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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Drawing;
using System.Windows.Forms.VisualStyles;
namespace System.Windows.Forms;
/// <summary>
/// This is a rendering class for the GroupBox control.
/// </summary>
public static class GroupBoxRenderer
{
// Make this per-thread, so that different threads can safely use these methods.
[ThreadStatic]
private static VisualStyleRenderer? t_visualStyleRenderer;
private static readonly VisualStyleElement s_groupBoxElement = VisualStyleElement.Button.GroupBox.Normal;
private const int TextOffset = 8;
private const int BoxHeaderWidth = 7; // The groupbox frame shows 7 pixels before the caption.
/// <summary>
/// If this property is true, then the renderer will use the setting from Application.RenderWithVisualStyles
/// to determine how to render.If this property is false, the renderer will always render with visualstyles.
/// </summary>
public static bool RenderMatchingApplicationState { get; set; } = true;
private static bool RenderWithVisualStyles
=> (!RenderMatchingApplicationState || Application.RenderWithVisualStyles);
/// <summary>
/// Returns true if the background corresponding to the given state is partially transparent, else false.
/// </summary>
public static bool IsBackgroundPartiallyTransparent(GroupBoxState state)
{
if (RenderWithVisualStyles)
{
InitializeRenderer((int)state);
return t_visualStyleRenderer.IsBackgroundPartiallyTransparent();
}
else
{
return false;
}
}
/// <summary>
/// This is just a convenience wrapper for VisualStyleRenderer.DrawThemeParentBackground. For downlevel,
/// this isn't required and does nothing.
/// </summary>
public static void DrawParentBackground(Graphics g, Rectangle bounds, Control childControl)
{
if (RenderWithVisualStyles)
{
InitializeRenderer(0);
t_visualStyleRenderer.DrawParentBackground(g, bounds, childControl);
}
}
/// <summary>
/// Renders a GroupBox control.
/// </summary>
public static void DrawGroupBox(Graphics g, Rectangle bounds, GroupBoxState state)
{
if (RenderWithVisualStyles)
{
DrawThemedGroupBoxNoText(g, bounds, state);
}
else
{
DrawUnthemedGroupBoxNoText(g, bounds);
}
}
/// <summary>
/// Renders a GroupBox control. Uses the text color specified by the theme.
/// </summary>
public static void DrawGroupBox(Graphics g, Rectangle bounds, string? groupBoxText, Font? font, GroupBoxState state)
=> DrawGroupBox(g, bounds, groupBoxText, font, TextFormatFlags.Top | TextFormatFlags.Left, state);
/// <summary>
/// Renders a GroupBox control.
/// </summary>
public static void DrawGroupBox(
Graphics g,
Rectangle bounds,
string? groupBoxText,
Font? font,
Color textColor,
GroupBoxState state)
=> DrawGroupBox(g, bounds, groupBoxText, font, textColor, TextFormatFlags.Top | TextFormatFlags.Left, state);
/// <summary>
/// Renders a GroupBox control. Uses the text color specified by the theme.
/// </summary>
public static void DrawGroupBox(
Graphics g,
Rectangle bounds,
string? groupBoxText,
Font? font,
TextFormatFlags flags,
GroupBoxState state)
=> DrawGroupBox((IDeviceContext)g, bounds, groupBoxText, font, flags, state);
internal static void DrawGroupBox(
IDeviceContext deviceContext,
Rectangle bounds,
string? groupBoxText,
Font? font,
TextFormatFlags flags,
GroupBoxState state)
{
if (RenderWithVisualStyles)
{
DrawThemedGroupBoxWithText(deviceContext, bounds, groupBoxText, font, DefaultTextColor(state), flags, state);
}
else
{
DrawUnthemedGroupBoxWithText(deviceContext, bounds, groupBoxText, font, DefaultTextColor(state), flags);
}
}
/// <summary>
/// Renders a GroupBox control.
/// </summary>
public static void DrawGroupBox(
Graphics g,
Rectangle bounds,
string? groupBoxText,
Font? font,
Color textColor,
TextFormatFlags flags,
GroupBoxState state)
=> DrawGroupBox((IDeviceContext)g, bounds, groupBoxText, font, textColor, flags, state);
internal static void DrawGroupBox(
IDeviceContext deviceContext,
Rectangle bounds,
string? groupBoxText,
Font? font,
Color textColor,
TextFormatFlags flags,
GroupBoxState state)
{
if (RenderWithVisualStyles)
{
DrawThemedGroupBoxWithText(deviceContext, bounds, groupBoxText, font, textColor, flags, state);
}
else
{
DrawUnthemedGroupBoxWithText(deviceContext, bounds, groupBoxText, font, textColor, flags);
}
}
/// <summary>
/// Draws a themed GroupBox with no text label.
