[text] add indent guides for blank lines

Author: tstack

src/base/string_util.cc

@@ -329,6 +329,24 @@ is_blank(const std::string& str)
         str.begin(), str.end(), [](const auto ch) { return isspace(ch); });
 }
 
+size_t
+compute_indent_size(const std::string& str)
+{
+    size_t retval = 0;
+    for (const auto& ch : str) {
+        if (ch == ' ') {
+            retval += 1;
+        } else if (ch == '\t') {
+            do {
+                retval += 1;
+            } while (retval % 8);
+        } else {
+            break;
+        }
+    }
+    return retval;
+}
+
 std::string
 scrub_ws(const char* in, ssize_t len)
 {

src/base/string_util.hh

@@ -209,6 +209,8 @@ utf8_string_length(const std::string& str)
 
 bool is_blank(const std::string& str);
 
+size_t compute_indent_size(const std::string& str);
+
 size_t abbreviate_str(char* str, size_t len, size_t max_len);
 
 size_t last_word_str(char* str, size_t len, size_t max_len);

src/plain_text_source.cc

@@ -30,6 +30,7 @@
 #include "plain_text_source.hh"
 
 #include "base/intern_string.hh"
+#include "base/string_util.hh"
 #include "base/itertools.hh"
 #include "config.h"
 #include "document.sections.hh"
@@ -175,16 +176,18 @@ plain_text_source::text_value_for_line(textview_curses& tc,
                                        text_sub_source::line_flags_t flags)
 {
     value_out = this->tds_lines[row].tl_value.get_string();
-    this->tds_line_indent_size = 0;
-    for (const auto& ch : value_out) {
-        if (ch == ' ') {
-            this->tds_line_indent_size += 1;
-        } else if (ch == '\t') {
-            do {
-                this->tds_line_indent_size += 1;
-            } while (this->tds_line_indent_size % 8);
-        } else {
-            break;
+    this->tds_line_indent_size = compute_indent_size(value_out);
+    if (this->tds_line_indent_size == 0 && value_out.empty()) {
+        for (auto next = row + 1;
+             next < (int) this->tds_lines.size();
+             ++next)
+        {
+            const auto& next_str
+                = this->tds_lines[next].tl_value.get_string();
+            this->tds_line_indent_size = compute_indent_size(next_str) + 1;
+            if (!next_str.empty()) {
+                break;
+            }
         }
     }
 

src/textfile_sub_source.cc

@@ -44,6 +44,7 @@
 #include "base/itertools.hh"
 #include "base/map_util.hh"
 #include "base/math_util.hh"
+#include "base/string_util.hh"
 #include "bound_tags.hh"
 #include "config.h"
 #include "data_scanner.hh"
@@ -186,15 +187,24 @@ textfile_sub_source::text_value_for_line(textview_curses& tc,
         if (meta.m_valid_utf && meta.m_has_ansi) {
             scrub_ansi_string(value_out, &this->tss_plain_line_attrs);
         }
-        for (const auto& ch : value_out) {
-            if (ch == ' ') {
-                this->tss_line_indent_size += 1;
-            } else if (ch == '\t') {
-                do {
-                    this->tss_line_indent_size += 1;
-                } while (this->tss_line_indent_size % 8);
-            } else {
-                break;
+        this->tss_line_indent_size = compute_indent_size(value_out);
+        if (this->tss_line_indent_size == 0 && value_out.empty()) {
+            for (auto next = line + 1;
+                 next < (ssize_t) lfo->lfo_filter_state.tfs_index.size();
+                 ++next)
+            {
+                auto next_ll
+                    = lf->begin() + lfo->lfo_filter_state.tfs_index[next];
+                auto next_result = lf->read_line(next_ll, read_opts);
+                if (next_result.isOk()) {
+                    auto next_sbr = next_result.unwrap();
+                    auto next_str = to_string(next_sbr);
+                    this->tss_line_indent_size
+                        = compute_indent_size(next_str) + 1;
+                    if (!next_str.empty()) {
+                        break;
+                    }
+                }
             }
         }
         if (lf->has_line_metadata() && this->tas_display_time_offset) {