Section painter improvements

I plan to improve SectionPainters API in next update. These painters are used in some complex components like JTree to paint some specific areas. For instance JTree has whole 5 section painters - rowPainter, nodePainter, selectionPainter, dropLocationPainter and selectorPainter.

They're used if specified in the style, here is the default tree style:

    <!-- Tree -->
    <style type="tree">
        <component>
            <opaque>true</opaque>
            <background>white</background>
            <foreground>black</foreground>
        </component>
        <ui>
            <selectionStyle>line</selectionStyle>
        </ui>
        <painter>
            <paintLines>true</paintLines>
            <dashedLines>true</dashedLines>
            <linesColor>gray</linesColor>
            <decorations>
                <decoration>
                    <BoundsShape />
                    <ColorBackground color="white" />
                </decoration>
            </decorations>

            <!-- Node background painter -->
            <nodePainter>
                <decorations>
                    <decoration states="enabled,unselected,hover" opacity="0.4">
                        <WebShape round="0" />
                        <GradientBackground>
                            <color>218,218,208</color>
                            <color>206,206,196</color>
                        </GradientBackground>
                    </decoration>
                </decorations>
            </nodePainter>

            <!-- Selection background painter -->
            <selectionPainter>
                <decorations>
                    <decoration opacity="0.75">
                        <WebShape round="0" />
                        <GradientBackground>
                            <color>218,218,208</color>
                            <color>206,206,196</color>
                        </GradientBackground>
                    </decoration>
                    <decoration states="focused" opacity="1" />
                    <decoration states="disabled" opacity="0.5" />
                </decorations>
            </selectionPainter>

            <!-- Tree drop location painter -->
            <dropLocationPainter>
                <decorations>
                    <decoration states="drop-on">
                        <WebShape round="0" />
                        <WebShadow type="inner" width="5" />
                        <LineBorder color="85,130,190" stroke="basic;1;round;round;0;4,5" />
                    </decoration>
                    <decoration states="drop-between" size="80,2">
                        <WebShape round="0" />
                        <LineBorder color="85,130,190" stroke="basic;1;round;round;0;4,5" />
                    </decoration>
                </decorations>
            </dropLocationPainter>

            <!-- Selector painter -->
            <selectorPainter>
                <decorations>
                    <decoration>
                        <WebShape round="0" />
                        <LineBorder color="gray" stroke="basic;1;round;round;0;3,3" />
                        <ColorBackground color="0,0,255,25" />
                    </decoration>
                </decorations>
            </selectorPainter>

        </painter>

        <!-- Label cell renderer -->
        <style type="label" id="renderer" padding="4,4,4,6" />

        <!-- Styled label cell renderer -->
        <style type="styledlabel" id="renderer" padding="4,4,4,6" />

        <!-- Text field cell editor -->
        <style type="textfield" id="editor" padding="0,3,0,2">
            <painter>
                <decorations overwrite="true">
                    <decoration>
                        <WebShape round="2" />
                        <LineBorder color="85,130,190" />
                        <ColorBackground color="white" />
                    </decoration>
                </decorations>
            </painter>

            <!-- Cell editor icon -->
            <style type="image" id="icon" padding="0,0,0,4" />

        </style>

    </style>

It uses 4 out of 5 available SectionPainters by default.

The improvement I'm going to make is basically a streamlined API for these section painters. Right now they are defined directly in parent Painter implementation, for instance in TreePainter for JTree. Each separate SectionPainter has it's own custom API and has to be approached differently because of that. There are also some internal issues with SectionPainter implementations performing a lot of unnecessary actions.

First thing that needs to be introduced is a Section interface that can be implemented for each separate section each component/painter can provide and which can then be used by a new streamlined API of SectionPainter.

Each Section implementation should be able to provide:

Unique identifier (or type) - it will be used in style to attach added section painter to a particular component section - for instance node for tree node background painter
Bounds to be used by the SectionPainter - will simply provide bounds that are currently passed by Painter to it's section painters directly
States to be used by section decoration - currently these are provided within each separate SectionPainter implementation, but those are often identical between some sections and sometimes it's simply inconvenient to retrieve them there
Some other options might also be available in the API, like SectionPainter default or base class

Also something like SectionParameters interface might be required to separate Section from actual data used for bounds/states calculation for each particular case.

Next all currently available section painters will be replaced with the new streamlined approach, both in the code and the style, for instance <nodePainter> will be replaced with:

            <!-- Node background painter -->
            <SectionPainter type="node">
                <decorations>
                    <decoration states="enabled,unselected,hover" opacity="0.4">
                        <WebShape round="0" />
                        <GradientBackground>
                            <color>218,218,208</color>
                            <color>206,206,196</color>
                        </GradientBackground>
                    </decoration>
                </decorations>
            </SectionPainter>

Where node type is the identifier of TreePainter section.

This is just an early stage idea, but I will be working on it in v1.2.12 update since it will allow me to improve quite a few things internally and also slightly improve UI performance.

mgarin / weblaf

Section painter improvements #593