[LLDB][GUI] Refactor form drawing using subsurfaces

This patch adds a new method SubSurface to the Surface class. The method
returns another surface that is a subset of this surface. This is
important to further abstract away drawing from the ncurses objects. For
instance, fields could previously be drawn on subpads only but can now
be drawn on any surface. This is needed to create the file search
dialogs and similar functionalities.

There is an opportunity to refactor window drawing in general using
surfaces, but we shall consider this separately later.

Reviewed By: clayborg

Differential Revision: https://reviews.llvm.org/D107182

Author: OmarEmaraDev

lldb/source/Core/IOHandlerCursesGUI.cpp

@@ -352,6 +352,19 @@ class Surface {
 
   operator WINDOW *() { return m_window; }
 
+  Surface SubSurface(Rect bounds) {
+    Surface subSurface;
+    if (is_pad(m_window))
+      subSurface.m_window =
+          ::subpad(m_window, bounds.size.height, bounds.size.width,
+                   bounds.origin.y, bounds.origin.x);
+    else
+      subSurface.m_window =
+          ::derwin(m_window, bounds.size.height, bounds.size.width,
+                   bounds.origin.y, bounds.origin.x);
+    return subSurface;
+  }
+
   // Copy a region of the surface to another surface.
   void CopyToSurface(Surface &target, Point source_origin, Point target_origin,
                      Size size) {
@@ -1025,7 +1038,7 @@ class FieldDelegate {
   // Draw the field in the given subpad surface. The surface have a height that
   // is equal to the height returned by FieldDelegateGetHeight(). If the field
   // is selected in the form window, then is_selected will be true.
-  virtual void FieldDelegateDraw(SubPad &surface, bool is_selected) = 0;
+  virtual void FieldDelegateDraw(Surface &surface, bool is_selected) = 0;
 
   // Handle the key that wasn't handled by the form window or a container field.
   virtual HandleCharResult FieldDelegateHandleChar(int key) {
@@ -1112,7 +1125,7 @@ class TextFieldDelegate : public FieldDelegate {
 
   int GetContentLength() { return m_content.length(); }
 
-  void DrawContent(SubPad &surface, bool is_selected) {
+  void DrawContent(Surface &surface, bool is_selected) {
     surface.MoveCursor(0, 0);
     const char *text = m_content.c_str() + m_first_visibile_char;
     surface.PutCString(text, surface.GetWidth());
@@ -1131,17 +1144,17 @@ class TextFieldDelegate : public FieldDelegate {
       surface.AttributeOff(A_REVERSE);
   }
 
-  void DrawField(SubPad &surface, bool is_selected) {
+  void DrawField(Surface &surface, bool is_selected) {
     surface.TitledBox(m_label.c_str());
 
     Rect content_bounds = surface.GetFrame();
     content_bounds.Inset(1, 1);
-    SubPad content_surface = SubPad(surface, content_bounds);
+    Surface content_surface = surface.SubSurface(content_bounds);
 
     DrawContent(content_surface, is_selected);
   }
 
-  void DrawError(SubPad &surface) {
+  void DrawError(Surface &surface) {
     if (!FieldDelegateHasError())
       return;
     surface.MoveCursor(0, 0);
@@ -1152,12 +1165,12 @@ class TextFieldDelegate : public FieldDelegate {
     surface.AttributeOff(COLOR_PAIR(RedOnBlack));
   }
 
-  void FieldDelegateDraw(SubPad &surface, bool is_selected) override {
+  void FieldDelegateDraw(Surface &surface, bool is_selected) override {
     Rect frame = surface.GetFrame();
     Rect field_bounds, error_bounds;
     frame.HorizontalSplit(GetFieldHeight(), field_bounds, error_bounds);
-    SubPad field_surface = SubPad(surface, field_bounds);
-    SubPad error_surface = SubPad(surface, error_bounds);
+    Surface field_surface = surface.SubSurface(field_bounds);
+    Surface error_surface = surface.SubSurface(error_bounds);
 
     DrawField(field_surface, is_selected);
     DrawError(error_surface);
@@ -1406,7 +1419,7 @@ class BooleanFieldDelegate : public FieldDelegate {
   // Boolean fields are have a single line.
   int FieldDelegateGetHeight() override { return 1; }
 
-  void FieldDelegateDraw(SubPad &surface, bool is_selected) override {
+  void FieldDelegateDraw(Surface &surface, bool is_selected) override {
     surface.MoveCursor(0, 0);
     surface.PutChar('[');
     if (is_selected)
@@ -1486,7 +1499,7 @@ class ChoicesFieldDelegate : public FieldDelegate {
     return std::min(index, GetNumberOfChoices()) - 1;
   }
 
