/// <devdoc>
/// <para>
/// The GDI DrawText does not do multiline alignment when IntTextFormatFlags.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.
/// </para>
/// </devdoc>
public static Rectangle AdjustForVerticalAlignment(HandleRef hdc, string text, Rectangle bounds, IntTextFormatFlags flags, IntNativeMethods.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 IntTextFormatFlags.Top because it is 0), single line text or measuring text.
bool isTop = (flags & IntTextFormatFlags.Bottom) == 0 && (flags & IntTextFormatFlags.VerticalCenter) == 0;
if (isTop || ((flags & IntTextFormatFlags.SingleLine) != 0) || ((flags & IntTextFormatFlags.CalculateRectangle) != 0))
{
return(bounds);
}
IntNativeMethods.RECT rect = new IntNativeMethods.RECT(bounds);
// Get the text bounds.
flags |= IntTextFormatFlags.CalculateRectangle;
int textHeight = IntUnsafeNativeMethods.DrawTextEx(hdc, text, ref rect, (int)flags, 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 & IntTextFormatFlags.VerticalCenter) != 0) // Middle
{
adjustedBounds.Y = adjustedBounds.Top + adjustedBounds.Height / 2 - textHeight / 2;
}
else // Bottom.
{
adjustedBounds.Y = adjustedBounds.Bottom - textHeight;
}
return(adjustedBounds);
}
/// <devdoc>
/// 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.
/// </devdoc>
public Size MeasureText(string text, WindowsFont font, Size proposedSize, IntTextFormatFlags 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.
//
IntNativeMethods.DRAWTEXTPARAMS dtparams = null;
#if OPTIMIZED_MEASUREMENTDC
// use the cache if we've got it
if (MeasurementDCInfo.IsMeasurementDC(this.DeviceContext))
{
dtparams = MeasurementDCInfo.GetTextMargins(this, font);
}
#endif
if (dtparams == null)
{
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;
}
IntNativeMethods.RECT rect = IntNativeMethods.RECT.FromXYWH(0, 0, proposedSize.Width, proposedSize.Height);
HandleRef hdc = new HandleRef(null, this.dc.Hdc);
if (font != null)
{
this.dc.SelectFont(font);
}
// If proposedSize.Height >= MaxSize.Height it is assumed bounds needed. If flags contain SingleLine and
// VerticalCenter 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 VerticalCenter and Bottom flags to
// get the actual text bounds.
if (proposedSize.Height >= MaxSize.Height && (flags & IntTextFormatFlags.SingleLine) != 0)
{
// Clear vertical-alignment flags.
flags &= ~(IntTextFormatFlags.Bottom | IntTextFormatFlags.VerticalCenter);
}
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 &= ~(IntTextFormatFlags.WordBreak);
}
flags |= IntTextFormatFlags.CalculateRectangle;
IntUnsafeNativeMethods.DrawTextEx(hdc, text, ref rect, (int)flags, dtparams);
/* No need to restore previous objects into the dc (see comments on top of the class).
*
* if( hOldFont != IntPtr.Zero )
* {
* this.dc.SelectObject(hOldFont);
* }
*/
return(rect.Size);
}
/// <devdoc>
/// 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.
/// </devdoc>
public void DrawText(string text, WindowsFont font, Rectangle bounds, Color foreColor, Color backColor, IntTextFormatFlags 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 & IntTextFormatFlags.CalculateRectangle) == 0, "CalculateRectangle flag is set, text won't be drawn");
HandleRef hdc = new HandleRef(this.dc, this.dc.Hdc);
// DrawText requires default text alignment.
if (this.dc.TextAlignment != DeviceContextTextAlignment.Default)
{
this.dc.SetTextAlignment(DeviceContextTextAlignment.Default);
}
// color empty means use the one currently selected in the dc.
if (!foreColor.IsEmpty && foreColor != this.dc.TextColor)
{
this.dc.SetTextColor(foreColor);
}
if (font != null)
{
this.dc.SelectFont(font);
}
DeviceContextBackgroundMode newBackGndMode = (backColor.IsEmpty || backColor == Color.Transparent) ?
DeviceContextBackgroundMode.Transparent :
DeviceContextBackgroundMode.Opaque;
if (this.dc.BackgroundMode != newBackGndMode)
{
this.dc.SetBackgroundMode(newBackGndMode);
}
if (newBackGndMode != DeviceContextBackgroundMode.Transparent && backColor != this.dc.BackgroundColor)
{
this.dc.SetBackgroundColor(backColor);
}
IntNativeMethods.DRAWTEXTPARAMS dtparams = GetTextMargins(font);
bounds = AdjustForVerticalAlignment(hdc, text, bounds, flags, dtparams);
// Adjust unbounded rect to avoid overflow since Rectangle ctr does not do param validation.
if (bounds.Width == MaxSize.Width)
{
bounds.Width = bounds.Width - bounds.X;
}
if (bounds.Height == MaxSize.Height)
{
bounds.Height = bounds.Height - bounds.Y;
}
IntNativeMethods.RECT rect = new IntNativeMethods.RECT(bounds);
IntUnsafeNativeMethods.DrawTextEx(hdc, text, ref rect, (int)flags, dtparams);
/* No need to restore previous objects into the dc (see comments on top of the class).
*
* if (hOldFont != IntPtr.Zero)
* {
* IntUnsafeNativeMethods.SelectObject(hdc, new HandleRef( null, hOldFont));
* }
*
* if( foreColor != textColor )
* {
* this.dc.SetTextColor(textColor);
* }
*
* if( backColor != bkColor )
* {
* this.dc.SetBackgroundColor(bkColor);
* }
*
* if( bckMode != newMode )
* {
* this.dc.SetBackgroundMode(bckMode);
* }
*
* if( align != DeviceContextTextAlignment.Default )
* {
* // Default text alignment required by DrewText.
* this.dc.SetTextAlignment(align);
* }
*/
}
