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PtLabel

A text, bitmap, or image label

Class hierarchy:

PtWidgetPtBasicPtLabel

Immediate subclasses:

For more information, see the diagram of the widget hierarchy.

PhAB icon:

PtLabel button in PhAB

Public header:

<photon/PtLabel.h>

Description:

The PtLabel class provides a text string, bitmap, or image for labeling other widgets. You can have text pop up in a balloon to provide further meaning to the label.


PtLabel


A text string in a PtLabel widget.

As their name implies, labels are tags attached to objects to identify their name or nature. Label widgets are usually positioned beside the other widget they're describing, although in some cases (e.g. lists), the label appears above the object.

The most frequent use of a label is to identify the name of an input field. For example, a mail program must provide input fields for indicating the recipient and the subject of a mail message being composed. The label widget lets you attach “To:” and “Subject:” tags to those input fields.

Creating labels

The default label type is a null-terminated text string. To specify the type of label, use the Pt_ARG_LABEL_TYPE resource. The possible values for this resource are:

Pt_Z_STRING
The label is a null-terminated ASCII string. This is the default.
Pt_IMAGE
The label is an image, typically a small icon.
Pt_TEXT_IMAGE
The label displays an image and text. To specify the positioning of these two elements relative to each other, set Pt_ARG_BALLOON_POSITION. Use Pt_ARG_TEXT_IMAGE_SPACING to specify the number of pixels between the image and text.

Different resources are used for the label data for different label types. This is particularly useful when you wish to switch quickly between image labels and text labels, so you can give the user a choice between using icons and textual descriptions of operations.

At the push of a button, the user can switch your interface from an iconic representation of commands to a textual representation of the same labels. You can switch the label from an icon to text simply by changing the label type resource.

Text labels

When the label type is textual, the label widget gets the text to be displayed from the Pt_ARG_TEXT_STRING resource.

To specify the font for the text, set Pt_ARG_TEXT_FONT.

The label widget defines its own margins in addition to the margin width defined by the PtBasic widget class. There are separate left, right, top, and bottom margins, which you can specify using:

These margins are cumulative, so that the actual margin of one edge of the widget is the corresponding resource value added to the margin width.

The text label may be aligned independently to the left or right margin, or centered horizontally within the margins of the widget. The Pt_ARG_HORIZONTAL_ALIGNMENT resource controls this behavior. Pt_ARG_SECONDARY_H_ALIGN controls how the text is aligned when the label is smaller than the text (that is, when the text is clipped). If this resource is not set, the value from Pt_ARG_HORIZONTAL_ALIGNMENT is used. The values to specify for these horizontal alignment resources are:

For example, you may want to set Pt_ARG_HORIZONTAL_ALIGNMENT to Pt_CENTER, but ensure that the beginning of the text is readable if the label becomes smaller than the text (for example, if the window is resized, and the label's resize policies allow clipping) by setting Pt_ARG_SECONDARY_V_ALIGN to Pt_LEFT.

You can also control the vertical alignment, i.e. whether the text is aligned to the widget's top or bottom margin, or centered vertically between the two margins. The Pt_ARG_VERTICAL_ALIGNMENT resource controls this behavior. Pt_ARG_SECONDARY_V_ALIGN controls the alignment of clipped text. The values to specify for the vertical alignment are:

By default, the text displayed in the label widget is left-aligned horizontally, and centered vertically. The baseline is calculated by adding the ascender of the label font to the top margin. When text is aligned to the bottom of the widget, the baseline is calculated by subtracting the descender of the label font from the widget's bottom margin.

You can align the baselines of labels drawn with different fonts by selecting bottom alignment for each of the widgets and choosing appropriate margins for them. In this case, make sure you specify a widget height large enough to accommodate the height of the largest font used.

The desired baseline for your aligned widgets is adjusted by the size of the maximum descender of all the fonts used. For each label, add the difference between this descender and the descender of that label's font, then add this difference to the widget's bottom margin. Keep track of this value so that you can recalculate the correct margin setting if you want to change the base margin or the font later on.

Image and bitmap labels

When the label is an image, the label widget gets the image from the Pt_ARG_LABEL_IMAGE resource, which contains a pointer to an image structure, of type PhImage_t, which is described in the Photon Library Reference.

The members of the image structure used by the label and button widgets are:

type
Specifies the type of image. This determines which other members of the image structure are significant and defines the format of the raw image data.

Images can be palette-based or raw. Palette-based images, including bitmaps, have a color palette that serves as a lookup table for determining what color should be displayed for each pixel. Each pixel in the image is encoded as an index into the lookup table, and the pixel is displayed using the color contained in the corresponding table entry.

Raw images have actual RGB color values encoded in the image data.

