/// <summary>
/// Returns the Size of the given text using the specified font if not null, otherwise the font currently
/// set in the dc is used.
/// This method is used to get the size in points of a line of text; it uses GetTextExtentPoint32 function
/// which computes the width and height of the text ignoring TAB\CR\LF characters.
/// A text extent is the distance between the beginning of the space and a character that will fit in the space.
/// </summary>
public Size GetTextExtent(string text, WindowsFont font)
{
if (string.IsNullOrEmpty(text))
{
return(Size.Empty);
}
Size size = new Size();
if (font != null)
{
DeviceContext.SelectFont(font);
}
Gdi32.GetTextExtentPoint32W(DeviceContext.Hdc, text, text.Length, ref size);
// Unselect, but not from Measurement DC as it keeps the same
// font selected for perf reasons.
if (font != null && !MeasurementDCInfo.IsMeasurementDC(DeviceContext))
{
DeviceContext.ResetFont();
}
return(new Size(size.Width, size.Height));
}
/// <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).
}
