Platform: default to 32-bit RGBA framebuffer instead of 24-bit RGB.

macOS and Android is known to degrade 24-bit to 16-bit colors, this
prevents them from doing that.

doc/changelog.dox

@@ -374,6 +374,11 @@ See also:
 -   Calling @ref Platform::Sdl2Application::exit() "Platform::*Application::exit()"
     directly in the application constructor will now make it exit right after
     constructor finished, without any event processing (see [mosra/magnum#429](https://github.com/mosra/magnum/issues/429))
+-   @ref Platform::AndroidApplication, @ref Platform::EmscriptenApplication,
+    @ref Platform::GlfwApplication and @ref Platform::Sdl2Application now
+    default to 32-bit RGBA color buffer instead of 24-bit RGB, to avoid the
+    framebuffer degrading to 16-bit colors on some platforms (see
+    [mosra/magnum-integration#59](https://github.com/mosra/magnum-integration/issues/59))
 
 @subsubsection changelog-latest-changes-trade Trade library
 

src/Magnum/Platform/AndroidApplication.cpp

@@ -277,7 +277,7 @@ std::int32_t AndroidApplication::inputEvent(android_app* state, AInputEvent* eve
 }
 
 AndroidApplication::GLConfiguration::GLConfiguration():
-    _colorBufferSize{8, 8, 8, 0}, _depthBufferSize{24}, _stencilBufferSize{0} {}
+    _colorBufferSize{8, 8, 8, 8}, _depthBufferSize{24}, _stencilBufferSize{0} {}
 
 void AndroidApplication::exec(android_app* state, Containers::Pointer<AndroidApplication>(*instancer)(const Arguments&)) {
     state->onAppCmd = commandEvent;

src/Magnum/Platform/AndroidApplication.h

@@ -475,7 +475,7 @@ class AndroidApplication::GLConfiguration {
         /**
          * @brief Set color buffer size
          *
-         * Default is @cpp {8, 8, 8, 0} @ce (8-bit-per-channel RGB, no alpha).
+         * Default is @cpp {8, 8, 8, 8} @ce (8-bit-per-channel RGBA).
          * @see @ref setDepthBufferSize(), @ref setStencilBufferSize()
          */
         GLConfiguration& setColorBufferSize(const Vector4i& size) {

src/Magnum/Platform/EmscriptenApplication.cpp

@@ -692,7 +692,7 @@ void EmscriptenApplication::textInputEvent(TextInputEvent&) {}
 
 #ifdef MAGNUM_TARGET_GL
 EmscriptenApplication::GLConfiguration::GLConfiguration():
-    _colorBufferSize{8, 8, 8, 0}, _depthBufferSize{24}, _stencilBufferSize{0} {}
+    _colorBufferSize{8, 8, 8, 8}, _depthBufferSize{24}, _stencilBufferSize{0} {}
 #endif
 
 int EmscriptenApplication::exec() {

src/Magnum/Platform/EmscriptenApplication.h

@@ -1043,7 +1043,7 @@ class EmscriptenApplication::GLConfiguration {
         /**
          * @brief Set color buffer size
          *
-         * Default is @cpp {8, 8, 8, 0} @ce (8-bit-per-channel RGB, no alpha).
+         * Default is @cpp {8, 8, 8, 8} @ce (8-bit-per-channel RGBA).
          * @see @ref setDepthBufferSize(), @ref setStencilBufferSize()
          */
         GLConfiguration& setColorBufferSize(const Vector4i& size) {

src/Magnum/Platform/GlfwApplication.cpp

@@ -875,7 +875,7 @@ void GlfwApplication::stopTextInput() {
 
 #ifdef MAGNUM_TARGET_GL
 GlfwApplication::GLConfiguration::GLConfiguration():
-    _colorBufferSize{8, 8, 8, 0}, _depthBufferSize{24}, _stencilBufferSize{0},
+    _colorBufferSize{8, 8, 8, 8}, _depthBufferSize{24}, _stencilBufferSize{0},
     _sampleCount{0}, _version{GL::Version::None},
     #ifndef MAGNUM_TARGET_GLES
     _flags{Flag::ForwardCompatible},

src/Magnum/Platform/GlfwApplication.h

@@ -884,7 +884,7 @@ class GlfwApplication::GLConfiguration {
         /**
          * @brief Set color buffer size
          *
-         * Default is @cpp {8, 8, 8, 0} @ce (8-bit-per-channel RGB, no alpha).
+         * Default is @cpp {8, 8, 8, 8} @ce (8-bit-per-channel RGBA).
          * @see @ref setDepthBufferSize(), @ref setStencilBufferSize()
          */
         GLConfiguration& setColorBufferSize(const Vector4i& size) {

src/Magnum/Platform/Sdl2Application.cpp

@@ -1170,7 +1170,7 @@ void Sdl2Application::textEditingEvent(TextEditingEvent&) {}
 
 #ifdef MAGNUM_TARGET_GL
 Sdl2Application::GLConfiguration::GLConfiguration():
-    _colorBufferSize{8, 8, 8, 0}, _depthBufferSize{24}, _stencilBufferSize{0},
+    _colorBufferSize{8, 8, 8, 8}, _depthBufferSize{24}, _stencilBufferSize{0},
     _sampleCount(0)
     #ifndef CORRADE_TARGET_EMSCRIPTEN
     , _version(GL::Version::None),

src/Magnum/Platform/Sdl2Application.h

@@ -1369,7 +1369,7 @@ class Sdl2Application::GLConfiguration {
         /**
          * @brief Set color buffer size
          *
-         * Default is @cpp {8, 8, 8, 0} @ce (8-bit-per-channel RGB, no alpha).
+         * Default is @cpp {8, 8, 8, 8} @ce (8-bit-per-channel RGBA).
          * @see @ref setDepthBufferSize(), @ref setStencilBufferSize()
          */
         GLConfiguration& setColorBufferSize(const Vector4i& size) {