[cmds] add sticky headers

Related to #1385

Author: tstack

NEWS.md

@@ -54,6 +54,14 @@ Features:
   definitions.  Fields with this kind will be parsed
   and displayed in the local timezone, and SQL
   queries will return them in a normalized format.
+* Added the `:toggle-sticky-header` command to pin a
+  line to the top of the view as a sticky header.
+  Sticky headers remain visible as you scroll past
+  them, making it easy to keep context lines in view.
+  The `:clear-all-sticky-headers` command removes all
+  sticky headers in the current view.  A hidden
+  `log_sticky_mark` column is available in log tables
+  to get/set the sticky state via SQL.
 * Introducing "Log-Oriented Debugging", a collection of
   features to streamline mapping log messages back to
   the source code that generated them.  For example,

src/cmds.bookmarks.cc

@@ -53,6 +53,65 @@ com_mark(exec_context& ec, std::string cmdline, std::vector<std::string>& args)
     return Ok(retval);
 }
 
+static Result<std::string, lnav::console::user_message>
+com_sticky_header(exec_context& ec,
+                  std::string cmdline,
+                  std::vector<std::string>& args)
+{
+    std::string retval;
+
+    if (lnav_data.ld_view_stack.empty()) {
+    } else if (!ec.ec_dry_run) {
+        auto* tc = *lnav_data.ld_view_stack.top();
+        auto sel = tc->get_selection();
+        if (sel) {
+            auto result = tc->toggle_user_mark(
+                &textview_curses::BM_STICKY, sel.value());
+            tc->set_needs_update();
+
+            if (result.mtr_marked > 0) {
+                retval = fmt::format(
+                    FMT_STRING("info: line {} pinned as a sticky header"),
+                    (int) sel.value());
+            } else {
+                retval = fmt::format(
+                    FMT_STRING("info: line {} unpinned from sticky headers"),
+                    (int) sel.value());
+            }
+        }
+    }
+
+    return Ok(retval);
+}
+
+static Result<std::string, lnav::console::user_message>
+com_clear_sticky_headers(exec_context& ec,
+                         std::string cmdline,
+                         std::vector<std::string>& args)
+{
+    std::string retval;
+
+    if (lnav_data.ld_view_stack.empty()) {
+    } else if (!ec.ec_dry_run) {
+        auto* tc = *lnav_data.ld_view_stack.top();
+        auto& bv = tc->get_bookmarks()[&textview_curses::BM_STICKY];
+        auto count = bv.size();
+        // Copy to avoid modifying while iterating
+        std::vector<vis_line_t> sticky_lines;
+        for (const auto& row : bv.bv_tree) {
+            sticky_lines.push_back(row);
+        }
+        for (const auto& row : sticky_lines) {
+            tc->toggle_user_mark(&textview_curses::BM_STICKY, row);
+        }
+        tc->set_needs_update();
+        retval = fmt::format(
+            FMT_STRING("info: cleared {} sticky header(s)"), count);
+    }
+
+    return Ok(retval);
+}
+
 static Result<std::string, lnav::console::user_message>
 com_goto_mark(exec_context& ec,
               std::string cmdline,
@@ -65,6 +124,7 @@ com_goto_mark(exec_context& ec,
         &textview_curses::BM_USER_EXPR,
         &textview_curses::BM_META,
         &textview_curses::BM_PARTITION,
+        &textview_curses::BM_STICKY,
     };
 
     auto* tc = get_textview_for_mode(lnav_data.ld_mode);
@@ -204,6 +264,26 @@ init_lnav_bookmark_commands(readline_context::command_map_t& cmd_map)
                 .with_example({"To go to the previous error", "error"})
                 .with_tags({"bookmarks", "navigation"}),
         },
+
+        {
+            "toggle-sticky-header",
+            com_sticky_header,
+
+            help_text(":toggle-sticky-header")
+                .with_summary(
+                    "Toggle the sticky header state for the focused line "
+                    "in the current view")
+                .with_tags({"bookmarks", "display"}),
+        },
+        {
+            "clear-all-sticky-headers",
+            com_clear_sticky_headers,
+
+            help_text(":clear-all-sticky-headers")
+                .with_summary(
+                    "Clear all sticky header bookmarks in the current view")
+                .with_tags({"bookmarks", "display"}),
+        },
     };
 
