/// <summary>
/// Returns the Size in logical units of the given text using the given Font, and according to the formatting flags.
/// The proposed size is used to create a bounding rectangle as follows:
/// - If there are multiple lines of text, DrawText uses the width of the rectangle pointed to by
/// the lpRect parameter and extends the base of the rectangle to bound the last line of text.
/// - If the largest word is wider than the rectangle, the width is expanded.
/// - If the text is less than the width of the rectangle, the width is reduced.
/// - If there is only one line of text, DrawText modifies the right side of the rectangle so that
/// it bounds the last character in the line.
/// If the font is null, the hdc's current font will be used.
///
/// Note for vertical fonts (if ever supported): DrawTextEx uses GetTextExtentPoint32 for measuring the text and this
/// function has the following limitation (from MSDN):
/// - This function assumes that the text is horizontal, that is, that the escapement is always 0. This is true for both
/// the horizontal and vertical measurements of the text. The application must convert it explicitly.
/// </summary>
public static Size MeasureText(
this Gdi32.HDC hdc,
string?text,
FontCache.FontScope font,
Size proposedSize,
User32.DT flags)
{
ValidateFlags(flags);
if (string.IsNullOrEmpty(text))
{
return(Size.Empty);
}
// DrawText returns a rectangle useful for aligning, but not guaranteed to encompass all
// pixels (its not a FitBlackBox, if the text is italicized, it will overhang on the right.)
// So we need to account for this.
User32.DRAWTEXTPARAMS dtparams = GetTextMargins(font);
// If Width / Height are < 0, we need to make them larger or DrawText will return
// an unbounded measurement when we actually trying to make it very narrow.
int minWidth = 1 + dtparams.iLeftMargin + dtparams.iRightMargin;
if (proposedSize.Width <= minWidth)
{
proposedSize.Width = minWidth;
}
if (proposedSize.Height <= 0)
{
proposedSize.Height = 1;
}
var rect = new RECT(0, 0, proposedSize.Width, proposedSize.Height);
using var fontSelection = new Gdi32.SelectObjectScope(hdc, font);
// If proposedSize.Height >= MaxSize.Height it is assumed bounds needed. If flags contain SINGLELINE and
// VCENTER or BOTTOM options, DrawTextEx does not bind the rectangle to the actual text height since
// it assumes the text is to be vertically aligned; we need to clear the VCENTER and BOTTOM flags to
// get the actual text bounds.
if (proposedSize.Height >= TextRenderer.MaxSize.Height && (flags & User32.DT.SINGLELINE) != 0)
{
// Clear vertical-alignment flags.
flags &= ~(User32.DT.BOTTOM | User32.DT.VCENTER);
}
if (proposedSize.Width == TextRenderer.MaxSize.Width)
{
// PERF: No constraining width means no word break.
// in this case, we dont care about word wrapping - there should be enough room to fit it all
flags &= ~(User32.DT.WORDBREAK);
}
flags |= User32.DT.CALCRECT;
User32.DrawTextExW(hdc, text, text.Length, ref rect, flags, ref dtparams);
return(rect.Size);
}
public static Size MeasureText(
this DeviceContextHdcScope hdc,
string?text,
FontCache.FontScope font,
Size proposedSize,
User32.DT flags)
=> MeasureText(hdc.HDC, text, font, proposedSize, flags);
public static void DrawText(
this DeviceContextHdcScope hdc,
string?text,
FontCache.FontScope font,
Rectangle bounds,
Color foreColor,
User32.DT flags,
Color backColor = default,
TextPaddingOptions padding = default)
=> DrawText(hdc.HDC, text, font, bounds, foreColor, flags, backColor, padding);
/// <summary>
/// Draws the text in the given bounds, using the given Font, foreColor and backColor, and according to the specified
/// TextFormatFlags flags.
///
/// If font is null, the font currently selected in the hdc is used.
///
/// If foreColor and/or backColor are Color.Empty, the hdc current text and/or background color are used.
/// </summary>
public static void DrawText(
this Gdi32.HDC hdc,
string?text,
FontCache.FontScope font,
Rectangle bounds,
Color foreColor,
User32.DT flags,
Color backColor = default,
TextPaddingOptions padding = default)
{
if (string.IsNullOrEmpty(text) || foreColor == Color.Transparent)
{
return;
}
ValidateFlags(flags);
// DrawText requires default text alignment.
using var alignment = new Gdi32.SetTextAlignmentScope(hdc, default);
// Color empty means use the one currently selected in the dc.
using var textColor = foreColor.IsEmpty ? default : new Gdi32.SetTextColorScope(hdc, foreColor);
using var fontSelection = new Gdi32.SelectObjectScope(hdc, font);
Gdi32.BKMODE newBackGroundMode = (backColor.IsEmpty || backColor == Color.Transparent) ?
Gdi32.BKMODE.TRANSPARENT :
Gdi32.BKMODE.OPAQUE;
using var backgroundMode = new Gdi32.SetBkModeScope(hdc, newBackGroundMode);
using var backgroundColor = newBackGroundMode != Gdi32.BKMODE.TRANSPARENT
? new Gdi32.SetBackgroundColorScope(hdc, backColor)
: default;
User32.DRAWTEXTPARAMS dtparams = GetTextMargins(font, padding);
bounds = AdjustForVerticalAlignment(hdc, text, bounds, flags, ref dtparams);
// Adjust unbounded rect to avoid overflow since Rectangle ctr does not do param validation.
if (bounds.Width == TextRenderer.MaxSize.Width)
{
bounds.Width -= bounds.X;
}
if (bounds.Height == TextRenderer.MaxSize.Height)
{
bounds.Height -= bounds.Y;
}
RECT rect = bounds;
User32.DrawTextExW(hdc, text, text.Length, ref rect, flags, ref dtparams);
}
/// <summary>
/// Get the bounding box internal text padding to be used when drawing text.
/// </summary>
public static User32.DRAWTEXTPARAMS GetTextMargins(
this FontCache.FontScope font,
TextPaddingOptions padding = default)
{
// DrawText(Ex) adds a small space at the beginning of the text bounding box but not at the end,
// this is more noticeable when the font has the italic style. We compensate with this factor.
int leftMargin = 0;
int rightMargin = 0;
float overhangPadding;
switch (padding)
{
case TextPaddingOptions.GlyphOverhangPadding:
// [overhang padding][Text][overhang padding][italic padding]
overhangPadding = font.FontHeight / 6f;
leftMargin = (int)Math.Ceiling(overhangPadding);
rightMargin = (int)Math.Ceiling(overhangPadding * (1 + ItalicPaddingFactor));
break;
case TextPaddingOptions.LeftAndRightPadding:
// [2 * overhang padding][Text][2 * overhang padding][italic padding]
overhangPadding = font.FontHeight / 6f;
leftMargin = (int)Math.Ceiling(2 * overhangPadding);
rightMargin = (int)Math.Ceiling(overhangPadding * (2 + ItalicPaddingFactor));
break;
case TextPaddingOptions.NoPadding:
default:
break;
}
return(new User32.DRAWTEXTPARAMS
{
iLeftMargin = leftMargin,
iRightMargin = rightMargin
});
}
