[LLDB][GUI] Add Platform Plugin Field

[OmarEmaraDev]

Summary

This patch adds a new Platform Plugin Field. It is a choices field that
lists all the available platform plugins and can retrieve the name of the
selected plugin. The default selected plugin is the currently selected
one. This patch also allows for arbitrary scrolling to make scrolling
easier when setting choices.

[clayborg]

Actually this doesn't apply cleanly to top of tree right now. Can you resolve the conflicts and update the patch? Two other of your patches recently have been committed.

[OmarEmaraDev]

• Rebase on main and fix conflicts.

lldb/source/Core/IOHandlerCursesGUI.cpp

for (int i = 0; i < choices_to_draw; i++) {
       surface.PutChar(current_choice == m_choice ? ACS_DIAMOND : ' ');
       surface.PutCString(text);
       if (highlight)
         surface.AttributeOff(A_REVERSE);
     }
   }
 
   void FieldDelegateDraw(SubPad &surface, bool is_selected) override {
+    UpdateScrolling();
+
     surface.TitledBox(m_label.c_str());
 
     Rect content_bounds = surface.GetFrame();
     content_bounds.Inset(1, 1);
     SubPad content_surface = SubPad(surface, content_bounds);
 
     DrawContent(content_surface, is_selected);
   }
 
   void SelectPrevious() {
     if (m_choice > 0)
       m_choice--;
   }
 
   void SelectNext() {
     if (m_choice < GetNumberOfChoices() - 1)
       m_choice++;
   }
 
-  // If the cursor moved past the first visible choice, scroll up by one
-  // choice.
-  void ScrollUpIfNeeded() {
-    if (m_choice < m_first_visibile_choice)
-      m_first_visibile_choice--;
+  void UpdateScrolling() {
+    if (m_choice > GetLastVisibleChoice()) {
+      m_first_visibile_choice = m_choice - (m_number_of_visible_choices - 1);
+      return;
     }
 
-  // If the cursor moved past the last visible choice, scroll down by one
-  // choice.
-  void ScrollDownIfNeeded() {
-    if (m_choice > GetLastVisibleChoice())
-      m_first_visibile_choice++;
+    if (m_choice < m_first_visibile_choice)
+      m_first_visibile_choice = m_choice;
   }
 
   HandleCharResult FieldDelegateHandleChar(int key) override {
     switch (key) {
     case KEY_UP:
       SelectPrevious();
-      ScrollUpIfNeeded();
       return eKeyHandled;
     case KEY_DOWN:
       SelectNext();
-      ScrollDownIfNeeded();
       return eKeyHandled;
     default:
       break;
     }
     return eKeyNotHandled;
   }
 
   // Returns the content of the choice as a string.
   std::string GetChoiceContent() { return m_choices[m_choice]; }
 
   // Returns the index of the choice.
   int GetChoice() { return m_choice; }
 
+  void SetChoice(const std::string &choice) {
+    for (int i = 0; i < GetNumberOfChoices(); i++) {
+      if (choice == m_choices[i]) {
+        m_choice = i;
+        return;
+      }
+    }
+  }
+
 protected:
   std::string m_label;
   int m_number_of_visible_choices;
   std::vector<std::string> m_choices;
   // The index of the selected choice.
   int m_choice;
   // The index of the first visible choice in the field.
   int m_first_visibile_choice;
 };
 
+class PlatformPluginFieldDelegate : public ChoicesFieldDelegate {
+public:
+  PlatformPluginFieldDelegate(Debugger &debugger)
+      : ChoicesFieldDelegate("Platform Plugin", 3, GetPossiblePluginNames()) {
+    PlatformSP platform_sp = debugger.GetPlatformList().GetSelectedPlatform();
+    if (platform_sp)
+      SetChoice(platform_sp->GetName().AsCString());
+  }
+
+  std::vector<std::string> GetPossiblePluginNames() {
+    std::vector<std::string> names;
+    size_t i = 0;
+    while (auto name = PluginManager::GetPlatformPluginNameAtIndex(i++))
+      names.push_back(name);
+    return names;
+  }
+
+  std::string GetPluginName() {
+    std::string plugin_name = GetChoiceContent();
+    return plugin_name;
+  }
+};
+
 class ProcessPluginFieldDelegate : public ChoicesFieldDelegate {
 public:
   ProcessPluginFieldDelegate()
       : ChoicesFieldDelegate("Process Plugin", 3, GetPossiblePluginNames()) {}
 
   std::vector<std::string> GetPossiblePluginNames() {
     std::vector<std::string> names;
     names.push_back("<default>");
public:
   ChoicesFieldDelegate *AddChoicesField(const char *label, int height,
                                         std::vector<std::string> choices) {
     ChoicesFieldDelegate *delegate =
         new ChoicesFieldDelegate(label, height, choices);
     m_fields.push_back(FieldDelegateUP(delegate));
     return delegate;
   }
 
+  PlatformPluginFieldDelegate *AddPlatformPluginField(Debugger &debugger) {
+    PlatformPluginFieldDelegate *delegate =
+        new PlatformPluginFieldDelegate(debugger);
+    m_fields.push_back(FieldDelegateUP(delegate));
+    return delegate;
+  }
+
   ProcessPluginFieldDelegate *AddProcessPluginField() {
     ProcessPluginFieldDelegate *delegate = new ProcessPluginFieldDelegate();
     m_fields.push_back(FieldDelegateUP(delegate));
     return delegate;
   }
 
   template <class T>
   ListFieldDelegate<T> *AddListField(const char *label, T default_field) {