zcatgui/src/core/command.zig

//! DrawCommand - Rendering commands for the software rasterizer
//!
//! The immediate mode UI generates a list of DrawCommands each frame.
//! The software rasterizer then processes these commands to produce pixels.
//!
//! This is the "command list" approach (like microui), not vertex buffers.

const Style = @import("style.zig");

/// A single draw command
pub const DrawCommand = union(enum) {
    /// Draw a filled rectangle
    rect: RectCommand,

    /// Draw text
    text: TextCommand,

    /// Draw a line
    line: LineCommand,

    /// Draw a rectangle outline (border)
    rect_outline: RectOutlineCommand,

    /// Begin clipping to a rectangle
    clip: ClipCommand,

    /// End clipping
    clip_end,

    /// No operation (placeholder)
    nop,
};

/// Draw a filled rectangle
pub const RectCommand = struct {
    x: i32,
    y: i32,
    w: u32,
    h: u32,
    color: Style.Color,
};

/// Draw text at a position
pub const TextCommand = struct {
    x: i32,
    y: i32,
    text: []const u8,
    color: Style.Color,
    /// null means default font
    font: ?*anyopaque = null,
};

/// Draw a line between two points
pub const LineCommand = struct {
    x1: i32,
    y1: i32,
    x2: i32,
    y2: i32,
    color: Style.Color,
};

/// Draw a rectangle outline
pub const RectOutlineCommand = struct {
    x: i32,
    y: i32,
    w: u32,
    h: u32,
    color: Style.Color,
    thickness: u32 = 1,
};

/// Begin clipping to a rectangle
pub const ClipCommand = struct {
    x: i32,
    y: i32,
    w: u32,
    h: u32,
};

// =============================================================================
// Helper constructors
// =============================================================================

/// Create a rect command
pub fn rect(x: i32, y: i32, w: u32, h: u32, color: Style.Color) DrawCommand {
    return .{ .rect = .{
        .x = x,
        .y = y,
        .w = w,
        .h = h,
        .color = color,
    } };
}

/// Create a text command
pub fn text(x: i32, y: i32, str: []const u8, color: Style.Color) DrawCommand {
    return .{ .text = .{
        .x = x,
        .y = y,
        .text = str,
        .color = color,
    } };
}

/// Create a line command
pub fn line(x1: i32, y1: i32, x2: i32, y2: i32, color: Style.Color) DrawCommand {
    return .{ .line = .{
        .x1 = x1,
        .y1 = y1,
        .x2 = x2,
        .y2 = y2,
        .color = color,
    } };
}

/// Create a rect outline command
pub fn rectOutline(x: i32, y: i32, w: u32, h: u32, color: Style.Color) DrawCommand {
    return .{ .rect_outline = .{
        .x = x,
        .y = y,
        .w = w,
        .h = h,
        .color = color,
    } };
}

/// Create a clip command
pub fn clip(x: i32, y: i32, w: u32, h: u32) DrawCommand {
    return .{ .clip = .{
        .x = x,
        .y = y,
        .w = w,
        .h = h,
    } };
}

/// Create a clip end command
pub fn clipEnd() DrawCommand {
    return .clip_end;
}

// =============================================================================
// Tests
// =============================================================================

const std = @import("std");

test "DrawCommand creation" {
    const cmd = rect(10, 20, 100, 50, Style.Color.red);
    switch (cmd) {
        .rect => |r| {
            try std.testing.expectEqual(@as(i32, 10), r.x);
            try std.testing.expectEqual(@as(i32, 20), r.y);
            try std.testing.expectEqual(@as(u32, 100), r.w);
            try std.testing.expectEqual(@as(u32, 50), r.h);
        },
        else => unreachable,
    }
}