Repository: microsoft/terminal (language: cpp)

Issue:
Bad default selection background color with light schemes
# Environment

```none
Windows build number: 10.0.18363.0
Windows Terminal version: 1.4.3243.0
```

# Steps to reproduce

1. Update settings.json to use the `One Half Light`, `Solarized Light`, or `Tango Light` color schemes.
1. Use the mouse to highlight some text.

# Expected behavior

It's easy to see which text was selected.

# Actual behavior

It's hard to see which text was selected because the default selectionBackground value is white, and that doesn't work well with light color schemes.

# Proposed solution

Add selectionBackground values to all of the color schemes in defaults.json (or at least the light color schemes).

# Related to

This issue is related to #3326, #3561, and #3580.


Discussion / hints:
Okay, you're not wrong here. Part of the trick with these schemes is that they don't canonically include a selection color. Usually, they're just defined as a set of (foreground, background, 16-color table). The selection color is almost always just set by the terminal emulator. So if we were to add selection BG colors to these schemes, that would be some other customization that we're making to these schemes other than their usual definitions. 

Though, I think I agree - until #3561 lands, the experience with these themes is just _bad_. I wonder if we could just use the "bright black" color for each of these schemes and have it work _good enough_.

> **Note**
> ## Walkthrough

Go through each of the "light" color schemes in `defaults.json`, and add a `selectionBackground` property which is set to the scheme's `brightBlack`. 

This will probably end up in a team discussion, but it'll be helpful to have a concrete example to drive that discussion. 

Fix patch:
diff --git a/src/cascadia/TerminalSettingsModel/defaults.json b/src/cascadia/TerminalSettingsModel/defaults.json
index 360f37afaad..08e817aa1c0 100644
--- a/src/cascadia/TerminalSettingsModel/defaults.json
+++ b/src/cascadia/TerminalSettingsModel/defaults.json
@@ -174,7 +174,7 @@
             "foreground": "#383A42",
             "background": "#FAFAFA",
             "cursorColor": "#4F525D",
-            "selectionBackground": "#4F525D",
+            "selectionBackground": "#383A42",
             "black": "#383A42",
             "red": "#E45649",
             "green": "#50A14F",
@@ -219,7 +219,7 @@
             "foreground": "#657B83",
             "background": "#FDF6E3",
             "cursorColor": "#002B36",
-            "selectionBackground": "#073642",
+            "selectionBackground": "#2C4D57",
             "black": "#002B36",
             "red": "#DC322F",
             "green": "#859900",
@@ -264,7 +264,7 @@
             "foreground": "#555753",
             "background": "#FFFFFF",
             "cursorColor": "#000000",
-            "selectionBackground": "#555753",
+            "selectionBackground": "#141414",
             "black": "#000000",
             "red": "#CC0000",
             "green": "#4E9A06",


Test patch: