/// <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,
ReadOnlySpan <char> text,
FontCache.Scope font,
Size proposedSize,
TextFormatFlags flags)
{
(User32.DT dt, TextPaddingOptions padding) = SplitTextFormatFlags(flags);
if (text.IsEmpty)
{
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, padding);
// 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.Object);
// 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 && (dt & User32.DT.SINGLELINE) != 0)
{
// Clear vertical-alignment flags.
dt &= ~(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
dt &= ~(User32.DT.WORDBREAK);
}
dt |= User32.DT.CALCRECT;
User32.DrawTextExW(hdc, text, ref rect, dt, ref dtparams);
return(rect.Size);
}
/// GetTextMargins - checks to see if we have cached information about the current font,
/// returns info about it.
/// An MRU of Font margins was considered, but seems like overhead.
internal static User32.DRAWTEXTPARAMS GetTextMargins(WindowsGraphics wg, WindowsFont font)
{
// PERF: operate on a local reference rather than party directly on the thread static one.
CachedInfo currentCachedInfo = cachedMeasurementDCInfo;
if (currentCachedInfo != null && currentCachedInfo.LeftTextMargin > 0 && currentCachedInfo.RightTextMargin > 0 && font == currentCachedInfo.LastUsedFont)
{
// we have to return clones as DrawTextEx will modify this struct
return(new User32.DRAWTEXTPARAMS
{
iLeftMargin = currentCachedInfo.LeftTextMargin,
iRightMargin = currentCachedInfo.RightTextMargin
});
}
else if (currentCachedInfo == null)
{
currentCachedInfo = new CachedInfo();
cachedMeasurementDCInfo = currentCachedInfo;
}
User32.DRAWTEXTPARAMS drawTextParams = wg.GetTextMargins(font);
currentCachedInfo.LeftTextMargin = drawTextParams.iLeftMargin;
currentCachedInfo.RightTextMargin = drawTextParams.iRightMargin;
// returning a copy here to be consistent with the return value from the cache.
return(new User32.DRAWTEXTPARAMS
{
iLeftMargin = currentCachedInfo.LeftTextMargin,
iRightMargin = currentCachedInfo.RightTextMargin
});
}
public static void DrawString(Control context, Font font, string text, Rectangle textBounds, bool useMnemonics, GdiTextDrawMode textMode)
{
IntPtr hdc = User32.GetDC(context.Handle);
try
{
Gdi32.SetBkColor(hdc, Gdi32.ToColorRef(context.BackColor));
Gdi32.SetTextColor(hdc, Gdi32.ToColorRef(context.ForeColor));
try
{
IntPtr hFont = font.ToHfont();
try
{
IntPtr hPrevFont = Gdi32.SelectObject(hdc, hFont);
try
{
StringBuilder sb = new StringBuilder(text);
RECT rect = textBounds;
User32.DRAWTEXTPARAMS dtparams = new User32.DRAWTEXTPARAMS();
dtparams.cbSize = (uint)Marshal.SizeOf(typeof(User32.DRAWTEXTPARAMS));
User32.DT flags =
textMode == GdiTextDrawMode.EndEllipsis ? User32.DT.END_ELLIPSIS
: textMode == GdiTextDrawMode.WordBreak ? User32.DT.WORDBREAK | User32.DT.END_ELLIPSIS
: User32.DT.WORDBREAK;
if (useMnemonics)
{
flags |= User32.DT.NOPREFIX;
}
if (0 == User32.DrawTextEx(hdc, sb, sb.Length, ref rect, flags, ref dtparams))
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
}
finally
{
Gdi32.SelectObject(hdc, hPrevFont);
}
}
finally
{
Gdi32.DeleteObject(hFont);
}
}
finally
{
}
}
finally
{
User32.ReleaseDC(context.Handle, hdc);
}
}
/// <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,
ReadOnlySpan <char> text,
FontCache.Scope font,
Rectangle bounds,
Color foreColor,
User32.DT flags,
Color backColor = default,
TextPaddingOptions padding = default)
{
if (text.IsEmpty || 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, (Gdi32.HFONT)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, ref rect, flags, ref dtparams);
}
public void Font_GetTextMargins(string family, float size, int left, int right)
{
using Font font = new Font(family, size);
if (font.Name != family)
{
// Not installed on this machine
return;
}
using var hfont = GdiCache.GetHFONT(font, Gdi32.QUALITY.CLEARTYPE);
User32.DRAWTEXTPARAMS margins = hfont.GetTextMargins();
Assert.Equal(left, margins.iLeftMargin);
Assert.Equal(right, margins.iRightMargin);
}
public void Font_GetTextMargins(string family, float size, int left, int right)
{
using Font font = new Font(family, size);
if (font.Name != family)
{
// Not installed on this machine
return;
}
using WindowsFont windowsFont = WindowsFont.FromFont(font, Gdi32.QUALITY.CLEARTYPE);
WindowsGraphics graphics = WindowsGraphicsCacheManager.MeasurementGraphics;
User32.DRAWTEXTPARAMS margins = graphics.GetTextMargins(windowsFont);
Assert.Equal(left, margins.iLeftMargin);
Assert.Equal(right, margins.iRightMargin);
}
/// <summary>
/// The GDI DrawText does not do multiline alignment when User32.DT.SINGLELINE is not set. This
/// adjustment is to workaround that limitation. We don't want to duplicate SelectObject calls here,
/// so put your Font in the dc before calling this.
