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Qt Painted Widgets (Experimental/WIP)

Simple DSL-like library for creating complex QWidget's design in declerative compile-time manner.

The Main Goal: utilize boilerplate during creation widgets, which appearance based on custom QWidget::paintEvent(QPaintEvent*) implementation. For example in embedded-like software, where QSS and QML may drop perfomance drastically. TL;DR: as said Bjarne Stroustrup: "Make Simple Tasks Simple".

Language version: C++11. Sorry, I use it in embedded, where compilers still not so smart.

Inspired by: Flutter, SwiftUI and QML

Usage

In your *.pro file add next line:

inlude(<path/to>/QPaintedWidgets/q_painted_widgets.pri)
  • Advantages:
    • All types known in compile time, no types erasure
    • Easily extentible & opened for aliases
    • Drawing of multiple (event nested/packed) components can be easily combined with custom painting code (before and after).
    • Method chaining: most of the Component's setters allow chaining like 
      text.setText("Lorem Ipsum")
    .setAlignment(Qt::AlignLeft | Qt::AlignVCenter)
    .setFontBold(true)
    .setFontPixelSize(24)
    .setPen(Qt::blue);
    • Built-in support for styling and auto update next states: Normal, Hovered, Pressed, Disabled
  • Disadvantages:
    • Not dynamic: you cannot add/remove components in run-time
    • On components properties change - repainted the whole widget (by calling QWidget::update() internally)
    • Size of nested/packed components un-acessible (calculated during drawing)
    • Written in c++11, without such useful things as: concepts, if constexpr, fold expressions, using parameter pack
    • Due to templated-nature, debugging kinda difficult

Examples of usage

  • Simple single-component widgets in widgets/ directory

Components usage (simplest case)

  1. Describe component look: 
    using View
    = TupleVertical < ComponentsTuple <
        components::Text, // Top    text
        components::Text, // Middle Text
        components::Text  // Bottom text
    > >;
  2. Use component inside widget: 
    class MyWidget : public QWidget
{
    Q_OBJECT

    View graphics { this };

public:
    explicit MyWidget(QWidget* parent = nullptr)
        : QWidget(parent)
    {}

    QSize minimumSizeHint() const override {
        return graphics.minimumSize(); // Restrict widget mimimum size
    }

    // Accessors for setting text
    void setTextTop   (const QString& text) { graphics.get<0>()->setText(text); }
    void setTextMiddle(const QString& text) { graphics.get<1>()->setText(text); }
    void setTextBottom(const QString& text) { graphics.get<2>()->setText(text); }

protected:
    void paintEvent(QPaintEvent* ) override {
        QPainter p(this);
        graphics.draw(p, this->rect()); // Draw graphics inside widget
    }
}

PIMPL

To make compilation time shorter and not distribute QPaintedWidgets types over your project, useful to use PIMPL idiom for hiding everything related to graphics in source files.

Header (HorizontalIconButton.hpp):

#include <QAbstractButton>

#include <memory> // for std::unique_ptr<T>

/*  ┌──────────────────┐
    │ ┌────┐           │
    │ │icon│    Text   │
    │ └────┘           │
    └──────────────────┘   */

class HorizontalIconButton : public QAbstractButton
{
    Q_OBJECT

    // PIMPL
    class Gfx;
    std::unique_ptr<Gfx> gfx;

    // Default methods disallowed (here, in private section) to prevent miss-usage
    using QAbstractButton::setText;
    using QAbstractButton::text;

    using QAbstractButton::setIcon;
    using QAbstractButton::icon;

    using QAbstractButton::setIconSize;
    using QAbstractButton::iconSize;

public:

    explicit HorizontalIconButton(QWidget *parent = nullptr);
    virtual ~HorizontalIconButton(); // Needed for std::unique_ptr

    // ---------------------------------------------

    void setText(const QString& text);
    QString getText() const;

    // ---------------------------------------------

    void setIcon(const QIcon& icon);

    // ---------------------------------------------

    QSize minimumSizeHint() const override; // For mimimum size restrictnment

protected:
    void paintEvent(QPaintEvent *) override; // Major place - drawing 
};

Source (HorizontalIconButton.cpp):

#include "HorizontalIconButton.hpp"

#include "QPaintedWidgets/components/Icon.hpp"
#include "QPaintedWidgets/components/TextStatic.hpp"
#include "QPaintedWidgets/components/RectFilledRounded.hpp"
#include "QPaintedWidgets/components/RectFilledRoundedWithBorder.hpp"

#include "QPaintedWidgets/composed/generic/ComponentsPair.hpp"
#include "QPaintedWidgets/composed/generic/tuple_aligned/TupleHorizontalStretched.hpp"
#include "QPaintedWidgets/composed/generic/WithPadding.hpp"
#include "QPaintedWidgets/composed/generic/WithSpacing.hpp"
#include "QPaintedWidgets/composed/generic/WithMinSize.hpp"
#include "QPaintedWidgets/composed/generic/Nested.hpp"

using namespace QPaintedWidgets;

