Transparent blitter stacking

.drone.yml

@@ -5,7 +5,7 @@ name: debian-unstable
 
 steps:
 - name: debian-build
-  image: dankamongmen/unstable_builder:2021-01-02a
+  image: dankamongmen/unstable_builder:2021-02-01a
   commands:
     - export LANG=en_US.UTF-8
     - mkdir build
@@ -66,7 +66,7 @@ name: ubuntu-focal
 
 steps:
 - name: ubuntu-build
-  image: dankamongmen/hirsute:2021-01-02a
+  image: dankamongmen/hirsute:2021-02-01a
   commands:
     - export LANG=es_ES.UTF-8
     - mkdir build

USAGE.md

@@ -1601,11 +1601,22 @@ manner.
 //    characters, followed by a NUL terminator.
 //
 // Multi-column characters can only have a single style/color throughout.
+// Existence is suffering, and thus wcwidth() is not reliable. It's just
+// quoting whether or not the EGC contains a "Wide Asian" double-width
+// character. This is set for some things, like most emoji, and not set for
+// other things, like cuneiform. True display width is a *function of the
+// font and terminal*. Among the longest Unicode codepoints is
+//
+//    U+FDFD ARABIC LIGATURE BISMILLAH AR-RAHMAN AR-RAHEEM ﷽
+//
+// wcwidth() rather optimistically claims this most exalted glyph to occupy
+// a single column. BiDi text is too complicated for me to even get into here.
+// Be assured there are no easy answers; ours is indeed a disturbing Universe.
 //
 // Each nccell occupies 16 static bytes (128 bits). The surface is thus ~1.6MB
 // for a (pretty large) 500x200 terminal. At 80x43, it's less than 64KB.
-// Dynamic requirements can add up to 16MB to an ncplane, but such large pools
-// are unlikely in common use.
+// Dynamic requirements (the egcpool) can add up to 16MB to an ncplane, but
+// such large pools are unlikely in common use.
 //
 // We implement some small alpha compositing. Foreground and background both
 // have two bits of inverted alpha. The actual grapheme written to a cell is
@@ -1624,6 +1635,9 @@ manner.
 // meaningfully set transparency, but it can be mixed into a cascading color.
 // RGB is used if neither default terminal colors nor palette indexing are in
 // play, and fully supports all transparency options.
+//
+// This structure is exposed only so that most functions can be inlined. Do not
+// directly modify or access the fields of this structure; use the API.
 typedef struct nccell {
   // These 32 bits, together with the associated plane's associated egcpool,
   // completely define this cell's EGC. Unless the EGC requires more than four
@@ -1665,12 +1679,13 @@ typedef struct nccell {
   // can be determined by checking whether ->gcluster is zero.
   uint8_t width;              // 1B → 6B (8 bits of EGC column width)
   uint16_t stylemask;         // 2B → 8B (16 bits of NCSTYLE_* attributes)
-  // (channels & 0x8000000000000000ull): reserved, must be 0
+  // (channels & 0x8000000000000000ull): blitted to upper-left quadrant
   // (channels & 0x4000000000000000ull): foreground is *not* "default color"
   // (channels & 0x3000000000000000ull): foreground alpha (2 bits)
   // (channels & 0x0800000000000000ull): foreground uses palette index
-  // (channels & 0x0400000000000000ull): glyph is entirely foreground
-  // (channels & 0x0300000000000000ull): reserved, must be 0
+  // (channels & 0x0400000000000000ull): blitted to upper-right quadrant
+  // (channels & 0x0200000000000000ull): blitted to lower-left quadrant
+  // (channels & 0x0100000000000000ull): blitted to lower-right quadrant
   // (channels & 0x00ffffff00000000ull): foreground in 3x8 RGB (rrggbb)
   // (channels & 0x0000000080000000ull): reserved, must be 0
   // (channels & 0x0000000040000000ull): background is *not* "default color"

doc/man/man3/notcurses_render.3.md

@@ -121,5 +121,6 @@ purposes of color blending.
 **notcurses_plane(3)**,
 **notcurses_refresh(3)**,
 **notcurses_stats(3)**,
+**notcurses_visual(3)**,
 **console_codes(4)**,
 **utf-8(7)**

doc/man/man3/notcurses_visual.3.md

@@ -159,7 +159,39 @@ The different **ncblitter_e** values select from among available glyph sets:
 * **NCBLIT_SIXEL**: Not yet implemented.
 