More than one pixel may be encoded in each byte of the image data, so image-scan lines are padded out to a byte boundary.

Bitmaps are encoded with 1 bit-per-pixel, with the most significant bit first. The types are:

The other types of palette-based images are:

Raw images are all encoded using 16, 24, or 32 bits-per-pixel. The types of raw images are:

bpl
The number of bytes used to encode each scan line. This depends on the image type and size.
size
The width and height of the image in pixels.
colors
The number of colors used in the image for palette-based images. It's used for determining how many color palette entries are significant.
palette
The color lookup table for determining the color of each pixel in the image.
image
The raw image data.

For more information about manipulating images and image data formats, see the Raw Drawing and Animation chapter of the Photon Programmer's Guide.

Balloons

Balloons are a very handy feature of the PtLabel widget class. You can use a balloon to display a line of text when the pointer pauses on top of a widget for more than a second.

This can be very useful in an application with a lot of icons. Whenever you pause on an icon, a little text box pops up beside it to display the name or action the icon represents.

To use balloons with label class widgets:

  1. Set the Pt_SHOW_BALLOON bit in the Pt_ARG_LABEL_FLAGS resource.
  2. Set the Pt_ARG_BALLOON_POSITION resource to define the location.

The Pt_ARG_BALLOON_TEXT resource defines the text displayed in the balloon. If this resource is not set, the Pt_ARG_TEXT_STRING is displayed instead. This allows you to choose one of the two main uses of balloons, either to give further information to the user, or to display the label text in cases where the label has been truncated.

New resources:

Resource C type Pt type Default
Pt_ARG_ACCEL_KEY char * String NULL
Pt_ARG_BALLOON_COLOR PgColor_t Scalar Pg_BLACK
Pt_ARG_BALLOON_FILL_COLOR PgColor_t Scalar Pt_BALLOONCOLOR
Pt_ARG_BALLOON_POSITION short Scalar Pt_BALLOON_RIGHT
Pt_ARG_BALLOON_TEXT char * String NULL
Pt_ARG_HORIZONTAL_ALIGNMENT unsigned char Scalar Pt_LEFT
Pt_ARG_LABEL_BALLOON PtWidget_t * (*)() Pointer PtInflateBalloon
Pt_ARG_LABEL_FLAGS char Flag Pt_LABEL_SELECT_SHIFT
Pt_ARG_LABEL_IMAGE PhImage_t * Image NULL
Pt_ARG_LABEL_TYPE char Scalar Pt_Z_STRING
Pt_ARG_LINE_SPACING unsigned short Scalar 0
Pt_ARG_MARGIN_BOTTOM unsigned short Scalar 0
Pt_ARG_MARGIN_LEFT unsigned short Scalar 0
Pt_ARG_MARGIN_RIGHT unsigned short Scalar 0
Pt_ARG_MARGIN_TOP unsigned short Scalar 0
Pt_ARG_SECONDARY_H_ALIGN signed short Scalar -1 (Not used)
Pt_ARG_SECONDARY_V_ALIGN signed short Scalar -1 (Not used)
Pt_ARG_TEXT_FONT char * String "TextFont09"
Pt_ARG_TEXT_IMAGE_SPACING int Scalar 2
Pt_ARG_TEXT_STRING char * String NULL
Pt_ARG_UNDERLINE1 PgColor_t Scalar Pg_BLACK
Pt_ARG_UNDERLINE2 PgColor_t Scalar Pg_TRANSPARENT
Pt_ARG_UNDERLINE_TYPE unsigned short Scalar Pt_NO_ULINE
Pt_ARG_VERTICAL_ALIGNMENT unsigned char Scalar Pt_CENTER

Pt_ARG_ACCEL_KEY

C type Pt type Default
char * String NULL

The accelerator key to underline within the widget's text string. You typically use this resource for hotkeys.

Pt_ARG_BALLOON_COLOR

C type Pt type Default
PgColor_t Scalar Pg_BLACK

The balloon's text color. See PgColor_t in the Photon Library Reference.

Pt_ARG_BALLOON_FILL_COLOR

C type Pt type Default
PgColor_t Scalar Pt_BALLOONCOLOR

The balloon's fill color. See PgColor_t in the Photon Library Reference.

Pt_ARG_BALLOON_POSITION

C type Pt type Default
short Scalar Pt_BALLOON_RIGHT

Indicates where the balloon with the label's text pops up. If Pt_ARG_LABEL_TYPE is Pt_TEXT_IMAGE, this resource also controls the positioning of the text and image elements relative to each other. Possible values:

Pt_ARG_BALLOON_TEXT

C type Pt type Default
char * String NULL

The text string to display in the balloon. If left blank, the Pt_ARG_TEXT_STRING is used for balloons.

