theme the selection colors

1 files changed, 80 insertions, 25 deletions

diff --git a/src/pardes.zig b/src/pardes.zig
index 471817f7..aa2ec398 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -2226,18 +2226,18 @@ pub const bash_rc =
 
 // ---- theme ----
 
-// per-button selection highlight: distinct muted colors per mouse button
-const SEL_BG = [3][3]u8{ .{ 0x2c, 0x46, 0x74 }, .{ 0x2c, 0x60, 0x38 }, .{ 0x64, 0x2c, 0x58 } };
-const sel_fg = [3]u8{ 0xd2, 0xd2, 0xd2 };
-// modal line/char selection: warm tan, reads as keyboard-driven
-const msel_bg = [3]u8{ 0x4a, 0x3a, 0x1e };
-const msel_fg = [3]u8{ 0xd8, 0xc8, 0xa8 };
-// the OTHER cursors of a multi-selection: the same tan turned down, so the
-// primary is the one that reads as "here" at a glance (helix does the same
-// with its two selection styles). Each secondary's own cursor cell is then
-// painted msel_fg-on-msel_bg — there is only one hardware cursor.
-const msel2_bg = [3]u8{ 0x2e, 0x26, 0x16 };
-const msel2_fg = [3]u8{ 0xa8, 0x9c, 0x84 };
+/// Halfway between two colors, channel by channel. Every selection tint pardes
+/// paints is a mix of theme colors — the per-mouse-button ones pull the theme's
+/// selection toward one of its own accents, a quarter of the way and so a mix
+/// of a mix; the extra cursors' pulls it back toward the page — and renderPane
+/// makes seven of those, which is six more than spelling the same three-channel
+/// loop out at the call site is worth.
+fn mix(a: [3]u8, b: [3]u8) [3]u8 {
+    var out: [3]u8 = undefined;
+    for (&out, a, b) |*c, x, y| c.* = @intCast((@as(u16, x) + y) / 2);
+    return out;
+}
+
 const UNDO_MAX = 256;
 const EDIT_UNDO_MAX = 64; // terminal snapshots copy the edit buffer; cap tighter
 
@@ -2249,10 +2249,18 @@ const EDIT_UNDO_MAX = 64; // terminal snapshots copy the edit buffer; cap tighte
 /// piece of loud chrome on screen. The overlay/drag greys that were also
 /// hardcoded turned out to be the dark theme's own scroll_track/lineno/tag_fg
 /// spelled a second time, so they read those fields now instead.
+///
+/// Selection is ONE pair, `sel_bg`/`sel_fg`, and the rest is arithmetic: the
+/// three per-mouse-button tints and the dimmed extra cursors are mixed off it in
+/// renderPane rather than named here. A theme author gets their selection colour
+/// right and would get four more by accident — and every source gen_themes reads
+/// names exactly one selection anyway.
 pub const Theme = struct {
     name: []const u8,
     bg: ?[3]u8,
     fg: ?[3]u8,
+    sel_bg: [3]u8,
+    sel_fg: [3]u8,
     tag_bg: [3]u8,
     tag_fg: [3]u8,
     box: [3]u8, // move box, focused pane
@@ -10194,9 +10202,15 @@ pub const Pardes = struct {
         }
         if (pv.selection) |selection| {
             try highlights.ensureUnusedCapacity(arena, selection.quads.len);
+            // a page is not a grid of cells, so this is the one selection that
+            // paints as a translucent wash over rendered pixels rather than as
+            // a cell's background — but it is the same selection, so it is the
+            // same colour. The alpha stays hardcoded: it is what makes the
+            // glyphs underneath readable, and no theme has an opinion on it.
+            const sel = p.theme().sel_bg;
             for (selection.quads) |quad| highlights.appendAssumeCapacity(pdf_impl.Highlight.init(
                 quad,
-                .{ 0x55, 0xa7, 0xff, 0x78 },
+                .{ sel[0], sel[1], sel[2], 0x78 },
                 .selection,
             ));
         }
@@ -11615,6 +11629,11 @@ pub const Pardes = struct {
         // scrollbar's second column. `.default` means the host terminal's own
         // background, which is what a themeless dark pane wants.
         const pane_bg: Color = if (th.bg) |c| .{ .rgb = c } else .default;
+        // ...and the same background as a colour to do arithmetic on, which the
+        // dimmed selections below need. A theme with a null bg cannot say what
+        // the host's own cell looks like, so its tag bar stands in — the
+        // substitution pdfTintColors already makes.
+        const page_rgb = th.bg orelse th.tag_bg;
 
