message: Explicitly document what capturing frame 0 means.
diff: @@ -156,6 +156,17 @@ This option is slightly different from the others in that it doesn't change anyt
  This option allows you to queue up a precise capture of a given frame number after the program has started.
  +Queueing up a capture beginning at frame 0 has a special meaning: Frames are defined as the period between two presents of a window. Frame 0 is defined as starting at initialisation and ending at the first presentation.
  +
  +The definition of 'initialisation' varies by API, since it can be hard to clearly define initialisation time cleanly:
  +
  +* On Vulkan, frame 0 begins at the first ``VkDevice`` that is created. Since capture is instance-local, only this device's parent instance will be capturing.
  +* On D3D11, frame 0 begins at the first swapchain that is created, since it is common to create and destroy many ``ID3D11Device`` objects for enumeration purposes. Note that since capture is device-local, only the device associated with this first swapchain will be capturing and no frame will be captured if this device or swapchain are destroyed before they is used for presentation.
  +* On D3D12, frame 0 begins at the first ``ID3D12Device`` that is created. Since capture is device-local, only this device will be capturing.
  +* On OpenGL, frame 0 begins at the first GL context that is created with an ``CreateContextAttribs`` create function such as ``wglCreateContextAttribs`` or ``glXCreateContextAttribs``. This is because many programs create and destroy 'trampoline' GL contexts before creating their first real context. Since capture is API-wide, the capture will include all work on other contexts up until the first presentation on any context, even if the presentation happens on a different context.
  +
  +If no presentation happens in the program at all, frame 0 is still undefined and will most likely not capture anything. For purely headless programs you should use the :doc:`in-application API <../in_application_api>` to define the start and end of where you want to capture.
  +
  .. _child-process-hook:
  Child Processes
  