subtle ncplane bugfixes

ncplane_dup(): properly set target plane attributes/channels
ncplane_move_below_unsafe(): speedup, at most one traversal
ncplane_rgba(): accept null glyph
ncvisual_from_plane(): dup the plane, own it in ncvisual
normal: spin the visual

NEWS.md

@@ -3,6 +3,13 @@ rearrangements of Notcurses.
 
 * 1.4.2 (not yet released)
   * Added `notcurses_canutf8()`, to verify use of UTF-8 encoding.
+  * Fixed bug in `ncvisual_from_plane()` when invoked on the standard plane.
+  * `ncvisual_from_plane()` now accepts the same four geometric parameters
+    as other plane selectors. To reproduce the old behavior, for `ncv`, call
+    it as `ncvisual_from_plane(ncv, 0, 0, -1, -1)`.
+  * `ncvisual_from_plane()`, `ncplane_move_below_unsafe()`, `ncplane_dup()`,
+    and `ncplane_move_above_unsafe()` now accept `const` arguments where they
+    did not before.
 
 * 1.4.1 (2020-05-11)
   * No user-visible changes (fixed two unit tests).

include/notcurses/notcurses.h

@@ -990,7 +990,7 @@ API struct ncplane* ncplane_reparent(struct ncplane* n, struct ncplane* newparen
 // Duplicate an existing ncplane. The new plane will have the same geometry,
 // will duplicate all content, and will start with the same rendering state.
 // The new plane will be immediately above the old one on the z axis.
-API struct ncplane* ncplane_dup(struct ncplane* n, void* opaque);
+API struct ncplane* ncplane_dup(const struct ncplane* n, void* opaque);
 
 // provided a coordinate relative to the origin of 'src', map it to the same
 // absolute coordinate relative to thte origin of 'dst'. either or both of 'y'
@@ -1126,7 +1126,7 @@ API int ncplane_move_bottom(struct ncplane* n);
 
 // Splice ncplane 'n' out of the z-buffer, and reinsert it above 'above'.
 API int ncplane_move_above_unsafe(struct ncplane* RESTRICT n,
-                                  struct ncplane* RESTRICT above);
+                                  const struct ncplane* RESTRICT above);
 
 static inline int
 ncplane_move_above(struct ncplane* n, struct ncplane* above){
@@ -1138,7 +1138,7 @@ ncplane_move_above(struct ncplane* n, struct ncplane* above){
 
 // Splice ncplane 'n' out of the z-buffer, and reinsert it below 'below'.
 API int ncplane_move_below_unsafe(struct ncplane* RESTRICT n,
-                                  struct ncplane* RESTRICT below);
+                                  const struct ncplane* RESTRICT below);
 
 static inline int
 ncplane_move_below(struct ncplane* n, struct ncplane* below){
@@ -2802,7 +2802,8 @@ API int ncplane_qrcode(struct ncplane* n, int maxversion, const void* data, size
 // in a NULL being returned. This function exists so that planes can be
 // subjected to ncvisual transformations. If possible, it's usually better
 // to create the ncvisual from memory using ncvisual_from_rgba().
-API struct ncvisual* ncvisual_from_plane(struct ncplane* n);
+API struct ncvisual* ncvisual_from_plane(const struct ncplane* n,
+                          int begy, int begx, int leny, int lenx);
 
 #define NCREADER_OPTION_HORSCROLL  0x0001
 #define NCREADER_OPTION_VERSCROLL  0x0002

src/demo/normal.c

@@ -36,6 +36,7 @@ offset(uint32_t* rgba, int y, int x, int dx){
 int normal_demo(struct notcurses* nc){
   int dy, dx;
   struct ncplane* n = notcurses_stddim_yx(nc, &dy, &dx);
+  ncplane_erase(n);
   dy *= VSCALE; // double-block trick means both 2x resolution and even linecount yay
   uint32_t* rgba = malloc(sizeof(*rgba) * dy * dx);
   if(!rgba){
@@ -66,5 +67,20 @@ int normal_demo(struct notcurses* nc){
     DEMO_RENDER(nc);
   }
   free(rgba);
+  struct ncvisual* ncv = ncvisual_from_plane(n, 0, 0, -1, -1);
+  if(!ncv){
+    return -1;
+  }
+  // FIXME use smaller rotations once supported
+  for(int i = 1 ; i < 4 ; ++i){
+    if(ncvisual_rotate(ncv, M_PI / 2)){
+      return -1;
+    }
+    if(ncvisual_render(ncv, 0, 0, -1, -1) <= 0){
+      return -1;
+    }
+    DEMO_RENDER(nc);
+  }
+  ncvisual_destroy(ncv);
   return 0;
 }

src/lib/notcurses.c

@@ -367,7 +367,7 @@ inline int ncplane_cursor_move_yx(ncplane* n, int y, int x){
   return 0;
 }
 
