damage.h File Reference

Enumerations
enum	{   DAMAGE_VALUE, DAMAGE_PUSHED, DAMAGE_SCROLL, DAMAGE_OVERLAY,   DAMAGE_HIGHLIGHT, DAMAGE_CHILD, DAMAGE_CHILD_LABEL, DAMAGE_EXPOSE,   DAMAGE_CONTENTS, DAMAGE_ALL }

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Detailed Description

Values of the bits stored in Widget::damage().

When redrawing your widgets you should look at the damage bits to see what parts of your widget need redrawing. The Widget::handle() method can then set individual damage bits to limit the amount of drawing that needs to be done, and the Widget::draw() method can test these bits to decide what to draw:

MyClass::handle(int event) {
  ...
  if (change_to_part1) damage(1);
  if (change_to_part2) damage(2);
  if (change_to_part3) damage(4);
}

MyClass::draw() {
  if (damage() & DAMAGE_ALL) {
    ... draw frame/box and other static stuff ...
  }
  if (damage() & (DAMAGE_ALL | 1)) draw_part1();
  if (damage() & (DAMAGE_ALL | 2)) draw_part2();
  if (damage() & (DAMAGE_ALL | 4)) draw_part3();
}

Except for DAMAGE_ALL, each widget is allowed to assign any meaning to any of the bits it wants. The enumerations are just to provide suggested meanings.

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Enumeration Type Documentation

anonymous enum

Enumeration values: DAMAGE_VALUE  A widget may use this to indicate that the displayed value has changed. DAMAGE_PUSHED  A widget may use this to indicate that the user has pushed or released a button. DAMAGE_SCROLL  A widget may use this to indicate that the displayed data has scrolled moved horizontally and/or vertically. DAMAGE_OVERLAY  Same value as DAMAGE_SCROLL. DAMAGE_HIGHLIGHT  A widget may use this to indicate that the mouse has entered/exited part of the widget. DAMAGE_CHILD  A child of this group widget needs to be redrawn (non-group widgets can use this bit for their own purposes). DAMAGE_CHILD_LABEL  An outside label of this widget needs to be redrawn. This is handled (and this bit is cleared) by the parent group. Because anti-aliasing cannot be redrawn atop itself, this is not used anymore. Instead if an outside label needs to change the entire parent widget is redrawn. DAMAGE_EXPOSE  Damage caused by damage() or by expose events from the operating system. If this and DAMAGE_ALL is on the widget should draw every pixel inside it's region. DAMAGE_CONTENTS  Same as DAMAGE_EXPOSE but if DAMAGE_ALL is off a widget can use this for it's own purposes. DAMAGE_ALL  This bit is set by redraw() and indicates that all of the widget (but not "holes" where the background shows through) needs to be redraw.

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