Box Layer

The boxlayer functions provide way to make it easier to use cached offscreen images (layers) in your drawing. More...

Collaboration diagram for Box Layer:

Functions
t_max_err	jbox_invalidate_layer (t_object *b, t_object *view, t_symbol *name)
	Invalidate a layer, indicating that it needs to be re-drawn. More...
t_jgraphics *	jbox_start_layer (t_object *b, t_object *view, t_symbol *name, double width, double height)
	Create a layer, and ready it for drawing commands. More...
t_max_err	jbox_end_layer (t_object *b, t_object *view, t_symbol *name)
	Conclude a layer, indicating that it is complete and ready for painting. More...
t_max_err	jbox_paint_layer (t_object *b, t_object *view, t_symbol *name, double x, double y)
	Paint a layer at a given position. More...

Detailed Description

The boxlayer functions provide way to make it easier to use cached offscreen images (layers) in your drawing.

The general idea is to do something like this:

t_jgraphics *g;
g = jbox_start_layer(box, view, layername, width, height);
if (g) {
    // draw to your new offscreen context here
    // the second time you call jbox_start_layer() it will return NULL
    // since you already drew it -- you don't have to do drawing the second time
    jbox_end_layer(box, view, layername);
}
jbox_paint_layer(box, view, layername, xpos, ypos);

Then, if something changes where you would need to redraw the layer you invalidate it:

jbox_invalidate_layer(box, view, layername);

or

jbox_invalidate_layer(box, NULL, layername); // to invalidate for all views

Each view has its own layer stored since if a patcher has multiple views each could be at a different zoom level.

Function Documentation

jbox_end_layer()

t_max_err jbox_end_layer	(	t_object *	b,
		t_object *	view,
		t_symbol *	name
	)

Conclude a layer, indicating that it is complete and ready for painting.

Parameters

b	The object/box for the layer opened by jbox_start_layer().
view	The patcherview for the object opened by jbox_start_layer().
name	The name of the layer.

Returns

A Max error code.

jbox_invalidate_layer()

t_max_err jbox_invalidate_layer	(	t_object *	b,
		t_object *	view,
		t_symbol *	name
	)

Invalidate a layer, indicating that it needs to be re-drawn.

Parameters

b	The object/box to invalidate.
view	The patcherview for the object which should be invalidated, or NULL for all patcherviews.
name	The name of the layer to invalidate.

Returns

A Max error code.

jbox_paint_layer()

t_max_err jbox_paint_layer	(	t_object *	b,
		t_object *	view,
		t_symbol *	name,
		double	x,
		double	y
	)

Paint a layer at a given position.

Note that the current color alpha value is used when painting layers to allow you to blend layers. The same is also true for jgraphics_image_surface_draw() and jgraphics_image_surface_draw_fast().

Parameters

b	The object/box to be painted.
view	The patcherview for the object which should be painted, or NULL for all patcherviews.
name	The name of the layer to paint.
x	The x-coordinate for the position at which to paint the layer.
y	The y-coordinate for the position at which to paint the layer.

Returns

A Max error code.

jbox_start_layer()

t_jgraphics* jbox_start_layer	(	t_object *	b,
		t_object *	view,
		t_symbol *	name,
		double	width,
		double	height
	)

Create a layer, and ready it for drawing commands.

The layer drawing commands must be wrapped with a matching call to jbox_end_layer() prior to calling jbox_paint_layer().

Parameters

b	The object/box to which the layer is attached.
view	The patcherview for the object to which the layer is attached.
name	A name for this layer.
width	The width of the layer.
height	The height of the layer.

Returns

A t_jgraphics context for drawing into the layer.