-  void DrawContent(SubPad &surface, bool is_selected) {
+  void DrawContent(Surface &surface, bool is_selected) {
     int choices_to_draw = GetLastVisibleChoice() - m_first_visibile_choice + 1;
     for (int i = 0; i < choices_to_draw; i++) {
       surface.MoveCursor(0, i);
@@ -1502,14 +1515,14 @@ class ChoicesFieldDelegate : public FieldDelegate {
     }
   }
 
-  void FieldDelegateDraw(SubPad &surface, bool is_selected) override {
+  void FieldDelegateDraw(Surface &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);
+    Surface content_surface = surface.SubSurface(content_bounds);
 
     DrawContent(content_surface, is_selected);
   }
@@ -1684,7 +1697,7 @@ template <class T> class ListFieldDelegate : public FieldDelegate {
     return context;
   }
 
-  void DrawRemoveButton(SubPad &surface, int highlight) {
+  void DrawRemoveButton(Surface &surface, int highlight) {
     surface.MoveCursor(1, surface.GetHeight() / 2);
     if (highlight)
       surface.AttributeOn(A_REVERSE);
@@ -1693,7 +1706,7 @@ template <class T> class ListFieldDelegate : public FieldDelegate {
       surface.AttributeOff(A_REVERSE);
   }
 
-  void DrawFields(SubPad &surface, bool is_selected) {
+  void DrawFields(Surface &surface, bool is_selected) {
     int line = 0;
     int width = surface.GetWidth();
     for (int i = 0; i < GetNumberOfFields(); i++) {
@@ -1702,8 +1715,8 @@ template <class T> class ListFieldDelegate : public FieldDelegate {
       Rect field_bounds, remove_button_bounds;
       bounds.VerticalSplit(bounds.size.width - sizeof(" [Remove]"),
                            field_bounds, remove_button_bounds);
-      SubPad field_surface = SubPad(surface, field_bounds);
-      SubPad remove_button_surface = SubPad(surface, remove_button_bounds);
+      Surface field_surface = surface.SubSurface(field_bounds);
+      Surface remove_button_surface = surface.SubSurface(remove_button_bounds);
 
       bool is_element_selected = m_selection_index == i && is_selected;
       bool is_field_selected =
@@ -1718,7 +1731,7 @@ template <class T> class ListFieldDelegate : public FieldDelegate {
     }
   }
 
-  void DrawNewButton(SubPad &surface, bool is_selected) {
+  void DrawNewButton(Surface &surface, bool is_selected) {
     const char *button_text = "[New]";
     int x = (surface.GetWidth() - sizeof(button_text) - 1) / 2;
     surface.MoveCursor(x, 0);
@@ -1731,16 +1744,16 @@ template <class T> class ListFieldDelegate : public FieldDelegate {
       surface.AttributeOff(A_REVERSE);
   }
 
-  void FieldDelegateDraw(SubPad &surface, bool is_selected) override {
+  void FieldDelegateDraw(Surface &surface, bool is_selected) override {
     surface.TitledBox(m_label.c_str());
 
     Rect content_bounds = surface.GetFrame();
     content_bounds.Inset(1, 1);
     Rect fields_bounds, new_button_bounds;
     content_bounds.HorizontalSplit(content_bounds.size.height - 1,
                                    fields_bounds, new_button_bounds);
-    SubPad fields_surface = SubPad(surface, fields_bounds);
-    SubPad new_button_surface = SubPad(surface, new_button_bounds);
+    Surface fields_surface = surface.SubSurface(fields_bounds);
+    Surface new_button_surface = surface.SubSurface(new_button_bounds);
 
     DrawFields(fields_surface, is_selected);
     DrawNewButton(new_button_surface, is_selected);
@@ -1936,12 +1949,12 @@ class MappingFieldDelegate : public FieldDelegate {
                     m_value_field.FieldDelegateGetHeight());
   }
 
-  void DrawArrow(SubPad &surface) {
+  void DrawArrow(Surface &surface) {
     surface.MoveCursor(0, 1);
     surface.PutChar(ACS_RARROW);
   }
 
-  void FieldDelegateDraw(SubPad &surface, bool is_selected) override {
+  void FieldDelegateDraw(Surface &surface, bool is_selected) override {
     Rect bounds = surface.GetFrame();
     Rect key_field_bounds, arrow_and_value_field_bounds;
     bounds.VerticalSplit(bounds.size.width / 2, key_field_bounds,
@@ -1950,9 +1963,9 @@ class MappingFieldDelegate : public FieldDelegate {
     arrow_and_value_field_bounds.VerticalSplit(1, arrow_bounds,
                                                value_field_bounds);
 
-    SubPad key_field_surface = SubPad(surface, key_field_bounds);
-    SubPad arrow_surface = SubPad(surface, arrow_bounds);
-    SubPad value_field_surface = SubPad(surface, value_field_bounds);
+    Surface key_field_surface = surface.SubSurface(key_field_bounds);
+    Surface arrow_surface = surface.SubSurface(arrow_bounds);
+    Surface value_field_surface = surface.SubSurface(value_field_bounds);
 
     bool key_is_selected =
         m_selection_type == SelectionType::Key && is_selected;
@@ -2088,7 +2101,7 @@ class FormAction {
   }
 
