Clamp the multisample level to the max level to prevent screen smeari…

…ng glitch.

The bug could be triggered after switching from a graphics card that
supported a higher multisample level to one with a lower max than what
was configured. The glitch caused the visuals to be dark and elements
would blur on the screen.

src/bzflag/playing.cxx

@@ -6374,10 +6374,14 @@ void drawFrame(const float dt)
  else
  {
  // bind the multisample framebuffer, if enabled
- bool useMultisampling = OpenGLGState::getMaxSamples() > 1 && BZDB.evalInt("multisample") > 1;
+ int maxSamples = OpenGLGState::getMaxSamples();
+ bool useMultisampling = maxSamples > 1 && BZDB.evalInt("multisample") > 1;
  if(useMultisampling)
  {
- glFramebuffer.checkState(mainWindow->getWidth(), mainWindow->getHeight(), BZDB.evalInt("multisample"));
+ int samples = BZDB.evalInt("multisample");
+ if (samples > maxSamples)
+ samples = maxSamples;
+ glFramebuffer.checkState(mainWindow->getWidth(), mainWindow->getHeight(), samples);
  glBindFramebuffer(GL_FRAMEBUFFER, glFramebuffer.getFramebuffer());
  }