Make sure spacers gets an NA glyph

r-lib · Jan 14, 2025 · dc2d3b7 · dc2d3b7
1 parent 2afb95d
commit dc2d3b7
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Showing 3 changed files with 10 additions and 8 deletions.
diff --git a/src/string_metrics.cpp b/src/string_metrics.cpp
@@ -1,3 +1,4 @@
+#include "R_ext/Arith.h"
 #include "cpp11/logicals.hpp"
 #include "cpp11/protect.hpp"
 #define R_NO_REMAP
@@ -211,7 +212,7 @@ list get_string_shape_c(strings string, integers id, strings path, integers inde
         int n_glyphs = shaper.glyph_id.size();
         for (int j = 0; j < n_glyphs; j++) {
           glyph.push_back((int) shaper.glyph_cluster[j] + 1);
-          glyph_id.push_back((int) shaper.glyph_id[j]);
+          glyph_id.push_back((int) (shaper.glyph_id[j] == SPACER_CHAR ? R_NaInt : shaper.glyph_id[j]));
           metric_id.push_back(pen_x.size() + 1);
           string_id.push_back(shaper.string_id[j] + 1);
           x_offset.push_back(double(shaper.x_pos[j]) / 64.0);

diff --git a/src/string_shape.cpp b/src/string_shape.cpp
@@ -59,7 +59,7 @@ bool HarfBuzzShaper::add_string(const char* string, FontSettings& font_info,
 
   if (n_chars == 0) {
     // Empty run - we treat is as a 0-width spacer to capture the font ascend and descend
-    return add_spacer(font_info, size, 0);
+    return add_spacer(font_info, size, 0, EMPTY_CHAR);
   }
 
   full_string.insert(full_string.end(), utc_string, utc_string + n_chars);
@@ -83,7 +83,7 @@ bool HarfBuzzShaper::add_string(const char* string, FontSettings& font_info,
   return true;
 }
 
-bool HarfBuzzShaper::add_spacer(FontSettings& font_info, double height, double width) {
+bool HarfBuzzShaper::add_spacer(FontSettings& font_info, double height, double width, uint32_t filler) {
   width *= 64.0 / 72.0;
   int32_t ascend = height * 64.0 * cur_res / 72.0;
   int32_t descend = 0;
@@ -110,7 +110,7 @@ bool HarfBuzzShaper::add_spacer(FontSettings& font_info, double height, double w
   //  width/x-advance giving the width
   info.font_info = font_info;
   info.embeddings.push_back({
-    {SPACER_CHAR}, // glyph_id
+    {filler}, // glyph_id
     {0}, // glyph_cluster
     {info.index}, // string_id
     {int32_t(width)}, // x_advance
@@ -191,7 +191,7 @@ bool HarfBuzzShaper::finish_string() {
             pen_x = 0;
           }
         }
-        if (iter->glyph_id[i] != SPACER_CHAR) {
+        if (iter->glyph_id[i] != EMPTY_CHAR) { // Avoid adding made up glyph info for empty text runs
           glyph_id.push_back(iter->glyph_id[i]);
           glyph_cluster.push_back(iter->glyph_cluster[i]);
           fontfile.push_back(iter->fallbacks[iter->font[i]].file);
@@ -243,7 +243,7 @@ bool HarfBuzzShaper::finish_string() {
     pen_y -= (line_ascend - previous_line_descend) * (line_width.size() == 1 ? 1 : cur_lineheight);
     for (auto iter = line.begin(); iter != line.end(); ++iter) {
       for (size_t i = 0; i < iter->glyph_id.size(); ++i) {
-        if (iter->glyph_id[i] != SPACER_CHAR) {
+        if (iter->glyph_id[i] != EMPTY_CHAR) { // Avoid adding made up glyph info for empty text runs
           y_pos.push_back(pen_y + iter->y_offset[i]);
         }
         previous_line_descend = std::min(previous_line_descend, iter->descenders[i]);

diff --git a/src/string_shape.h b/src/string_shape.h
@@ -16,7 +16,8 @@
 #include "utils.h"
 #include "cache_lru.h"
 
-static const uint32_t SPACER_CHAR = 0xffffffff; // Largest possible value. Unlikely any font would use that
+static const uint32_t EMPTY_CHAR = 0xffffffff; // Largest possible value. Unlikely any font would use that
+static const uint32_t SPACER_CHAR = 0xffffffff - 1; // Second largest possible value. Also unlikely any font would use that
 
 struct ShapeID {
   size_t string_hash;
@@ -357,7 +358,7 @@ class HarfBuzzShaper {
   bool add_string(const char* string, FontSettings& font_info,
                   double size, double tracking, bool spacer,
                   std::vector<int>& soft_wrap, std::vector<int>& hard_wrap);
-  bool add_spacer(FontSettings& font_info, double height, double width);
+  bool add_spacer(FontSettings& font_info, double height, double width, uint32_t filler = SPACER_CHAR);
   bool finish_string();
 
   void shape_text_run(ShapeInfo &text_run, bool ltr);