rust: several fixes

- rename Alpha to AlphaBits
- fix pixel alpha mask
- fix syntax errors

rust/src/channel.rs

@@ -62,7 +62,7 @@
 
 use crate as ffi;
 
-use crate::types::{Alpha, Channel, ChannelPair, Color, Rgb};
+use crate::types::{AlphaBits, Channel, ChannelPair, Color, Rgb};
 
 /// Extract the 8-bit red component from a 32-bit channel.
 #[inline]
@@ -108,13 +108,13 @@ pub fn channel_set(channel: &mut Channel, rgb: Rgb) {
 
 /// Extract the 2-bit alpha component from a 32-bit channel.
 #[inline]
-pub fn channel_alpha(channel: Channel) -> Alpha {
+pub fn channel_alpha(channel: Channel) -> AlphaBits {
     channel & ffi::NCCHANNEL_ALPHA_MASK
 }
 
 /// Set the 2-bit alpha component of the 32-bit channel.
 #[inline]
-pub fn channel_set_alpha(channel: &mut Channel, alpha: Alpha) {
+pub fn channel_set_alpha(channel: &mut Channel, alpha: AlphaBits) {
     let alpha_clean = alpha & ffi::NCCHANNEL_ALPHA_MASK;
     *channel = alpha_clean | (*channel & !ffi::NCCHANNEL_ALPHA_MASK);
 
@@ -197,14 +197,14 @@ pub fn channels_bg(channels: ChannelPair) -> Channel {
 /// Extract 2 bits of foreground alpha from 'channels', shifted to LSBs.
 // TODO: TEST
 #[inline]
-pub fn channels_fg_alpha(channels: ChannelPair) -> Alpha {
+pub fn channels_fg_alpha(channels: ChannelPair) -> AlphaBits {
     channel_alpha(channels_fchannel(channels))
 }
 
 /// Extract 2 bits of background alpha from 'channels', shifted to LSBs.
 // TODO: TEST
 #[inline]
-pub fn channels_bg_alpha(channels: ChannelPair) -> Alpha {
+pub fn channels_bg_alpha(channels: ChannelPair) -> AlphaBits {
     channel_alpha(channels_bchannel(channels))
 }
 
@@ -273,7 +273,7 @@ pub fn channels_set_bg(channels: &mut ChannelPair, rgb: Rgb) {
 /// Set the 2-bit alpha component of the foreground channel.
 // TODO: TEST
 #[inline]
-pub fn channels_set_fg_alpha(channels: &mut ChannelPair, alpha: Alpha) {
+pub fn channels_set_fg_alpha(channels: &mut ChannelPair, alpha: AlphaBits) {
     let mut channel = channels_fchannel(*channels);
     channel_set_alpha(&mut channel, alpha);
     *channels = (channel as ChannelPair) << 32 | *channels & 0xffffffff_u64;
@@ -282,7 +282,7 @@ pub fn channels_set_fg_alpha(channels: &mut ChannelPair, alpha: Alpha) {
 /// Set the 2-bit alpha component of the background channel.
 // TODO: TEST
 #[inline]
-pub fn channels_set_bg_alpha(channels: &mut ChannelPair, alpha: Alpha) {
+pub fn channels_set_bg_alpha(channels: &mut ChannelPair, alpha: AlphaBits) {
     let mut alpha_clean = alpha;
     if alpha == ffi::CELL_ALPHA_HIGHCONTRAST {
         // forbidden for background alpha, so makes it opaque

rust/src/pixel.rs

@@ -29,6 +29,13 @@
 
 use crate::types::{Color, Pixel};
 
+// Pixel Structure:
+//
+// 0xff000000 8 bit Alpha
+// 0x00ff0000 8 bit Green
+// 0x0000ff00 8 bit Blue
+// 0x000000ff 8 bit Red
+
 /// Get an RGB pixel from RGB values
 pub fn ncpixel(r: Color, g: Color, b: Color) -> Pixel {
     0xff000000 as Pixel | r as Pixel | (b as Pixel) << 8 | (g as Pixel) << 16
@@ -36,7 +43,7 @@ pub fn ncpixel(r: Color, g: Color, b: Color) -> Pixel {
 
 /// Extract the 8-bit alpha component from a pixel
 pub fn ncpixel_a(pixel: Pixel) -> Color {
-    ((pixel & 0xff0000ff) >> 24) as Color
+    ((pixel & 0xff000000) >> 24) as Color
 }
 
 /// Extract the 8 bit green component from a pixel

rust/src/plane.rs

@@ -139,7 +139,7 @@ use core::ptr::null_mut;
 use cstr_core::CString;
 
 use crate as ffi;
-use ffi::types::{Alpha, Channel, Color, IntResult};
+use ffi::types::{AlphaBits, Channel, Color, IntResult};
 
 pub fn ncplane_putstr(plane: *mut ffi::ncplane, _str: &str) -> i32 {
     unsafe {
@@ -518,14 +518,14 @@ pub fn ncplane_bg(plane: &ffi::ncplane) -> Channel {
 /// Extract 2 bits of foreground alpha from 'struct ncplane', shifted to LSBs.
 // TODO: TEST
 #[inline]
-pub fn ncplane_fg_alpha(plane: &ffi::ncplane) -> Alpha {
+pub fn ncplane_fg_alpha(plane: &ffi::ncplane) -> AlphaBits {
     ffi::channels_fg_alpha(unsafe { ffi::ncplane_channels(plane)})
 }
 
 /// Extract 2 bits of background alpha from 'struct ncplane', shifted to LSBs.
 // TODO: TEST
 #[inline]
-pub fn ncplane_bg_alpha(plane: &ffi::ncplane) -> Alpha {
+pub fn ncplane_bg_alpha(plane: &ffi::ncplane) -> AlphaBits {
     ffi::channels_bg_alpha(unsafe { ffi::ncplane_channels(plane)})
 }
 

rust/src/types.rs

@@ -43,7 +43,7 @@ pub type Channel = u32;
 ///
 /// ~~AA~~~~ -------- -------- --------
 ///
-pub type Alpha = u32;
+pub type AlphaBits = u32;
 
 /// Channels: 64 bits containing a foreground and background channel
 ///
@@ -128,7 +128,7 @@ pub type IntResult = i32;     // -1 == err
 ///
 /// NOTE: WIP unstable
 /// https://github.com/dankamongmen/notcurses/issues/884
-pub type Attribute: u32;
+pub type Attribute = u32;
 
 
 /// GCluster: 32 bits representing
@@ -139,7 +139,7 @@ pub type Attribute: u32;
 ///
 /// NOTE: WIP unstable
 /// https://github.com/dankamongmen/notcurses/issues/830
-pub type GraphemeCluster: u32;
+pub type GraphemeCluster = u32;
 
 // Cell: 128 bits tying together a:
 //