[tui] Simplify editor buffer post mutation validation

Remove the complexity of having an editor_engine_internal_api.rs apply_changes()
function that accepts a closure by using a Drop impl on the struct returned by
editor_buffer_struct.rs get_mut().

Also fix this bug:
#343

Closes #343

Author: nazmulidris

core/src/stack_alloc_types/make_new.rs

@@ -15,7 +15,7 @@
  *   limitations under the License.
  */
 
- // BOOKM: Clever Rust, use of decl macro w/ `tt` to allow any number of arguments.
+// BOOKM: Clever Rust, use of decl macro w/ `tt` to allow any number of arguments.
 
 /// This macro joins a collection of items into a [crate::StringStorage] (which is
 /// allocated and returned) with a specified delimiter and format. It iterates over the

core/src/tui_core/dimens/position.rs

@@ -144,6 +144,8 @@ impl Position {
 }
 
 pub mod position_math_ops {
+    use std::ops::Sub;
+
     use super::*;
 
     impl AddAssign<ChUnit> for Position {
@@ -193,6 +195,16 @@ pub mod position_math_ops {
             }
         }
     }
+
+    impl Sub<Position> for Position {
+        type Output = Position;
+        fn sub(self, other: Position) -> Self {
+            Self {
+                col_index: self.col_index - other.col_index,
+                row_index: self.row_index - other.row_index,
+            }
+        }
+    }
 }
 
 pub mod convert_position_to_other_type {

tui/src/tui/editor/editor_buffer/editor_buffer_selection_support.rs

@@ -51,7 +51,7 @@ impl EditorBufferApi {
                     end_display_col_index: cmp::max(previous, current),
                 };
 
-                let editor_buffer_mut = editor_buffer.get_mut();
+                let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
 
                 editor_buffer_mut.selection_map.insert(
                     row_index,
@@ -119,7 +119,7 @@ impl EditorBufferApi {
                 let delta = previous - current;
                 let new_range = range.shrink_end_by(delta);
 
-                let editor_buffer_mut = editor_buffer.get_mut();
+                let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
                 editor_buffer_mut.selection_map.insert(
                     row_index,
                     new_range,
@@ -138,7 +138,7 @@ impl EditorBufferApi {
                 let delta = range_start - current;
                 let new_range = range.grow_start_by(delta);
 
-                let editor_buffer_mut = editor_buffer.get_mut();
+                let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
                 editor_buffer_mut.selection_map.insert(
                     row_index,
                     new_range,
@@ -157,7 +157,7 @@ impl EditorBufferApi {
                 let delta = current - range_end;
                 let new_range = range.grow_end_by(delta);
 
-                let editor_buffer_mut = editor_buffer.get_mut();
+                let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
                 editor_buffer_mut.selection_map.insert(
                     row_index,
                     new_range,
@@ -177,7 +177,7 @@ impl EditorBufferApi {
                 let delta = current - range_start;
                 let new_range = range.shrink_start_by(delta);
 
-                let editor_buffer_mut = editor_buffer.get_mut();
+                let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
                 editor_buffer_mut.selection_map.insert(
                     row_index,
                     new_range,
@@ -196,7 +196,7 @@ impl EditorBufferApi {
         // `handle_selection_multiline_caret_movement`.
         if let Some(range) = editor_buffer.get_selection_map().get(row_index) {
             if range.start_display_col_index == range.end_display_col_index {
-                let editor_buffer_mut = editor_buffer.get_mut();
+                let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
                 editor_buffer_mut.selection_map.remove(
                     row_index,
                     SelectionRange::caret_movement_direction_left_right(
@@ -498,7 +498,7 @@ impl EditorBufferApi {
 
         let row_index = current.row_index; // Same as previous.row_index.
 
