From 41ea36f8acf1d09ab91b0ef8d93650b281ad970b Mon Sep 17 00:00:00 2001
From: Khan Winter <35942988+thecoolwinter@users.noreply.github.com>
Date: Thu, 9 Jan 2025 21:52:25 -0600
Subject: [PATCH] Inset Selection Rect By Edge Insets (#60)

### Description

Insets the drawn selection box by the text view's edge insets.

### Related Issues

* #59

### Checklist

<!--- Add things that are not yet implemented above -->

- [x] I read and understood the [contributing guide](https://github.com/CodeEditApp/CodeEdit/blob/main/CONTRIBUTING.md) as well as the [code of conduct](https://github.com/CodeEditApp/CodeEdit/blob/main/CODE_OF_CONDUCT.md)
- [x] The issues this PR addresses are related to each other
- [x] My changes generate no new warnings
- [x] My code builds and runs on my machine
- [x] My changes are all related to the related issue above
- [x] I documented my code

### Screenshots


https://github.com/user-attachments/assets/74f8a8bd-4467-4b65-b068-96544c230dad
---
 .../TextSelectionManager+FillRects.swift      | 29 ++++++++++++++-----
 1 file changed, 21 insertions(+), 8 deletions(-)

diff --git a/Sources/CodeEditTextView/TextSelectionManager/TextSelectionManager+FillRects.swift b/Sources/CodeEditTextView/TextSelectionManager/TextSelectionManager+FillRects.swift
index 5b3b9a2b..46f56758 100644
--- a/Sources/CodeEditTextView/TextSelectionManager/TextSelectionManager+FillRects.swift
+++ b/Sources/CodeEditTextView/TextSelectionManager/TextSelectionManager+FillRects.swift
@@ -8,7 +8,12 @@
 import Foundation
 
 extension TextSelectionManager {
-    /// Calculate a set of rects for a text selection suitable for highlighting the selection.
+    /// Calculate a set of rects for a text selection suitable for filling with the selection color to indicate a
+    /// multi-line selection.
+    ///
+    /// The returned rects are inset by edge insets passed to the text view, the given `rect` parameter can be the 'raw'
+    /// rect to draw in, no need to inset it before this method call.
+    ///
     /// - Parameters:
     ///   - rect: The bounding rect of available draw space.
     ///   - textSelection: The selection to use.
@@ -25,27 +30,35 @@ extension TextSelectionManager {
             return []
         }
 
+        let insetXPos = max(layoutManager.edgeInsets.left, rect.minX)
+        let insetWidth = max(0, rect.maxX - insetXPos - layoutManager.edgeInsets.right)
+        let insetRect = NSRect(x: insetXPos, y: rect.origin.y, width: insetWidth, height: rect.height)
+
         // Calculate the first line and any rects selected
         // If the last line position is not the same as the first, calculate any rects from that line.
         // If there's > 0 space between the first and last positions, add a rect between them to cover any
         // intermediate lines.
 
-        fillRects.append(contentsOf: getFillRects(in: rect, selectionRange: range, forPosition: firstLinePosition))
-
-        if lastLinePosition.range != firstLinePosition.range {
-            fillRects.append(contentsOf: getFillRects(in: rect, selectionRange: range, forPosition: lastLinePosition))
+        let firstLineRects = getFillRects(in: rect, selectionRange: range, forPosition: firstLinePosition)
+        let lastLineRects: [CGRect] = if lastLinePosition.range != firstLinePosition.range {
+            getFillRects(in: rect, selectionRange: range, forPosition: lastLinePosition)
+        } else {
+            []
         }
 
+        fillRects.append(contentsOf: firstLineRects + lastLineRects)
+
         if firstLinePosition.yPos + firstLinePosition.height < lastLinePosition.yPos {
             fillRects.append(CGRect(
-                x: rect.minX,
+                x: insetXPos,
                 y: firstLinePosition.yPos + firstLinePosition.height,
-                width: rect.width,
+                width: insetWidth,
                 height: lastLinePosition.yPos - (firstLinePosition.yPos + firstLinePosition.height)
             ))
         }
 
-        return fillRects
+        // Pixel align these to avoid aliasing on the edges of each rect that should be a solid box.
+        return fillRects.map { $0.intersection(insetRect).pixelAligned }
     }
 
     /// Find fill rects for a specific line position.