     for (auto& cmd : BOOKMARK_COMMANDS) {

src/field_overlay_source.cc

@@ -938,6 +938,36 @@ field_overlay_source::list_static_overlay(const listview_curses& lv,
 {
     auto& exec_phase = injector::get<lnav::exec_phase&>();
     if (media != media_t::display) {
+        auto& tc = dynamic_cast<textview_curses&>(
+            const_cast<listview_curses&>(lv));
+        const auto& sticky_bv
+            = tc.get_bookmarks()[&textview_curses::BM_STICKY];
+        if (!sticky_bv.empty()) {
+            auto top = lv.get_top();
+            int sticky_index = 0;
+            for (auto iter = sticky_bv.bv_tree.begin();
+                 iter != sticky_bv.bv_tree.end();
+                 ++iter)
+            {
+                if (*iter >= top) {
+                    break;
+                }
+                if (y == sticky_index) {
+                    tc.textview_value_for_row(*iter, value_out);
+                    value_out.with_attr_for_all(
+                        VC_ROLE.value(role_t::VCR_STATUS));
+                    auto next_iter = std::next(iter);
+                    if (next_iter == sticky_bv.bv_tree.end()
+                        || *next_iter >= top)
+                    {
+                        value_out.with_attr_for_all(
+                            VC_STYLE.value(text_attrs::with_underline()));
+                    }
+                    return true;
+                }
+                sticky_index++;
+            }
+        }
         return false;
     }
 
@@ -1043,7 +1073,12 @@ field_overlay_source::list_static_overlay(const listview_curses& lv,
         auto top = lv.get_top();
         if (top < vis_line_t(this->fos_lss.text_line_count())) {
             auto cl = this->fos_lss.at(top);
-            if (!this->fos_header_line || this->fos_header_line.value() != cl
+            auto& tc = dynamic_cast<textview_curses&>(
+                const_cast<listview_curses&>(lv));
+            auto has_sticky
+                = !tc.get_bookmarks()[&textview_curses::BM_STICKY].empty();
+            if (has_sticky || !this->fos_header_line
+                || this->fos_header_line.value() != cl
                 || !this->fos_header_line_context
                 || this->fos_header_line_context.value()
                     != this->fos_lss.get_line_context()
@@ -1067,6 +1102,19 @@ field_overlay_source::list_static_overlay(const listview_curses& lv,
                         header_top -= 1_vl;
                     }
                     this->fos_static_lines.clear();
+
+                    // Add sticky header lines that are above the viewport
+                    const auto& sticky_bv
+                        = tc.get_bookmarks()[&textview_curses::BM_STICKY];
+                    for (const auto& sticky_vl : sticky_bv.bv_tree) {
+                        if (sticky_vl >= top) {
+                            break;
+                        }
+                        auto al = attr_line_t();
+                        tc.textview_value_for_row(sticky_vl, al);
+                        this->fos_static_lines.emplace_back(al);
+                    }
+
                     if (header_top < 0_vl) {
                         auto al = attr_line_t();
                         auto filtered_before
@@ -1084,17 +1132,12 @@ field_overlay_source::list_static_overlay(const listview_curses& lv,
                         al.with_attr_for_all(
                             VC_STYLE.value(text_attrs::with_italic()));
                         this->fos_static_lines.emplace_back(al);
-                        apply_status_attrs(this->fos_static_lines);
                     } else {
-                        this->fos_static_lines.resize(1);
-                        auto& al = this->fos_static_lines.front();
-                        auto& tc = dynamic_cast<textview_curses&>(
-                            const_cast<listview_curses&>(lv));
+                        auto al = attr_line_t();
                         tc.textview_value_for_row(header_top, al);
-                        if ((top - header_top) > 1 && line->is_continued()) {
-                            apply_status_attrs(this->fos_static_lines);
-                        }
+                        this->fos_static_lines.emplace_back(al);
                     }
+                    apply_status_attrs(this->fos_static_lines);
                     this->fos_header_line = cl;
                     this->fos_header_line_context
                         = this->fos_lss.get_line_context();