USING: ui.gadgets ui.pens ui.gestures help.markup help.syntax
kernel classes strings opengl opengl.gl models
math.rectangles math colors ;
IN: ui.render

HELP: gadget
{ $class-description "An object which displays itself on the screen and acts on user input gestures. Gadgets have the following slots:"
    { $list
        { { $snippet "pref-dim" } " - a cached value for " { $link pref-dim } "; do not read or write this slot directly." }
        { { $snippet "parent" } " - the gadget containing this one, or " { $link f } " if this gadget is not part of the visible gadget hierarchy." }
        { { $snippet "children" } " - a vector of child gadgets. Do not modify this vector directly, instead use " { $link add-gadget } ", " { $link add-gadgets } ", " { $link unparent } " or " { $link clear-gadget } "." }
        { { $snippet "orientation" } " - an orientation specifier. This slot is used by layout gadgets." }
        { { $snippet "layout-state" } " - stores the layout state of the gadget. Do not read or write this slot directly, instead call " { $link relayout } " and " { $link relayout-1 } " if the gadget needs to be re-laid out." }
        { { $snippet "visible?" } " - a boolean indicating if the gadget should display and receive user input." }
        { { $snippet "root?" } " - if set to " { $link t } ", layout changes in this gadget will not propagate to the gadget's parent." }
        { { $snippet "clipped?" } " - a boolean indicating if clipping will be enabled when drawing this gadget's children." }
        { { $snippet "interior" } " - an implementation of the " { $link "ui-pen-protocol" } }
        { { $snippet "boundary" } " - an implementation of the " { $link "ui-pen-protocol" } }
        { { $snippet "model" } " - a " { $link model } " or " { $link f } "; see " { $link "ui-control-impl" } }
    }
"Gadgets subclass the " { $link rect } " class, and thus all instances have " { $snippet "loc" } " and " { $snippet "dim" } " instances holding their location and dimensions." }
{ $notes
"Other classes may inherit from " { $link gadget } " in order to re-implement generic words such as " { $link draw-gadget* } " and " { $link user-input* } ", or to define gestures with " { $link set-gestures } "." } ;

HELP: clip
{ $var-description "The current clipping rectangle." } ;

HELP: draw-gadget*
{ $values { "gadget" gadget } } 
{ $contract "Draws the gadget by making OpenGL calls. The top-left corner of the gadget should be drawn at the location stored in the " { $link origin } " variable." }
{ $notes "This word should not be called directly. To force a gadget to redraw, call " { $link relayout-1 } "." } ;

ARTICLE: "ui-paint" "Customizing gadget appearance"
"The UI carries out the following steps when drawing a gadget:"
{ $list
    { "The " { $link draw-interior } " generic word is called on the value of the " { $snippet "interior" } " slot." }
    { "The " { $link draw-gadget* } " generic word is called on the gadget." }
    { "The gadget's visible children are drawn, determined by calling " { $link visible-children } " on the gadget." }
    { "The " { $link draw-boundary } " generic word is called on the value of the " { $snippet "boundary" } " slot." }
}
"Now, each one of these steps will be covered in detail."
{ $subsections
    "ui-pen-protocol"
    "ui-paint-custom"
} ;

ARTICLE: "ui-paint-coord" "The UI co-ordinate system"
"The UI uses a co-ordinate system where the y axis is oriented down. The OpenGL " { $link GL_MODELVIEW } " matrix is saved or restored when rendering a gadget, and the origin is translated to the gadget's origin within the window. The current origin is stored in a variable:"
{ $subsections origin }
"Gadgets must not draw outside of their bounding box, however clipping is not enforced by default, for performance reasons. This can be changed by setting the " { $slot "clipped?" } " slot to " { $link t } " in the gadget's constructor." ;

ABOUT: "ui-paint"