[terminfo] only interrogate for sixel when pixel geometry is defined #1511 #1506

src/lib/debug.c

@@ -20,7 +20,7 @@ tinfo_debug_caps(const tinfo* ti, FILE* debugfp, int rows, int cols,
           indent, capyn(ti->sgr), capyn(ti->sgr0));
   fprintf(debugfp, "%sop: %c fgop: %c bgop: %c\n",
           indent, capyn(ti->op), capyn(ti->fgop), capyn(ti->bgop));
-  fprintf(debugfp, "%srows: %u cols: %u rpix: %u cpix: %u (%dx%d)\n",
+  fprintf(debugfp, "%srows: %u cols: %u rpx: %u cpx: %u (%dx%d)\n",
           indent, rows, cols, ti->cellpixy, ti->cellpixx, rows * ti->cellpixy, cols * ti->cellpixx);
   if(!ti->pixel_query_done){
     fprintf(debugfp, "%sno bitmap graphics information yet\n", indent);

src/lib/terminfo.c

@@ -372,6 +372,9 @@ query_sixel(tinfo* ti, int fd){
 }
 
 // fd must be a real terminal. uses the query lock of |ti| to only act once.
+// we ought already have performed a TIOCGWINSZ ioctl() to verify that the
+// terminal reports cell area in pixels, as that's necessary for our use of
+// sixel (or any other bitmap protocol).
 int query_term(tinfo* ti, int fd){
   if(fd < 0){
     return -1;
@@ -383,16 +386,22 @@ int query_term(tinfo* ti, int fd){
   int ret = 0;
   pthread_mutex_lock(&ti->pixel_query);
   if(!ti->pixel_query_done){
-    if(flags & O_NONBLOCK){
-      fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);
-    }
-    ret = query_sixel(ti, fd);
-    ti->pixel_query_done = true;
-    if(ti->sixel_supported){
-      ti->pixel_init(fd);
-    }
-    if(flags & O_NONBLOCK){
-      fcntl(fd, F_SETFL, flags);
+    // if the terminal reported 0 pixels for cell dimensions, bypass any
+    // interrogation, and assume no bitmap support.
+    if(!ti->cellpixx || !ti->cellpixy){
+      ti->pixel_query_done = true;
+    }else{
+      if(flags & O_NONBLOCK){
+        fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);
+      }
+      ret = query_sixel(ti, fd);
+      ti->pixel_query_done = true;
+      if(ti->sixel_supported){
+        ti->pixel_init(fd);
+      }
+      if(flags & O_NONBLOCK){
+        fcntl(fd, F_SETFL, flags);
+      }
     }
   }
   pthread_mutex_unlock(&ti->pixel_query);