rust: add a lot of info about types

rust/src/types.rs

@@ -1,8 +1,171 @@
-pub type Channel = u32;
-pub type ChannelPair = u64;
-pub type Color = u8;
+//! # Types in notcurses
+//!
+//! The types are defined and explined here
+//!
+
+
+/// RGB: 24 bits broken into 3x 8bpp channels.
+///
+/// -------- RRRRRRRR GGGGGGGG BBBBBBBB
+///
+/// type in C: no data type
+///
 pub type Rgb = u32;
+
+
+/// 8 bpp channel
+///
+/// CCCCCCCC (1 Byte)
+///
+/// Used both for R/G/B color and 8 bit alpha
+///
+/// type in C: no data type
+///
+pub type Color = u8;
+
+/// Channel: 32 bits of context-dependent info
+/// containing RGB + 2 bits of alpha + crap
+///
+/// ~~AA~~~~ RRRRRRRR GGGGGGGG BBBBBBBB
+///
+/// type in C: channel (uint32_t)
+///
+/// It is:
+/// - an RGB value
+/// - plus 2 bits of alpha
+/// - plus context-dependent info
+///
+/// The context details are documented in ChannelPair,
+///
+pub type Channel = u32;
+
+/// 2 bits of (alpha + crap) which is part of a Channel
+///
+/// ~~AA~~~~ -------- -------- --------
+///
 pub type Alpha = u32;
+
+/// Channels: 64 bits containing a foreground and background channel
+///
+/// ~~AA~~~~|RRRRRRRR|GGGGGGGG|BBBBBBBB|~~AA~~~~|RRRRRRRR|GGGGGGGG|BBBBBBBB
+/// ↑↑↑↑↑↑↑↑↑↑↑↑ foreground ↑↑↑↑↑↑↑↑↑↑↑|↑↑↑↑↑↑↑↑↑↑↑↑ background ↑↑↑↑↑↑↑↑↑↑↑
+///
+/// type in C: channels (uint64_t) // + 8B == 16B
+///
+/// The hairy details: (source from include/notcurses/notcurses.h)
+///
+/// part of a wide glyph
+/// 10000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 = 80000000 00000000
+///
+/// foreground is *not* "default color"
+/// 01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 = 40000000 00000000
+///
+/// foreground alpha (2bits)
+/// 00110000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 = 30000000 00000000
+///
+/// foreground uses palette index
+/// 00001000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 = 08000000 00000000
+///
+/// glyph is entirely foreground
+/// 00000100 00000000 00000000 00000000 00000000 00000000 00000000 00000000 = 04000000 00000000
+///
+/// reserved, must be 0
+/// 00000011 00000000 00000000 00000000 00000000 00000000 00000000 00000000 = 03000000 00000000
+///
+/// foreground in 3x8 RGB (rrggbb)
+/// 00000000 11111111 11111111 11111111 00000000 00000000 00000000 00000000 = 00FFFFFF 00000000
+///
+/// reserved, must be 0
+/// 00000000 00000000 00000000 00000000 10000000 00000000 00000000 00000000 = 00000000 80000000
+///
+/// background is *not* "default color"
+/// 00000000 00000000 00000000 00000000 01000000 00000000 00000000 00000000 = 00000000 40000000
+///
+/// background alpha (2 bits)
+/// 00000000 00000000 00000000 00000000 00110000 00000000 00000000 00000000 = 00000000 30000000
+///
+/// background uses palette index
+/// 00000000 00000000 00000000 00000000 00001000 00000000 00000000 00000000 = 00000000 08000000
+///
+/// reserved, must be 0
+/// 00000000 00000000 00000000 00000000 00000111 00000000 00000000 00000000 = 00000000 07000000
+///
+/// background in 3x8 RGB (rrggbb)
+/// 00000000 00000000 00000000 00000000 00000000 11111111 11111111 11111111 = 00000000 00FFFFFF
+///
+///
+/// At render time, these 24-bit values are quantized down to terminal
+/// capabilities, if necessary. There's a clear path to 10-bit support should
+/// we one day need it, but keep things cagey for now. "default color" is
+/// best explained by color(3NCURSES). ours is the same concept. until the
+/// "not default color" bit is set, any color you load will be ignored.
+///
+pub type ChannelPair = u64;
+
+/// Pixel (RGBA): 32 bits broken into RGB + 8-bit alpha
+///
+/// AAAAAAAA GGGGGGGG BBBBBBBB RRRRRRRR
+///
+/// type in C: ncpixel (uint32_t)
+///
+/// ncpixel has 8 bits of alpha, and no other gunk.
+///
+/// we map the 8 bits of alpha to 2 bits of alpha via a level function,
+//
+// NOTE: the order of the colors is different than channel. Why.
 pub type Pixel = u32;
+
 pub type PaletteIndex = u8;
+
 pub type IntResult = i32;     // -1 == err
+
+/// Attrword: 32 bits of styling, including:
+///
+/// - 16 "classic" NCURSES bits
+/// - 16 bits for palette-indexed color
+///
+/// type in C:  attrword (uint32_t)
+///
+/// NOTE: WIP unstable
+/// https://github.com/dankamongmen/notcurses/issues/884
+pub type Attribute: u32;
+
+
+/// GCluster: 32 bits representing
+/// either a directly-encoded ASCII-1968 value of 7 bits
+/// or a 25-bit index into an egcpool
+///
+///  type in C: gcluster (uint32_t)
+///
+/// NOTE: WIP unstable
+/// https://github.com/dankamongmen/notcurses/issues/830
+pub type GraphemeCluster: u32;
+
+// Cell: 128 bits tying together a:
+//
+// - GCluster (32b)
+// - Attrword (32b)
+// - Channels (64b)
+//
+// type in C: cell (struct)
+
+// Plane: fundamental drawing surface. unites a:
+//
+// - CellMatrix
+// - EGCPool
+//
+// type in C: ncplane (struct)
+
+// EGCPool: contiguous region chopped up into NUL-terminated UTF8 EGCs, one per plane
+//
+// type in C: egcpool (struct)
+//
+// NOTE: need more info
+
+
+// CellMatrix: rectilinear array of Cells
+// one -- fb per plane, and transients show up ?
+//
+// NOTE: need more info
+
+