/// </summary>
private static void DrawThemedGroupBoxNoText(Graphics g, Rectangle bounds, GroupBoxState state)
{
InitializeRenderer((int)state);
t_visualStyleRenderer.DrawBackground(g, bounds);
}
/// <summary>
/// Draws a themed GroupBox with a text label.
/// </summary>
private static void DrawThemedGroupBoxWithText(
IDeviceContext deviceContext,
Rectangle bounds,
string? groupBoxText,
Font? font,
Color textColor,
TextFormatFlags flags,
GroupBoxState state)
{
InitializeRenderer((int)state);
// Calculate text area, and render text inside it
Rectangle textBounds = bounds;
textBounds.Width -= 2 * BoxHeaderWidth;
Size measuredBounds = TextRenderer.MeasureText(
deviceContext,
groupBoxText,
font,
new Size(textBounds.Width, textBounds.Height),
flags);
textBounds.Width = measuredBounds.Width;
textBounds.Height = measuredBounds.Height;
if ((flags & TextFormatFlags.Right) == TextFormatFlags.Right)
{
// +1 to account for the margin built in the MeasureText result
textBounds.X = bounds.Right - textBounds.Width - BoxHeaderWidth + 1;
}
else
{
// -1 to account for the margin built in the MeasureText result
textBounds.X += BoxHeaderWidth - 1;
}
TextRenderer.DrawText(deviceContext, groupBoxText, font, textBounds, textColor, flags);
// Calculate area for background box
Rectangle boxBounds = bounds;
if (font is not null)
{
boxBounds.Y += font.Height / 2;
boxBounds.Height -= font.Height / 2;
}
// Break box into three segments, that don't overlap the text area
Rectangle clipLeft = boxBounds;
Rectangle clipMiddle = boxBounds;
Rectangle clipRight = boxBounds;
clipLeft.Width = BoxHeaderWidth;
clipMiddle.Width = Math.Max(0, textBounds.Width - 3); // -3 to account for the margin built in the MeasureText result
if ((flags & TextFormatFlags.Right) == TextFormatFlags.Right)
{
clipLeft.X = boxBounds.Right - BoxHeaderWidth;
clipMiddle.X = clipLeft.Left - clipMiddle.Width;
clipRight.Width = clipMiddle.X - boxBounds.X;
}
else
{
clipMiddle.X = clipLeft.Right;
clipRight.X = clipMiddle.Right;
clipRight.Width = boxBounds.Right - clipRight.X;
}
clipMiddle.Y = textBounds.Bottom;
clipMiddle.Height -= (textBounds.Bottom - boxBounds.Top);
Debug.Assert(textBounds.Y <= boxBounds.Y, "if text below box, need to render area of box above text");
// Render clipped portion of background in each segment
t_visualStyleRenderer.DrawBackground(deviceContext, boxBounds, clipLeft);
t_visualStyleRenderer.DrawBackground(deviceContext, boxBounds, clipMiddle);
t_visualStyleRenderer.DrawBackground(deviceContext, boxBounds, clipRight);
}
/// <summary>
/// Draws an un-themed GroupBox with no text label.
/// </summary>
private static void DrawUnthemedGroupBoxNoText(Graphics g, Rectangle bounds)
{
Color backColor = SystemColors.Control;
using var light = ControlPaint.Light(backColor, 1.0f).GetCachedPenScope();
using var dark = ControlPaint.Dark(backColor, 0f).GetCachedPenScope();
// left
g.DrawLine(light, bounds.Left + 1, bounds.Top + 1, bounds.Left + 1, bounds.Height - 1);
g.DrawLine(dark, bounds.Left, bounds.Top + 1, bounds.Left, bounds.Height - 2);
// bottom
g.DrawLine(light, bounds.Left, bounds.Height - 1, bounds.Width - 1, bounds.Height - 1);
g.DrawLine(dark, bounds.Left, bounds.Height - 2, bounds.Width - 1, bounds.Height - 2);
// top
g.DrawLine(light, bounds.Left + 1, bounds.Top + 1, bounds.Width - 1, bounds.Top + 1);
g.DrawLine(dark, bounds.Left, bounds.Top, bounds.Width - 2, bounds.Top);
// right
g.DrawLine(light, bounds.Width - 1, bounds.Top, bounds.Width - 1, bounds.Height - 1);
g.DrawLine(dark, bounds.Width - 2, bounds.Top, bounds.Width - 2, bounds.Height - 2);
}
/// <summary>
/// Draws an un-themed GroupBox with a text label. Variation of the logic in GroupBox.DrawGroupBox().
