nontrivial stacking unit test #1068

NEWS.md

@@ -1,6 +1,11 @@
 This document attempts to list user-visible changes and any major internal
 rearrangements of Notcurses.
 
+* 2.1.5 (not yet released):
+  * `ncplane_putstr_yx()`, `ncplane_putstr_stained()`, and
+    `ncplane_putnstr_yx()` now return the number of columns output, as
+    long documented (they were mistakenly returning the number of bytes).
+
 * 2.1.4 (2021-01-03):
   * Direct mode now supports `NCDIRECT_OPTION_NO_QUIT_SIGHANDLERS`, and by
     default installs signal handlers similar to those of fullscreen mode.

USAGE.md

@@ -996,7 +996,7 @@ int ncplane_putchar_stained(struct ncplane* n, char c);
 
 // Replace the nccell at the specified coordinates with the provided wide char
 // 'w'. Advance the cursor by the character's width as reported by wcwidth().
-// On success, returns 1. On failure, returns -1.
+// On success, returns the number of columns written. On failure, returns -1.
 static inline int
 ncplane_putwc_yx(struct ncplane* n, int y, int x, wchar_t w){
   wchar_t warr[2] = { w, L'\0' };

include/notcurses/notcurses.h

@@ -1606,7 +1606,7 @@ ncplane_putwstr(struct ncplane* n, const wchar_t* gclustarr){
 
 // Replace the cell at the specified coordinates with the provided wide char
 // 'w'. Advance the cursor by the character's width as reported by wcwidth().
-// On success, returns 1. On failure, returns -1.
+// On success, returns the number of columns written. On failure, returns -1.
 static inline int
 ncplane_putwc_yx(struct ncplane* n, int y, int x, wchar_t w){
   wchar_t warr[2] = { w, L'\0' };

tests/stacking.cpp

@@ -0,0 +1,53 @@
+#include "main.h"
+
+// These tests address cases where box characters on two overlapping planes
+// interact in non-trivial ways. A simple example is a U2580 UPPER HALF BLOCK
+// (▀) with a white foreground and transparent background, above a U2584 LOWER
+// HALF BLOCK (▄) with a white foreground and transparent background. One might
+// expect the result to be an entirely white cell, but by typical Notcurses
+// rendering rules, we would instead get a white upper half and transparent
+// lower half:
+//
+// - after first cell, glyph is locked U2584, fg is locked white, bg transparent
+// - second cell can't override glyph nor fg, and background remains transparent
+//
+// we will instead special-case block-drawing characters.
+// see https://github.com/dankamongmen/notcurses/issues/1068
+TEST_CASE("Stacking") {
+  auto nc_ = testing_notcurses();
+  if(!nc_){
+    return;
+  }
+  if(!notcurses_canutf8(nc_)){
+    CHECK(0 == notcurses_stop(nc_));
+    return;
+  }
+  int dimy, dimx;
+  struct ncplane* n_ = notcurses_stddim_yx(nc_, &dimy, &dimx);
+  REQUIRE(nullptr != n_);
+
+
+  SUBCASE("UpperAtopLowerWhite") {
+    struct ncplane_options opts = {
+      0, 0, 1, 1, nullptr, "top", nullptr, 0,
+    };
+    auto top = ncplane_create(n_, &opts);
+    REQUIRE(nullptr != top);
+    CHECK(0 == ncplane_set_fg_rgb(top, 0xffffff));
+    CHECK(0 == ncplane_set_fg_rgb(n_, 0xffffff));
+    CHECK(1 == ncplane_putwc(top, L'\u2580'));
+    CHECK(1 == ncplane_putwc(n_, L'\u2584'));
+    CHECK(0 == notcurses_render(nc_));
+    uint64_t channels;
+    auto egc = notcurses_at_yx(nc_, 0, 0, nullptr, &channels);
+    REQUIRE(nullptr != egc);
+    // ought yield space with white background
+    WARN(0 == strcmp(" ", egc));
+    WARN(0xffffff == channels_fg_rgb(channels));
+    WARN(0xffffff == channels_bg_rgb(channels));
+    ncplane_destroy(top);
+  }
+
+  // common teardown
+  CHECK(0 == notcurses_stop(nc_));
+}