[db] avoid reusing the same chart colors

This just covers the basic case and doesn't address reuse
with JSON values.

Related to #1047

src/base/string_attr_type.hh

@@ -143,6 +143,13 @@ struct text_attrs {
         };
     }
 
+    bool operator==(const text_attrs& other) const
+    {
+        return this->ta_attrs == other.ta_attrs &&
+            this->ta_fg_color == other.ta_fg_color &&
+            this->ta_bg_color == other.ta_bg_color;
+    }
+
     int32_t ta_attrs{0};
     nonstd::optional<short> ta_fg_color;
     nonstd::optional<short> ta_bg_color;

src/command_executor.cc

@@ -925,8 +925,17 @@ sql_callback(exec_context& ec, sqlite3_stmt* stmt)
 
             dls.push_header(colname, type, graphable);
             if (graphable) {
-                auto attrs = vc.attrs_for_ident(colname);
+                auto name_for_ident_attrs = colname;
+                auto attrs = vc.attrs_for_ident(name_for_ident_attrs);
+                for (size_t attempt = 0;
+                     chart.attrs_in_use(attrs) && attempt < 3;
+                     attempt++)
+                {
+                    name_for_ident_attrs += " ";
+                    attrs = vc.attrs_for_ident(name_for_ident_attrs);
+                }
                 chart.with_attrs_for_ident(colname, attrs);
+                dls.dls_headers.back().hm_title_attrs = attrs;
             }
         }
         set_vars = true;

src/db_sub_source.cc

@@ -293,9 +293,9 @@ db_overlay_source::list_overlay_count(const listview_curses& lv)
         return retval;
     }
 
-    view_colors& vc = view_colors::singleton();
-    vis_line_t top = lv.get_top();
-    const std::vector<const char*>& cols = this->dos_labels->dls_rows[top];
+    auto& vc = view_colors::singleton();
+    auto top = lv.get_top();
+    const auto& cols = this->dos_labels->dls_rows[top];
     unsigned long width;
     vis_line_t height;
 
@@ -404,8 +404,6 @@ db_overlay_source::list_value_for_overlay(const listview_curses& lv,
                                           vis_line_t row,
                                           attr_line_t& value_out)
 {
-    view_colors& vc = view_colors::singleton();
-
     if (y == 0) {
         this->list_overlay_count(lv);
         std::string& line = value_out.get_string();
@@ -436,7 +434,7 @@ db_overlay_source::list_value_for_overlay(const listview_curses& lv,
 
             text_attrs attrs;
             if (this->dos_labels->dls_headers[lpc].hm_graphable) {
-                attrs = vc.attrs_for_ident(dls->dls_headers[lpc].hm_name)
+                attrs = dls->dls_headers[lpc].hm_title_attrs
                     | text_attrs{A_REVERSE};
             } else {
                 attrs.ta_attrs = A_UNDERLINE;

src/db_sub_source.hh

@@ -111,6 +111,7 @@ public:
         unsigned int hm_sub_type{0};
         bool hm_graphable{false};
         size_t hm_column_size{0};
+        text_attrs hm_title_attrs;
     };
 
     stacked_bar_chart<std::string> dls_chart;

src/hist_source.hh

@@ -53,10 +53,8 @@ STRONG_INT_TYPE(int, bucket_type);
 struct stacked_bar_chart_base {
     virtual ~stacked_bar_chart_base() = default;
 
-    struct show_none {
-    };
-    struct show_all {
-    };
+    struct show_none {};
+    struct show_all {};
     struct show_one {
         size_t so_index;
 
@@ -94,6 +92,15 @@ public:
         return *this;
     }
 
+    bool attrs_in_use(const text_attrs& attrs) const {
+        for (const auto& ident : this->sbc_idents) {
+            if (ident.ci_attrs == attrs) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     show_state show_next_ident(direction dir)
     {
         bool single_ident = this->sbc_idents.size() == 1;
@@ -322,29 +329,17 @@ public:
         HT__MAX
     } hist_type_t;
 
-    hist_source2()
-    {
-        this->clear();
-    }
+    hist_source2() { this->clear(); }
 
     ~hist_source2() override = default;
 
     void init();
 
-    void set_time_slice(int64_t slice)
-    {
-        this->hs_time_slice = slice;
-    }
+    void set_time_slice(int64_t slice) { this->hs_time_slice = slice; }
 
-    int64_t get_time_slice() const
-    {
-        return this->hs_time_slice;
-    }
+    int64_t get_time_slice() const { return this->hs_time_slice; }
 
-    size_t text_line_count() override
-    {
-        return this->hs_line_count;
-    }
+    size_t text_line_count() override { return this->hs_line_count; }
 
     size_t text_line_width(textview_curses& curses) override
     {