gregExtractor/DarkTheme.cs

using System.Drawing;
using System.Windows.Forms;

namespace gregExtractor;

internal static class DarkTheme
{
    public static readonly Color Background = Color.FromArgb(30, 30, 30);
    public static readonly Color Surface = Color.FromArgb(37, 37, 38);
    public static readonly Color SurfaceAlt = Color.FromArgb(45, 45, 48);
    public static readonly Color Border = Color.FromArgb(62, 62, 66);
    public static readonly Color Foreground = Color.FromArgb(241, 241, 241);
    public static readonly Color MutedForeground = Color.FromArgb(185, 185, 185);
    public static readonly Color Accent = Color.FromArgb(14, 99, 156);

    public static void Apply(Form form)
    {
        form.BackColor = Background;
        form.ForeColor = Foreground;

        ApplyToControlTree(form);
        EnableDarkTabs(form);
    }

    private static void ApplyToControlTree(Control root)
    {
        foreach (Control control in root.Controls)
        {
            ApplyToControl(control);
            if (control.HasChildren)
                ApplyToControlTree(control);
        }
    }

    private static void ApplyToControl(Control control)
    {
        switch (control)
        {
            case TabControl tabControl:
                tabControl.BackColor = Background;
                tabControl.ForeColor = Foreground;
                tabControl.DrawMode = TabDrawMode.OwnerDrawFixed;
                tabControl.DrawItem -= OnTabControlDrawItem;
                tabControl.DrawItem += OnTabControlDrawItem;
                break;

            case TabPage tabPage:
                tabPage.BackColor = Background;
                tabPage.ForeColor = Foreground;
                break;

            case GroupBox groupBox:
                groupBox.BackColor = Surface;
                groupBox.ForeColor = Foreground;
                break;

            case SplitContainer split:
                split.BackColor = Surface;
                split.ForeColor = Foreground;
                break;

            case FlowLayoutPanel flow:
                flow.BackColor = Surface;
                flow.ForeColor = Foreground;
                break;

            case TableLayoutPanel table:
                table.BackColor = Surface;
                table.ForeColor = Foreground;
                break;

            case Panel panel:
                panel.BackColor = Surface;
                panel.ForeColor = Foreground;
                break;

            case TextBox textBox:
                ApplyTextBoxTheme(textBox);
                break;

            case RichTextBox richTextBox:
                richTextBox.BackColor = SurfaceAlt;
                richTextBox.ForeColor = Foreground;
                richTextBox.BorderStyle = BorderStyle.FixedSingle;
                break;

            case DataGridView grid:
                ApplyDataGridTheme(grid);
                break;

            case Button button:
                ApplyButtonTheme(button);
                break;

            case CheckBox checkBox:
                checkBox.BackColor = Surface;
                checkBox.ForeColor = Foreground;
                break;

            case ComboBox comboBox:
                comboBox.BackColor = SurfaceAlt;
                comboBox.ForeColor = Foreground;
                comboBox.FlatStyle = FlatStyle.Flat;
                break;

            case Label label:
                label.BackColor = Color.Transparent;
                label.ForeColor = Foreground;
                break;

            default:
                control.BackColor = Surface;
                control.ForeColor = Foreground;
                break;
        }
    }

    private static void ApplyTextBoxTheme(TextBox textBox)
    {
        textBox.BackColor = SurfaceAlt;
        textBox.ForeColor = Foreground;
        textBox.BorderStyle = BorderStyle.FixedSingle;

        if (textBox.ReadOnly)
        {
            textBox.BackColor = Color.FromArgb(42, 42, 42);
            textBox.ForeColor = MutedForeground;
        }
    }

    private static void ApplyButtonTheme(Button button)
    {
        button.BackColor = SurfaceAlt;
        button.ForeColor = Foreground;
        button.FlatStyle = FlatStyle.Flat;
        button.FlatAppearance.BorderColor = Border;
        button.FlatAppearance.BorderSize = 1;
        button.FlatAppearance.MouseOverBackColor = Color.FromArgb(55, 55, 60);
        button.FlatAppearance.MouseDownBackColor = Accent;
        button.UseVisualStyleBackColor = false;
    }

    private static void ApplyDataGridTheme(DataGridView grid)
    {
        grid.BackgroundColor = Surface;
        grid.GridColor = Border;
        grid.BorderStyle = BorderStyle.None;

        grid.EnableHeadersVisualStyles = false;
        grid.ColumnHeadersBorderStyle = DataGridViewHeaderBorderStyle.Single;
        grid.RowHeadersBorderStyle = DataGridViewHeaderBorderStyle.Single;

        grid.ColumnHeadersDefaultCellStyle.BackColor = Color.FromArgb(51, 51, 55);
        grid.ColumnHeadersDefaultCellStyle.ForeColor = Foreground;
        grid.ColumnHeadersDefaultCellStyle.SelectionBackColor = Color.FromArgb(62, 62, 66);
        grid.ColumnHeadersDefaultCellStyle.SelectionForeColor = Foreground;

        grid.RowHeadersDefaultCellStyle.BackColor = Color.FromArgb(51, 51, 55);
        grid.RowHeadersDefaultCellStyle.ForeColor = Foreground;
        grid.RowHeadersDefaultCellStyle.SelectionBackColor = Color.FromArgb(62, 62, 66);
        grid.RowHeadersDefaultCellStyle.SelectionForeColor = Foreground;

        grid.DefaultCellStyle.BackColor = SurfaceAlt;
        grid.DefaultCellStyle.ForeColor = Foreground;
        grid.DefaultCellStyle.SelectionBackColor = Accent;
        grid.DefaultCellStyle.SelectionForeColor = Color.White;

        grid.AlternatingRowsDefaultCellStyle.BackColor = Color.FromArgb(39, 39, 42);
        grid.AlternatingRowsDefaultCellStyle.ForeColor = Foreground;
        grid.AlternatingRowsDefaultCellStyle.SelectionBackColor = Accent;
        grid.AlternatingRowsDefaultCellStyle.SelectionForeColor = Color.White;
    }

    private static void EnableDarkTabs(Control root)
    {
        foreach (Control control in root.Controls)
        {
            if (control is TabControl tabControl)
            {
                tabControl.DrawMode = TabDrawMode.OwnerDrawFixed;
                tabControl.DrawItem -= OnTabControlDrawItem;
                tabControl.DrawItem += OnTabControlDrawItem;
            }

            if (control.HasChildren)
                EnableDarkTabs(control);
        }
    }

    private static void OnTabControlDrawItem(object? sender, DrawItemEventArgs eventArgs)
    {
        if (sender is not TabControl tabControl)
            return;

        Rectangle rectangle = eventArgs.Bounds;
        bool selected = (eventArgs.State & DrawItemState.Selected) == DrawItemState.Selected;

        Color back = selected ? SurfaceAlt : Surface;
        Color fore = selected ? Foreground : MutedForeground;

        using var backgroundBrush = new SolidBrush(back);
        using var textBrush = new SolidBrush(fore);
        using var borderPen = new Pen(Border);

        eventArgs.Graphics.FillRectangle(backgroundBrush, rectangle);
        eventArgs.Graphics.DrawRectangle(borderPen, rectangle);

        string text = tabControl.TabPages[eventArgs.Index].Text;
        TextRenderer.DrawText(
            eventArgs.Graphics,
            text,
            tabControl.Font,
            rectangle,
            fore,
            TextFormatFlags.HorizontalCenter | TextFormatFlags.VerticalCenter);
    }
}