panel: reuse single rich str instead two alloc rich str

Reallocation rich string inside body for loop may be impractical with freeing inside, same applies to new and old rich strings, it would be more logical to use one object and reuse it to save memory

Author: GermanAizek

Panel.c

@@ -219,6 +219,12 @@ void Panel_splice(Panel* this, Vector* from) {
    this->needsRedraw = true;
 }
 
+static void RichString_reset(RichString* this) {
+   this->chlen = 0;
+   this->highlightAttr = 0;
+   RichString_setChar(this, 0, 0);
+}
+
 void Panel_draw(Panel* this, bool force_redraw, bool focus, bool highlightSelected, bool hideFunctionBar) {
    assert (this != NULL);
 
@@ -278,10 +284,11 @@ void Panel_draw(Panel* this, bool force_redraw, bool focus, bool highlightSelect
       : CRT_colors[PANEL_SELECTION_UNFOCUS];
 
    if (this->needsRedraw || force_redraw) {
+      RichString_begin(item);
       int line = 0;
       for (int i = first; line < h && i < upTo; i++) {
          const Object* itemObj = Vector_get(this->items, i);
-         RichString_begin(item);
+         RichString_reset(&item);
          Object_display(itemObj, &item);
          int itemLen = RichString_sizeVal(item);
          int amt = MINIMUM(itemLen - scrollH, this->w);
@@ -298,37 +305,39 @@ void Panel_draw(Panel* this, bool force_redraw, bool focus, bool highlightSelect
             RichString_printoffnVal(item, y + line, x, scrollH, amt);
          if (item.highlightAttr)
             attrset(CRT_colors[RESET_COLOR]);
-         RichString_delete(&item);
          line++;
       }
+      RichString_delete(&item);
       while (line < h) {
          mvhline(y + line, x, ' ', this->w);
          line++;
       }
 
    } else {
+      RichString_begin(rs);
+
       const Object* oldObj = Vector_get(this->items, this->oldSelected);
-      RichString_begin(old);
-      Object_display(oldObj, &old);
-      int oldLen = RichString_sizeVal(old);
-      const Object* newObj = Vector_get(this->items, this->selected);
-      RichString_begin(new);
-      Object_display(newObj, &new);
-      int newLen = RichString_sizeVal(new);
-      this->selectedLen = newLen;
+      Object_display(oldObj, &rs);
+      int oldLen = RichString_sizeVal(rs);
       mvhline(y + this->oldSelected - first, x + 0, ' ', this->w);
       if (scrollH < oldLen)
-         RichString_printoffnVal(old, y + this->oldSelected - first, x,
+         RichString_printoffnVal(rs, y + this->oldSelected - first, x,
             scrollH, MINIMUM(oldLen - scrollH, this->w));
+
+      const Object* newObj = Vector_get(this->items, this->selected);
+      RichString_reset(&rs);
+      Object_display(newObj, &rs);
+      int newLen = RichString_sizeVal(rs);
+      this->selectedLen = newLen;
       attrset(selectionColor);
       mvhline(y + this->selected - first, x + 0, ' ', this->w);
-      RichString_setAttr(&new, selectionColor);
+      RichString_setAttr(&rs, selectionColor);
       if (scrollH < newLen)
-         RichString_printoffnVal(new, y + this->selected - first, x,
+         RichString_printoffnVal(rs, y + this->selected - first, x,
             scrollH, MINIMUM(newLen - scrollH, this->w));
       attrset(CRT_colors[RESET_COLOR]);
-      RichString_delete(&new);
-      RichString_delete(&old);
+
+      RichString_delete(&rs);
    }
 
    if (focus && (this->needsRedraw || force_redraw || !this->wasFocus)) {