         // text area resets to terminal-default cells (vaxis clear semantics);
         // light themes paint the page over it.
@@ -11681,7 +11700,13 @@ pub const Pardes = struct {
             if (w < tw) _ = s.print(tx + tw - w, r.y, w, ibuf[0..iw], tag_style);
         }
         // tag char selection highlight (helix v/x, or a tagline sweep),
-        // inclusive [lo, hi] — rendered-tag columns, so no conversion
+        // inclusive [lo, hi] — rendered-tag columns, so no conversion.
+        //
+        // Every selection on screen paints in the LIVE theme (`th`) and not in
+        // `chrome`: a highlight is not attached to any geometry, it appears
+        // under the range you just swept, so it has to arrive with the theme
+        // the way syntax colours do rather than slide in over the chrome
+        // animation's frames.
         if (pane.tag_edit and pane.tag_sel) {
             const b = tagSelBounds(pane);
             var col: usize = b.lo;
@@ -11689,8 +11714,8 @@ pub const Pardes = struct {
             while (col <= end and col < tw) : (col += 1) {
                 const cell = s.at(tx + @as(u16, @intCast(col)), r.y);
                 cell.default = false;
-                cell.style.bg = .{ .rgb = msel_bg };
-                cell.style.fg = .{ .rgb = msel_fg };
+                cell.style.bg = .{ .rgb = th.sel_bg };
+                cell.style.fg = .{ .rgb = th.sel_fg };
             }
         }
         // cursor while editing the tag: a rendered-tag column, verbatim
@@ -11774,6 +11799,28 @@ pub const Pardes = struct {
         // mouse selections (pane-local coords), one pass per button — later
         // buttons win on overlap. A left .done stays highlighted after release;
         // middle/right .done are transient (they fire their action on release).
+        //
+        // Which button drew a sweep is worth seeing, so each gets the theme's
+        // selection tinted toward one of the theme's own syntax accents: three
+        // colours that are visibly not each other on a dark theme and on a
+        // light one, without asking a theme to name three more. A QUARTER of
+        // the accent, which is the mix of a mix — at a half, an accent as
+        // bright as the theme's text lands on top of sel_fg and the selected
+        // text stops being readable on a couple of dozen generated themes.
+        // `num` gives way to `comment` when a theme paints numbers and strings
+        // alike — the shipped helix theme does, 24 of the generated ones do —
+        // because two buttons landing on one colour is the whole thing this
+        // avoids.
+        // ponytail: 20 of the 228 themes colour two of these three scopes the
+        // same anyway and still collapse two buttons. Upgrade path is to walk
+        // the theme for a third colour far enough from the other two, rather
+        // than naming the scopes here.
+        const accent2 = if (std.mem.eql(u8, &th.num, &th.str)) th.comment else th.num;
+        const sel_btn = [3][3]u8{
+            mix(th.sel_bg, mix(th.sel_bg, th.kw)),
+            mix(th.sel_bg, mix(th.sel_bg, th.str)),
+            mix(th.sel_bg, mix(th.sel_bg, accent2)),
+        };
         for (pane.sel, 0..) |sl, b| {
             if (sl.state == .none) continue;
             if (sl.state == .done and b != 0) continue;
@@ -11788,8 +11835,8 @@ pub const Pardes = struct {
                 while (col <= c1 and col < tw) : (col += 1) {
                     const cell = s.at(tx + @as(u16, @intCast(col)), r.y + row);
                     cell.default = false;
-                    cell.style.bg = .{ .rgb = SEL_BG[b] };
-                    cell.style.fg = .{ .rgb = sel_fg };
+                    cell.style.bg = .{ .rgb = sel_btn[b] };
+                    cell.style.fg = .{ .rgb = th.sel_fg };
                 }
             }
         }
@@ -11804,8 +11851,8 @@ pub const Pardes = struct {
                 while (col < tw) : (col += 1) {
                     const cell = s.at(tx + col, r.y + row);
                     cell.default = false;
-                    cell.style.bg = .{ .rgb = msel_bg };
-                    cell.style.fg = .{ .rgb = msel_fg };
+                    cell.style.bg = .{ .rgb = th.sel_bg };
+                    cell.style.fg = .{ .rgb = th.sel_fg };
                 }
             }
         }
@@ -11838,8 +11885,16 @@ pub const Pardes = struct {
                     .acol = if (pane.vsel.active) pane.vsel.col else pane.cur_col,
                 } else pane.sels[si];
                 const bnd = cellBounds(sr);
-                const bg = if (primary) msel_bg else msel2_bg;
-                const fg = if (primary) msel_fg else msel2_fg;
+                // an extra cursor is the selection colour turned down: the
+                // highlight pulled halfway back to the page, so the primary is
+                // the one that reads as "here" at a glance. On a light theme
+                // that dims toward white rather than toward black, which is the
+                // same statement. The INK stays put — helix's two selection
+                // styles differ in their background too, and dimming both ends
+                // walks the text and its cell toward each other until neither
+                // is readable on the themes whose selection is already close to
+                // the page.
+                const bg = if (primary) th.sel_bg else mix(th.sel_bg, page_rgb);
                 var ar: i32 = bnd.lo_row;
                 while (ar <= bnd.hi_row) : (ar += 1) {
                     const prow = ar - off + @as(i32, BOX_H);
@@ -11851,7 +11906,7 @@ pub const Pardes = struct {
                         const cell = s.at(tx + @as(u16, @intCast(col)), r.y + @as(u16, @intCast(prow)));
                         cell.default = false;
                         cell.style.bg = .{ .rgb = bg };
-                        cell.style.fg = .{ .rgb = fg };
+                        cell.style.fg = .{ .rgb = th.sel_fg };
                     }
                 }
                 if (primary and !preview) continue; // the hardware cursor IS the primary's
@@ -11860,8 +11915,8 @@ pub const Pardes = struct {
                 if (crow >= BOX_H and crow < @as(i32, r.h) and ccol >= vpfx and ccol < tw) {
                     const cell = s.at(tx + @as(u16, @intCast(ccol)), r.y + @as(u16, @intCast(crow)));
                     cell.default = false;
-                    cell.style.bg = .{ .rgb = msel_fg };
-                    cell.style.fg = .{ .rgb = msel_bg };
+                    cell.style.bg = .{ .rgb = th.sel_fg };
+                    cell.style.fg = .{ .rgb = th.sel_bg };
                 }
             }
         }