class TAttText

Text Attributes class

This class is used (in general by secondary inheritance) by many other classes (graphics, histograms). It holds all the text attributes.

Text attributes

Text attributes are:

• Text Alignment.
• Text Angle.
• Text Color.
• Text Size.
• Text Font and Precision.
• Font quality and speed.
• How to use True Type Fonts.
• List of the currently supported fonts.

Text Alignment

The text alignment is an integer number (align) allowing to control the horizontal and vertical position of the text string with respect to the text position. The text alignment of any class inheriting from TAttText can be changed using the method SetTextAlign and retrieved using the method GetTextAlign.

   align = 10*HorizontalAlign + VerticalAlign

For horizontal alignment the following convention applies:

   1=left adjusted, 2=centered, 3=right adjusted

For vertical alignment the following convention applies:

   1=bottom adjusted, 2=centered, 3=top adjusted

For example:

   align = 11 = left adjusted and bottom adjusted
   align = 32 = right adjusted and vertically centered

Text Angle

Text angle in degrees. The text angle of any class inheriting from TAttText can be changed using the method SetTextAngle and retrieved using the method GetTextAngle. The following picture shows the text angle:

Mnemonic constants are available:
<pre>
kHAlignLeft   = 10, kHAlignCenter = 20, kHAlignRight = 30,
kVAlignBottom = 1,  kVAlignCenter = 2,  kVAlignTop   = 3
</pre>
They allow to write:
<pre>
object->SetTextAlign(kHAlignLeft+kVAlignTop);
</pre>

Text Color

The text color is a color index (integer) pointing in the ROOT color table. The text color of any class inheriting from TAttText can be changed using the method SetTextColor and retrieved using the method GetTextColor. The following table shows the first 50 default colors.

Color transparency

SetTextColorAlpha(), allows to set a transparent color. In the following example the text color of the text text is set to blue with a transparency of 35%. The color kBlue itself remains fully opaque.

text->SetTextColorAlpha(kBlue, 0.35);

The transparency is available on all platforms when the flagOpenGL.CanvasPreferGL is set to 1 in $ROOTSYS/etc/system.rootrc, or on Mac with the Cocoa backend. On the file output it is visible with PDF, PNG, Gif, JPEG, SVG ... but not PostScript.

Text Size

If the text precision (see next paragraph) is smaller than 3, the text size (textsize) is a fraction of the current pad size. Therefore the same textsize value can generate text outputs with different absolute sizes in two different pads. The text size in pixels (charheight) is computed the following way:

   pad_width  = gPad->XtoPixel(gPad->GetX2());
   pad_height = gPad->YtoPixel(gPad->GetY1());
   if (pad_width < pad_height)  charheight = textsize*pad_width;
   else                         charheight = textsize*pad_height;

If the text precision is equal to 3, the text size doesn't depend on the pad's dimensions. A given textsize value always generates the same absolute size. The text size (charheight) is given in pixels:

   charheight = textsize;

Note that to scale fonts to the same size as the old True Type package a scale factor of 0.93376068 is apply to the text size before drawing.

The text size of any class inheriting from TAttText can be changed using the method SetTextSize and retrieved using the method GetTextSize.

Text Font and Precision

The text font code is combination of the font number and the precision.

   Text font code = 10*fontnumber + precision

Font numbers must be between 1 and 14.

The precision can be:
precision = 0 fast hardware fonts (steps in the size)
precision = 1 scalable and rotatable hardware fonts (see below)
precision = 2 scalable and rotatable hardware fonts
precision = 3 scalable and rotatable hardware fonts. Text size is given in pixels.

The text font and precision of any class inheriting from TAttText can be changed using the method SetTextFont and retrieved using the method GetTextFont.

Font quality and speed

When precision 0 is used, only the original non-scaled system fonts are used. The fonts have a minimum (4) and maximum (37) size in pixels. These fonts are fast and are of good quality. Their size varies with large steps and they cannot be rotated. Precision 1 and 2 fonts have a different behaviour depending if the True Type Fonts (TTF) are used or not. If TTF are used, you always get very good quality scalable and rotatable fonts. However TTF are slow.

How to use True Type Fonts

One can activate the TTF by adding (or activating) the following line in the .rootrc file:

   Unix.*.Root.UseTTFonts:     true

It is possible to check the TTF are in use in a Root session with the command:

   gEnv->Print();

If the TTF are in use the following line will appear at the beginning of the printout given by this command:

   Unix.*.Root.UseTTFonts:   true                           [Global]

List of the currently supported fonts

   Font number         X11 Names             Win32/TTF Names
       1 :       times-medium-i-normal      "Times New Roman"
       2 :       times-bold-r-normal        "Times New Roman"
       3 :       times-bold-i-normal        "Times New Roman"
       4 :       helvetica-medium-r-normal  "Arial"
       5 :       helvetica-medium-o-normal  "Arial"
       6 :       helvetica-bold-r-normal    "Arial"
       7 :       helvetica-bold-o-normal    "Arial"
       8 :       courier-medium-r-normal    "Courier New"
       9 :       courier-medium-o-normal    "Courier New"
      10 :       courier-bold-r-normal      "Courier New"
      11 :       courier-bold-o-normal      "Courier New"
      12 :       symbol-medium-r-normal     "Symbol"
      13 :       times-medium-r-normal      "Times New Roman"
      14 :                                  "Wingdings"
      15 :       Symbol italic (derived from Symbol)

The following picture shows how each font looks. The number on the left is the "text font code". In this picture precision 2 was selected.