/// </summary>
private static void DrawUnthemedGroupBoxWithText(
IDeviceContext deviceContext,
Rectangle bounds,
string? groupBoxText,
Font? font,
Color textColor,
TextFormatFlags flags)
{
// Calculate text area, and render text inside it
Rectangle textBounds = bounds;
textBounds.Width -= TextOffset;
Size measuredBounds = TextRenderer.MeasureText(
deviceContext,
groupBoxText,
font,
new Size(textBounds.Width, textBounds.Height),
flags);
textBounds.Width = measuredBounds.Width;
textBounds.Height = measuredBounds.Height;
if ((flags & TextFormatFlags.Right) == TextFormatFlags.Right)
{
textBounds.X = bounds.Right - textBounds.Width - TextOffset;
}
else
{
textBounds.X += TextOffset;
}
TextRenderer.DrawText(deviceContext, groupBoxText, font, textBounds, textColor, flags);
// Pad text area to stop background from touching text
if (textBounds.Width > 0)
{
textBounds.Inflate(2, 0);
}
int boxTop = bounds.Top;
if (font is not null)
{
boxTop += font.Height / 2;
}
using DeviceContextHdcScope hdc = deviceContext.ToHdcScope();
ReadOnlySpan<int> darkLines =
[
bounds.Left, boxTop - 1, bounds.Left, bounds.Height - 2, // Left
bounds.Left, bounds.Height - 2, bounds.Width - 1, bounds.Height - 2, // Right
bounds.Left, boxTop - 1, textBounds.X - 3, boxTop - 1, // Top-left
textBounds.X + textBounds.Width + 2, boxTop - 1, bounds.Width - 2, boxTop - 1, // Top-right
bounds.Width - 2, boxTop - 1, bounds.Width - 2, bounds.Height - 2 // Right
];
using CreatePenScope hpenDark = new(SystemColors.ControlDark);
hdc.DrawLines(hpenDark, darkLines);
ReadOnlySpan<int> lightLines =
[
bounds.Left + 1, boxTop, bounds.Left + 1, bounds.Height - 1, // Left
bounds.Left, bounds.Height - 1, bounds.Width, bounds.Height - 1, // Right
bounds.Left + 1, boxTop, textBounds.X - 2, boxTop, // Top-left
textBounds.X + textBounds.Width + 1, boxTop, bounds.Width - 1, boxTop, // Top-right
bounds.Width - 1, boxTop, bounds.Width - 1, bounds.Height - 1 // Right
];
using CreatePenScope hpenLight = new(SystemColors.ControlLight);
hdc.DrawLines(hpenLight, lightLines);
}
private static Color DefaultTextColor(GroupBoxState state)
{
if (RenderWithVisualStyles)
{
InitializeRenderer((int)state);
return t_visualStyleRenderer.GetColor(ColorProperty.TextColor);
}
else
{
return SystemColors.ControlText;
}
}
[MemberNotNull(nameof(t_visualStyleRenderer))]
private static void InitializeRenderer(int state)
{
int part = s_groupBoxElement.Part;
if (SystemInformation.HighContrast
&& ((GroupBoxState)state == GroupBoxState.Disabled)
&& VisualStyleRenderer.IsCombinationDefined(
s_groupBoxElement.ClassName,
VisualStyleElement.Button.GroupBox.HighContrastDisabledPart))
{
part = VisualStyleElement.Button.GroupBox.HighContrastDisabledPart;
}
if (t_visualStyleRenderer is null)
{
t_visualStyleRenderer = new VisualStyleRenderer(s_groupBoxElement.ClassName, part, state);
}
else
{
t_visualStyleRenderer.SetParameters(s_groupBoxElement.ClassName, part, state);
}
}
}
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