-        let editor_buffer_mut = editor_buffer.get_mut();
+        let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
 
         call_if_true!(DEBUG_TUI_COPY_PASTE, {
             let message = "📜🔼🔽 handle_selection_multiline_caret_movement_hit_top_or_bottom_of_document";
@@ -660,7 +660,7 @@ mod multiline_select_helpers {
             SelectionRange::new(start_col, end_col)
         };
 
-        let editor_buffer_mut = editor_buffer.get_mut();
+        let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
         editor_buffer_mut.selection_map.insert(
             first.row_index,
             first_row_range,
@@ -688,7 +688,7 @@ mod multiline_select_helpers {
         let first_line_width = editor_buffer.get_line_display_width(first.row_index);
 
         // Mutably borrow the selection map.
-        let editor_buffer_mut = editor_buffer.get_mut();
+        let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
 
         // Extend the existing range (in selection map) for the first row to end of line.
         if let Some(first_row_range) =
@@ -735,7 +735,7 @@ mod multiline_select_helpers {
         let first_line_width = editor_buffer.get_line_display_width(first.row_index);
 
         // Mutably borrow the selection map.
-        let editor_buffer_mut = editor_buffer.get_mut();
+        let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
 
         // FIRST ROW.
         if let Some(first_row_range) =
@@ -808,7 +808,7 @@ mod multiline_select_helpers {
         let last = previous;
 
         // Mutably borrow the selection map.
-        let editor_buffer_mut = editor_buffer.get_mut();
+        let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
 
         // Drop the existing range (in selection map) for the last row.
         if editor_buffer_mut
@@ -860,7 +860,7 @@ mod multiline_select_helpers {
         let last = current;
 
         // Mutably borrow the selection map.
-        let editor_buffer_mut = editor_buffer.get_mut();
+        let editor_buffer_mut = editor_buffer.get_mut(ch(0), ch(0));
 
         // Drop the existing range (in selection map) for the first row.
         if editor_buffer_mut

tui/src/tui/editor/editor_buffer/editor_buffer_struct.rs

@@ -14,7 +14,6 @@
  *   See the License for the specific language governing permissions and
  *   limitations under the License.
  */
-
 use std::{collections::HashMap,
           fmt::{Debug, Formatter, Result}};
 
@@ -40,7 +39,8 @@ use sizing::VecEditorContentLines;
 use smallvec::{smallvec, SmallVec};
 
