feat: support selection foreground being cell foreground

[dal-liu]

This resolves #2685.

Changes

• Created SelectionColor tagged union that can take a Color, cell-foreground, or cell-background
• Used the new union to implement the feature for Metal and OpenGL
• Removed the use of invert_selection_fg_bg during rendering as suggested in the issue

Demo

macOS:

demo.mov

Ubuntu:

demo2.mov

Any feedback would be helpful, I'm sure there's a lot of room for improvement here.

[kjmph]

I like this patch. A couple of minor things, when there are inverted cells, this patch shows the original foreground, rather than the inverted foreground. If you compare to Terminal.app, it will always show the inverted foreground when selecting inverted cells. Additionally, very oddly, the theme's cursor-text seems to not be honored with this patch, unless this is a main vs 1.0.1 change?

If any example code could help, here is my personal patch (from the 1.0.1 tag) that demonstrates equivalence with Terminal.app selection & cursor behavior, with the exception that I have a custom theme with no selection-foreground specified. I also made a change to cursor rendering so that the cell-foreground is used. Can we support cell-foreground with cursor-text as well?

diff --git a/src/renderer/Metal.zig b/src/renderer/Metal.zig
index b37f440f..a2ef6c16 100644
--- a/src/renderer/Metal.zig
+++ b/src/renderer/Metal.zig
@@ -2435,8 +2435,17 @@ fn rebuildCells(
                 if (selected and !self.config.invert_selection_fg_bg) {
                     // If we don't have invert selection fg/bg set
                     // then we just use the selection foreground if
-                    // set, otherwise the default bg color.
-                    break :fg self.config.selection_foreground orelse self.background_color orelse self.default_background_color;
+                    // set, otherwise the exisitng fg color.
+                    if (style.flags.inverse) {
+                        break :fg self.config.selection_foreground orelse bg_style orelse self.background_color orelse self.default_background_color;
+                    } else {
+                        break :fg self.config.selection_foreground orelse fg_style;
+                    }
+                    // Except, all themes set selection_foreground! We
+                    // want a theme that doesn't set
+                    // selection_foreground. We could always force
+                    // fg_style, but that isn't a general solution
+                    //break :fg fg_style;
                 }
 
                 // Whether we need to use the bg color as our fg color:
@@ -2671,8 +2680,14 @@ fn rebuildCells(
                 break :blk sty.bg(screen.cursor.page_cell, color_palette) orelse self.background_color orelse self.default_background_color;
             } else if (self.config.cursor_text) |txt|
                 txt
-            else
-                self.background_color orelse self.default_background_color;
+            else base: {
+                const sty = screen.cursor.page_pin.style(screen.cursor.page_cell);
+                if (sty.flags.inverse) {
+                    break :base sty.bg(screen.cursor.page_cell, color_palette) orelse self.background_color orelse self.default_background_color;
+                } else {
+                    break :base sty.fg(color_palette, self.config.bold_is_bright) orelse self.foreground_color orelse self.default_foreground_color;
+                }
+            };
 
             self.uniforms.cursor_color = .{
                 uniform_color.r,

[dal-liu]

@kjmph Thanks for catching the inverted cell issue, it should hopefully be fixed now. I've also made cursor-text and cursor-color accept cell-foreground and cell-background the same way that the selection colors do.

[kjmph]

Haha, great improvement! Except for two things. 1) If the cursor-color is cell-foreground then it wipes out the cell's text. If cursor-color is cell-background then it can't be seen because it blends in. I think it wise to remove the support from cursor-color since it will lead people astray into odd configuration territory. 2) The cursor foreground is wiped out with inverted cells. I don't understand why that happens with your PR, unless it exists in the upstream main branch? I'm personally working on the 1.0.1 tag.

Here is an image showing this patch (and cursor-text = cell-foreground) with inverted cells:

Here is an image showing the patch I shared against 1.0.1 with inverted cells:

I'll give a test against main.

[kjmph]

Oh!!! The cursor wiping out the foreground is a problem upstream, it isn't a regression with this patch. I bet most people allow the shell integration for cursors and because it is a bar, don't notice the color mishap. Will have to open a ticket unless you want to fix it in this patch too?

[dal-liu]

To me, changing cursor-color to accept cell colors makes sense since we should have more control over the colors, plus it was suggested in the original issue as well. That being said, if a 3rd opinion disagrees then I'll gladly revert the changes, so I will leave it for now.

As for the cursor-text thing, it's definitely worth opening a discussion about it.

[gpanders]

Nice work for a first time contributor :) This is imo a nice simplification of some of this code which was starting to get a bit hairy.

This PR makes selection-invert-fg-bg and cursor-invert-fg-bg no-ops, which is a breaking change. I'll leave it to Mitchell to determine how to approach that, but at the least the doc strings for those options should be updated to indicate that they no longer do anything.

[gpanders]

Indentation looks off here, run this through zig fmt if you haven't already.

[gpanders]

It's probably not a big deal, but we are computing these styles even if they're not needed when the cursor color is set to an explicit style. I don't think there is a significant runtime cost though. If we wanted to avoid that we could first check to see if the enum has the .color tag and only compute the styles if it does not (this would be a perfect use case for ziglang/zig#12863)

[gpanders]

Probably not for this PR (and maybe never), but I wonder if we should unify the terminology for cursor and selection, so that instead of cursor-text and cursor-color we use cursor-foreground and cursor-background.