/// 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 Interop.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 Interop.User32.DRAWTEXTPARAMS
{
iLeftMargin = currentCachedInfo.LeftTextMargin,
iRightMargin = currentCachedInfo.RightTextMargin
});
}
else if (currentCachedInfo == null)
{
currentCachedInfo = new CachedInfo();
cachedMeasurementDCInfo = currentCachedInfo;
}
Interop.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 Interop.User32.DRAWTEXTPARAMS
{
iLeftMargin = currentCachedInfo.LeftTextMargin,
iRightMargin = currentCachedInfo.RightTextMargin
});
}
/// <summary>
/// The GDI DrawText does not do multiline alignment when Interop.User32.TextFormatFlags.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, Interop.User32.TextFormatFlags flags, ref Interop.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 Interop.User32.TextFormatFlags.Top because it is 0), single line text or measuring text.
bool isTop = (flags & Interop.User32.TextFormatFlags.DT_BOTTOM) == 0 && (flags & Interop.User32.TextFormatFlags.DT_VCENTER) == 0;
if (isTop || ((flags & Interop.User32.TextFormatFlags.DT_SINGLELINE) != 0) || ((flags & Interop.User32.TextFormatFlags.DT_CALCRECT) != 0))
{
return(bounds);
}
Interop.RECT rect = new Interop.RECT(bounds);
// Get the text bounds.
flags |= Interop.User32.TextFormatFlags.DT_CALCRECT;
int textHeight = Interop.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 & Interop.User32.TextFormatFlags.DT_VCENTER) != 0) // Middle
{
adjustedBounds.Y = adjustedBounds.Top + adjustedBounds.Height / 2 - textHeight / 2;
}
else // Bottom.
{
adjustedBounds.Y = adjustedBounds.Bottom - textHeight;
}
return(adjustedBounds);
}
/// <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, Interop.User32.TextFormatFlags 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
Interop.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
Interop.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 Interop.RECT(0, 0, proposedSize.Width, proposedSize.Height);
if (font != null)
{
dc.SelectFont(font);
}
// If proposedSize.Height >= MaxSize.Height it is assumed bounds needed. If flags contain DT_SINGLELINE and
// DT_VCENTER or DT_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 DT_VCENTER and DT_BOTTOM flags to
// get the actual text bounds.
if (proposedSize.Height >= MaxSize.Height && (flags & Interop.User32.TextFormatFlags.DT_SINGLELINE) != 0)
{
// Clear vertical-alignment flags.
flags &= ~(Interop.User32.TextFormatFlags.DT_BOTTOM | Interop.User32.TextFormatFlags.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 &= ~(Interop.User32.TextFormatFlags.DT_WORDBREAK);
}
flags |= Interop.User32.TextFormatFlags.DT_CALCRECT;
Interop.User32.DrawTextExW(dc.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, Interop.User32.TextFormatFlags 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 & Interop.User32.TextFormatFlags.DT_CALCRECT) == 0, "DT_CALCRECT flag is set, text won't be drawn");
HandleRef hdc = new HandleRef(dc, dc.Hdc);
// DrawText requires default text alignment.
if (dc.TextAlignment != DeviceContextTextAlignment.Default)
{
dc.SetTextAlignment(DeviceContextTextAlignment.Default);
}
// color empty means use the one currently selected in the dc.
if (!foreColor.IsEmpty && foreColor != dc.TextColor)
{
dc.SetTextColor(foreColor);
}
if (font != null)
{
dc.SelectFont(font);
}
DeviceContextBackgroundMode newBackGndMode = (backColor.IsEmpty || backColor == Color.Transparent) ?
DeviceContextBackgroundMode.Transparent :
DeviceContextBackgroundMode.Opaque;
if (dc.BackgroundMode != newBackGndMode)
{
dc.SetBackgroundMode(newBackGndMode);
}
if (newBackGndMode != DeviceContextBackgroundMode.Transparent && backColor != dc.BackgroundColor)
{
dc.SetBackgroundColor(backColor);
}
Interop.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 Interop.RECT(bounds);
Interop.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).
}
