I'm new around these parts, and also to C/C++ (having used much higher level languages in the past).
At first I went on a bit of a binge watching the first few weeks' episodes from the YouTube archive just to get a feel for what things were going to be like before diving in and coding along.
I've just recently gone back to the beginning and begun coding and have gotten through the first 4 days and although for the most part I can understand the code well enough, there are a few things that are just not sitting well for me.
We have our Message processing loop which pull messages from a message queue and puts them into a MSG structure through the PeekMessage() function and then we pass them along to the TranslateMessage() and DispatchMessage() functions. But what I don't quite understand is exactly how the switch clause in Win32MainWindowCallback() manages to get a hold of these messages? I can see that it takes a Message as one of its parameters but we don't call the function anywhere to pass the message along.
Is it something that is beyond our control, that only Windows can handle? Is it solely handled by DispatchMessage()? And how does DispatchMessage() even know where to send them (messages) to, after all Win32MainWindowCallback() was defined by us?
Does DispatchMessage() look into our WNDCLASS structure and find that lpfnWndProc has been set to point to our Win32MainWindowCallback() function? And does the DispatchMessage() function call into it passing the message? It isn't really clear how things are moving around with all these Windows things in the way, I'm not used to programming to an API I guess and usually everything is very explicit and clear with no opaque structures and functions prohibiting my view.
Something else that is perplexing me a little is the way the RenderWeirdGradient() and Win32UpdateWindow() work.
I think I understand what is going on in the RenderWeirdGradient() function, but I guess what I want to know is the following:
*Row is pointing to the same memory as our global void *BitmapMemory, which is the memory that was given to us by VirtualAlloc() inside Win32ResizeDIBSection(), is that right? Only we have cast in into byte sized chunks? Then we do our for loops which write the values into memory in 4 byte chunks placing the iterated values into the spots for blue and green etc etc.
Now here comes my question. Are we filling up a huge region of memory with ALL the values required to write a WHOLE window full of pixels' individual RGB values and then writing them all to the screen with Win32UpdateWindow() and StretchDIBits() and then once everything is written to the screen we ReleaseDC() and increment offsets and go back through the nested loops and all that jazz all over again, over and over? And in this process do our offsets keep growing to the max size of an int before wrapping but because they are being added to the X and Y values inside RenderWeirdGradient() and assigned to uint8_t variables (Blue and Green) they wrap after reaching 255? What happens when the offsets reach the maximum int value and wrap around? Wont that cause some problem? Or will it just align and when the ints wrap the uint_t's will wrap at the same time with both becoming zero and starting all over again? If for instance we were incrementing the YOffset by a number that the maximum int value was not divisible by would we have an issue of not wrapping around to zero in sync with our Green value?
Sorry. I might not be very clear. I had more questions, but in the process of typing this up and looking through the code I have managed to answer them myself and they were quite obvious once I really drilled down into it and stepped through the code using the Watch and Memory Windows. This is so much more fun than Python or any other high level language. I am sorry if I may be answering my own questions in places here.
Anyhow. I would very much appreciate some clarification, and if my assumptions are right, some validation of my guesses, and if not then corrections and explanations to the things I have mentioned.
If you have read through all this, thank you, I know I very much tend to waffle on and always find it hard to get directly to my point/s when typing things up.