Add a few structuring comments

Author: mgeier

src/rtmixer.c

@@ -79,6 +79,8 @@ int callback(const void* input, void* output, frame_t frameCount
     }
     const bool playing = type == PLAY_BUFFER || type == PLAY_RINGBUFFER;
 
+    // Check if the action is due to start in the current block
+
     PaTime io_time = playing ? timeInfo->outputBufferDacTime
                              : timeInfo->inputBufferAdcTime;
     frame_t offset = 0;
@@ -115,6 +117,8 @@ int callback(const void* input, void* output, frame_t frameCount
       }
     }
 
+    // Handle CANCEL action
+
     if (action->type == CANCEL)
     {
       for (struct action** i = &(action->next); *i; i = &((*i)->next))
@@ -141,6 +145,8 @@ int callback(const void* input, void* output, frame_t frameCount
       continue;
     }
 
+    // Get number of remaining frames in the current block
+
     frame_t frames = action->total_frames - action->done_frames;
 
     if (frameCount < frames)
@@ -153,6 +159,8 @@ int callback(const void* input, void* output, frame_t frameCount
       frames = frameCount - offset;
     }
 
+    // Shove audio data around
+
     float* device_data
       = playing ? (float*)output + offset * state->output_channels
                 : (float*) input + offset * state->input_channels;
@@ -261,6 +269,8 @@ int callback(const void* input, void* output, frame_t frameCount
       }
     }
 
+    // Clean up, prepare next iteration
+
     if (action->done_frames == action->total_frames)
     {
       remove_action(actionaddr, state);