9e189dbc

Clarify row rebuild cache contract

a73x   2026-04-08 19:16

---

diff --git a/src/main.zig b/src/main.zig
index f15c3be..d3b59bc 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -750,7 +750,7 @@ test "rebuildRowInstances emits expected instances for a colored glyph row" {
        atlas.cursorUV(),
    );

    try std.testing.expect(rebuilt);
    try std.testing.expect(rebuilt.len_changed);
    try std.testing.expectEqual(@as(usize, 2), cache.instances.items.len);

    const colors = term.cellColors(row_cells.get(0));
@@ -784,6 +784,8 @@ test "rebuildRowInstances replaces stale cached contents without layout dirtines

    var cache = RowInstanceCache{};
    defer cache.instances.deinit(std.testing.allocator);
    cache.gpu_offset_instances = 17;
    cache.gpu_len_instances = 29;
    try cache.instances.append(std.testing.allocator, .{
        .cell_pos = .{ 99.0, 99.0 },
        .glyph_size = .{ 1.0, 1.0 },
@@ -817,10 +819,17 @@ test "rebuildRowInstances replaces stale cached contents without layout dirtines
        atlas.cursorUV(),
    );

    try std.testing.expect(!rebuilt);
    try std.testing.expect(!rebuilt.len_changed);
    try std.testing.expectEqual(@as(usize, 2), cache.instances.items.len);
    try std.testing.expectEqualDeep([2]f32{ 0.0, 0.0 }, cache.instances.items[0].cell_pos);
    try std.testing.expectEqualDeep([2]f32{ 0.0, 0.0 }, cache.instances.items[1].cell_pos);
    try std.testing.expectEqualDeep([2]f32{ @floatFromInt(face.cellWidth()), @floatFromInt(face.cellHeight()) }, cache.instances.items[0].glyph_size);
    try std.testing.expectEqualDeep(term.cellColors(row_cells.get(0)).bg, cache.instances.items[0].fg);
    try std.testing.expectEqualDeep(term.cellColors(row_cells.get(0)).bg, cache.instances.items[0].bg);
    try std.testing.expectEqualDeep(term.cellColors(row_cells.get(0)).fg, cache.instances.items[1].fg);
    try std.testing.expectEqualDeep(term.cellColors(row_cells.get(0)).bg, cache.instances.items[1].bg);
    try std.testing.expectEqual(@as(u32, 0), cache.gpu_offset_instances);
    try std.testing.expectEqual(@as(u32, 0), cache.gpu_len_instances);
}

test "RenderCache resizeRows preserves surviving row caches" {
@@ -1011,6 +1020,10 @@ const RowPackResult = struct {
    cursor_len_instances: u32,
};

const RowRebuildResult = struct {
    len_changed: bool,
};

fn repackRowCaches(
    alloc: std.mem.Allocator,
    packed_instances: *std.ArrayListUnmanaged(renderer.Instance),
@@ -1056,9 +1069,11 @@ fn rebuildRowInstances(
    baseline: u32,
    default_bg: [4]f32,
    bg_uv: font.GlyphUV,
) !bool {
) !RowRebuildResult {
    const old_len = cache.instances.items.len;
    cache.instances.clearRetainingCapacity();
    cache.gpu_offset_instances = 0;
    cache.gpu_len_instances = 0;

    const raw_cells = row_cells.items(.raw);
    var col_idx: u32 = 0;
@@ -1085,7 +1100,9 @@ fn rebuildRowInstances(
        );
    }

    return markLayoutDirtyOnLenChange(old_len, cache.instances.items.len);
    return .{
        .len_changed = markLayoutDirtyOnLenChange(old_len, cache.instances.items.len),
    };
}

fn markLayoutDirtyOnLenChange(old_len: usize, new_len: usize) bool {