-ncplane* ncplane_dup(ncplane* n, void* opaque){
+ncplane* ncplane_dup(const ncplane* n, void* opaque){
   int dimy = n->leny;
   int dimx = n->lenx;
   int aty = n->absy;
@@ -383,8 +383,8 @@ ncplane* ncplane_dup(ncplane* n, void* opaque){
       return NULL;
     }else{
       ncplane_cursor_move_yx(newn, y, x);
-      n->attrword = attr;
+      newn->attrword = attr;
-      n->channels = chan;
+      newn->channels = chan;
       ncplane_move_above_unsafe(newn, n);
       memmove(newn->fb, n->fb, sizeof(*n->fb) * dimx * dimy);
     }
@@ -499,7 +499,7 @@ int ncplane_resize(ncplane* n, int keepy, int keepx, int keepleny,
 // find the pointer on the z-index referencing the specified plane. writing to
 // this pointer will remove the plane (and everything below it) from the stack.
 static ncplane**
-find_above_ncplane(ncplane* n){
+find_above_ncplane(const ncplane* n){
   notcurses* nc = n->nc;
   ncplane** above = &nc->top;
   while(*above){
@@ -1189,7 +1189,7 @@ const char* cell_extended_gcluster(const ncplane* n, const cell* c){
 }
 
 // 'n' ends up above 'above'
-int ncplane_move_above_unsafe(ncplane* restrict n, ncplane* restrict above){
+int ncplane_move_above_unsafe(ncplane* restrict n, const ncplane* restrict above){
   if(n->z == above){
     return 0;
   }
@@ -1201,24 +1201,37 @@ int ncplane_move_above_unsafe(ncplane* restrict n, ncplane* restrict above){
   if(aa == NULL){
     return -1;
   }
+  ncplane* deconst_above = *aa;
   *an = n->z; // splice n out
-  n->z = above; // attach above below n
+  n->z = deconst_above; // attach above below n
   *aa = n; // spline n in above
   return 0;
 }
 
 // 'n' ends up below 'below'
-int ncplane_move_below_unsafe(ncplane* restrict n, ncplane* restrict below){
+int ncplane_move_below_unsafe(ncplane* restrict n, const ncplane* restrict below){
   if(below->z == n){
     return 0;
   }
-  ncplane** an = find_above_ncplane(n);
+  ncplane* deconst_below = NULL;
+  ncplane** an = &n->nc->top;
+  // go down, looking for n and below. if we find below, mark it. if we
+  // find n, break from the loop.
+  while(*an){
+    if(*an == below){
+      deconst_below = *an;
+    }else if(*an == n){
+      *an = n->z; // splice n out
+    }
+  }
   if(an == NULL){
     return -1;
   }
-  *an = n->z; // splice n out
+  while(deconst_below != below){
-  n->z = below->z; // reattach subbelow list to n
+    deconst_below = deconst_below->z;
-  below->z = n; // splice n in below
+  }
+  n->z = deconst_below->z; // reattach subbelow list to n
+  deconst_below->z = n; // splice n in below
   return 0;
 }
 
@@ -2054,7 +2067,7 @@ uint32_t* ncplane_rgba(const ncplane* nc, int begy, int begx, int leny, int lenx
         // FIXME how do we deal with transparency?
         uint32_t frgba = (fr << 24u) + (fg << 16u) + (fb << 8u) + 0xff;
         uint32_t brgba = (br << 24u) + (bg << 16u) + (bb << 8u) + 0xff;
-        if(strcmp(c, " ") == 0){
+        if((strcmp(c, " ") == 0) || (strcmp(c, "") == 0)){
           *top = *bot = brgba;
         }else if(strcmp(c, "▄") == 0){
           *top = frgba;

src/lib/visual.cpp

@@ -105,8 +105,9 @@ auto ncvisual_create(float timescale) -> ncvisual* {
   return ret;
 }
 
-auto ncvisual_from_plane(ncplane* n) -> ncvisual* {
+auto ncvisual_from_plane(const ncplane* n, int begy, int begx, int leny, int lenx)
-  uint32_t* rgba = ncplane_rgba(n, 0, 0, -1, -1);
+                         -> ncvisual* {
+  uint32_t* rgba = ncplane_rgba(n, begx, begy, leny, lenx);
   if(rgba == nullptr){
     return nullptr;
   }
@@ -118,8 +119,8 @@ auto ncvisual_from_plane(ncplane* n) -> ncvisual* {
     return nullptr;
   }
   ncplane_destroy(ncv->ncp);
-  ncv->ncp = n;
+  ncv->ncp = ncplane_dup(n, nullptr);
-  ncv->ncobj = nullptr;
+  ncv->ncobj = n->nc;
   return ncv;
 }