Element: graphic_window.pre_redraw { }
Element: graphic_window.pre_redraw { }callback
One of the command procedures to be executed when graphic_window is repainted due to a recalculation of its contents.
When window redraw procedures are defined and invoked, the following
steps are executed:
The window pre_redraw procedure (if defined) is called.
The window background layers ( background and/or cloth) are painted.
The window redraw procedure (if defined) is called. Within this procedure, manual calls to draw graphics can be made.
Other layers are painted individually. For each vector layer, a call is made to the window populate procedure (if defined) before painting, passing the group corresponding to the vector layer as a parameter.
After the last vector layer has been painted, the window post_redraw procedure (if defined) is called. Within this procedure, manual calls to draw graphics can be made.
Any other non-vector layers (e.g. grid, vane, scalebar) which have not already been painted are painted.
Any graphic primitives on the window overlay group are painted.
When a pre_redraw procedure is executed, the window identifier is passed to the procedure as a parameter.
The pre_redraw procedure is not invoked on repaints due to simple window exposure, but only on a change of window size and/or a redefinition of its corners.
Within a pre_redraw procedure commands which change the contents or view of the window are permitted, but requests to redraw the window contents or draw grapics into the window will be ignored. This procedure is typically used for last-minute view changes prior to redrawing.
New windows have a pre_redraw procedure of null.
window.pre_redraw(<window>)
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