OpenGL projection matrix to fit the content to the window while preserving the aspect ratio

gistfile1.cpp

int shorterSide = std::min(width, height);
GLfloat marginX = 1.0f + GLfloat(width - shorterSide) / (GLfloat)shorterSide;
GLfloat marginY = 1.0f + GLfloat(height - shorterSide) / (GLfloat)shorterSide;
glm::mat4 projection = glm::ortho(-marginX, marginX, -marginY, marginY);