invalidate (called automatically, e.g. by setcaption) adds the widget's client area to its window's update region
Source position: msegui.pas line 2355
public procedure twidget.paint( |
const canvas: tcanvas |
); virtual; |
invalidate (called automatically, e.g. by setcaption) adds the widget's client area to its window's update region; once the main event queue is empty, the update regions of all windows are painted, widget by widget, bottom-up in z-order, by paint. If the widget's color is not cl_transparent, the area is first filled with that color; then, if active, frame is painted (filling its own client area with colorclient if that is not cl_transparent), then, if active, face; the widget's own content (e.g. a caption) is painted last, on top of that background. When code changes a widget's widgetrect directly rather than through a property that does it automatically, it must invalidate the old widgetrect before the change and the new one after, so both the vacated and the newly covered area get repainted.