Screenshot

Four lines of a narrow font at a 6-pixel pitch, none of them on the tile grid, composed in RAM and sent to VRAM: the text module puts one glyph per tile, and a game that wants proportional text, or a label at any x and y, composes its own 2bpp layer. The primitive is tileBlitGlyph2bpp(), which ORs rows of a glyph into one tile and the tile to its right at a pixel shift; two calls per glyph cover the four tiles a glyph at (x, y) can touch. Press A and every line moves one pixel right, the glyphs crossing tile boundaries as they go. No assets: a 5x7 font declared as bits becomes 2bpp glyphs at boot.

SNES Concepts

A 2bpp tile is 16 bytes, planes 0 and 1 interleaved per row. A layer of 160 tiles is 2560 bytes in FAR RAM, and tile n of the layer is tile n of the sheet in VRAM: the tilemap only places the tiles, the pixels are whatever the layer holds.
A glyph at x covers tile x / 8 and, shifted by x % 8, the tile after it; at y it covers rows y % 8 to 7 of one tile row and rows 0 to y % 8 - 1 of the next. The slot to the right is the next tile of the layer, the slot below is one row of tiles further.
The call only ORs, so the layer is cleared with memset() before a new layout, and glyphs may overlap.
After a change the layer goes to VRAM in two halves of 1280 bytes, one per VBlank, inside the DMA budget of a frame.
Cost: about 12 000 master cycles a glyph for its two calls (measured on luna), where the same work in C costs 40 000 to 50 000.

Controls

Button	Action
A	Shift every line one pixel to the right (six steps, then back)

How to Build

make

Modules Used

console, dma, background, input, tile, string