///
/// AdjustForVerticalAlignment is only used when the text is multiline and it fits inside the bounds passed in.
/// In that case we want the horizontal center of the multiline text to be at the horizontal center of the bounds.
///
/// If the text is multiline and it does not fit inside the bounds passed in, then return the bounds that were passed in.
/// This way we paint the top of the text at the top of the bounds passed in.
/// </summary>
public static Rectangle AdjustForVerticalAlignment(
this Gdi32.HDC hdc,
ReadOnlySpan <char> text,
Rectangle bounds,
User32.DT flags,
ref User32.DRAWTEXTPARAMS dtparams)
{
ValidateFlags(flags);
// Ok if any Top (Cannot test User32.DT.Top because it is 0), single line text or measuring text.
bool isTop = (flags & User32.DT.BOTTOM) == 0 && (flags & User32.DT.VCENTER) == 0;
if (isTop || ((flags & User32.DT.SINGLELINE) != 0) || ((flags & User32.DT.CALCRECT) != 0))
{
return(bounds);
}
RECT rect = new RECT(bounds);
// Get the text bounds.
flags |= User32.DT.CALCRECT;
int textHeight = User32.DrawTextExW(hdc, text, ref rect, flags, ref dtparams);
// if the text does not fit inside the bounds then return the bounds that were passed in
if (textHeight > bounds.Height)
{
return(bounds);
}
Rectangle adjustedBounds = bounds;
if ((flags & User32.DT.VCENTER) != 0)
{
// Middle
adjustedBounds.Y = adjustedBounds.Top + adjustedBounds.Height / 2 - textHeight / 2;
}
else
{
// Bottom
adjustedBounds.Y = adjustedBounds.Bottom - textHeight;
}
return(adjustedBounds);
}
/// <summary>
/// The GDI DrawText does not do multiline alignment when User32.DT.SINGLELINE is not set. This
/// adjustment is to workaround that limitation. We don't want to duplicate SelectObject calls here,
/// so put your Font in the dc before calling this.
///
/// AdjustForVerticalAlignment is only used when the text is multiline and it fits inside the bounds passed in.
/// In that case we want the horizontal center of the multiline text to be at the horizontal center of the bounds.
///
/// If the text is multiline and it does not fit inside the bounds passed in, then return the bounds that were passed in.
/// This way we paint the top of the text at the top of the bounds passed in.
/// </summary>
public static Rectangle AdjustForVerticalAlignment(
HandleRef hdc,
string text,
Rectangle bounds,
User32.DT flags,
ref User32.DRAWTEXTPARAMS dtparams)
{
Debug.Assert(((uint)flags & GdiUnsupportedFlagMask) == 0, "Some custom flags were left over and are not GDI compliant!");
// Ok if any Top (Cannot test User32.DT.Top because it is 0), single line text or measuring text.
bool isTop = (flags & User32.DT.BOTTOM) == 0 && (flags & User32.DT.VCENTER) == 0;
if (isTop || ((flags & User32.DT.SINGLELINE) != 0) || ((flags & User32.DT.CALCRECT) != 0))
{
return(bounds);
}
RECT rect = new RECT(bounds);
// Get the text bounds.
flags |= User32.DT.CALCRECT;
int textHeight = User32.DrawTextExW(hdc, text, text.Length, ref rect, flags, ref dtparams);
// if the text does not fit inside the bounds then return the bounds that were passed in
if (textHeight > bounds.Height)
{
return(bounds);
}
Rectangle adjustedBounds = bounds;
if ((flags & User32.DT.VCENTER) != 0) // Middle
{
adjustedBounds.Y = adjustedBounds.Top + adjustedBounds.Height / 2 - textHeight / 2;
}
else // Bottom.