 use super::SelectionList;
-use crate::{EditorEngine,
+use crate::{validate_editor_buffer_change::EditorBufferMut,
+            EditorEngine,
             EditorEngineApi,
             HasFocus,
             RenderArgs,
@@ -69,17 +69,16 @@ use crate::{EditorEngine,
 ///
 /// These functions take any one of the following args:
 /// 1. [crate::EditorArgsMut]
-/// 2. [crate::EditorArgs]
 /// 3. [EditorBuffer] and [EditorEngine]
 ///
 /// # Accessing and mutating the fields (w/ validation)
 ///
 /// All the fields in this struct are private. In order to access them you have to use the
 /// accessor associated functions. To mutate them, you have to use the
-/// [get_mut](EditorBuffer::get_mut) method, which returns a tuple w/ mutable references
-/// to the fields. This rather strange design allows for all mutations to be tracked
-/// easily and allows for validation operations to be applied post mutation (by
-/// [crate::validate_editor_buffer_change::apply_change]).
+/// [get_mut](EditorBuffer::get_mut) method, which returns a struct of mutable references
+/// to the fields. This struct [EditorBufferMut] implements the [Drop] trait, which allows
+/// for validation [crate::validate_editor_buffer_change] operations to be applied post
+/// mutation.
 ///
 /// # Different kinds of caret positions
 ///
@@ -439,16 +438,28 @@ pub mod access_and_mutate {
         /// 2. [CaretKind::ScrollAdjusted] -> The caret position adjusted for scrolling using
         ///    scroll_offset.
         pub fn get_caret(&self, kind: CaretKind) -> Position {
+            Self::get_caret_adjusted(
+                self.editor_content.caret_display_position,
+                self.editor_content.scroll_offset,
+                kind,
+            )
+        }
+
+        pub fn get_caret_adjusted(
+            caret_display_position: Position,
+            scroll_offset: ScrollOffset,
+            kind: CaretKind,
+        ) -> Position {
             match kind {
-                CaretKind::Raw => self.editor_content.caret_display_position,
+                CaretKind::Raw => caret_display_position,
                 CaretKind::ScrollAdjusted => {
                     let col_index = Self::calc_scroll_adj_caret_col(
-                        &self.editor_content.caret_display_position,
-                        &self.editor_content.scroll_offset,
+                        &caret_display_position,
+                        &scroll_offset,
                     );
                     let row_index = Self::calc_scroll_adj_caret_row(
-                        &self.editor_content.caret_display_position,
-                        &self.editor_content.scroll_offset,
+                        &caret_display_position,
+                        &scroll_offset,
                     );
                     position!(col_index: col_index, row_index: row_index)
                 }
@@ -478,15 +489,25 @@ pub mod access_and_mutate {
         // REFACTOR: [ ] return struct, not tuple, add drop impl to it, to update lines_us? or drop lines_us?
         // REFACTOR: [ ] after mutations to lines, lines_us must be recomputed! consider remove this from the struct & computing it only when needed
         /// Even though this struct is mutable by editor_ops.rs, this method is provided
-        /// to mark when mutable access is made to this struct. This makes it easy to
-        /// determine what code mutates this struct, since it is necessary to validate
-        /// things after mutation quite a bit in editor_ops.rs.
-        pub fn get_mut(&mut self) -> EditorBufferMut<'_> {
+        /// to mark when mutable access is made to this struct.
+        ///
+        /// This makes it easy to determine what code mutates this struct, since it is
+        /// necessary to validate things after mutation quite a bit in editor_ops.rs.
+        ///
+        /// [EditorBufferMut] implements the [Drop] trait, which ensures that any
+        /// validation changes are applied after making changes to the [EditorBuffer].
+        pub fn get_mut(
+            &mut self,
+            viewport_width: ChUnit,
+            viewport_height: ChUnit,
+        ) -> EditorBufferMut<'_> {
             EditorBufferMut::new(
                 &mut self.editor_content.lines,
                 &mut self.editor_content.caret_display_position,
                 &mut self.editor_content.scroll_offset,
                 &mut self.editor_content.selection_list,
+                viewport_width,
+                viewport_height,
             )
         }
 
@@ -500,37 +521,6 @@ pub mod access_and_mutate {
             &self.editor_content.selection_list
         }
     }
-
-    pub struct EditorBufferMut<'a> {
-        pub lines: &'a mut VecEditorContentLines,
-        pub caret: &'a mut Position,
-        pub scroll_offset: &'a mut ScrollOffset,
-        pub selection_map: &'a mut SelectionList,
-    }
-
-    // BOOKM: Clever Rust, use of Drop to perform transaction close / end.
-    
-    impl Drop for EditorBufferMut<'_> {
-        fn drop(&mut self) {
-            // REFACTOR: [ ] do all the validation here?
-        }
-    }
-
-    impl<'a> EditorBufferMut<'a> {
-        pub fn new(
-            lines: &'a mut VecEditorContentLines,
-            caret: &'a mut Position,
-            scroll_offset: &'a mut ScrollOffset,
-            selection_map: &'a mut SelectionList,
-        ) -> Self {
-            Self {
-                lines,
-                caret,
-                scroll_offset,
-                selection_map,
-            }
-        }
-    }
 }
 
 pub mod history {

tui/src/tui/editor/editor_buffer/selection_list.rs

@@ -128,7 +128,7 @@ impl SelectionList {
         // Column is the last row of the range.
         let indices = self.get_ordered_indices();
         let first_row_index = indices.first()?;
-        let last_row_index = indices.first()?;
+        let last_row_index = indices.last()?;
         Some(position!(
             col_index: self.get(*last_row_index)?.start_display_col_index,
             row_index: *first_row_index

tui/src/tui/editor/editor_engine/editor_engine_api.rs

@@ -381,7 +381,7 @@ impl EditorEngineApi {
                 unicode_string: string,
                 ..
             }) =
-                EditorEngineInternalApi::string_at_caret(editor_buffer, editor_engine)
+                EditorEngineInternalApi::string_at_caret(editor_buffer)
             {
                 // PERF: [ ] perf
                 string