/// <devdoc>
/// <para>
/// 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.
/// </para>
/// </devdoc>
public Size GetTextExtent(string text, WindowsFont font)
{
if (string.IsNullOrEmpty(text))
{
return(Size.Empty);
}
IntNativeMethods.SIZE size = new IntNativeMethods.SIZE();
HandleRef hdc = new HandleRef(null, this.dc.Hdc);
if (font != null)
{
this.dc.SelectFont(font);
}
IntUnsafeNativeMethods.GetTextExtentPoint32(hdc, text, size);
// Unselect, but not from Measurement DC as it keeps the same
// font selected for perf reasons.
if (font != null && !MeasurementDCInfo.IsMeasurementDC(this.dc))
{
this.dc.ResetFont();
}
return(new Size(size.cx, size.cy));
}
/// <devdoc>
/// Selects the specified object into the dc. If the specified object is the same as the one currently selected
/// in the dc, the object is not set and a null value is returned.
/// </devdoc>
public IntPtr SelectFont(WindowsFont font)
{
// Fonts are one of the most expensive objects to select in an hdc and in many cases we are passed a Font that is the
// same as the one already selected in the dc so to avoid a perf hit we get the hdc font's log font and compare it
// with the one passed in before selecting it in the hdc.
// Also, we avoid performing GDI operations that if done on an enhanced metafile DC would add an entry to it, hence
// reducing the size of the metafile.
if (font.Equals(this.Font))
{
return(IntPtr.Zero);
}
IntPtr result = SelectObject(font.Hfont, GdiObjectType.Font);
WindowsFont previousFont = selectedFont;
selectedFont = font;
hCurrentFont = font.Hfont;
// the measurement DC always leaves fonts selected for pref reasons.
// in this case, we need to diposse the font since the original
// creator didn't fully dispose.
if (previousFont != null)
{
#if DEBUG
//Disabling this assert until DevDiv Bugs 95968 gets fixed
//Debug.Assert(previousFont.Hfont != IntPtr.Zero, "A font has been disposed before it was unselected from the DC. This will leak a GDI handle on Win9x! Call ResetFont()");
#endif
if (MeasurementDCInfo.IsMeasurementDC(this))
{
previousFont.Dispose();
}
}
#if OPTIMIZED_MEASUREMENTDC
// once we've changed the font, update the last used font.
if (MeasurementDCInfo.IsMeasurementDC(this))
{
if (result != IntPtr.Zero)
{
MeasurementDCInfo.LastUsedFont = font;
}
else
{
// there was an error selecting the Font into the DC, we dont know anything about it.
MeasurementDCInfo.Reset();
}
}
#endif
return(result);
}
/// <devdoc>
/// Restores the device context to the specified state. The DC is restored by popping state information off a
/// stack created by earlier calls to the SaveHdc function.
/// The stack can contain the state information for several instances of the DC. If the state specified by the
/// specified parameter is not at the top of the stack, RestoreDC deletes all state information between the top
/// of the stack and the specified instance.
/// Specifies the saved state to be restored. If this parameter is positive, nSavedDC represents a specific
/// instance of the state to be restored. If this parameter is negative, nSavedDC represents an instance relative
/// to the current state. For example, -1 restores the most recently saved state.
/// See MSDN for more info.
/// </devdoc>
public void RestoreHdc()
{
#if TRACK_HDC
bool result =
#endif
// Note: Don't use the Hdc property here, it would force handle creation.
IntUnsafeNativeMethods.RestoreDC(new HandleRef(this, this.hDC), -1);
#if TRACK_HDC
// Note: Winforms may call this method during app exit at which point the DC may have been finalized already causing this assert to popup.
Debug.WriteLine(DbgUtil.StackTraceToStr(String.Format("ret[0]=DC.RestoreHdc(hDc=0x{1:x8})", result, unchecked ((int)this.hDC))));
#endif
Debug.Assert(contextStack != null, "Someone is calling RestoreHdc() before SaveHdc()");
if (contextStack != null)
{
GraphicsState g = (GraphicsState)contextStack.Pop();
hCurrentBmp = g.hBitmap;
hCurrentBrush = g.hBrush;
hCurrentPen = g.hPen;
hCurrentFont = g.hFont;
#if !DRAWING_NAMESPACE
if (g.font != null && g.font.IsAlive)
{
selectedFont = g.font.Target as WindowsFont;
}
else
{
WindowsFont previousFont = selectedFont;
selectedFont = null;
if (previousFont != null && MeasurementDCInfo.IsMeasurementDC(this))
{
previousFont.Dispose();
}
}
#endif
}
#if OPTIMIZED_MEASUREMENTDC
// in this case, GDI will copy back the previously saved font into the DC.
// we dont actually know what the font is in our measurement DC so
// we need to clear it off.
MeasurementDCInfo.ResetIfIsMeasurementDC(this.hDC);
#endif
}
/// <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);
}