From 8924b3fb5b20774b3ec9d2b14036fb8bf8c698a1 Mon Sep 17 00:00:00 2001
From: thataboy <dearbart@yahoo.com>
Date: Tue, 15 Oct 2024 10:10:01 -0700
Subject: [PATCH] Fix block cursor obscuring placeholder text and editor text
 in some cases (#18114)

---
 crates/editor/src/element.rs | 39 ++++++++++++++++++++++++++++++------
 1 file changed, 33 insertions(+), 6 deletions(-)

diff --git a/crates/editor/src/element.rs b/crates/editor/src/element.rs
index 89fa23ab1caacb2e63d81ed57a1fcf6ecc0604f7..8a2ec5cd0d527286d1fdd1065a988bb82ca769bb 100644
--- a/crates/editor/src/element.rs
+++ b/crates/editor/src/element.rs
@@ -64,7 +64,7 @@ use std::{
     sync::Arc,
 };
 use sum_tree::Bias;
-use theme::{ActiveTheme, PlayerColor};
+use theme::{ActiveTheme, Appearance, PlayerColor};
 use ui::prelude::*;
 use ui::{h_flex, ButtonLike, ButtonStyle, ContextMenu, Tooltip};
 use util::RangeExt;
@@ -1015,8 +1015,20 @@ impl EditorElement {
                         block_width = em_width;
                     }
                     let block_text = if let CursorShape::Block = selection.cursor_shape {
-                        snapshot.display_chars_at(cursor_position).next().and_then(
-                            |(character, _)| {
+                        snapshot
+                            .display_chars_at(cursor_position)
+                            .next()
+                            .or_else(|| {
+                                if cursor_column == 0 {
+                                    snapshot
+                                        .placeholder_text()
+                                        .and_then(|s| s.chars().next())
+                                        .map(|c| (c, cursor_position))
+                                } else {
+                                    None
+                                }
+                            })
+                            .and_then(|(character, _)| {
                                 let text = if character == '\n' {
                                     SharedString::from(" ")
                                 } else {
@@ -1031,6 +1043,22 @@ impl EditorElement {
                                     })
                                     .unwrap_or(self.style.text.font());
 
+                                // Invert the text color for the block cursor. Ensure that the text
+                                // color is opaque enough to be visible against the background color.
+                                //
+                                // 0.75 is an arbitrary threshold to determine if the background color is
+                                // opaque enough to use as a text color.
+                                //
+                                // TODO: In the future we should ensure themes have a `text_inverse` color.
+                                let color = if cx.theme().colors().editor_background.a < 0.75 {
+                                    match cx.theme().appearance {
+                                        Appearance::Dark => Hsla::black(),
+                                        Appearance::Light => Hsla::white(),
+                                    }
+                                } else {
+                                    cx.theme().colors().editor_background
+                                };
+
                                 cx.text_system()
                                     .shape_line(
                                         text,
@@ -1038,15 +1066,14 @@ impl EditorElement {
                                         &[TextRun {
                                             len,
                                             font,
-                                            color: self.style.background,
+                                            color,
                                             background_color: None,
                                             strikethrough: None,
                                             underline: None,
                                         }],
                                     )
                                     .log_err()
-                            },
-                        )
+                            })
                     } else {
                         None
                     };