SymbolPane: improve tooltips for C tags (#1636)

* Override add_tooltip(s) for CtagsSymbolOutline

* Look on previous line for method type

---------

Co-authored-by: Ryan Kornheisl <[email protected]>

Author: jeremypw

src/SymbolPane/C/CtagsSymbolOutline.vala

@@ -275,10 +275,42 @@ public class Scratch.Services.CtagsSymbolOutline : Scratch.Services.SymbolOutlin
             destroy_root (root);
             root = new_root;
 
+            add_tooltips (store.root);
             return false;
         });
     }
 
+    protected override void add_tooltips (Code.Widgets.SourceList.ExpandableItem root) {
+        foreach (var parent in root.children) {
+            if (parent is Code.Widgets.SourceList.ExpandableItem) {
+                add_tooltip ((Code.Widgets.SourceList.ExpandableItem) parent);
+            }
+        }
+    }
+
+    private void add_tooltip (Code.Widgets.SourceList.ExpandableItem parent) {
+        if (parent is CtagsSymbol) {
+            var item = ((CtagsSymbol)parent);
+            var start = item.line;
+            var end = item.line;
+            // The type of a method is often on the previous line
+            if (item.symbol_type == SymbolType.METHOD) {
+                start = start > 0 ? start - 1 : start;
+            }
+
+            item.tooltip = Markup.escape_text ("%s".printf (
+                doc.get_slice (
+                    start,
+                    0,
+                    end,
+                    0
+                )
+            ));
+        }
+
+        add_tooltips (parent);
+    }
+
     private void destroy_root (Code.Widgets.SourceList.ExpandableItem to_destroy) {
         var children = iterate_children (to_destroy);
         to_destroy.clear ();