// Icon placed in rounded rectangle
using Gfx_Icon_in_Rect
    = Nested < ComponentsPair <
        WithMinSize< components::RectFilledRoundedWithBorder >,
        components::Icon
    > >;

// Icon on left side, Text on right side (filling all space)
using Gfx_Items
    = TupleHorizontalStretched < WithSpacing < ComponentsPair <
        Gfx_Icon_in_Rect,
        components::TextStatic
    > >, 0, 1>;

// All items displayed over rounded rectangle
using GfxView
    = Nested < ComponentsPair <
        components::RectFilledRounded,
        WithPadding < Gfx_Items >
    > >;

struct HorizontalIconButton::Gfx : public GfxView
{
    using base_t = GfxView;
    
    explicit Gfx(QWidget* widget)
        : base_t(widget)
    {
        item_bg()->setBrush( QColor(Qt::red) ); // Custom styling
    }

    // -------------------
    // Convenient aliases for easier access

    auto item_bg() -> decltype( this->first() )
    {
        return this->first();
    }

    auto item_items() -> decltype ( this->second() )
    {
        return this->second();
    }

    // -------------------

    auto item_icon_in_rect() -> decltype ( item_items()->first() )
    {
        return item_items()->first();
    }

    auto item_text() -> decltype ( item_items()->second() )
    {
        return item_items()->second();
    }

    // -------------------

    auto item_icon_rect() -> decltype ( item_icon_in_rect()->first() )
    {
        return item_icon_in_rect()->first();
    }

    auto item_icon() -> decltype ( item_icon_in_rect()->second() )
    {
        return item_icon_in_rect()->second();
    }
};

// std::make_unique for c++11 (via: https://stackoverflow.com/a/17903225)
template<typename T, typename... Args>
inline std::unique_ptr<T> make_unique(Args&&... args)
{
    return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
}

HorizontalIconButton::HorizontalIconButton(QWidget *parent)
    : QAbstractButton(parent)
{
    gfx = make_unique<Gfx>(this);

    // Example of usage - restyling
    gfx->item_items()->setContentPadding({4, 4, 4, 4});
    gfx->item_items()->setSpacing(8);

    gfx->item_icon()->setSize({32, 32});
    gfx->item_icon_rect()->setCustomMinSize({60, 60});
}

HorizontalIconButton::~HorizontalIconButton()
{ }

// -----------------------------------------------------------------------------

void HorizontalIconButton::setText(const QString &text)
{
    gfx->item_text()->setText(text);
}

QString HorizontalIconButton::getText() const
{
    return gfx->item_text()->getText();
}

// -----------------------------------------------------------------------------

void HorizontalIconButton::setIcon(const QIcon &icon)
{
    gfx->item_icon()->setIcon(icon);
}

// -----------------------------------------------------------------------------

QSize HorizontalIconButton::minimumSizeHint() const
{
    return gfx->minimumSize();
}

#include <QPainter>

void HorizontalIconButton::paintEvent(QPaintEvent *)
{
    QPainter p(this);

    gfx->draw(p, this->rect());
}

Complex aliases

template <typename ComponentT, std::size_t STRETCH = 0>
struct Stretch
{
    using component_t = ComponentT;
    static constexpr std::size_t stretch = STRETCH;
};

// { Stretch<ComponentT, StretchT> ... } unpacked as { ComponentT ... , StretchT ... }
template <template <typename ...> class BaseT, typename ... StretchesT>
struct MyHBox : public
    TupleHorizontalStretched <
        BaseT<typename StretchesT::component_t ...>,
        StretchesT::stretch ...
    >
{
    // Same as above, sorry for duplicate :/
    using base_t
        = TupleHorizontalStretched <
            BaseT<typename StretchesT::component_t ...>,
            StretchesT::stretch ...
        >;

    using base_t::base_t;
};

To write:

MyHBox < ComponentsTuple,

    Stretch< components::Text, 2>,
    Stretch< components::Text, 3>,
    Stretch< components::Text, 5>

>

instead of:

TupleHorizontalStretched < ComponentsTuple
<
    components::Text,
    components::Text,
    components::Text

>, 2, 3, 5>

Fixme

  • cannot be combined with additional attributes
    • so: TupleHorizontalStretched < WithSpacing < ComponentsTuple
    • cannot be: MyHBox < WithSpacing<ComponentsTuple>, Stretches... >

Currently unresolved issues

  • TupleHorizontal & TupleVertical currently not handle zero-sizes (aka hidden components via MayBeHidden) (have no time, fix it later, sorry)
  • Text component size() always works in multiline text mode
  • WithMaxMargin - not implemented. Flexible wrapper, same as WithMargin but margin-offset may be shrinked, if space not enought
  • widgets/TextWidget & widgets/StaticTextWidget must use pimpl idiom
  • Implement Pixmap & PixmapAspectRatio & Circle & Triangles

End

Feel free to fork & hack :) If this was useful to you, please add ⭐ on github :)