Optimized general cursor moves #483

src/lib/internal.h

@@ -118,6 +118,11 @@ typedef struct renderstate {
   FILE* mstreamfp;// FILE* for rendering memstream
   size_t mstrsize;// size of rendering memstream
 
+  // the current cursor position. this is independent of whether the cursor is
+  // visible. it is the cell at which the next write will take place. this is
+  // modified by: output, cursor moves, clearing the screen (during refresh)
+  int y, x;
+
   uint32_t curattr;// current attributes set (does not include colors)
   unsigned lastr;  // foreground rgb, overloaded for palindexed fg
   unsigned lastg;
@@ -296,6 +301,7 @@ typedef struct notcurses {
   int colors;     // number of colors terminfo reported usable for this screen
   char* cup;      // move cursor
   char* cuf;      // move n cells right
+  char* cub;      // move n cells right
   char* cuf1;     // move 1 cell right
   char* cub1;     // move 1 cell left
   char* civis;    // hide cursor

src/lib/notcurses.c

@@ -602,8 +602,9 @@ interrogate_terminfo(notcurses* nc, const notcurses_options* opts, int* dimy, in
   term_verify_seq(&nc->cleareol, "el");
   term_verify_seq(&nc->clearbol, "el1");
   term_verify_seq(&nc->cuf, "cuf"); // n non-destructive spaces
+  term_verify_seq(&nc->cub, "cub"); // n non-destructive backspaces
   term_verify_seq(&nc->cuf1, "cuf1"); // non-destructive space
-  term_verify_seq(&nc->cub1, "cub1");
+  term_verify_seq(&nc->cub1, "cub1"); // non-destructive backspace
   term_verify_seq(&nc->smkx, "smkx"); // set application mode
   if(nc->smkx){
     if(putp(tiparm(nc->smkx)) != OK){

src/lib/render.c

@@ -801,6 +801,40 @@ update_palette(notcurses* nc, FILE* out){
   return 0;
 }
 
+// sync the cursor to the specified location with as little overhead as
+// possible (with nothing, if already at the right location).
+// FIXME fall back to synthesized moves in the absence of capabilities (i.e.
+// textronix lacks cup; fake it with horiz+vert moves)
+static inline int
+stage_cursor(notcurses* nc, FILE* out, int y, int x){
+  int ret;
+  if(nc->rstate.y == y){
+    if(nc->rstate.x == x){
+      return 0;
+    }else if(nc->rstate.x < x){
+      if(nc->rstate.x == x - 1){
+        ret = term_emit("cuf1", tiparm(nc->cuf1), out, false);
+      }else{
+        ret = term_emit("cuf", tiparm(nc->cuf, x - nc->rstate.x), out, false);
+      }
+    }else{
+      if(nc->rstate.x == x + 1){
+        ret = term_emit("cub1", tiparm(nc->cub1), out, false);
+      }else{
+        ret = term_emit("cub", tiparm(nc->cub, nc->rstate.x - x), out, false);
+      }
+    }
+  }else{
+    if((ret = term_emit("cup", tiparm(nc->cup, y, x), out, false)) >= 0){
+      nc->rstate.y = y;
+    }
+  }
+  if(ret >= 0){
+    nc->rstate.x = x;
+  }
+  return ret;
+}
+
 // Producing the frame requires three steps:
 //  * render -- build up a flat framebuffer from a set of ncplanes
 //  * rasterize -- build up a UTF-8 stream of escapes and EGCs
@@ -852,12 +886,7 @@ notcurses_rasterize(notcurses* nc, const struct crender* rvec){
         }
       }else{
         ++nc->stats.cellemissions;
-        if(needmove == 1 && nc->cuf1){
-          ret |= term_emit("cuf1", tiparm(nc->cuf1), out, false);
-        }else if(needmove){ // FIXME might want to use cufN for horizontal move
-          ret |= term_emit("cup", tiparm(nc->cup, y, x), out, false);
-        }
-        needmove = 0;
+        ret |= stage_cursor(nc, out, y, x);
         // set the style. this can change the color back to the default; if it
         // does, we need update our elision possibilities.
         bool normalized;
@@ -962,7 +991,11 @@ fprintf(stderr, "RAST %u [%c] to %d/%d\n", srccell->gcluster, srccell->gcluster,
 }else{
 fprintf(stderr, "RAST %u [%s] to %d/%d\n", srccell->gcluster, egcpool_extended_gcluster(&nc->pool, srccell), y, x);
 }*/
-        ret |= term_putc(out, &nc->pool, srccell);
+        if(term_putc(out, &nc->pool, srccell) == 0){
+          nc->rstate.x += 1 + cell_wide_left_p(srccell);
+        }else{
+          ret = -1;
+        }
       }
       if(cell_wide_left_p(srccell)){
         ++x;
@@ -989,14 +1022,19 @@ fprintf(stderr, "RAST %u [%s] to %d/%d\n", srccell->gcluster, egcpool_extended_g
 // the screen if need be.
 static int
 home_cursor(notcurses* nc, bool flush){
+  int ret = -1;
   if(nc->home){
-    return term_emit("home", nc->home, nc->ttyfp, flush);
+    ret = term_emit("home", nc->home, nc->ttyfp, flush);
   }else if(nc->cup){
-    return term_emit("cup", tiparm(nc->cup, 1, 1), nc->ttyfp, flush);
+    ret = term_emit("cup", tiparm(nc->cup, 1, 1), nc->ttyfp, flush);
   }else if(nc->clearscr){
-    return term_emit("clear", nc->clearscr, nc->ttyfp, flush);
+    ret = term_emit("clear", nc->clearscr, nc->ttyfp, flush);
   }
-  return -1;
+  if(ret >= 0){
+    nc->rstate.x = 0;
+    nc->rstate.y = 0;
+  }
+  return ret;
 }
 
 int notcurses_refresh(notcurses* nc, int* restrict dimy, int* restrict dimx){