Allow VRAM presence only in optional bank.
control: Implement banks.
The BAR is 64MB.
The little-endian/big-endian ranges repeat every 16MB.
An endian range can be addressed in d128 (wide) mode or d64 mode.
In d128 mode, there is a 4MB range followed by an undefined 4MB range. bytes 0..7 belong to the standard bank and bytes 8..15 belong to the optional bank.
In d64 mode:
- 2MB mirror ranges at 0MB and 2MB (both have the same read/write behavor: write to both banks or read from the standard bank.
- 2MB standard bank rage at 4MB.
- 2MB optional bank range at 6MB.
- Read 8 bytes at a time instead of just 1.
- Remove multiply operations from loop. We just need increments or additions.
- Change compares with int to compares with zero.
CUR_HORZ_OFF becomes non-zero when the cursor needs to be drawn to the left of the left edge of the frame buffer.
CUR_VERT_OFF is handled differently. When CUR_VERT_OFF is non-zero, CUR_OFFSET is changed to point to the first line of the cursor that will be drawn, so CUR_VERT_OFF is the number of lines to remove from the total height of the cursor.
Alternatively, we could handle CUR_VERT_OFF the same way as CUR_HORZ_OFF by leaving the cursor height constant, drawing the cursor starting from the CUR_VERT_OFF line, and adjusting cursor Y position by negative CUR_VERT_OFF.
- Read 8 bytes at a time instead of just 1.
- Remove multiply operations from loop. We just need increments or additions.
- Change compares with int to compares with zero.
CUR_HORZ_OFF becomes non-zero when the cursor needs to be drawn to the left of the left edge of the frame buffer.
CUR_VERT_OFF is handled differently. When CUR_VERT_OFF is non-zero, CUR_OFFSET is changed to point to the first line of the cursor that will be drawn, so CUR_VERT_OFF is the number of lines to remove from the total height of the cursor.
Alternatively, we could handle CUR_VERT_OFF the same way as CUR_HORZ_OFF by leaving the cursor height constant, drawing the cursor starting from the CUR_VERT_OFF line, and adjusting cursor Y position by negative CUR_VERT_OFF.