Pt_ARG_HORIZONTAL_ALIGNMENT

C type Pt type Default
unsigned char Scalar Pt_LEFT

The horizontal alignment for the text string. Possible values:

Pt_ARG_LABEL_BALLOON

C type Pt type Default
PtWidget_t * (*)() Pointer PtInflateBalloon

By default, when you pause the pointer over this widget, the widget displays a small balloon. If you want to change the look of the balloon, you can use this resource to override the default inflate function.

Here's the prototype of the inflate function:

PtWidget_t * InflateBalloon( PtWidget_t *window,
                             PtWidget_t *widget,
                             int position,
                             char *text,
                             char *font,
                             PgColor_t fill_color,
                             PgColor_t text_color );
        

The arguments are:

window
The window widget of the widget that requires the balloon.
widget
The widget that requires the balloon.
position
Where the balloon is to pop up:
text
The text to display in the balloon.
font
The font for the text.
fill_color
The balloon's fill color.
text_color
The color of text in the balloon.

You can use the supplied values in your inflate function or ignore them and use your own values.

Pt_ARG_LABEL_FLAGS

C type Pt type Default
char Flag Pt_LABEL_SELECT_SHIFT

Possible values:

Pt_BACKFILL_TEXT
If this is set, the widget fills the text background with the widget's fill color before rendering the text.
Pt_LABEL_SELECT_SHIFT
If this is set, the text shifts down and to the right by one pixel when the widget is armed. Otherwise, the text doesn't shift.
Pt_SHOW_BALLOON
If the pointer remains motionless for 1.25 seconds over the label, a balloon pops up with the label's text.
Pt_BALLOON_AS_REQUIRED
Same as Pt_SHOW_BALLOON, except the balloon is inflated only if the label is clipped by its parent container.
Pt_USE_ELLIPSIS
Replace part of the text with an ellipsis () if there isn't enough space to display all of it.
Pt_ELLIPSIS_MIDDLE
Put the ellipsis into the middle of the text string, instead of at its end(s). This flag is used only when you've set Pt_USE_ELLIPSIS.

Pt_ARG_LABEL_IMAGE

C type Pt type Default
PhImage_t * Image NULL

A pointer to a PhImage_t structure (see the Photon Library Reference) that defines the image to be used if the label type (see Pt_ARG_LABEL_TYPE, below) is Pt_IMAGE or Pt_TEXT_IMAGE.


Note: When you set this resource, the widget copies the PhImage_t structure but not the data pointed to by the members of the structure. After setting this resource, you can free() the PhImage_t if you don't need it, but don't free() the members of it.

Set the flags member of the PhImage_t structure to:

Ph_RELEASE_IMAGE | Ph_RELEASE_PALETTE |
Ph_RELEASE_TRANSPARENCY_MASK | Ph_RELEASE_GHOST_BITMAP

before providing the image to the widget. If you do this, the memory used for the image is released when image is replaced or the widget is unrealized or destroyed.

Pt_ARG_LABEL_TYPE

C type Pt type Default
char Scalar Pt_Z_STRING

The type of information displayed by the label. Possible values:

Pt_Z_STRING
Use Pt_ARG_TEXT_STRING to display the text.
Pt_IMAGE
Use Pt_ARG_LABEL_IMAGE to display an image.
Pt_TEXT_IMAGE
Display the image and text of the label. You can specify the positioning of these two elements relative to each other by setting Pt_ARG_BALLOON_POSITION.

Pt_ARG_LINE_SPACING

C type Pt type Default
unsigned short Scalar 0

The space, in pixels, between the lines of text in the label.

Pt_ARG_MARGIN_BOTTOM

C type Pt type Default
unsigned short Scalar 0

The amount of space between the bottom of the label's canvas and the canvas defined by the basic widget.

Pt_ARG_MARGIN_LEFT

C type Pt type Default
unsigned short Scalar 0

The amount of space between the left side of the label's canvas and the canvas defined by the basic widget.

Pt_ARG_MARGIN_RIGHT

C type Pt type Default
unsigned short Scalar 0

The amount of space between the right side of the label's canvas and the canvas defined by the basic widget.

Pt_ARG_MARGIN_TOP

C type Pt type Default
unsigned short Scalar 0

The amount of space between the top of the label's canvas and the canvas defined by the basic widget.

Pt_ARG_SECONDARY_H_ALIGN

C type Pt type Default
signed short Scalar -1

The horizontal alignment for the text string, if the text string is clipped. Possible values:

Pt_ARG_SECONDARY_V_ALIGN

C type Pt type Default
signed short Scalar -1

The vertical alignment for the text string, if the text string is clipped. Possible values:

Pt_ARG_TEXT_FONT

C type Pt type Default
char * String "TextFont09"

The font used for the label's text string; see PgSetFont().

