From fb13b148e95d6a4c2151c2e3c4fe7a19c41fa4b3 Mon Sep 17 00:00:00 2001
From: nick black <dankamongmen@gmail.com>
Date: Sat, 6 Jun 2020 19:34:48 -0400
Subject: [PATCH] add Pixel API

---
 NEWS.md                       |  1 +
 USAGE.md                      | 42 +++++++++++++++++++++++++++++++++++
 include/notcurses/notcurses.h | 36 ++++++++++++++++++++++++++++++
 src/demo/yield.c              | 17 +++++---------
 src/lib/visual.cpp            |  1 -
 5 files changed, 85 insertions(+), 12 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 348353941..bce28d8c7 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -6,6 +6,7 @@ rearrangements of Notcurses.
     with a `const struct ncvisual_options*`. `NCBLIT_DEFAULT` will use
     `NCBLITTER_2x1` (with fallback) in this context. The `->n` field must
     be non-`NULL`--new planes will not be created.
+  * Added a Pixel API for working directly with the contents of `ncvisual`s.
   * Added `ncplane_notcurses_const()`.
 
 * 1.4.4.1 (2020-06-01)
diff --git a/USAGE.md b/USAGE.md
index 9c91a28b6..868fd8470 100644
--- a/USAGE.md
+++ b/USAGE.md
@@ -2638,6 +2638,48 @@ struct ncvisual* ncvisual_from_file(const char* file, nc_err_e* ncerr);
 nc_err_e ncvisual_decode(struct ncvisual* nc);
 ```
 
+### Pixels
+
+It is sometimes desirable to modify the pixels of an `ncvisual` directly.
+
+```c
+static inline int
+pixel_set_r(uint32_t* pixel, int r){
+  if(r > 255 || r < 0){
+    return -1;
+  }
+  *pixel = (*pixel & 0xffffff00ul) | (r);
+  return 0;
+}
+
+static inline int
+pixel_set_g(uint32_t* pixel, int g){
+  if(g > 255 || g < 0){
+    return -1;
+  }
+  *pixel = (*pixel & 0xff00fffful) | (g << 16u);
+  return 0;
+}
+
+static inline int
+pixel_set_b(uint32_t* pixel, int b){
+  if(b > 255 || b < 0){
+    return -1;
+  }
+  *pixel = (*pixel & 0xffff00fful) | (b << 8u);
+  return 0;
+}
+
+// set the RGB values of an RGB pixel
+static inline int
+pixel_set_rgb(uint32_t* pixel, int r, int g, int b){
+  if(pixel_set_r(pixel, r) || pixel_set_g(pixel, g) || pixel_set_b(pixel, b)){
+    return -1;
+  }
+  return 0;
+}
+```
+
 ## C++
 
 Marek Habersack has contributed (and maintains) C++ wrappers installed to
diff --git a/include/notcurses/notcurses.h b/include/notcurses/notcurses.h
index f6d3c49cf..3ec27aaed 100644
--- a/include/notcurses/notcurses.h
+++ b/include/notcurses/notcurses.h
@@ -193,6 +193,42 @@ channel_set_rgb(unsigned* channel, int r, int g, int b){
   return 0;
 }
 
+static inline int
+pixel_set_r(uint32_t* pixel, int r){
+  if(r > 255 || r < 0){
+    return -1;
+  }
+  *pixel = (*pixel & 0xffffff00ul) | (r);
+  return 0;
+}
+
+static inline int
+pixel_set_g(uint32_t* pixel, int g){
+  if(g > 255 || g < 0){
+    return -1;
+  }
+  *pixel = (*pixel & 0xff00fffful) | (g << 16u);
+  return 0;
+}
+
+static inline int
+pixel_set_b(uint32_t* pixel, int b){
+  if(b > 255 || b < 0){
+    return -1;
+  }
+  *pixel = (*pixel & 0xffff00fful) | (b << 8u);
+  return 0;
+}
+
+// set the RGB values of an RGB pixel
+static inline int
+pixel_set_rgb(uint32_t* pixel, int r, int g, int b){
+  if(pixel_set_r(pixel, r) || pixel_set_g(pixel, g) || pixel_set_b(pixel, b)){
+    return -1;
+  }
+  return 0;
+}
+
 // Set the three 8-bit components of a 32-bit channel, and mark it as not using
 // the default color. Retain the other bits unchanged. r, g, and b will be
 // clipped to the range [0..255].
diff --git a/src/demo/yield.c b/src/demo/yield.c
index 6d246c53b..a3e738039 100644
--- a/src/demo/yield.c
+++ b/src/demo/yield.c
@@ -31,21 +31,19 @@ int yield_demo(struct notcurses* nc){
   int vy, vx, vscaley, vscalex;
   ncvisual_geom(nc, wmv, vopts.blitter, &vy, &vx, &vscaley, &vscalex);
   struct timespec scaled;
-  int threshold_painted = vy * vx * 10 / 9;
-  const int ITER = 128;
-  timespec_div(&demodelay, ITER, &scaled);
+  int threshold_painted = (vy * vscaley) * (vx * vscalex) / 2;
+  timespec_div(&demodelay, 128, &scaled);
   int tfilled = 0;
-  for(int i = 0 ; i < ITER ; ++i){
+  while(tfilled < threshold_painted){
     int pfilled;
     do{
       int x = random() % (vx);
       int y = random() % (vy);
       uint32_t pixel = 0;
       ncvisual_at_yx(wmv, y, x, &pixel);
-      uint32_t channel = 0;
-      channel_set_rgb(&channel, 0x80, channel_g(pixel), channel_b(pixel));
-//fprintf(stderr, "POLY: %d/%d\n", y, x);
-      pfilled = ncvisual_polyfill_yx(wmv, y, x, channel);
+      uint32_t newpixel = 0;
+      pixel_set_rgb(&newpixel, 0xff, channel_g(pixel), channel_b(pixel));
+      pfilled = ncvisual_polyfill_yx(wmv, y, x, newpixel);
       if(pfilled < 0){
         ncvisual_destroy(wmv);
         return -1;
@@ -58,9 +56,6 @@ int yield_demo(struct notcurses* nc){
     }
     DEMO_RENDER(nc);
     demo_nanosleep(nc, &scaled);
-    if(tfilled >= threshold_painted){
-      break;
-    }
   }
 
   ncvisual_destroy(wmv);
diff --git a/src/lib/visual.cpp b/src/lib/visual.cpp
index c9797c8a2..48749a634 100644
--- a/src/lib/visual.cpp
+++ b/src/lib/visual.cpp
@@ -538,7 +538,6 @@ auto ncvisual_polyfill_recurse(ncvisual* n, int y, int x,
   if(*pixel != match || *pixel == rgba){
     return 0;
   }
-//fprintf(stderr, "%d/%d: %08x -> %08x\n", y, x, *pixel, rgba);
   *pixel = rgba;
   int ret = 1;
   ret += ncvisual_polyfill_recurse(n, y - 1, x, rgba, match);