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How to draw the instancesYou can use the following methods to draw the instances.
To control drawing Description setAbsoluteDraw(Boolean) Sets the flag of forced drawing. draw() draws if needs. redraw() clears and draws cdraw() draws the instance and its children. clear() clears the instance. update() draws if needs.
How to update the instanceUsually, it executes updating the instance at the end of the event procedures. If you want to update at once, you can do it with the method: update().let event_procedure obj = (* change a property. *) obj -> setProperty ("labelString", "new text"); (* updating. *) obj -> update(); () let _ = Callback.register "event_procedure" event_procedureThe method: update() updates the instance, if it needs to reflect the change of the properties.
How to draw the instanceThere are following cases to draw the instances.
- Drawing compulsory
You make the flag of forced drawing "True" to draw compulsory, and call the method:draw(), because the method: draw() does not draw if not need.obj -> redraw();
- Drawing (ordinary)
Usually , we use the method: draw() to draw the instance. it has a good performance, because it do not draw if do not need.obj->setAbsoluteDraw(_True); obj->draw();
- Clearing the instance (no exposed event)
You can clear the instance with the method: clear(), and draw it with draw(). The method: clear() does not create the exposed event, so, if the other instance which are overlapped exists, its area is invalidated. In such case, use redraw() method which creates the exposed event.obj -> draw();
- Clearing the instance (creates the exposed event)
You can redraw the instance with the method: redraw(). it creates the exposed event so that the other overlapped instances are updated. it can make the performance worse if there are many instances.obj -> clear(); obj -> setAbsoluteDraw(_True); obj -> draw();
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