Pt_ARG_TEXT_IMAGE_SPACING

C type Pt type Default
int Scalar 2

The space, in pixels, between the text and the image in the label.

Pt_ARG_TEXT_STRING

C type Pt type Default
char * String NULL

The text string to be displayed if Pt_ARG_LABEL_TYPE is Pt_Z_STRING or Pt_TEXT_IMAGE, as well as the text to display in the balloon if Pt_ARG_BALLOON_TEXT is blank.

Pt_ARG_UNDERLINE1

C type Pt type Default
PgColor_t Scalar Pg_BLACK

The underline color for the first line.

Pt_ARG_UNDERLINE2

C type Pt type Default
PgColor_t Scalar Pg_TRANSPARENT

The underline color for the second line (used to create thick or beveled underlines).

Pt_ARG_UNDERLINE_TYPE

C type Pt type Default
unsigned short Scalar Pt_NO_ULINE

The type of underline. Possible values:

Pt_ARG_VERTICAL_ALIGNMENT

C type Pt type Default
unsigned char Scalar Pt_CENTER

The vertical alignment for the text string. Possible values:

Inherited resources:

If the widget modifies an inherited resource, the “Default override” column indicates the new value. This modification affects any subclasses of the widget.

Resource Inherited from Default override
Pt_ARG_ANCHOR_FLAGS PtWidget
Pt_ARG_ANCHOR_OFFSETS PtWidget
Pt_ARG_AREA PtWidget
Pt_ARG_BANDWIDTH_THRESHOLD PtBasic Not used by this class.
Pt_ARG_BASIC_FLAGS PtBasic
Pt_ARG_BEVEL_WIDTH PtWidget
Pt_ARG_BITMAP_CURSOR PtWidget
Pt_ARG_BEVEL_COLOR PtBasic
Pt_ARG_BEVEL_CONTRAST PtBasic
Pt_ARG_COLOR PtBasic
Pt_ARG_CONTRAST PtBasic
Pt_ARG_CURSOR_COLOR PtWidget
Pt_ARG_CURSOR_TYPE PtWidget
Pt_ARG_DARK_BEVEL_COLOR PtBasic
Pt_ARG_DARK_FILL_COLOR PtBasic
Pt_ARG_DATA PtWidget
Pt_ARG_DIM PtWidget
Pt_ARG_EFLAGS PtWidget
Pt_ARG_EXTENT PtWidget
Pt_ARG_FILL_COLOR PtBasic
Pt_ARG_FILL_PATTERN PtBasic
Pt_ARG_FLAGS PtWidget
Pt_ARG_GRID_LAYOUT_DATA PtWidget
Pt_ARG_HEIGHT PtWidget
Pt_ARG_HELP_TOPIC PtWidget
Pt_ARG_HIGHLIGHT_ROUNDNESS PtBasic
Pt_ARG_INLINE_COLOR PtBasic
Pt_ARG_LAYOUT_DATA PtWidget
Pt_ARG_LIGHT_BEVEL_COLOR PtBasic
Pt_ARG_LIGHT_FILL_COLOR PtBasic
Pt_ARG_MARGIN_HEIGHT PtBasic 2
Pt_ARG_MARGIN_WIDTH PtBasic 2
Pt_ARG_MAXIMUM_DIM PtWidget
Pt_ARG_MINIMUM_DIM PtWidget
Pt_ARG_OUTLINE_COLOR PtBasic
Pt_ARG_POINTER PtWidget
Pt_ARG_POS PtWidget
Pt_ARG_RESIZE_FLAGS PtWidget Pt_RESIZE_XY_AS_REQUIRED
Pt_ARG_ROW_LAYOUT_DATA PtWidget
Pt_ARG_STYLE PtBasic
Pt_ARG_TRANS_PATTERN PtBasic
Pt_ARG_USER_DATA PtWidget
Pt_ARG_WIDTH PtWidget
Pt_CB_ACTIVATE PtBasic
Pt_CB_ARM PtBasic
Pt_CB_BLOCKED PtWidget
Pt_CB_DESTROYED PtWidget
Pt_CB_DISARM PtBasic
Pt_CB_DND PtWidget
Pt_CB_FILTER PtWidget
Pt_CB_GOT_FOCUS PtBasic
Pt_CB_HOTKEY PtWidget
Pt_CB_IS_DESTROYED PtWidget
Pt_CB_LOST_FOCUS PtBasic
Pt_CB_MENU PtBasic
Pt_CB_OUTBOUND PtWidget
Pt_CB_RAW PtWidget
Pt_CB_REALIZED PtWidget
Pt_CB_REPEAT PtBasic
Pt_CB_UNREALIZED PtWidget

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