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2011-06-25T17:48:26Z

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Mandingo: Created page with "skinning_engine * Skinning Engine o Summary and Rationale o Current System o Requirements o..."

2011-06-25T17:46:23Z

Created page with "skinning_engine * Skinning Engine o Summary and Rationale o Current System o Requirements o..."

New page

skinning_engine

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Skinning Engine
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Summary and Rationale
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Current System
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Requirements
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Skinning Engine Proposals
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How QT Quick and QML might be used in QT 4.7.x
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Forum discussion
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Ideas for Skinning Engines
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Qt 4 based Skinning Engine

Skinning Engine
Summary and Rationale

Status: This specification is in drafting. Please feel free to add comments.

Supported Widgets

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Push-buttons
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Multi-state push buttons
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Sliders
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horizontal or vertical
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Text labels
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Knobs
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VU meter
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Embed library widget
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Status light

Requirements

Metadata/Manifest

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Include the following metadata:
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author
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title
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description
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language
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skin version
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license
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update-URL
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suggested screen resolution
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min screen resolution

Base Widget

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Nameable
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Position, Size
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Potentially offer absolute positioning mode for legacy support, but in general deprecate absolute positioning.
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Use size-hints (max-min size) instead of single size.
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Tooltip
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Connections
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EmitOnDownPress and EmitOnRelease properties (to obviate need for double-connections)
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Choose mouse button.
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Tab ordering?

Widget Layout

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Widget Grouping
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Nameable
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Have a size hint and optionally an absolute position.
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Provide a hide/show-control. Uses the group's name.
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Layouts
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Allow a widget group to have a layout assigned to it.
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Windows
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Windows are the root of each hierarchy of widgets
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Widget Templates
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Ability to specify some template for a widget for saving time, sanity.

Widgets

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Buttons
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Allow multi-state button or push-button.
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Support pixmaps for each button position
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Allow non-pixmap buttons. Use QSS to styling.
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Slider
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Allow vertical or horizontal orientation
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Separate image for slider and knob
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Allow non-pixmap sliders. Use QSS for styling.
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Drop-down Chooser
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Allow styling via QSS.
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No pixmap option, as it's text-only.
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Requires Control 2.0, since if you connect it to a text control it must know what values it may take on.
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Knobs
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Single knob image that is rotated plus background image.
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Allow specification of 'translation' function (i.e. log-potmeter or potmeter)
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Allow non-pixmap knobs. Use QSS for styling.
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Library Widget
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Still a monolithic widget. Don't think it adds value to allow much customization here.
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Use QSS for all appearance styling.
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Text labels
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Make use of Controls to display text instead of hard-coding text.
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Potentially allow scripts to dynamically affect what is shown.
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Allow Marquee effect so you can read text that goes out of the control.
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VU Meter
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Allow QSS styling (how???) or pixmaps.
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Status light
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Connects to a control and dynamically switches its pixmap or QSS property based on the control's value
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Sampler Widget
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Requirements unknown.
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Effects Widget
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Requirements unknown.
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Potentially with a much better control system we can support neat things

Skinning Engine Proposals

Given the above requirements, list various proposals for skin formats here:

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Qt4, Qt Style Sheet-based approach
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Qt 4.7 QML/Kinetic-based approach
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HTML/CSS Based Skins

How QT Quick and QML might be used in QT 4.7.x

It might be possible to describe a Mixxx skin by using pure QML. According to http://doc.qt.nokia.com/4.7-snapshot/qml-extending-tutorial-index.html QML can be extended to match our own language concepts. In other words, we may extend our existing widget classes in a way they can be accessed by QML,see http://doc.qt.nokia.com/4.7-snapshot/declarative-tutorials-extending-chapter1-basics.html for a simple example.

Tobias Rafreider has created a branch for that purpose.

More information about Qt Quick and QML may be found on http://doc.qt.nokia.com/4.7-snapshot/declarativeui.html

Ideas for Skinning Engines

Feel free to add your cons and pros for any of the ideas to this page

The current ideas are:
Qt 4 based Skinning Engine

Qt 4 is the cross-platform framework.

For the creation of a skinning system, Qt supports many things: layouts, style sheets, vector graphics, raster/OpenVG/OpenGL rendering, useful low-level painting system, XML, animation framework (since 4.6 or as official add-on), declarative UI technology (since 4.6)…

By combining some of these technologies it should be possible to create an advanced skinning engine for LMCE.
To investigate

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Explore the Declarative UI Technology in Qt 4.6 to see if it can help in creating a skinning engine.
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It looks very promising: http://labs.trolltech.com/blogs/category/labs/graphics/kinetic/declarative_ui/
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Explore QWidget versus QGraphicsView for layout.
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How does the performance stack up?
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QWidgets can be rendered in a QGV, but how does this affect performance?
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But when the visualization is rendered in OpenGL, we'll probably have to render the whole QGV in OpenGL
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QGV will give us a really cool and flexible UI in combination with the Animation/DUI framework
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QGV will give us fast software-based UI rendering, as well as support for rendering the UI through OpenGL and since Qt 4.6 also OpenVG
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Explore if and how style sheets can help
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Style sheets are very useful to skin stuff like scrollbars and other default widgets
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The more important stuff like buttons should probably be skinned by reimplementing paintEvent, because this gives more possibilities
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Style sheets may be slower than reimplementing paintEvent - although it has to be investigated to be sure
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More advanced animations (besides simple hover/overroll effects) cannot be created with style sheets only

Pro

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Support pixmap skins (porting of current skins will be easier this way, and performance will probably be higher than using SVG)
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Support SVG skins (for those who want, SVG skins should be an option as well
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Performance may be lower, but we could optionally render SVG as pixmaps to improve performance
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Possibility to implement a layout system (because interface elements should not stretch)
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The window itself should be themable/deformable too. Could be achieved by either composite or with a mask (or both)

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