Play UI: row numbers; cell selection; hysteresis

programs/server/play.html

@@ -278,13 +278,24 @@
             display: none;
         }
 
-        /* When mouse pointer is over table cell, will display full text (with wrap) instead of cut. */
-        td.left:hover
+        /* When mouse pointer is over table cell, will display full text (with wrap) instead of cut.
+         * We also keep it for some time on mouseout for "hysteresis" effect.
+         */
+        td.left:hover, .td-hover-hysteresis
         {
             white-space: pre-wrap;
             max-width: none;
         }
 
+        .td-selected
+        {
+            white-space: pre-wrap;
+            max-width: none;
+            background-color: var(--table-hover-color);
+            border: 2px solid var(--border-color);
+            display: block;
+        }
+
         td.transposed
         {
             max-width: none;
@@ -298,6 +309,13 @@
             vertical-align: middle;
         }
 
+        .row-number
+        {
+            text-align: right;
+            background-color: var(--table-header-color);
+            color: var(--misc-text-color);
+        }
+
         div.empty-result
         {
             opacity: 10%;
@@ -793,7 +811,17 @@
             return;
         }
 
+        const should_display_row_numbers = response.data.length > 3;
+
         let thead = document.createElement('thead');
+
+        if (should_display_row_numbers) {
+            let th = document.createElement('th');
+            th.className = 'row-number';
+            th.appendChild(document.createTextNode('№'));
+            thead.appendChild(th);
+        }
+
         for (let idx in response.meta) {
             let th = document.createElement('th');
             const name = document.createTextNode(response.meta[idx].name);
@@ -803,7 +831,9 @@
 
         /// To prevent hanging the browser, limit the number of cells in a table.
         /// It's important to have the limit on number of cells, not just rows, because tables may be wide or narrow.
+        /// Also we permit rendering of more records but only if elapsed time is not large.
         const max_rows = 10000 / response.meta.length;
+        const max_render_ms = 200;
         let row_num = 0;
 
         const column_is_number = response.meta.map(elem => !!elem.type.match(/^(Nullable\()?(U?Int|Decimal|Float)/));
@@ -819,18 +849,41 @@
             column_need_render_bars: column_need_render_bars,
         };
 
+        const start_time = performance.now();
+
+        function tdMouseEnter(e) {
+            let elem = e.target;
+            elem.classList.add('td-hover-hysteresis');
+            elem.onmouseleave = _ => {
+                setTimeout(() => { elem && elem.classList.remove('td-hover-hysteresis') }, 1000);
+            }
+        }
+
+        function tdClick(e) {
+            let elem = e.target;
+            elem.classList.add('td-selected');
+        }
+
         let tbody = document.createElement('tbody');
         for (let row_idx in response.data) {
             let tr = document.createElement('tr');
+            if (should_display_row_numbers) {
+                let td = document.createElement('td');
+                td.className = 'row-number';
+                td.appendChild(document.createTextNode(1 + +row_idx));
+                tr.appendChild(td);
+            }
             for (let col_idx in response.data[row_idx]) {
                 let cell = response.data[row_idx][col_idx];
                 const td = renderCell(cell, col_idx, settings);
+                td.onmouseenter = tdMouseEnter;
+                td.onclick = tdClick;
                 tr.appendChild(td);
             }
             tbody.appendChild(tr);
 
             ++row_num;
-            if (row_num >= max_rows) {
+            if (row_num >= max_rows && performance.now() - start_time >= max_render_ms) {
                 break;
             }
         }