title: OpenGL can only bind to GL_TEXTURE0
body: <p>I'm trying to bind multiple textures to my shader but when I use some other enum than <code>GL_TEXTURE0</code> my shader shows unpredictable behaviour (e.g. all inout variables get zero).
  This is how I bind the textures (in other projects this works prefectly)</p>
  
  <pre><code>glActiveTexture(GL_TEXTURE0);
  sceneTex-&gt;bind();
  
  glActiveTexture(GL_TEXTURE1);
  depthTex-&gt;bind();
  
  glEnableVertexAttribArray(0);
  glEnableVertexAttribArray(1);
  VBO-&gt;bind(GL_ARRAY_BUFFER);
  unsigned int stride = 2 * sizeof(float) + 2 * sizeof(float);
  glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, stride, (void*)0);
  glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, stride, (void*)(2 * sizeof(float)));
  
  glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
  
  glDisableVertexAttribArray(0);
  glDisableVertexAttribArray(1);
  VBO-&gt;unbind(GL_ARRAY_BUFFER);
  
  glActiveTexture(GL_TEXTURE0);
  sceneTex-&gt;unbind();
  
  glActiveTexture(GL_TEXTURE1);
  depthTex-&gt;unbind();
  </code></pre>
  
  <p>When I remove <code>glActiveTexture(GL_TEXTURE1)</code> everything works fine. When I remove <code>glActiveTexture(GL_TEXTURE0)</code> I still get the problem. The same problem occurs if I try to use <code>GL_TEXTURE2</code> or some other enum.</p>
  
  <p>This is my fragment shader:</p>
  
  <pre><code>#version 440
  
  out vec4 fragColor;
  
  layout(binding = 0) uniform sampler2D colorMap;
  layout(binding = 1) uniform sampler2D depthMap;
  
  in vec2 texUV;
  
  void main()
  {
      fragColor = texture(colorMap, texUV) / 2.0 + texture(depthMap, texUV) / 2.0;
  }
  </code></pre>
  
  <p>When I check the states with <code>glGetIntegerv</code> everything seems fine. But it isn't.</p>