editor: Add support for no scroll margin in full mode (#41838)

Noticed this whilst testing the Docker debugger. I randomly scrolled the
console off screen and was confused briefly as to why this was the case.

Release Notes:

- The debugger query console will no longer needlessly overscroll.

crates/editor/src/editor.rs

@@ -452,6 +452,20 @@ pub enum SelectMode {
     All,
 }
 
+#[derive(Copy, Clone, Default, PartialEq, Eq, Debug)]
+pub enum SizingBehavior {
+    /// The editor will layout itself using `size_full` and will include the vertical
+    /// scroll margin as requested by user settings.
+    #[default]
+    Default,
+    /// The editor will layout itself using `size_full`, but will not have any
+    /// vertical overscroll.
+    ExcludeOverscrollMargin,
+    /// The editor will request a vertical size according to its content and will be
+    /// layouted without a vertical scroll margin.
+    SizeByContent,
+}
+
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub enum EditorMode {
     SingleLine,
@@ -464,8 +478,8 @@ pub enum EditorMode {
         scale_ui_elements_with_buffer_font_size: bool,
         /// When set to `true`, the editor will render a background for the active line.
         show_active_line_background: bool,
-        /// When set to `true`, the editor's height will be determined by its content.
-        sized_by_content: bool,
+        /// Determines the sizing behavior for this editor
+        sizing_behavior: SizingBehavior,
     },
     Minimap {
         parent: WeakEntity<Editor>,
@@ -477,7 +491,7 @@ impl EditorMode {
         Self::Full {
             scale_ui_elements_with_buffer_font_size: true,
             show_active_line_background: true,
-            sized_by_content: false,
+            sizing_behavior: SizingBehavior::Default,
         }
     }
 

crates/editor/src/editor_tests.rs

@@ -14217,7 +14217,7 @@ async fn test_completion_in_multibuffer_with_replace_range(cx: &mut TestAppConte
                     EditorMode::Full {
                         scale_ui_elements_with_buffer_font_size: false,
                         show_active_line_background: false,
-                        sized_by_content: false,
+                        sizing_behavior: SizingBehavior::Default,
                     },
                     multi_buffer.clone(),
                     Some(project.clone()),

crates/editor/src/element.rs

@@ -8,8 +8,8 @@ use crate::{
     HandleInput, HoveredCursor, InlayHintRefreshReason, JumpData, LineDown, LineHighlight, LineUp,
     MAX_LINE_LEN, MINIMAP_FONT_SIZE, MULTI_BUFFER_EXCERPT_HEADER_HEIGHT, OpenExcerpts, PageDown,
     PageUp, PhantomBreakpointIndicator, Point, RowExt, RowRangeExt, SelectPhase,
-    SelectedTextHighlight, Selection, SelectionDragState, SoftWrap, StickyHeaderExcerpt, ToPoint,
-    ToggleFold, ToggleFoldAll,
+    SelectedTextHighlight, Selection, SelectionDragState, SizingBehavior, SoftWrap,
+    StickyHeaderExcerpt, ToPoint, ToggleFold, ToggleFoldAll,
     code_context_menus::{CodeActionsMenu, MENU_ASIDE_MAX_WIDTH, MENU_ASIDE_MIN_WIDTH, MENU_GAP},
     display_map::{
         Block, BlockContext, BlockStyle, ChunkRendererId, DisplaySnapshot, EditorMargins,
@@ -8441,11 +8441,11 @@ impl Element for EditorElement {
                         window.request_layout(style, None, cx)
                     }
                     EditorMode::Full {
-                        sized_by_content, ..
+                        sizing_behavior, ..
                     } => {
                         let mut style = Style::default();
                         style.size.width = relative(1.).into();
-                        if sized_by_content {
+                        if sizing_behavior == SizingBehavior::SizeByContent {
                             let snapshot = editor.snapshot(window, cx);
                             let line_height =
                                 self.style.text.line_height_in_pixels(window.rem_size());
@@ -8609,7 +8609,8 @@ impl Element for EditorElement {
                         EditorMode::SingleLine
                             | EditorMode::AutoHeight { .. }
                             | EditorMode::Full {
-                                sized_by_content: true,
+                                sizing_behavior: SizingBehavior::ExcludeOverscrollMargin
+                                    | SizingBehavior::SizeByContent,
                                 ..
                             }
                     ) {