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SpyderTL wrote:The bga page has details about the bits per pixel register, and the memory layout.

Is this what you are looking for?

SpyderTL wrote:The "pitch" when using Bochs will always be the screen width * bits per pixel / 8.

There is no hidden memory between one row of pixels and the next. (Unless you have enabled virtual screen space.)

void draw_pixel(unsigned x, unsigned y, unsigned color)
{
	unsigned *vga = (unsigned*)VBE_DISPI_LFB_PHYSICAL_ADDRESS;
	unsigned pitch = (SCREEN_WIDTH * 24 / 8);
	unsigned offset = (y * SCREEN_WIDTH + x) * pitch;
	vga[offset] = color;
}

//and I call
draw_pixel(0,0,0x00ff00);
draw_pixel(1,0,0x00ff00);

beyondsociety wrote:If your using your own bootloader, im not sure if there is a way to get that info besides switching to real mode, using Vesa functions and switching back to protected mode. Hopefully someone may know better. If your using grub to load your os, then you can use the graphics fields of multiboot to clear the screen and plot pixels like with bga and as an added bonus multiboot will give you that info.

The main difference between the two is that once you are in graphics mode with grub, writing to the screen doesn't work like before. So if you were using grub, you would have to rewrite your print function for graphics which uses pixels instead. I started working on the exact same thing as you and started to rewrite my print function using grub and life got in the way, I plan to eventually come back to this and finish it.

SpyderTL wrote:It should be offset = (y * pitch) + (x * stride)

Where stride = bits per pixel / 8

Edit: You shouldn't be using "unsigned" ints (which are 4 bytes each), if you are using 24 bit pixels (which are 3 bytes each).

You either need to use an array of structs with 3 one byte fields, or you need to change your video mode to 32-bits per pixel.

You also need to change your offset to match your pixel size, so divide by 3 for 24-bit or divide by 4 for 32 bit, since you are using an array.

void draw_pixel(unsigned x, unsigned y, unsigned color)
{
	unsigned *vga = (unsigned*)VBE_DISPI_LFB_PHYSICAL_ADDRESS;
	unsigned pitch  = (SCREEN_WIDTH * VBE_DISPI_BPP_32 / 8);
	unsigned stride = (VBE_DISPI_BPP_32 / 8); 
	unsigned offset = (y * pitch) + (x * stride);
	vga[offset/4] = color;
}