 **NCBLIT_4x1** and **NCBLIT_8x1** are intended for use with plots, and are
-not really applicable for general visuals.
+not really applicable for general visuals. **NCBLIT_BRAILLE** doesn't tend
+to work out very well for images, but (depending on the font) can be very
+good for plots.
+
+In the absence of scaling, for a given set of pixels, more rows and columns in
+the blitter will result in a smaller output image. An image rendered with
+**NCBLIT_1x1** will be twice as tall as the same image rendered with
+**NCBLIT_2x1**, which will be twice as wide as the same image rendered with
+**NCBLIT_2x2**. The same image rendered with **NCBLIT_3x2** will be one-third
+as tall and one-half as wide as the original **NCBLIT_1x1** render (again, this
+depends on **NCSCALE_NONE**). If the output size is held constant (using for
+instance **NCSCALE_SCALE_HIRES** and a large image), more rows and columns will
+result in more effective resolution.
+
+Assuming a cell is twice as tall as it is wide, **NCBLIT_1x1** (and indeed
+any NxN blitter) will stretch an image by a factor of 2 in the vertical
+dimension. **NCBLIT_2x1** will not distort the image whatsoever, as it maps a
+vector two pixels high and one pixel wide to a single cell. **NCBLIT_3x2** will
+stretch an image by a factor of 1.5.
+
+The cell's dimension in pixels is ideally evenly divisible by the blitter
+geometry. If **NCBLIT_3x2** is used together with a cell 8 pixels wide and
+14 pixels tall, two of the vertical segments will be 5 pixels tall, while one
+will be 4 pixels tall. Such unequal distributions are more likely with larger
+blitter geometries. Likewise, there are only ever two colors available to us in
+a given cell. **NCBLIT_1x1** and **NCBLIT_2x2** can be perfectly represented
+with two colors per cell. Blitters of higher geometry are increasingly likely
+to require some degree of interpolation. Transparency is always honored with
+complete fidelity.
+
+Finally, rendering operates slightly differently when two planes have both been
+blitted, and one lies atop the other. See **notcurses_render(3)** for more
+information.
 
 # RETURN VALUES
 
@@ -210,11 +242,14 @@ radians for **rads**, but this will change soon.
 among terminals.
 
 Bad font support can ruin **NCBLIT_2x2**, **NCBLIT_3x2**, **NCBLIT_4x1**,
-**NCBLIT_BRAILLE**, and **NCBLIT_8x1**.
+**NCBLIT_BRAILLE**, and **NCBLIT_8x1**. Braille glyphs ought ideally draw only
+the raised dots, rather than drawing all eight dots with two different styles.
+It's often best for the emulator to draw these glyphs itself.
 
 # SEE ALSO
 
 **notcurses(3)**,
 **notcurses_capabilities(3)**,
 **notcurses_plane(3)**,
+**notcurses_render(3)**,
 **utf-8(7)**

include/notcurses/notcurses.h

@@ -15,7 +15,7 @@
 #include <stdbool.h>
 // take host byte order and turn it into network (reverse on LE, no-op on BE),
 // then reverse that, guaranteeing LE. htole(x) == ltohe(x).
-#ifdef __linux__
+#if defined(__linux__) || defined(__gnu_hurd__)
 #include <byteswap.h>
 #define htole(x) (bswap_32(htonl(x)))
 #else
@@ -109,7 +109,6 @@ API int notcurses_ucs32_to_utf8(const char32_t* ucs32, unsigned ucs32count,
 #define CELL_ALPHA_BLEND        0x10000000ull
 #define CELL_ALPHA_OPAQUE       0x00000000ull
 
-#define CELL_NOBACKGROUND_MASK  0x0400000000000000ull
 // if this bit is set, we are *not* using the default background color
 #define CELL_BGDEFAULT_MASK     0x0000000040000000ull
 // if this bit is set, we are *not* using the default foreground color
@@ -548,6 +547,9 @@ channels_set_bg_default(uint64_t* channels){
 // meaningfully set transparency, but it can be mixed into a cascading color.
 // RGB is used if neither default terminal colors nor palette indexing are in
 // play, and fully supports all transparency options.
+//
+// This structure is exposed only so that most functions can be inlined. Do not
+// directly modify or access the fields of this structure; use the API.
 typedef struct nccell {
   // These 32 bits, together with the associated plane's associated egcpool,
   // completely define this cell's EGC. Unless the EGC requires more than four
@@ -589,19 +591,20 @@ typedef struct nccell {
   // can be determined by checking whether ->gcluster is zero.
   uint8_t width;              // 1B → 6B (8 bits of EGC column width)
   uint16_t stylemask;         // 2B → 8B (16 bits of NCSTYLE_* attributes)
-  // (channels & 0x8000000000000000ull): reserved, must be 0
+  // (channels & 0x8000000000000000ull): blitted to upper-left quadrant
   // (channels & 0x4000000000000000ull): foreground is *not* "default color"
   // (channels & 0x3000000000000000ull): foreground alpha (2 bits)
   // (channels & 0x0800000000000000ull): foreground uses palette index
-  // (channels & 0x0400000000000000ull): glyph is entirely foreground
-  // (channels & 0x0300000000000000ull): reserved, must be 0
-  // (channels & 0x00ffffff00000000ull): foreground in 3x8 RGB (rrggbb)
+  // (channels & 0x0400000000000000ull): blitted to upper-right quadrant
+  // (channels & 0x0200000000000000ull): blitted to lower-left quadrant
+  // (channels & 0x0100000000000000ull): blitted to lower-right quadrant
+  // (channels & 0x00ffffff00000000ull): foreground in 3x8 RGB (rrggbb) / pindex
   // (channels & 0x0000000080000000ull): reserved, must be 0
   // (channels & 0x0000000040000000ull): background is *not* "default color"
   // (channels & 0x0000000030000000ull): background alpha (2 bits)
   // (channels & 0x0000000008000000ull): background uses palette index
   // (channels & 0x0000000007000000ull): reserved, must be 0
-  // (channels & 0x0000000000ffffffull): background in 3x8 RGB (rrggbb)
+  // (channels & 0x0000000000ffffffull): background in 3x8 RGB (rrggbb) / pindex
   // 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

