Added notes to documentation and adjusted OpenGL example as a workaround for the side effects of making static functions that require a context work. If the user wants to make use of both sfml-graphics and OpenGL, they should make sure sf::Texture::getMaximumSize() and/or sf::Shader::isAvailable() are called at least once before setting their final context active as those functions will cause a context switch the first time they are called.

examples/opengl/OpenGL.cpp

@@ -22,9 +22,6 @@ int main()
     sf::RenderWindow window(sf::VideoMode(800, 600), "SFML graphics with OpenGL", sf::Style::Default, contextSettings);
     window.setVerticalSyncEnabled(true);
 
-    // Make it the active window for OpenGL calls
-    window.setActive();
-
     // Create a sprite for the background
     sf::Texture backgroundTexture;
     if (!backgroundTexture.loadFromFile("resources/background.jpg"))
@@ -39,6 +36,13 @@ int main()
     text.setColor(sf::Color(255, 255, 255, 170));
     text.setPosition(250.f, 450.f);
 
+    // Make the window the active target for OpenGL calls
+    // Note: If using sf::Texture or sf::Shader with OpenGL,
+    // be sure to call sf::Texture::getMaximumSize() and/or
+    // sf::Shader::isAvailable() at least once before calling
+    // setActive(), as those functions will cause a context switch
+    window.setActive();
+
     // Load an OpenGL texture.
     // We could directly use a sf::Texture as an OpenGL texture (with its Bind() member function),
     // but here we want more control on it (generate mipmaps, ...) so we create a new one from an image

include/SFML/Graphics/Shader.hpp

@@ -486,6 +486,9 @@ public :
     /// the shader features. If it returns false, then
     /// any attempt to use sf::Shader will fail.
     ///
+    /// Note: The first call to this function, whether by your
+    /// code or SFML will result in a context switch.
+    ///
     /// \return True if shaders are supported, false otherwise
     ///
     ////////////////////////////////////////////////////////////

include/SFML/Graphics/Texture.hpp

@@ -460,6 +460,9 @@ public :
     /// You can expect a value of 512 pixels for low-end graphics
     /// card, and up to 8192 pixels or more for newer hardware.
     ///
+    /// Note: The first call to this function, whether by your
+    /// code or SFML will result in a context switch.
+    ///
     /// \return Maximum size allowed for textures, in pixels
     ///
     ////////////////////////////////////////////////////////////