Context;
-    delete configuration;
+    return true;
 }
 
 Sdl2Application::~Sdl2Application() {

src/Platform/Sdl2Application.h

@@ -95,6 +95,9 @@ class Sdl2Application {
         /** @copydoc GlutApplication::createContext() */
         void createContext(Configuration* configuration);
 
+        /** @copydoc GlutApplication::tryCreateContext() */
+        bool tryCreateContext(Configuration* configuration);
+
         /** @{ @name Drawing functions */
 
         /** @copydoc GlutApplication::viewportEvent() */
@@ -167,6 +170,8 @@ class Sdl2Application {
         typedef Corrade::Containers::EnumSet<Flag, UnsignedByte> Flags;
         CORRADE_ENUMSET_FRIEND_OPERATORS(Flags)
 
+        void initialize();
+
         SDL_Window* window;
         SDL_GLContext context;