   // Draw a centered [Label].
-  void Draw(SubPad &surface, bool is_selected) {
+  void Draw(Surface &surface, bool is_selected) {
     int x = (surface.GetWidth() - m_label.length()) / 2;
     surface.MoveCursor(x, 0);
     if (is_selected)
@@ -2357,7 +2370,7 @@ class FormWindowDelegate : public WindowDelegate {
     return context;
   }
 
-  void UpdateScrolling(DerivedWindow &surface) {
+  void UpdateScrolling(Surface &surface) {
     ScrollContext context = GetScrollContext();
     int content_height = GetContentHeight();
     int surface_height = surface.GetHeight();
@@ -2381,7 +2394,7 @@ class FormWindowDelegate : public WindowDelegate {
     }
   }
 
-  void DrawError(SubPad &surface) {
+  void DrawError(Surface &surface) {
     if (!m_delegate_sp->HasError())
       return;
     surface.MoveCursor(0, 0);
@@ -2395,7 +2408,7 @@ class FormWindowDelegate : public WindowDelegate {
     surface.HorizontalLine(surface.GetWidth());
   }
 
-  void DrawFields(SubPad &surface) {
+  void DrawFields(Surface &surface) {
     int line = 0;
     int width = surface.GetWidth();
     bool a_field_is_selected = m_selection_type == SelectionType::Field;
@@ -2406,13 +2419,13 @@ class FormWindowDelegate : public WindowDelegate {
       bool is_field_selected = a_field_is_selected && m_selection_index == i;
       int height = field->FieldDelegateGetHeight();
       Rect bounds = Rect(Point(0, line), Size(width, height));
-      SubPad field_surface = SubPad(surface, bounds);
+      Surface field_surface = surface.SubSurface(bounds);
       field->FieldDelegateDraw(field_surface, is_field_selected);
       line += height;
     }
   }
 
-  void DrawActions(SubPad &surface) {
+  void DrawActions(Surface &surface) {
     int number_of_actions = m_delegate_sp->GetNumberOfActions();
     int width = surface.GetWidth() / number_of_actions;
     bool an_action_is_selected = m_selection_type == SelectionType::Action;
@@ -2421,19 +2434,19 @@ class FormWindowDelegate : public WindowDelegate {
       bool is_action_selected = an_action_is_selected && m_selection_index == i;
       FormAction &action = m_delegate_sp->GetAction(i);
       Rect bounds = Rect(Point(x, 0), Size(width, 1));
-      SubPad action_surface = SubPad(surface, bounds);
+      Surface action_surface = surface.SubSurface(bounds);
       action.Draw(action_surface, is_action_selected);
       x += width;
     }
   }
 
-  void DrawElements(SubPad &surface) {
+  void DrawElements(Surface &surface) {
     Rect frame = surface.GetFrame();
     Rect fields_bounds, actions_bounds;
     frame.HorizontalSplit(surface.GetHeight() - GetActionsHeight(),
                           fields_bounds, actions_bounds);
-    SubPad fields_surface = SubPad(surface, fields_bounds);
-    SubPad actions_surface = SubPad(surface, actions_bounds);
+    Surface fields_surface = surface.SubSurface(fields_bounds);
+    Surface actions_surface = surface.SubSurface(actions_bounds);
 
     DrawFields(fields_surface);
     DrawActions(actions_surface);
@@ -2442,7 +2455,7 @@ class FormWindowDelegate : public WindowDelegate {
   // Contents are first drawn on a pad. Then a subset of that pad is copied to
   // the derived window starting at the first visible line. This essentially
   // provides scrolling functionality.
-  void DrawContent(DerivedWindow &surface) {
+  void DrawContent(Surface &surface) {
     UpdateScrolling(surface);
 
     int width = surface.GetWidth();
@@ -2452,8 +2465,8 @@ class FormWindowDelegate : public WindowDelegate {
     Rect frame = pad.GetFrame();
     Rect error_bounds, elements_bounds;
     frame.HorizontalSplit(GetErrorHeight(), error_bounds, elements_bounds);
-    SubPad error_surface = SubPad(pad, error_bounds);
-    SubPad elements_surface = SubPad(pad, elements_bounds);
+    Surface error_surface = pad.SubSurface(error_bounds);
+    Surface elements_surface = pad.SubSurface(elements_bounds);
 
     DrawError(error_surface);
     DrawElements(elements_surface);
@@ -2473,7 +2486,7 @@ class FormWindowDelegate : public WindowDelegate {
 
     Rect content_bounds = window.GetFrame();
     content_bounds.Inset(2, 2);
-    DerivedWindow content_surface = DerivedWindow(window, content_bounds);
+    Surface content_surface = window.SubSurface(content_bounds);
 
     DrawContent(content_surface);
     return true;