rust/src/bindings.rs

@@ -54,7 +54,6 @@ pub use ffi::{
 // CELL_FG_ALPHA_MASK,
 // CELL_FG_PALETTE,
 // CELL_FG_RGB_MASK,
-// CELL_NOBACKGROUND_MASK,
 
 #[doc(inline)]
 pub use ffi::{

rust/src/cells/mod.rs

@@ -279,11 +279,6 @@ pub const NCCELL_FG_PALETTE: u64 = crate::bindings::ffi::CELL_FG_PALETTE;
 /// NOTE: When working with a single [`NcChannel`] use [`NCCELL_BG_RGB_MASK`];
 pub const NCCELL_FG_RGB_MASK: u64 = crate::bindings::ffi::CELL_FG_RGB_MASK;
 
-/// Indicates the glyph is entirely foreground
-///
-/// See the detailed diagram at [`NcChannelPair`][crate::NcChannelPair]
-pub const NCCELL_NOBACKGROUND_MASK: u64 = crate::bindings::ffi::CELL_NOBACKGROUND_MASK;
-
 // NcEgc
 //
 /// Extended Grapheme Cluster. A 32-bit [`char`]-like type

rust/src/channel/mod.rs

@@ -191,7 +191,6 @@ pub type NcAlphaBits = u32;
 /// - [`NCCELL_FG_ALPHA_MASK`][crate::NCCELL_FG_ALPHA_MASK]
 /// - [`NCCELL_FG_PALETTE`][crate::NCCELL_FG_PALETTE]
 /// - [`NCCELL_FG_RGB_MASK`][crate::NCCELL_FG_RGB_MASK]
-/// - [`NCCELL_NOBACKGROUND_MASK`][crate::NCCELL_NOBACKGROUND_MASK]
 ///
 pub type NcChannelPair = u64;
 

src/demo/intro.c

@@ -124,11 +124,16 @@ int intro(struct notcurses* nc){
     }
   }
   ncplane_off_styles(ncp, NCSTYLE_BOLD);
-  const wchar_t wstr[] = L"▏▁ ▂ ▃ ▄ ▅ ▆ ▇ █ █ ▇ ▆ ▅ ▄ ▃ ▂ ▁▕";
-  if(ncplane_putwstr_aligned(ncp, rows / 2 - 6, NCALIGN_CENTER, wstr) < 0){
+  const wchar_t nwstr[] = L"▏▁ ▂ ▃ ▄ ▅ ▆ ▇ █ █ ▇ ▆ ▅ ▄ ▃ ▂ ▁▕";
+  if(ncplane_putwstr_aligned(ncp, rows / 2 - 6, NCALIGN_CENTER, nwstr) < 0){
     return -1;
   }
-  const wchar_t iwstr[] = L"▏█ ▇ ▆ ▅ ▄ ▃ ▂ ▁ ▁ ▂ ▃ ▄ ▅ ▆ ▇ █▕";
+  const wchar_t* iwstr;
+  if(notcurses_cansextant(nc)){
+    iwstr = L"▏▔ 🮂 🮃 ▀ 🮄 🮅 🮆 █ █ 🮆 🮅 🮄 ▀ 🮃 🮂 ▔▕";
+  }else{
+    iwstr = L"▏█ ▇ ▆ ▅ ▄ ▃ ▂ ▁ ▁ ▂ ▃ ▄ ▅ ▆ ▇ █▕";
+  }
   if(ncplane_putwstr_aligned(ncp, rows / 2 + 1, NCALIGN_CENTER, iwstr) < 0){
     return -1;
   }