{
adjustedBounds.Y = adjustedBounds.Bottom - textHeight;
}
return(adjustedBounds);
}
public void Font_AdjustForVerticalAlignment(string family, float size, Rectangle bounds, uint dt, Rectangle expected)
{
using Font font = new Font(family, size);
if (font.Name != family)
{
// Not installed on this machine
return;
}
using var hfont = GdiCache.GetHFONT(font, Gdi32.QUALITY.CLEARTYPE);
using var screen = GdiCache.GetScreenHdc();
using var fontSelection = new Gdi32.SelectObjectScope(screen, hfont.Object);
User32.DRAWTEXTPARAMS param = default;
Rectangle result = screen.HDC.AdjustForVerticalAlignment(
"Windows Foundation Classes",
bounds,
(User32.DT)dt,
ref param);
Assert.Equal(expected, result);
}
public static Rectangle MeasureString(Control context, Font font, string text, Rectangle textBounds)
{
IntPtr hdc = User32.GetDC(context.Handle);
try
{
IntPtr hFont = font.ToHfont();
try
{
IntPtr hPrevFont = Gdi32.SelectObject(hdc, hFont);
try
{
StringBuilder sb = new StringBuilder(text);
RECT rect = textBounds;
rect.bottom = rect.top; // set height to 0
User32.DRAWTEXTPARAMS dtparams = new User32.DRAWTEXTPARAMS();
dtparams.cbSize = (uint)Marshal.SizeOf(typeof(User32.DRAWTEXTPARAMS));
if (0 == User32.DrawTextEx(hdc, sb, sb.Length, ref rect, User32.DT.CALCRECT | User32.DT.WORDBREAK | User32.DT.END_ELLIPSIS, ref dtparams))
{
throw new Win32Exception(Marshal.GetLastWin32Error());
}
return(rect);
}
finally
{
Gdi32.SelectObject(hdc, hPrevFont);
}
}
finally
{
Gdi32.DeleteObject(hFont);
}
}
finally
{
User32.ReleaseDC(context.Handle, hdc);
}
}
public void Font_AdjustForVerticalAlignment(string family, float size, Rectangle bounds, uint dt, Rectangle expected)
{
using Font font = new Font(family, size);
if (font.Name != family)
{
// Not installed on this machine
return;
}
using WindowsFont windowsFont = WindowsFont.FromFont(font, Gdi32.QUALITY.CLEARTYPE);
WindowsGraphics graphics = WindowsGraphicsCacheManager.MeasurementGraphics;
graphics.DeviceContext.SelectFont(windowsFont);
User32.DRAWTEXTPARAMS param = default;
Rectangle result = WindowsGraphics.AdjustForVerticalAlignment(
graphics,
"Windows Foundation Classes",
bounds,
(User32.DT)dt,
ref param);
Assert.Equal(expected, result);
}
/// <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 Size MeasureText(string text, WindowsFont font, Size proposedSize, User32.DT flags)
{
Debug.Assert(((uint)flags & GdiUnsupportedFlagMask) == 0, "Some custom flags were left over and are not GDI compliant!");
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.
#if OPTIMIZED_MEASUREMENTDC
User32.DRAWTEXTPARAMS dtparams;
// use the cache if we've got it
if (MeasurementDCInfo.IsMeasurementDC(DeviceContext))
{
dtparams = MeasurementDCInfo.GetTextMargins(this, font);
}
else
{
dtparams = GetTextMargins(font);
}
#else
User32.DRAWTEXTPARAMS dtparams = GetTextMargins(font);
#endif
// 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);
if (font != null)
{
DeviceContext.SelectFont(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 >= MaxSize.Height && (flags & User32.DT.SINGLELINE) != 0)
{
// Clear vertical-alignment flags.
flags &= ~(User32.DT.BOTTOM | User32.DT.VCENTER);
}
if (proposedSize.Width == 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(DeviceContext.Hdc, text, text.Length, ref rect, flags, ref dtparams);
return(rect.Size);
}
/// <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 void DrawText(string text, WindowsFont font, Rectangle bounds, Color foreColor, Color backColor, User32.DT flags)
{
if (string.IsNullOrEmpty(text) || foreColor == Color.Transparent)
{
return;
}
Debug.Assert(((uint)flags & GdiUnsupportedFlagMask) == 0, "Some custom flags were left over and are not GDI compliant!");
Debug.Assert((flags & User32.DT.CALCRECT) == 0, "CALCRECT flag is set, text won't be drawn");
HandleRef hdc = new HandleRef(DeviceContext, DeviceContext.Hdc);
// DrawText requires default text alignment.
if (DeviceContext.TextAlignment != default)
{
DeviceContext.TextAlignment = default;
}
// color empty means use the one currently selected in the dc.
if (!foreColor.IsEmpty && foreColor != DeviceContext.TextColor)
{
DeviceContext.TextColor = foreColor;
}
if (font != null)
{
DeviceContext.SelectFont(font);
}
Gdi32.BKMODE newBackGndMode = (backColor.IsEmpty || backColor == Color.Transparent) ?
Gdi32.BKMODE.TRANSPARENT :
Gdi32.BKMODE.OPAQUE;
if (DeviceContext.BackgroundMode != newBackGndMode)
{
DeviceContext.SetBackgroundMode(newBackGndMode);
}
if (newBackGndMode != Gdi32.BKMODE.TRANSPARENT && backColor != DeviceContext.BackgroundColor)
{
DeviceContext.BackgroundColor = backColor;
}
User32.DRAWTEXTPARAMS dtparams = GetTextMargins(font);
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 == MaxSize.Width)
{
bounds.Width -= bounds.X;
}
if (bounds.Height == MaxSize.Height)
{
bounds.Height -= bounds.Y;
}
var rect = new RECT(bounds);
User32.DrawTextExW(hdc, text, text.Length, ref rect, flags, ref dtparams);
// No need to restore previous objects into the dc (see comments on top of the class).
}
